DE112012007202B4 - Systems and methods for controlling regulators for maximum power point tracking - Google Patents

Abstract

Method for operating a controller (302; 1202) for maximum power point tracking (MPPT controller), which contains a switching circuit (326; 1226) with switching devices (328, 330; 1228, 1230), designed to deliver power between an input connection ( 308; 1208) and an output port (314; 1214), the MPPT controller (302; 1202) including at least one MPPT operating mode and a fixed duty cycle operating mode, the method comprising the steps of: determining that an amount a voltage across the output terminal (314; 1214) upon startup of the MPPT controller (302; 1202) prior to operation of the circuit (326; 1226) while the switching devices (328, 330; 1228, 1230) are in their non-conductive states , is greater than a threshold value; in response to determining that the magnitude of the voltage across the output terminal (314; 1214) upon startup of the MPPT controller (302; 1202) prior to operation of the circuit (326, 1226) while the SC holding devices (328, 330; 1228, 1230) are in their non-conductive states, is greater than the threshold value, operating the MPPT controller (302; 1202) in its operating mode with a fixed duty cycle.

Description

background

worin

IL =

photogenerierter Strom

RS =

Reihenwiderstand

RSH =

Nebenschlusswiderstand

I0 =

Sättigungs-Rückwärtsstrom

n =

Dioden-Idealitätsfaktor (1 für eine ideale Diode)

q =

Elementarladung

k =

Boltzmann-Konstante

T =

absolute Temperatur

I =

Ausgangsstrom an Zellenklemmen

V =

Spannung an Zellenklemmen

Für Silizium bei 25 °C: kT/q = 0,0259 V.Photovoltaic cells generate a voltage that varies with current, cell operating conditions, cell physics, cell defects, and cell lighting. A mathematical model for a photovoltaic cell as shown in 1 models the output current as: $$\mathrm{I.}={\mathrm{I.}}_{\mathrm{L.}}-{\mathrm{I.}}_0\left\{\text{exp}\left[\frac{q\left(V+\mathrm{I.}{\mathrm{R.}}_{\mathrm{S.}}\right)}{nkT}\right]-1\right\}-\frac{V+\mathrm{I.}{\mathrm{R.}}_{\mathrm{S.}}}{{\mathrm{R.}}_{\mathrm{S.}H}}$$

wherein

IL =

photogenerated electricity

RS =

Series resistance

RSH =

Shunt resistance

I0 =

Saturation reverse current

n =

Diode ideality factor ( 1 for an ideal diode)

q =

Elemental charge

k =

Boltzmann constant

T =

absolute temperature

I =

Output current at cell terminals

V =

Voltage at cell terminals

For silicon at 25 ° C: kT / q = 0.0259 V.

Typical cell output voltages are low and depend on the band gap of the material used to make the cell. Cell output voltages can be as little as half a volt for silicon cells, well below the voltage needed to charge batteries or drive most other loads. Because of these low voltages, cells are typically connected in series to form a module or assembly with an output voltage much higher than that produced by a single cell. In addition, sometimes two or more strings from several photovoltaic cells are electrically connected in parallel to increase the capacity.

Photovoltaic cells in the real world often have one or more microscopic defects. These cell defects can cause mismatches of series resistance Rs, shunt resistance R _SH, and photogenerated current I _L from cell to cell in a module. Furthermore, the cell lighting can vary from cell to cell in a system of photovoltaic cells and can even vary from cell to cell in a module for reasons such as shadows cast by trees, bird droppings that shade parts of a cell or module, dust, dirt and other effects. These lighting mismatches can vary from day to day and with the time of day - a shadow can shift over a module during a day, and rain can wash away any dust or dirt that is shading a cell.

According to Eq. 1, the output voltage is greatest at zero output current, and the output voltage V drops non-linearly with increasing output current I. 2 represents the effect of increasing current drawn from a photovoltaic device with constant lighting. When the current I is increased under constant lighting, the voltage V slowly drops, but when the current I is increased to an output current close to the photocurrent I _L , the output voltage V drops sharply. Similarly, as the current I increases, cell power, the product of current and voltage, increases until the decreasing voltage V overcomes the effect of the increasing current, whereupon further increases in the current I drawn from the cell cause the power P to increase rapidly decreased. For a given lighting, each cell, module, and arrangement of cells and modules therefore has a Maximum Power Point (MPP) which is the voltage-current combination at which the output power from the device is maximized. The MPP of a cell, module or arrangement changes with temperature and lighting, and therefore the photogenerated current II changes. The MPP of a cell, module or arrangement can also be influenced by factors such as shadowing and / or aging of the cell , the module or the arrangement.

Maximum Power Point Tracking (MPPT) controllers for operating a photovoltaic device at or near its maximum power point have been proposed. These regulators typically determine an MPP voltage and current for a photovoltaic device connected to its input and adjust its effective impedance to keep the photovoltaic device at the MPP.

Photovoltaic devices are typically subjected to one or more manufacturing tests. For example, a photovoltaic device is often identified using a "flash test" in which the device is exposed to light of known luminous intensity, such as from a "1 sun" (1000 watts per square meter) light source, while the device is loaded from open to short or the other way around passes through. Voltage and current data are recorded during the load cycle, and open circuit voltage (Voc), short circuit current (Isc) and power at the maximum power point (Pmp) of the device are determined from the recorded data. These device parameters are used, for example, to ensure the quality of the device and / or to sort out devices according to Voc, Isc and / or Pmp.

As another example, photovoltaic devices are often subjected to "electroluminescence tests" (EL tests) one or more times during manufacture of the device. EL testing involves driving test current through the photovoltaic device in a direction opposite to that in which the current normally flows through the device, thereby causing the device to emit infrared light. The infrared light is imaged to detect defects in the device, such as cracks in the device, and thereby helps to ensure the quality of the device.

A photovoltaic device can also be exposed to reverse current, i.e. current flowing through the device in a direction opposite to that in normal operation. For example, consider a scenario where first and second strings of photovoltaic devices are electrically connected in parallel and each string contains multiple photovoltaic devices connected in series. Forward current flows through both strings if the strings have identical current-voltage characteristics, the current-voltage characteristic of a string depending on both its physical properties and its operating conditions. For example, consider a situation where the first string is exposed to strong sunlight and the second string is mostly shaded. This difference in lighting causes the first string to generate a larger photo-generated current than the second string, so that the strings have different current-voltage characteristics, which possibly lead to reverse current flowing through the second string.

For example, the DE 10 2009 051 186 A1 , the DE 10 2008 004 675 B3 and the DE 10 2011 076 184 A1 MPPT controller for photovoltaic devices that work as a function of a threshold value of a voltage in an operating state with a fixed pulse duty factor of 100%. the US 2009/0146667 A1 and the US 2012/0217973 A1 each disclose methods for operating an MPPT controller in which the controller can be bypassed by a magnetic or manual actuation of a switch during a test process of the photovoltaic device.

summary

The invention relates to a method for operating an MPPT controller according to independent claims 1 and 41 and a method for testing a photovoltaic device electrically connected to an input connection of an MPPT controller according to independent claim 19. Furthermore, the invention relates to MPPT controller according to the independent claims 23 and 49.

In one embodiment, a method for operating a controller for maximum power point tracking (MPPT controller), which contains a circuit configured to transmit power between an input connection and an output connection, includes the following steps: (a) in a first operating mode of the MPPT controller causing a first switching device of the circuit to operate at a fixed duty cycle; and (b) in a second operating mode of the MPPT controller, causing a control switching device of the circuit to repeatedly switch between its conductive and non-conductive state in order to maximize an amount of power decoupled from a photovoltaic device electrically connected to the input connection.

In one embodiment, a method for testing a photovoltaic device electrically connected to an input connection of a controller for maximum power point tracking (MPPT controller), wherein the MPPT controller contains a circuit designed for this purpose, power between the input connection and an output connection of the MPPT To transmit the controller, the following steps: (a) driving a test current into the output port of the MPPT controller; (b) detecting the presence of the test current; and (c) in response to detecting the presence of the test current, causing the circuitry to provide a path for the test current from the output port to the photovoltaic device.

In one embodiment, a maximum power point tracking (MPPT) controller includes input and output ports, circuitry configured to transfer power between the input and output ports of the MPPT controller, and a control subsystem. The control subsystem is designed (a) in a first operating mode of the MPPT controller to cause a first switching device of the circuit to operate at a fixed duty cycle, and (b) in a second operating mode of the MPPT controller a control switching device of the To cause the circuit to repeatedly switch between its conductive and non-conductive state to one of one at the input terminal electrically connected photovoltaic device to maximize decoupled amount of electrical power.

Figure list

• 1 shows a model of a photovoltaic cell.
• 2 shows a curve of voltage and power as a function of current for a photovoltaic cell.
• 3 FIG. 10 illustrates a photovoltaic power generation system that includes an MPPT controller that includes at least two modes of operation, according to an embodiment.
• 4th simulates EL testing of a photovoltaic device of the power generation system 3 according to one embodiment.
• 5 simulates flash testing of the photovoltaic device of the power generation system 3 according to one embodiment.
• 6th replicates reverse power operation of the photovoltaic device of the power generation system 3 according to one embodiment.
• 7th represents a possible method for operating the MPPT controller 3 according to one embodiment.
• 8th According to one embodiment, FIG. 11 illustrates a method for determining whether an operating mode with a fixed duty cycle is suitable.
• 9 According to one embodiment, represents a further method for determining whether an operating mode with a fixed duty cycle is suitable.
• 10 shows, according to one embodiment, a method for determining when to exit an operating mode with a fixed duty cycle.
• 11th According to one embodiment, represents a further method for determining when to exit an operating mode with a fixed pulse duty factor.
• 12th shows, according to one embodiment, a further photovoltaic power generation system that contains an MPPT controller that comprises at least two operating modes.
• 13th shows, according to one embodiment, a photovoltaic power generation system that includes a plurality of MPPT controllers, each MPPT controller comprising at least two operating modes.
• 14th shows, according to one embodiment, a photovoltaic power generation system that includes three parallel-connected strings of the MPPT controller of 3 includes.
• 15th Figure 11 shows a curve of reverse current versus voltage for a photovoltaic cell.
• 16 shows, according to an embodiment, an example of a linear output current-voltage characteristic.
• 17th shows, according to an embodiment, an example of a non-linear output current-voltage characteristic.

Detailed description of the embodiments

As described above, an MPPT controller can be used to operate a photovoltaic device at or near its MPP. However, conventional MPPT controllers typically interfere with production testing of the photovoltaic device. For example, conventional MPPT controllers may prevent reverse test current and / or overheat when subjected to the EL test. As a further example, the transfer characteristics of conventional MPPT controllers change during the flash test and thus interfere with the determination of Voc, Isc and Pmp. Accordingly, photovoltaic devices typically may not be electrically connected to conventional MPPT controllers during manufacturing testing of the device.

This limitation of conventional MPPT controllers is a particularly serious drawback in applications where multiple MPPT controllers with multiple photovoltaic devices are packaged together. In these applications, the MPPT controllers typically provide part of the interconnection between the photovoltaic devices. Thus, temporary connectors are required to interconnect the photovoltaic devices during manufacturing testing, as the MPPT controllers may not be present during testing.

In addition, traditional MPPT controllers can overheat or otherwise malfunction when exposed to reverse current. Accordingly, conventional MPPT controllers may not be suitable for parallel string applications.

However, the applicants have developed MPPT controllers that partially or completely overcome one or more of the problems described above. These MPPT controllers include a fixed duty cycle operating mode in addition to one or more other operating modes, thereby enabling the controllers to be used during one or more manufacturing tests and / or with reverse current. For example support certain embodiments of the controller Flash or EL tests. Accordingly, the new MPPT controllers described herein potentially simplify manufacturing and testing of photovoltaic devices, particularly in applications that include a number of photovoltaic devices and MPPT controllers assembled into a housing.

3 represents a power generation system 300 that is an MPPT controller 302 contains, between a photovoltaic device 304 and a burden 306 is electrically connected. As described below, the MPPT controller supports 302 at least one operating mode with a fixed duty cycle and an MPPT operating mode and thereby potentially enables the production test of the photovoltaic device 304 with an electrically connected MPPT controller 302 and potentially supports reverse flow operation.

The MPPT controller 302 contains an input connector 308 containing the input terminals 310 , 312 , and an output connector 314 containing the output terminals 316 , 318 . A positive clamp 320 the photovoltaic device 304 is electrically connected to the input terminal 310 connected, and a negative terminal 322 the photovoltaic device 304 is electrically connected to the input terminal 312 connected so that the photovoltaic device 304 with the input connector 308 is electrically connected in series. The clamps 310 , 320 form part of a positive supply node or a supply rail ( Vddh ), and the terminals 312 , 322 form part of a reference supply node or supply rail ( Vss ). The photovoltaic device 304 is for example a photovoltaic module containing a plurality of interconnected photovoltaic cells, a single photovoltaic cell or a multiple photovoltaic cell.

The system 300 optionally contains one or more input capacitors 324 that is above the input connector 308 are electrically connected. The capacitors 324 help the ripple component of the input current lin of the regulator 302 and thereby help to minimize the amount of ripple current that is passed through the photovoltaic device 304 flows. A low amount of ripple current through the photovoltaic device 304 in turn promotes efficient functioning of the device. In certain embodiments where the MPPT controller 302 at a relatively high frequency, such as at 500 kilohertz or higher, the capacitors are switching 324 Multi-layer ceramic capacitors to favor small capacitor size and long capacitor life.

The MPPT controller 302 contains a circuit 326 that is above the input connector 308 is electrically connected. The circuit 326 contains a control switching device 328 that is between the input terminal 310 and a switching node Vx is electrically connected, and a free-wheeling switching device 330 that is between the switching node Vx and the input terminal 312 is electrically connected. The output terminal 316 is electrically connected to the switching node Vx, and the output terminal 318 is with the input terminal 312 electrically connected. In this document, a switching device includes, but is not limited to, a bipolar junction transistor, a field effect transistor (e.g., an N-channel or P-channel metal-oxide-semiconductor field effect transistor (MOSFET), such as a laterally diffused metal oxide Semiconductor transistor (LDMOS), a junction field effect transistor, a metal-semiconductor field effect transistor), a bipolar junction transistor with an insulated gate, a thyristor or a controllable silicon rectifier. Although the switching devices 328 , 330 shown as N-channel enhancement type field effect transistors, the switching devices could 328 , 330 be replaced by alternative switching devices without deviating from the scope of the present.

Weight 306 is with the output connector 314 electrically connected in series to form part of an output circuit 332 to form that the load 306 with the circuit 326 electrically connects. Weight 306 contains, for example, an inverter or a battery charger. One or more output capacitors 334 are over the load 306 electrically connected to absorb the ripple component of the output current Iout. The capacitors 334 however, are optionally omitted in embodiments where the load 306 contains significant capacity, such as in embodiments where the load 306 is an inverter with significant input capacitance. In certain embodiments where the MPPT controller 302 at a relatively high frequency, such as at 500 kilohertz or higher, the capacitors are switching 334 Multi-layer ceramic capacitors to favor small capacitor size and long capacitor life. The output circuit 332 contains an energy storage inductor 336 . In some embodiments, the energy storage includes inductance 336 one or more discrete inductors, as in 3 shown symbolically. However, in some other embodiments, discrete energy storage inductances are omitted and created to loop the output circuit 332 forms, the appropriate "parasitic" connection inductance serves as energy storage inductance 336 .

The MPPT controller 302 further includes a rule subsystem 338 . The circuit 326 , the Energy storage inductance 336 and the capacitors 334 together form one through the rule subsystem 338 regulated buck converter. In an MPPT operating mode of the controller 302 is the rule subsystem 338 designed switching the circuit 326 regulate so that the buck converter has power from the input port 308 to the output port 314 transfers and thereby power from the photovoltaic device 304 a burden 306 transmits. Specifically, the rule subsystem initiates 338 the control switching device 328 to repeatedly switch between their conductive and non-conductive states, typically at a frequency of at least 100 Kilohertz to power from the input port 308 to the output port 314 transferred to. The switching device 328 is referred to as a "control" switching device because the ratio of input voltage Vin to output voltage Vout across the load 306 a function of the duty cycle of the switching device 328 is.

The rule subsystem 338 also controls the switching of the freewheeling switching device 330 such that it performs a free-running function, or in other words, such that the free-running switching device 330 a path for the between the output terminals 316 , 318 provides flowing output current lout when the regulating switching device 328 is in its non-conductive state. In some alternative embodiments, the free-wheeling switching device is 330 replaced by an alternative free-wheeling device, such as a diode, whose anode is connected to the reference node Vss is electrically connected, and the cathode of which is electrically connected to the switching node Vx.

The MPPT controller 302 optionally further includes a stream reconstruction subsystem 340 , configured to generate a signal lo representing the output current Iout coming from the output terminal 314 flows. In some embodiments, the stream reconstruction subsystem uses 340 for generating the signal Io. Systems and methods described in one or more of U.S. Patents No. 6,160,441 and 6,445,244 to Stratakos et al. are disclosed, each of which is incorporated herein by reference. However, the Stream Reconstruction Subsystem 340 be carried out in other ways without departing from the scope of the present. In some embodiments, the signal lo is used for MPPT to test the photovoltaic device 304 to recognize and / or to recognize reverse current, ie when the output current lo has a negative value.

The MPPT controller 302 furthermore optionally contains a voltage regulator 342 who made Vddh / Vss a "self-operated" power supply node or rail ( Vcc ) generated. Vcc is for example used to at least partially control the subsystem 338 to supply as shown.

Though input capacitors 324 , Output capacitors 334 and energy storage inductance 336 as external to the MPPT controller 302 shown, one or more of these components could be in the controller 302 be integrated without deviating from the scope of the present. Also, some or all of the MPPT controller is 302 In certain embodiments, implemented in a common integrated circuit in order to favor small dimensions, small parasitic impedance between components and fast signal transmission times. In these embodiments, the integrated circuit is optional with the photovoltaic device 304 Packaged in a housing to ensure small system size and minimal impedance between the device 304 and the controller 302 to favor. However, the MPPT controller is 302 not limited to an implementation as an integrated circuit and could instead be partially or completely formed from discrete components.

As described above, the MPPT controller 302 at least two operating modes, namely an MPPT operating mode and an operating mode with a fixed duty cycle. In the MPPT operating mode, the control subsystem initiates 338 the control switching device 328 to repeatedly switch between their conductive and non-conductive states to at least substantially one of a photovoltaic device 304 decoupled and to the load 306 to maximize the amount of benefit delivered. For example, in some embodiments, the rules subsystem maximizes 338 the power into the input port 308 thereby maximizing the power of the photovoltaic device 304 decoupled power. In some other embodiments, the rules subsystem maximizes 338 the power from the output port 314 what effectively derives from the photovoltaic device 304 Decoupled power is maximized, since the power from the output connection 314 is the same as the power in the input port 308 if you have losses in the MPPT controller 302 neglected.

The MPPT controller 302 can be designed to directly maximize the performance of the input port or the output port in the MPPT operating mode. For example, in some embodiments, the rules subsystem estimates 338 the input power from the product of the input voltage Vin and the input current lin and controls the operation of the circuit 326 to maximize input power. As another example, appreciate the rules subsystem 338 the output power from the product of the output current Iout and the output voltage Vout or the mean value of the switching node voltage Vp and regulates the operation of the Circuit 326 to maximize output power. However, the MPPT controller can 302 alternatively, be configured to maximize input or output port power by maximizing a signal related to input or output port power. For example, the controller maximizes 338 in a particular embodiment in which the output current Iout is substantially constant, the output terminal power by maximizing the output voltage Vout or an average of the switching node / output terminal voltage Vp .

In the fixed duty cycle operating mode, the control subsystem initiates 338 the control switching device 328 to work at a fixed duty cycle to a known DC transform between input terminal 308 and output connector 314 to reach. In many embodiments, the rule subsystem initiates 338 the control switching device 328 to operate at a large fixed duty cycle, such as a ninety percent or one hundred percent duty cycle, to facilitate testing and minimize losses, as described below. In the context of this document, "duty cycle" refers to the part of each switching cycle in which a switching device operates in its conductive state. For example, consider a scenario in which the control switching device 328 between their conductive and non-conductive states at a frequency of 100 Kilohertz switches, so the switching device 328 has a switching period of ten microseconds. When the control switching device 328 nine microseconds of each switching period operates in its conductive state, the regulating switching device instructs 328 a duty cycle of ninety percent. When the control switching device 328 continuously operates in its conductive state, has the control switching device 328 a duty cycle of one hundred percent.

$$\text{Iout}=\text{Iin}/\text{D}$$

Operating the control switching device 328 a fixed duty cycle makes it easier to determine Voc, Isc and Pmp from measured Iout and Vout values during flash testing. In particular, the MPPT controller works 302 as a fixed DC voltage transformer when the control switching device 328 operates at a fixed duty cycle, so the following relationships hold during operation in the continuous conduction mode, where D is the duty cycle of the regulator switching device 328 is: $$\text{Vout}=\text{D.}*\text{Vin}$$

$$\text{Iout}=\text{Iin}/\text{D.}$$

Thus, the voltage and current of the photovoltaic device 304 can be determined simply by scaling the output voltage measured value Vo and the output current measured value lo by D during operation with a fixed pulse duty factor. When the MPPT controller 302 Conversely, while flash testing was not working at a fixed duty cycle, it would be difficult to measure the voltage and current of the photovoltaic device 304 to be determined from the measured values for Vo and lo, since the duty cycle would vary due to the MPPT function.

It also facilitates operation of the control switching device 328 EL testing at a fixed duty cycle by enabling the amount of test current through the photovoltaic device 304 to be determined without further ado. As described above, the ratio of controller input and output current is a function of the duty cycle. Thus, the amount of the EL test current through the photovoltaic device 304 simply by scaling the amount of to the output port 314 applied EL test current can be determined if the duty cycle is fixed. When the MPPT controller 302 Conversely, while EL testing was not operating at a fixed duty cycle, it would be difficult to determine the amount of current the photovoltaic device was running 304 from the to the output port 314 applied current, since the duty cycle would vary due to the MPPT function.

Operation of the control switching device is further facilitated 328 at a large duty cycle, flash and EL testing as well as reverse current operation by favoring low amount of current. As from Eq. 3, the amount of the controller output current is inversely proportional to the amount of the controller input current. Thus, for a given amount of input current, the amount of output current is minimized by operating at a large duty cycle, such as a duty cycle of at least ninety percent. A low amount of the output current in turn favors low losses of the controller 302 because there are losses in the controller 302 generally increase as the amount of output current increases. Low losses in the regulator 302 help minimize warming up during flash tests, EL tests, and reverse current operation. Low losses in the regulator 302 also help minimize the amount of current required during flash tests and EL tests. Low regulator losses 302 can be particularly important during EL testing because EL testing typically requires a relatively large amount of test current.

Although reverse current operation is generally described herein in connection with fixed duty cycle operation, it should be understood that the duty cycle during the Reverse current operation does not need to be fixed since a fixed DC transformation is not required. Instead, the duty cycle need only be large, such as ninety percent or greater, to achieve low losses, as described above.

4th Fig. 10 shows an example of the EL testing of the photovoltaic device 304 with the electrically connected MPPT controller 302 . One electrical to the output connector 314 test current source connected in series 402 injects a test current I_test into the output terminal 314 . I_test is considered a "reverse" test current because it flows into the output terminal 314 flows in a direction opposite to the output current Iout during normal system operation. The MPPT controller 302 operates in its fixed duty cycle mode, with the control subsystem 338 the control switching device 328 causes to operate at a fixed duty cycle and thereby a known DC transformation between input terminal 308 and output connector 314 to be provided. The current I_test flows through the photovoltaic device 304 in a direction opposite to that of normal operation what the photovoltaic device 304 causes infrared light 404 to be sent out, which is mapped for the purposes of quality assurance of the device. In embodiments where the energy storage inductance 336 consists of one or more discrete inductances, is the inductance 336 optionally omitted during the EL test.

5 Fig. 10 shows an example of flash testing the photovoltaic device 304 with the MPPT controller electrically connected to it 302 . A source of light 502 projects light 504 known intensity on the photovoltaic device 304 while a load 506 runs through from open circuit to short circuit. The output voltage Vout and the output current Iout are recorded during the load cycle and these values are used to calculate Voc, Isc and Pmp of the photovoltaic device 304 to determine. The MPPT controller 302 works in its fixed duty cycle mode during the flash test, so the control subsystem 338 the control switching device 328 caused to switch at a fixed duty cycle. Operate the control switching device 328 at a fixed duty cycle, there is a known direct current transformation between the photovoltaic device 304 and the load 506 and thereby facilitates measurement of the output current Iout during the load cycle. In embodiments where the energy storage inductance 336 consists of one or more discrete inductances, is the inductance 336 optionally omitted during the flash test.

6th Fig. 10 shows an example of the reverse flow operation of the photovoltaic device 304 with the electrically connected MPPT controller 302 . An external circuit (not shown), such as one or more photovoltaic devices connected in parallel, drives a reverse current I_reverse into the output terminal 314 . I_reverse is considered a "reverse" stream because it goes into the output port 314 flows in a direction opposite to the output current Iout during normal system operation. The MPPT controller 302 operates in its fixed duty cycle mode, with the control subsystem 338 the control switching device 328 caused to operate at a large duty cycle and thereby a path for the reverse current I_reverse to flow through the photovoltaic device 304 to be provided. As described above, no fixed duty cycle is required for reverse current operation. Thus, in some alternative embodiments, the control switching device operates 328 at a large, non-fixed duty cycle, such as ninety percent or greater, when conducting I_reverse.

The rule subsystem 338 is optionally designed, a duty cycle of the control switching device 328 to cause the MPPT controller to rise up to its fixed duty cycle when the MPPT controller is started 302 to operate in its operating mode with a fixed duty cycle instead of starting immediately at the fixed duty cycle. Such control of the change in duty cycle, sometimes referred to as "soft start", helps eliminate parasitic transients associated with changes in the operating condition.

In some embodiments, it triggers every time the MPPT controller 302 starts up, the rule subsystem 338 the MPPT controller 302 to work in its fixed duty cycle mode. In some other embodiments, the MPPT controller operates 302 in its fixed duty cycle mode in response to an external signal, such as a signal generated by test equipment designed to perform flash and / or EL testing. In certain embodiments, the rules subsystem determines 338 whether fixed duty cycle mode of operation is appropriate, and if so, it operates the controller 302 in its fixed duty cycle mode of operation.

For example poses 7th a procedure 700 to operate the MPPT controller 302 which includes determining whether fixed duty cycle mode operation is appropriate. The procedure 700 is, for example, when the MPPT controller starts up 302 executed so that the controller 302 starts in its fixed duty cycle mode, if appropriate. However, the procedure is 700 does not apply to the use when starting the controller 302 and could instead run in other situations, such as after a fault condition.

The procedure 700 begins with a decision step 702 determining whether fixed duty cycle mode operation is appropriate. An example of the step 702 is determined by the rule subsystem 338 whether operation in fixed duty cycle mode is appropriate. Some specific examples of the step 702 are below re 8th and 9 described. When the decision step 702 determines that fixed duty cycle mode operation is not appropriate, the procedure continues 700 advance to the MPPT operating mode 704 . An example of the step 704 is that the rule subsystem 338 the MPPT controller 302 operates in its MPPT operating mode.

On the other hand, if the decision step 702 determines that fixed duty cycle mode operation is appropriate, the procedure continues 700 move forward to step 706 with operation in fixed duty cycle mode. An example of step 706 is that the rule subsystem 338 the control switching device 328 made to operate at a fixed duty cycle of at least ninety percent. The decision step 708 determines whether the fixed duty cycle mode operation is completed. If not, operations are ongoing 706 in fixed duty cycle mode. If the fixed duty cycle mode operation is completed, the procedure proceeds to the MPPT operation mode 704 . An example of the step 708 is the determination by the rule subsystem 338 whether fixed duty cycle mode operation is complete. Some specific examples of the step 708 are below re 10 and 11th described.

The procedure 700 could be modified to include one or more additional operating modes in addition to MPPT mode 704 and to fixed duty cycle mode 706 to contain. For example, some alternative embodiments further include a bypass mode of operation in which the control switching device 328 works in its non-conductive state and the free-running switching device 330 works in their conducting state. In these alternative embodiments, for example, decision step is used in the bypass mode of operation 702 or 708 occurred if fixed duty cycle mode operation is inadequate or has completed and the magnitude of the input voltage Vin is too low to warrant MPPT operation. The operation then changes from bypass mode to MPPT operation mode 704 if, for example, the amount of Vin increases enough to support MPPT operation.

In some embodiments, the rules subsystem determines 338 Based on parameters of its operating environment, whether operation in fixed duty cycle mode is appropriate. For example poses 8th a procedure 800 to determine whether operating mode with fixed duty cycle is appropriate when starting up an MPPT controller. The procedure 800 is for example as part of the step 702 of the procedure 700 executed. However, the procedure is 800 not on use in the procedure 700 limited but could be used in other situations. Besides, the step is 702 not on use in the procedure 800 limited.

The procedure 800 starts with the decision step 802 detecting the presence of an output terminal voltage prior to operation of the circuit at start-up when the devices of the circuit are in their non-conductive states. The presence of an output terminal voltage under these conditions indicates that the MPPT controller is powered from its output terminal rather than its input terminal, indicating the possible presence of test current and an EL test. For example, consider the EL test example of FIG 4th . In this example, the test current source causes 402 that a tension Vp at the output port 314 is in place before the circuit 326 starts to work. If on the other hand the source 402 were absent, the output terminal voltage would be Vp before operating the circuit 326 typically essentially zero when the output port 314 would not be driven in any other way. Accordingly, the decision step determines 802 that operation in the fixed duty cycle mode is appropriate if the magnitude of the output terminal voltage is greater than a threshold value, the threshold value being zero or a smaller positive value. An example of the step 802 is that the rule subsystem 338 before operating the circuit 326 when starting up while the switching devices are in motion 328 , 330 are in their non-conductive states, the switch node or output terminal voltage Vp or a signal that Vp represents, compares with a threshold value and the MPPT controller 302 made to work in its fixed duty cycle mode if Vp is greater than a threshold value.

When the decision step 802 determines that fixed duty cycle mode operation is not appropriate, the procedure continues 800 to enter the MPPT operating mode in step 804 . However, in some alternative embodiments, the method enters step 804 instead of the MPPT mode, enter an alternative operating mode, such as the bypass mode described above.

On the other hand, if the decision step 802 determines that fixed duty cycle mode operation is appropriate, the procedure continues 800 first to enter the operating mode with a fixed duty cycle in step 806 . However, some embodiments of the method include 800 optional steps 808 and 810 , as shown. These steps delay entry into the fixed duty cycle operating mode until a power supply rail of the MPPT controller has reached a level necessary to support reliable controller operation.

In particular, the decision step compares 808 an amount of voltage on a regulator power supply rail, such as the amount of Vcc in the controller 302 , with a minimum value (Vmin) required for reliable MPPT controller operation. If the magnitude of the voltage on the power supply rail is greater than or equal to Vmin, the procedure goes to step 806 to enter the fixed duty cycle mode. Otherwise the operation goes ahead to step 810 , in which the circuit is deactivated so that its switching devices are in their non-conductive states. The procedure 800 returns from step 810 to step 808 back so that the circuit remains disabled until the power rail voltage reaches Vmin. An example of the steps 808 and 810 is that the rule subsystem 338 the switching devices 328 , 330 made to remain in their non-conductive states until Vcc one for reliable converter operation 302 required minimum value reached.

Include the optional steps 808 and 810 in the procedure 800 can, in some embodiments, start up the MPPT controller 302 accelerate. For example, consider again the EL test example of FIG 4th . The control switching device 328 converting transistor contains a body diode 344 with an anode electrically connected to the switching node Vx and an anode electrically connected to the input terminal 310 connected cathode. The test current I_test flows accordingly through the body diode 344 , as indicated by the current I_diode in 4th shown, in the positive power supply rail Vddh before the circuit 326 is in operation. The test current charges the positive power supply rail Vddh . In addition, the test current charges the in-house power supply rail Vcc via the positive power supply rail Vddh and the voltage regulator 342 . Accordingly, the power supply rails become Vddh and Vcc during EL test or during reverse current operation in fixed duty cycle mode from the output terminal 314 supplied here. Delaying operation in fixed duty cycle mode until Vcc one for reliable operation of the controller 302 Required minimum value is reached, favors fast loading of the Vddh / Vcc rails and subsequent operation in the mode with fixed duty cycle. On the other hand, if the steps 808 , 810 are omitted, the free-running switching device 330 conduct while loading the Vddh / Vcc rails, thereby delaying rail loading and operation in fixed duty cycle mode.

9 represents another procedure 900 for determining whether a fixed duty cycle mode is appropriate. The procedure 900 is for example as part of the step 702 of the procedure 700 executed. However, the procedure is 900 not on use in the procedure 700 limited but could be used in other situations. Besides, the step is 702 not on use in the procedure 900 limited.

The procedure 900 starts with step 902 determining whether current flowing from the output terminal of the MPPT controller has a negative value, or in other words whether current flowing into the output terminal. Such a condition is possible driving the converter with a test current and associated EL test or reverse current operation. For example, consider again the EL test example of FIG 4th . The test power source drives during the EL test 402 the test current I_test into the output terminal 314 so that lout is negative. As another example, consider the reverse flow example of 6th . An external circuit (not shown) drives a reverse current I_reverse into the output terminal 314 so that lout is negative. Accordingly, fixed duty cycle mode operation is adequate if the output current value is less than a threshold value Ith, where Ith is zero or a value close to zero. Though step 902 To detect when the output current is negative, it may still be desirable to set Ith to a value other than zero, such as a value slightly below zero, in order to erroneously trigger the fixed duty cycle mode due to errors in measuring the output current Iout to prevent. An example of the step 902 is comparison by the rule subsystem 338 of the signal Io, which is the current from the output terminal 314 having a threshold such as zero or a value near zero and determining that fixed duty cycle mode operation is appropriate if the magnitude of lo is less than the threshold.

When the decision step 902 determines that fixed duty cycle mode operation is not appropriate, the procedure continues 900 proceed to enter the MPPT mode in step 904 . However, in some alternative embodiments, the method enters step 904 instead of the MPPT Mode to an alternate operating mode, such as the bypass mode described above.

On the other hand, if the decision step 902 determines that fixed duty cycle mode operation is appropriate, the procedure continues 900 first to enter the operating mode with a fixed duty cycle in step 906 . However, some embodiments of the method include 900 optional steps 908 and 910 , as shown. These steps are analogous to the steps 808 and 810 from 8th delay the entry into the operating mode with fixed duty cycle until a power supply rail of the MPPT controller has reached a level that is necessary to support reliable controller operation.

10 represents a procedure 1000 of determining when to exit the fixed duty cycle operating mode. The procedure 1000 is for example as part of the step 708 of the procedure 700 executed. However, the procedure is 1000 not on use in the procedure 700 limited, but could instead be used to determine when to exit fixed duty cycle mode in other situations. Besides, the step is 708 not on use in the procedure 1000 limited.

The procedure 1000 begins with a decision step 1002 determining whether a predetermined period of time has passed. This predetermined period of time is chosen to allow sufficient time to complete applicable tests of the photovoltaic device, such as EL and flash tests. If the specified period has not yet elapsed, the step is repeated 1002 ; otherwise the procedure proceeds to enter the MPPT mode in step 1004 . An example of the steps 1002 , 1004 is that the rule subsystem 338 starts a timer at the start of operation in the fixed duty cycle mode and enters the MPPT mode after a predetermined period of time has elapsed. However, in some alternative embodiments, the method enters step 1004 instead of the MPPT mode, enter an alternative operating mode, such as the bypass mode described above.

11th represents a procedure 1100 of determining when to exit the fixed duty cycle operating mode. The procedure 1100 is for example as part of the step 708 of the procedure 700 executed. However is procedure 1100 not on use in the procedure 700 limited, but could instead be used to determine when to exit fixed duty cycle mode in other situations. Besides, the step is 708 not on use in the procedure 1100 limited.

The procedure 1100 begins with a decision step 1102 determining whether a voltage across the input terminal or a voltage that is a function of the input terminal voltage has fallen below a threshold value. The threshold is typically chosen to be zero or a value close to zero, so that the step 1102 detects when the input terminal voltage or an associated voltage is substantially zero. A zero input terminal voltage may indicate completion of testing of the photovoltaic device. For example, the input terminal voltage will be substantially zero at the completion of flash testing when a load cycles from open to short. As another example, after removing an EL test power source, the input terminal voltage may drop to near zero. If the voltage is not lower than the threshold value, step repeats 1102 ; otherwise the procedure proceeds to enter the MPPT mode in step 1104 .

An example of the steps 1102 , 1104 is that the rule subsystem 338 the input terminal voltage Vin or the power supply rail voltage Vcc compares to a threshold value and enters MPPT mode if the voltage is lower than the threshold value. However, in some alternative embodiments, the method enters step 1104 instead of the MPPT mode, enter an alternative operating mode, such as the bypass mode described above.

Flash testing can be difficult to detect in some applications because current flows through the photovoltaic device in its normal direction during flash testing. Accordingly, some embodiments of the controller are 302 designed to remain in their fixed duty cycle mode of operation after EL testing is complete to allow subsequent flash testing while remaining in the fixed duty cycle mode of operation. The fixed duty cycle mode could also operate in embodiments as described above with respect to 9 Detect negative output current by initially driving the output terminal with a reverse current.

Operating modes with a fixed duty cycle can also be implemented in MPPT controller applications with a topology other than a buck converter topology, such as a boost converter topology or a buck-boost converter topology. For example poses 12th a power generation system 1200 that is an MPPT controller 1202 contains, between a photovoltaic device 1204 and a burden 1206 is electrically connected. The MPPT controller 1202 is similar to the MPPT Regulator 302 , but is designed to support an up-converter topology instead of a down-converter topology.

The MPPT controller 1202 contains an input connector 1208 with the input terminals 1210 , 1212 and an output terminal 1214 with the output terminals 1216 , 1218 . A positive clamp 1220 the photovoltaic device 1204 is to the input terminal 1210 electrically connected, and a negative terminal 1222 the photovoltaic device 1204 is to the input terminal 1212 electrically connected so that the photovoltaic device 1204 with the input connector 1208 is electrically connected in series. The clamps 1210 , 1220 form part of a positive supply node or a supply rail ( Vddh ), and the terminals 1212 , 1222 form part of a reference supply node or a - supply rail ( Vss ). The photovoltaic device 1204 is, for example, a photovoltaic module containing a large number of interconnected photovoltaic cells, a single photovoltaic cell or a multiple photovoltaic cell.

The system 1200 optionally contains one or more input capacitors 1224 that is above the input connector 1208 are electrically connected. The capacitors 1224 help reduce the ripple component of the input current lin of the regulator 1202 and thereby help to minimize the amount of ripple current that is passed through the photovoltaic device 1204 flows. The MPPT controller 1202 further includes one between the input terminal 1210 and a switching node Vx electrically connected energy storage inductance 1236 . The energy storage inductance 1236 may include one or more discrete inductors as shown.

The MPPT controller 1202 further includes a between the energy storage inductance 1236 and the output connector 1214 electrically connected circuit 1226 . The circuit 1226 includes one between switch node Vx and the input and output connection terminals 1212 , 1218 electrically connected control switching device 1228 and one between switch node Vx and the output terminal 1216 electrically connected free-wheeling switching device 1230 . The output terminal 1218 is with the input terminal 1212 electrically connected. Although the switching devices 1228 , 1230 shown as N-channel enhancement type field effect transistors, the switching devices could 1228 , 1230 be replaced by alternative switching devices without deviating from the scope of the present.

Weight 1206 is with the output connector 1214 electrically connected in series. Weight 1206 contains, for example, an inverter or a battery charger. One or more output capacitors 1234 are over the load 1206 electrically connected to absorb the ripple component of the output current Iout. The capacitors 1234 however, are optionally omitted in embodiments in which the load 1206 contains significant capacity, such as in embodiments where the load 1206 is an inverter with significant input capacitance.

The MPPT controller 1202 further includes a rule subsystem 1238 . The circuit 1226 , the energy storage inductance 1236 and the capacitors 1234 together form one through the rule subsystem 1238 regulated boost converter. In an MPPT operating mode of the controller 1202 is the rule subsystem 1238 designed, switching the circuit 1226 regulate so that the boost converter has power from the input port 1208 to the output port 1214 transfers and thereby power from the photovoltaic device 1204 a burden 1206 transmits. Specifically, the rule subsystem initiates 1238 the control switching device 1228 to repeatedly switch between their conductive and non-conductive states, typically at a frequency of at least 100 Kilohertz to power from the input port 1208 to the output port 1214 transferred to. The switching device 1228 is referred to as a "control" switching device because the ratio of input voltage Vin to output voltage Vout across the load 1206 a function of the duty cycle of the switching device 1228 is.

The rule subsystem 1238 also controls the switching of the freewheeling switching device 1230 such that it performs a free-running function, or in other words such that the free-running switching device 1230 a path for the through the energy storage inductance 1236 Provides flowing current when the control switching device 1228 is in its non-conductive state.

The MPPT controller 1202 optionally further includes a stream reconstruction subsystem 1240 , designed to generate a signal lo corresponding to the output terminal 1214 represents flowing output current lout. Also, in some embodiments, includes the MPPT controller 1202 further a voltage regulator 1242 who made Vddh / Vss a "self-operated" power supply node or rail ( Vcc ) generated. Vcc is used, for example, to at least partially control the subsystem 1238 to supply as shown.

Though input capacitors 1224 and output capacitors 1234 as external to the MPPT controller 1202 shown could be one or several of these components in the controller 1202 be integrated without deviating from the scope of the present. Also, in cases where the energy storage inductance 1236 consists of one or more discrete inductances, the inductances external to the controller 1202 be arranged.

Next is some or all of the MPPT controller 1202 In certain embodiments, implemented in a common integrated circuit in order to favor small dimensions, small parasitic impedance between components and fast signal transmission times. In these embodiments, the integrated circuit is optional with the photovoltaic device 1204 Packaged in a housing to ensure small system size and minimal impedance between the device 1204 and the controller 1202 to favor. However, the MPPT controller is 1202 not limited to an implementation as an integrated circuit and could instead be partially or completely formed from discrete components.
The MPPT controller 1202 has at least two operating modes, namely an MPPT operating mode and an operating mode with a fixed duty cycle. In the MPPT operating mode, the control subsystem initiates 1238 the control switching device 1228 to repeatedly toggle between their conductive and non-conductive states by at least substantially an amount that comes from a photovoltaic device 1204 decoupled and to the load 1206 to maximize the performance delivered. For example, in some embodiments, the rules subsystem maximizes 1238 the power into the input port 1208 thereby maximizing the power of the photovoltaic device 1204 decoupled power. In some other embodiments, the rules subsystem maximizes 1238 the power from the output port 1214 what effectively derives from the photovoltaic device 1204 Decoupled power is maximized, since the power from the output connection 1214 is the same as the power in the input port 1208 if you consider the losses in the MPPT controller 1202 neglected.

In the fixed duty cycle operating mode, the control subsystem initiates 1238 the MPPT controller 1202 , a fixed DC transformation between the input and output terminals 1208 , 1214 provide for testing the photovoltaic device 1204 or to facilitate reverse flow operation, in a similar manner to the MPPT controller above 302 ( 3 ) described. Specifically, the rule subsystem initiates 1238 the control switching device 1228 to work at a fixed duty cycle to have a fixed DC transformation between input terminal 1208 and output connector 1214 to reach. However, in contrast to the MPPT controller, it causes 302 the rule subsystem 1238 typically the free-wheeling switching device 1230 instead of the control switching device 1228 to operate at a large duty cycle, such as a ninety percent duty cycle.

The rule subsystem 1238 is designed, for example, using one or more techniques similar to those above with respect to the MPPT controller 302 described to determine when the regulator 1202 to operate in its fixed duty cycle mode, and when to operate the regulator 1202 to switch from its fixed duty cycle mode to MPPT mode. For example is the rules subsystem 1238 construed in some embodiments in a manner similar to that relating to above 8th and 9 to determine that fixed duty cycle mode operation is reasonable if there is voltage across the output terminal at startup 1214 is present, or if the output current Iout has a negative value. Another example is the rules subsystem 1238 configured in some embodiments to exit the fixed duty cycle mode of operation after a predetermined period of time has elapsed, or if the voltage across the input terminal 1208 falls below a threshold, in a manner similar to that above with respect to 10 and 11th described.

In buck-boost topology applications, the regulator switching device is operated in a fixed duty cycle mode of operation at a fixed duty cycle, such as a fifty percent duty cycle, to achieve a fixed DC transformation.

The use of MPPT controllers that include fixed duty cycle modes is not limited to photovoltaic power generation systems with a single photovoltaic device and a single MPPT controller. For example poses 13th a photovoltaic power generation system 1300 represents, the N realizations of the MPPT controller 302 in a photovoltaic application, where N is an integer greater than one. In this document, reference may be made to certain implementations of an item by using a number in parentheses (e.g. MPPT controller 302 (1)), while numbers without brackets refer to any such item (e.g. MPPT controller 302 ). Some of the MPPT controller building blocks 302 are in 13th not shown to aid clarity.

The input connector 308 every MPPT controller 302 is to a respective photovoltaic device 1304 of a common photovoltaic module 1305 electrically connected. Photovoltaic devices 1304 are for example individual photovoltaic cells or groups of electrical interconnected photovoltaic cells. However, the arrangement of photovoltaic devices 1304 can be varied without deviating from the scope of the present. For example, in some alternative embodiments, are photovoltaic devices 1304 discrete photovoltaic devices and are not part of a common module. In another example, in some other embodiments, two or more photovoltaic devices have 1304 different arrangements. A respective input capacitor 1324 is also above each input port 308 electrically connected.

The output connectors 314 the MPPT controller 302 are with a burden 1306 electrically connected in series. One or more output capacitors 1334 are over the load 1306 electrically connected and are of each of the N MPPT controllers 1302 shared. However, in some alternative embodiments, includes the load 1306 significant capacitance, and the capacitors 1334 are therefore omitted. Also, in some alternative embodiments, each has an MPPT controller 302 a respective capacitor (not shown) connected via its output terminal 314 is electrically connected.

The MPPT controller 302 use the interconnect inductance 1336 an output circuit 1332 who made the circuits 326 with the load 1306 electrically connects, as an energy storage inductance. Although this interconnect inductance is shown symbolically as a single element, it is actually distributed along a loop that forms the output circuit 1332 forms. However, some alternative embodiments include one or more discrete inductors (not shown) that are connected to the output circuit 1332 are electrically connected in series. For example it is in embodiments in which each MPPT controller 302 a respective one above its output connector 314 having electrically connected capacitor, typically required that each MPPT controller 302 has a respective discrete inductance connected to its output terminal 314 is electrically connected in series.

Any MPPT controller 302 operates in essentially the same manner as described for power generation systems that use a single version of the MPPT controller 302 contain. For example, in an MPPT operating mode, each MPPT controller maximizes 302 those from its respective photovoltaic device 1304 decoupled power. In an operating mode with a fixed pulse duty factor, on the other hand, each MPPT controller works in such a way that its control switching device has a fixed pulse duty factor. Flash testing can be done, for example, by replacing the load 1306 by a variable load and cycling through the load resistance can be performed while the photovoltaic devices 1304 exposed to a light source of known strength. EL testing can be done by replacing the load 1306 by a test current source and driving a test current into the output terminals 314 in a direction opposite to the normal output current lout.

Operation in reverse current mode can cause problems with current sharing in applications with two or more MPPT controllers electrically connected in parallel 302 prepare. For example poses 14th a photovoltaic power generation system 1400 represents, the three strings connected in parallel 1403 contains, where each string contains three versions of the MPPT controller 302 with output connections electrically connected in series 314 contains. A respective photovoltaic device 1404 is to the input port 308 each controller 302 electrically connected. Only the input and output connections are for clarity of illustration 308 , 314 the regulator 302 shown.

Consider a scenario where the string 1403 (1) produces a larger photogenerated current than either string 1403 (2) or 1403 (3) , such as due to partial shading of the strings 1403 (2) , 1403 (3) . The forward current 1405 of the strong string 1403 (1) tensions the weaker strings 1403 (2) , 1403 (3) in forward direction, so that reverse currents 1407 , 1409 through the strings 1403 (2) or. 1403 (3) flow. If the strings 1403 (2) , 1403 (3) have the same current-voltage characteristics, is the magnitude of the reverse currents 1407 , 1409 same. If the strings 1403 (2) , 1403 (3) have different current-voltage characteristics, the reverse currents show 1407 , 1409 different amounts, so the strings 1403 (2) , 1403 (3) do not divide the reverse current equally.

The reverse current imbalance may be due to the current-voltage characteristics of the photovoltaic devices 1404 be great. In particular, a photovoltaic cell has a current-voltage characteristic curve similar to that of a diode, as shown by the model of FIG 1 indicated, which means that the cell voltage is relatively insensitive to the amount of current as soon as the cell conducts reverse current. Thus, any voltage imbalance that might exist between two discrete cells when biased with the same amount of reverse current can result in a large current imbalance when the cells are connected in parallel.

For example shows 15th a curve 1500 of reverse current versus voltage for a photovoltaic cell 1502 . Suppose the cell 1502 work with tension 1504 when they are with a Reverse current 1506 is biased. Now assume the cell 1502 be connected in parallel with another photovoltaic cell (not shown) with a different current-voltage characteristic, so that the cell 1502 due to the parallel connection of the voltage 1508 have to work. The amount of reverse current jumps to 1510 what a big change 1512 in the amount of reverse current results in a small change 1514 to compensate for the amount of tension. Thus, small differences in current-voltage characteristics between parallel connected photovoltaic devices can cause significant reverse current imbalance in the devices.

Unequal sharing of the reverse current can cause a string to experience too high an amount of reverse current, which possibly regulators 302 and / or photovoltaic devices 1404 of the string. Also, strings 1403 typically fused for safety reasons, and excessive reverse current in a string can blow the string's fuse, causing the string to be out of service and not generate power until the fuse is replaced.

Accordingly, certain embodiments of the MPPT controller are 302 designed to operate in a third mode of operation, sometimes referred to as the reverse flow operating mode, under reverse flow conditions. In these embodiments, the rules subsystem is 338 designed the control switching device 328 to cause to repeatedly switch between their conductive and non-conductive state at a duty cycle that maintains a predetermined output current-voltage characteristic of the regulator, viewed from a load in the output terminal 314 . Operating each MPPT controller in such a way that it has a common output current-voltage characteristic curve enables each string to have a common output current-voltage characteristic curve, which means that the current is shared equally among the strings 1403 favored in reverse flow operation. The rule subsystem 308 causes the MPPT controller 302 enters the reverse current operating mode if the magnitude of the signal lo is, for example, less than or equal to a threshold value, the threshold value representing negative or very small output current.

In some embodiments that support the reverse current operating mode, the predetermined output current-voltage characteristic curve is linear, so that the magnitude of the average voltage across the output terminal 314 linear with a change in the mean current into the output port 314 changes. 16 shows an example of a linear output current-voltage characteristic 1600 . In some other embodiments that support the reverse current operating mode, the predetermined output current-voltage characteristic is non-linear, so that the magnitude of the average voltage across the output terminal 314 non-linear with a change in the mean current into the output port 314 changes. 17th shows an example of a non-linear output current-voltage characteristic 1700 .

The fact that the characteristics 1600 , 1700 Having relatively large effective resistances, ie the value of the voltage over the current, also favors the current distribution. In particular, the resistance of a string leads to negative feedback because the resistance causes the string voltage to increase with the amount of current, thereby reducing the amount of current required to reach a given voltage. The non-linear characteristic 1700 has a particularly large effective resistance for large amounts of current, potentially resulting in large negative feedback for large amounts of current. A backward biased photovoltaic cell, on the other hand, has a relatively small effective resistance, which leads to less negative feedback in applications with parallel connection.

A reverse flow operating mode is optional in the MPPT controller 1202 ( 12th ) implemented in a similar way to the MPPT controller 302 .

Combinations of characteristics

• (A1) Ein Verfahren zum Betreiben eines Reglers für das Maximum Power Point Tracking (MPPT-Reglers), der einen Schaltkreis enthält, ausgelegt, Leistung zwischen einem Eingangsanschluss und einem Ausgangsanschluss zu übertragen, kann folgende Schritte enthalten: (a) in einem ersten Betriebsmodus des MPPT-Reglers Veranlassen einer ersten Schaltvorrichtung des Schaltkreises, bei einem festen Tastverhältnis zu arbeiten; und (b) in einem zweiten Betriebsmodus des MPPT-Reglers Veranlassen einer Regel-Schaltvorrichtung des Schaltkreises, wiederholt zwischen ihrem leitenden und nichtleitenden Zustand umzuschalten, um einen aus einer an den Eingangsanschluss elektrisch angeschlossenen Photovoltaikvorrichtung ausgekoppelten Betrag an Leistung zu maximieren.
• (A2) In dem als (A1) bezeichneten Verfahren kann die erste Schaltvorrichtung mindestens eins aus der Regel-Schaltvorrichtung des Schaltkreises und einer freilaufenden Schaltvorrichtung des Schaltkreises enthalten.
• (A3) In jedem der beiden als (A1) oder (A2) bezeichneten Verfahren kann das feste Tastverhältnis ein Tastverhältnis von mindestens neunzig Prozent sein.
• (A4) In jedem der beiden als (A1) oder (A2) bezeichneten Verfahren kann das feste Tastverhältnis ein Tastverhältnis von einhundert Prozent sein.
• (A5) Beliebige der als (A1) bis (A4) bezeichneten Verfahren können weiter enthalten: Betreiben des MPPT-Reglers in seinem ersten Betriebsmodus als Reaktion auf das Bestimmen vor dem Betrieb des Schaltkreises beim Anlauf des MPPT-Reglers, dass ein Betrag eines Signals, das die Spannung über dem Ausgangsanschluss darstellt, größer ist als ein erster Schwellwert.
• (A6) Beliebige der als (A1) bis (A5) bezeichneten Verfahren können weiter enthalten: Veranlassen des Schaltkreises, in seinem nichtleitenden Zustand zu arbeiten, bis ein Betrag einer Spannung auf einer Stromversorgungsschiene des MPPT-Reglers einen vorgegebenen Wert überschreitet.
• (A7) Das als (A6) bezeichnete Verfahren kann weiter enthalten: im ersten Betriebsmodus des MPPT-Reglers Versorgen der Stromversorgungsschiene des MPPT-Reglers vom Ausgangsanschluss her.
• (A8) in dem als (A7) bezeichneten Verfahren kann die erste Schaltvorrichtung einen ersten Transistor enthalten, und das Verfahren kann elektrisches Einspeisen von Strom in die Stromversorgungsschiene des MPPT-Reglers unter Verwendung einer Bodydiode des ersten Transistors enthalten.
• (A9) Beliebige der als (A1) bis (A8) bezeichneten Verfahren können weiter enthalten: Betreiben des MPPT-Reglers in seinem ersten Betriebsmodus als Reaktion auf das Bestimmen, dass ein Signal, das aus dem Ausgangsanschluss fließenden Strom darstellt, niedriger als ein oder gleich einem zweiten Schwellwert ist.
• (A10) In dem als (A9) bezeichneten Verfahren kann der zweite Schwellwert darstellen, dass Strom aus dem Ausgangsanschluss in einer negativen Richtung fließt.
• (A11) Weiter kann das als (A10) bezeichnete Verfahren Weiterbetreiben des MPPT-Reglers in seinem ersten Betriebsmodus enthalten, nachdem ein Betrag aus dem Ausgangsanschluss fließenden Stroms auf null gefallen ist.
• (A12) Beliebige der als (A1) bis (A11) bezeichneten Verfahren können weiter enthalten: Betreiben des MPPT-Reglers in seinem ersten Betriebsmodus als Reaktion auf ein externes Signal.
• (A13) Beliebige der als (A1) bis (A12) bezeichneten Verfahren können weiter enthalten: Betreiben des MPPT-Reglers in seinem ersten Betriebsmodus jedes Mal, wenn der MPPT-Regler anläuft.
• (A14) Beliebige der als (A1) bis (A13) bezeichneten Verfahren können weiter enthalten: Veranlassen, dass ein Tastverhältnis der ersten Schaltvorrichtung zum festen Tastverhältnis hochläuft, wenn der MPPT-Regler beginnt, in seinem ersten Betriebsmodus zu arbeiten.
• (A15) Beliebige der als (A1) bis (A14) bezeichneten Verfahren können weiter enthalten: Schalten vom ersten Betriebsmodus zu einem anderen Betriebsmodus des MPPT-Reglers nach einem vorgegebenen Zeitraum.
• (A16) Beliebige der als (A1) bis (A15) bezeichneten Verfahren können weiter enthalten: Schalten vom ersten Betriebsmodus zu einem anderen Betriebsmodus des MPPT-Reglers, wenn ein erstes Spannungssignal unter einen dritten Schwellwert fällt.
• (A17) In dem als (A16) bezeichneten Verfahren kann das erste Spannungssignal eine Funktion einer Spannung über dem Eingangsanschluss sein.
• (A18) In jedem der als (A15) bis (A17) bezeichneten Verfahren kann der andere Betriebsmodus der zweite Betriebsmodus des MPPT-Reglers sein.
• (A19) Beliebige der als (A1) bis (A18) bezeichneten Verfahren können weiter enthalten: Veranlassen der Regel-Schaltvorrichtung, in einem dritten Betriebsmodus des MPPT-Reglers wiederholt zwischen ihrem leitenden und nichtleitenden Zustand bei einem Tastverhältnis umzuschalten, das eine vorgegebene Ausgangs-Strom-Spannungs-Kennlinie des MPPT-Reglers beibehält.
• (A20) Das als (A19) bezeichnete Verfahren kann weiter enthalten: Betreiben des MPPT-Reglers in seinem dritten Betriebsmodus als Reaktion auf das Bestimmen, dass ein Signal, das aus dem Ausgangsanschluss fließenden Strom darstellet, niedriger als ein oder gleich einem vierten Schwellwert ist, wobei der vierte Schwellwert darstellen kann, dass Strom aus dem Ausgangsanschluss in einer negativen Richtung fließt.
• (A21) In jedem der beiden als (A19) und (A20) bezeichneten Verfahren kann die vorgegebene Ausgangs-Strom-Spannungs-Kennlinie des MPPT-Reglers linear sein, sodass sich der Betrag der mittleren Spannung über dem Ausgangsanschluss linear mit einer Änderung des Betrags eines in den Eingangsanschluss fließenden mittleren Stroms ändert.
• (A22) In jedem der beiden als (A19) und (A20) bezeichneten Verfahren kann die vorgegebene Ausgangs-Strom-Spannungs-Kennlinie des MPPT-Reglers nichtlinear sein, sodass sich der Betrag der mittleren Spannung über dem Ausgangsanschluss nichtlinear mit einer Änderung des Betrags eines in den Eingangsanschluss fließenden mittleren Stroms ändert.
• (B1) Ein Verfahren zum Prüfen einer mit einem Eingangsanschluss eines Reglers für das Maximum Power Point Tracking (MPPT-Reglers) elektrisch verbundenen Photovoltaikvorrichtung, wobei der MPPT-Regler einen Schaltkreis enthält, ausgelegt, Leistung zwischen dem Eingangsanschluss und einem Ausgangsanschluss des MPPT-Reglers zu übertragen, kann folgende Schritte enthalten: (a) Treiben eines Prüfstroms in den Ausgangsanschluss des MPPT-Reglers; (b) Erkennen des Vorhandenseins des Prüfstroms; und (c) als Reaktion auf das Erkennen des Vorhandenseins des Prüfstroms Veranlassen des Schaltkreises, einen Weg für den Prüfstrom vom Ausgangsanschluss zur Photovoltaikvorrichtung vorzusehen.
• (B2) In dem als (B1) bezeichneten Verfahren kann der Schritt des Veranlassens des Schaltkreises, einen Weg für den Prüfstrom vom Ausgangsanschluss zur Photovoltaikvorrichtung vorzusehen, das Veranlassen einer Schaltvorrichtung des Schaltkreises enthalten, bei einem festen Tastverhältnis zu arbeiten.
• (B3) In dem als (B2) bezeichneten Verfahren kann das feste Tastverhältnis ein Tastverhältnis von mindestens neunzig Prozent sein.
• (B4) In dem als (B2) bezeichneten Verfahren kann das feste Tastverhältnis ein Tastverhältnis von einhundert Prozent sein.
• (B5) In jedem der als (B1) bis (B4) bezeichneten Verfahren kann der Schritt des Veranlassens des Schaltkreises, einen Weg für den Prüfstrom vom Ausgangsanschluss zur Photovoltaikvorrichtung vorzusehen, das Veranlassen des MPPT-Reglers enthalten, als fester Gleichstromtransformator zu wirken, der den Prüfstrom mit der Photovoltaikvorrichtung elektrisch verbindet.
• (B6) In jedem der als (B1) bis (B5) bezeichneten Verfahren kann der Schritt des Erkennens des Vorhandenseins des Prüfstroms das Erkennen des Vorhandenseins von Strom enthalten, der von einer externen Quelle in den Ausgangsanschluss fließt.
• (B7) In jedem der als (B1) bis (B6) bezeichneten Verfahren kann der Schritt des Erkennens des Vorhandenseins des Prüfstroms das Erkennen von Spannung über dem Ausgangsanschluss des Schaltkreises enthalten.
• (B8) In dem als (B7) bezeichneten Verfahren kann der Schritt des Erkennens von Spannung über dem Ausgangsanschluss des Schaltkreises das Vergleichen eines Signals, das die Spannung über dem Ausgangsanschluss darstellt, mit einem Schwellwert enthalten.
• (C1) Ein Regler für das Maximum Power Point Tracking (MPPT-Regler) kann einen Eingangs- und einen Ausgangsanschluss, einen Schaltkreis, ausgelegt, Leistung zwischen dem Eingangs- und dem Ausgangsanschluss zu übertragen, und ein Regel-Untersystem enthalten. Das Regel-Untersystem kann ausgelegt sein, (a) in einem ersten Betriebsmodus des MPPT-Reglers eine erste Schaltvorrichtung des Schaltkreises zu veranlassen, bei einem festen Tastverhältnis zu arbeiten; und (b) in einem zweiten Betriebsmodus des MPPT-Reglers eine Regel-Schaltvorrichtung des Schaltkreises zu veranlassen, wiederholt zwischen ihrem leitenden und nichtleitenden Zustand umzuschalten, um einen aus einer an den Eingangsanschluss elektrisch angeschlossenen Photovoltaikvorrichtung ausgekoppelten Betrag an elektrischer Leistung zu maximieren.
• (C2) In dem als (C1) bezeichneten MPPT-Regler kann die erste Schaltvorrichtung mindestens eins aus der Regel-Schaltvorrichtung des Schaltkreises und einer freilaufenden Schaltvorrichtung des Schaltkreises enthalten.
• (C3) In jedem der beiden als (C1) oder (C2) bezeichneten MPPT-Regler kann das feste Tastverhältnis ein Tastverhältnis von mindestens neunzig Prozent sein.
• (C4) In jedem der beiden als (C1) oder (C2) bezeichneten MPPT-Regler kann das feste Tastverhältnis ein Tastverhältnis von einhundert Prozent sein.
• (C5) In jedem der als (C1) bis (C4) bezeichneten MPPT-Regler kann das Regel-Untersystem weiter ausgelegt sein: (a) vor dem Betrieb des Schaltkreises beim Anlauf des MPPT-Reglers einen Betrag eines Signals, das die Spannung über dem Ausgangsanschluss darstellt, mit einem ersten Schwellwert zu vergleichen; und (b) den MPPT-Regler in seinem ersten Betriebsmodus zu betreiben als Reaktion auf das Bestimmen, dass der Betrag des Signals, das Spannung über dem Ausgangsanschluss darstellt, größer ist als der erste Schwellwert.
• (C6) In jedem der als (C1) bis (C5) bezeichneten MPPT-Regler kann das Regel-Untersystem weiter ausgelegt sein, den Schaltkreis zu veranlassen, in seinem nichtleitenden Zustand zu arbeiten, bis ein Betrag einer Spannung auf einer Stromversorgungsschiene des MPPT-Reglers einen vorgegebenen Wert überschreitet.
• (C7) In dem als (C6) bezeichneten MPPT-Regler kann der MPPT-Regler weiter so ausgelegt sein, dass im ersten Betriebsmodus des MPPT-Reglers die Stromversorgungsschiene des MPPT-Reglers vom Ausgangsanschluss her versorgt ist.
• (C8) In jedem der als (C1) bis (C7) bezeichneten MPPT-Regler: (a) kann die Regel-Schaltvorrichtung zwischen einer ersten Klemme des Eingangsanschlusses und einer ersten Klemme des Ausgangsanschlusses elektrisch verbunden sein; (b) kann der Schaltkreis weiter eine freilaufende Vorrichtung enthalten, die zwischen der ersten Klemme des Ausgangsanschlusses und einer zweiten Klemme des Ausgangsanschlusses elektrisch verbunden ist, wobei die freilaufende Vorrichtung ausgelegt ist, einen Weg für zwischen der ersten und der zweiten Klemme des Ausgangsanschlusses fließenden Strom vorzusehen, wenn sich die Regel-Schaltvorrichtung in ihrem nichtleitenden Zustand befindet; (c) kann die erste Schaltvorrichtungen die Regel-Schaltvorrichtung sein; und (d) kann die erste Klemme des Ausgangsanschlusses mit einem Schaltknoten elektrisch verbunden sein.
• (C9) In dem als (C8) bezeichneten MPPT-Regler kann die Regel-Schaltvorrichtung ein Regel-Transistor sein, wobei der Regel-Transistor eine Bodydiode mit einer mit dem Schaltknoten elektrisch verbundenen Anode und einer mit der ersten Klemme des Eingangsanschlusses verbundenen Kathode enthält.
• (C10) In jedem der als (C1) bis (C9) bezeichneten MPPT-Regler kann das Regel-Untersystem weiter ausgelegt sein: (a) ein Signal, das aus dem Ausgangsanschluss fließenden Strom darstellt, mit einem zweiten Schwellwert zu vergleichen; und (b) den MPPT-Regler in seinem ersten Betriebsmodus zu betreiben als Reaktion auf das Bestimmen, dass das Signal, das aus dem Ausgangsanschluss fließenden Strom darstellt, niedriger als der oder gleich dem zweiten Schwellwert ist.
• (C11) In dem als (C10) bezeichneten Verfahren kann der zweite Schwellwert darstellen, dass Strom aus dem Ausgangsanschluss in einer negativen Richtung fließt.
• (C12) In dem als (C11) bezeichneten MPPT-Regler kann das Regel-Untersystem weiter ausgelegt sein, den MPPT-Regler weiter in seinem ersten Betriebsmodus zu betreiben, nachdem ein Betrag aus dem Ausgangsanschluss fließenden Stroms auf null gefallen ist.
• (C13) In jedem der als (C1) bis (C12) bezeichneten MPPT-Regler kann das Regel-Untersystem weiter ausgelegt sein, den MPPT-Regler als Reaktion auf ein externes Signal in seinem ersten Betriebsmodus zu betreiben.
• (C14) In jedem der als (C1) bis (C13) bezeichneten MPPT-Regler kann das Regel-Untersystem weiter ausgelegt sein, den MPPT-Regler jedes Mal, wenn der MPPT-Regler anläuft, in seinem ersten Betriebsmodus zu betreiben.
• (C15) In jedem der als (C1) bis (C14) bezeichneten MPPT-Regler kann das Regel-Untersystem weiter ausgelegt sein zu veranlassen, dass ein Tastverhältnis der ersten Schaltvorrichtung zum festen Tastverhältnis hochläuft, wenn der MPPT-Regler beginnt, in seinem ersten Betriebsmodus zu arbeiten.
• (C16) In jedem der als (C1) bis (C15) bezeichneten MPPT-Regler kann das Regel-Untersystem weiter ausgelegt sein, den MPPT-Regler zu veranlassen, nach einem vorgegebenen Zeitraum von seinem ersten Betriebsmodus zu einem anderen Betriebsmodus umzuschalten.
• (C17) In jedem der als (C1) bis (C16) bezeichneten MPPT-Regler kann das Regel-Untersystem weiter ausgelegt sein: (a) ein erstes Spannungssignal mit einem dritten Schwellwert zu vergleichen, wobei das erste Spannungssignal eine Funktion einer Spannung über dem Eingangsanschluss ist; und (b) den MPPT-Regler zu veranlassen, von seinem ersten Betriebsmodus zu einem anderen Betriebsmodus des MPPT-Reglers umzuschalten, wenn das erste Spannungssignal unter den dritten Schwellwert fällt.
• (C18) In jedem der beiden als (C16) oder (C17) bezeichneten Verfahren kann der andere Betriebsmodus der zweite Betriebsmodus des MPPT-Reglers sein.
• (C19) In jedem der als (C1) bis (C18) bezeichneten MPPT-Regler kann das Regel-Untersystem weiter ausgelegt sein, die Regel-Schaltvorrichtung zu veranlassen, in einem dritten Betriebsmodus des MPPT-Reglers wiederholt zwischen ihrem leitenden und nichtleitenden Zustand bei einem Tastverhältnis umzuschalten, das eine vorgegebene Ausgangs-Strom-Spannungs-Kennlinie des MPPT-Reglers beibehält.
• (C20) In dem als (C19) bezeichneten MPPT-Regler kann das Regel-Untersystem weiter ausgelegt sein: (a) ein Signal, das aus dem Ausgangsanschluss fließenden Strom darstellt, mit einem vierten Schwellwert zu vergleichen; und (b) den MPPT-Regler in seinem dritten Betriebsmodus zu betreiben als Reaktion auf das Bestimmen, dass das Signal, das aus dem Ausgangsanschluss fließenden Strom darstellt, niedriger als der oder gleich dem vierten Schwellwert ist.
• (C21) In dem als (C20) bezeichneten MPPT-Regler kann der vierte Schwellwert darstellen, dass Strom aus dem Ausgangsanschluss in einer negativen Richtung fließt.
• (C22) In jedem der als (C19) bis (C21) bezeichneten MPPT-Regler kann die vorgegebene Ausgangs-Strom-Spannungs-Kennlinie des MPPT-Reglers linear sein, sodass sich der Betrag der mittleren Spannung über dem Ausgangsanschluss linear mit einer Änderung des Betrags eines in den Eingangsanschluss fließenden mittleren Stroms ändert.
• (C23) In jedem der als (C19) bis (C21) bezeichneten MPPT-Regler kann die vorgegebene Ausgangs-Strom-Spannungs-Kennlinie des MPPT-Reglers nichtlinear sein, sodass sich der Betrag der mittleren Spannung über dem Ausgangsanschluss nichtlinear mit einer Änderung des Betrags eines in den Eingangsanschluss fließenden mittleren Stroms ändert.

The features described above and those claimed below can be combined in various ways without deviating from the present scope. The following examples show some possible combinations.

• (A1) A method for operating a controller for maximum power point tracking (MPPT controller), which contains a circuit designed to transfer power between an input connection and an output connection, can contain the following steps: (a) in a first operating mode causing the MPPT controller to cause a first switching device of the circuit to operate at a fixed duty cycle; and (b) in a second operating mode of the MPPT controller, causing a control switching device of the circuit to repeatedly switch between its conductive and non-conductive state in order to maximize an amount of power decoupled from a photovoltaic device electrically connected to the input connection.
• (A2) In the method referred to as (A1), the first switching device may include at least one of the control switching device of the switching circuit and a free-running switching device of the switching circuit.
• (A3) In either of the two methods designated as (A1) or (A2), the fixed duty cycle can be a duty cycle of at least ninety percent.
• (A4) In either of the two methods designated as (A1) or (A2), the fixed duty cycle can be a duty cycle of one hundred percent.
• (A5) Any of the methods identified as (A1) through (A4) may further include: operating the MPPT controller in its first operating mode in response to determining prior to operation of the circuit upon startup of the MPPT controller that an amount of a signal , which represents the voltage across the output terminal, is greater than a first threshold value.
• (A6) Any of the methods identified as (A1) to (A5) can further include: causing the circuit to operate in its non-conductive state until an amount of a voltage on a power supply rail of the MPPT controller exceeds a predetermined value.
• (A7) The method referred to as (A6) can further include: in the first operating mode of the MPPT controller, the power supply rail of the MPPT controller is supplied from the output connection.
• (A8) in the method referred to as (A7), the first switching device may include a first transistor, and the method may include electrically injecting current into the power supply rail of the MPPT controller using a body diode of the first transistor.
• (A9) Any of the methods identified as (A1) through (A8) may further include: operating the MPPT controller in its first mode of operation in response to determining that a signal representing current flowing out of the output port is lower than an or is equal to a second threshold value.
• (A10) In the method referred to as (A9), the second threshold value may represent that current flows from the output terminal in a negative direction.
• (A11) Furthermore, the method referred to as (A10) can include continued operation of the MPPT controller in its first operating mode after an amount of current flowing out of the output connection has fallen to zero.
• (A12) Any of the methods identified as (A1) to (A11) can further include: operating the MPPT controller in its first operating mode in response to an external signal.
• (A13) Any of the methods identified as (A1) to (A12) can further include: operating the MPPT controller in its first operating mode each time the MPPT controller starts up.
• (A14) Any of the methods identified as (A1) to (A13) can further include: causing a duty cycle of the first switching device to ramp up to the fixed duty cycle when the MPPT controller begins to work in its first operating mode.
• (A15) Any of the methods identified as (A1) to (A14) can further include: switching from the first operating mode to another operating mode of the MPPT controller after a predetermined period of time.
• (A16) Any of the methods identified as (A1) to (A15) can further include: switching from the first operating mode to another operating mode of the MPPT controller when a first voltage signal falls below a third threshold value.
• (A17) In the method referred to as (A16), the first voltage signal may be a function of a voltage across the input terminal.
• (A18) In each of the methods referred to as (A15) to (A17), the other operating mode can be the second operating mode of the MPPT controller.
• (A19) Any of the methods identified as (A1) to (A18) can further include: causing the control switching device to repeatedly switch between its conductive and non-conductive state in a third operating mode of the MPPT controller at a pulse duty factor that has a predetermined output Maintains the current-voltage characteristic of the MPPT controller.
• (A20) The method referred to as (A19) may further include: operating the MPPT controller in its third mode of operation in response to determining that a signal representing current flowing out of the output port is less than or equal to a fourth threshold value , wherein the fourth threshold value may represent that current flows from the output terminal in a negative direction.
• (A21) In each of the two methods referred to as (A19) and (A20), the specified output current-voltage characteristic curve of the MPPT controller can be linear, so that the amount of the mean voltage across the output connection changes linearly with a change in the amount of an average current flowing into the input terminal changes.
• (A22) In each of the two methods designated as (A19) and (A20), the specified output current-voltage characteristic curve of the MPPT controller can be non-linear, so that the amount of the mean voltage across the output connection changes non-linearly with a change in the amount of an average current flowing into the input terminal changes.
• (B1) A method for testing a photovoltaic device electrically connected to an input connection of a controller for maximum power point tracking (MPPT controller), wherein the MPPT controller contains a circuit designed for power between the input connection and an output connection of the MPPT controller may include the steps of: (a) driving a test current into the output port of the MPPT controller; (b) detecting the presence of the test current; and (c) in response to detecting the presence of the test current, causing the circuitry to provide a path for the test current from the output port to the photovoltaic device.
• (B2) In the method referred to as (B1), the step of causing the circuit to provide a path for the test current from the output terminal to the photovoltaic device may include causing a switching device of the circuit to operate at a fixed duty cycle.
• (B3) In the method referred to as (B2), the fixed pulse duty factor can be a pulse duty factor of at least ninety percent.
• (B4) In the method referred to as (B2), the fixed pulse duty factor can be a pulse duty factor of one hundred percent.
• (B5) In any of the methods identified as (B1) through (B4), the step of causing the circuit to provide a path for the test current from the output terminal to the photovoltaic device may include causing the MPPT controller to act as a fixed DC transformer which electrically connects the test current to the photovoltaic device.
• (B6) In any of the methods referred to as (B1) to (B5), the step of detecting the presence of the test current may include detecting the presence of current flowing into the output terminal from an external source.
• (B7) In any of the methods identified as (B1) through (B6), the step of detecting the presence of the test current may include detecting voltage across the output terminal of the circuit.
• (B8) In the method referred to as (B7), the step of detecting voltage across the output terminal of the circuit may include comparing a signal representing the voltage across the output terminal with a threshold value.
• (C1) A maximum power point tracking (MPPT) controller may include input and output ports, circuitry configured to transfer power between the input and output ports, and a control subsystem. The control subsystem can be designed to (a) in a first operating mode of the MPPT controller to cause a first switching device of the circuit to operate at a fixed duty cycle; and (b) in a second operating mode of the MPPT controller, causing a control switching device of the circuit to repeatedly switch between its conductive and non-conductive state in order to maximize an amount of electrical power decoupled from a photovoltaic device electrically connected to the input connection.
• (C2) In the MPPT controller referred to as (C1), the first switching device may include at least one of the control switching device of the circuit and a free-running switching device of the circuit.
• (C3) In each of the two MPPT controllers designated as (C1) or (C2), the fixed duty cycle can be a duty cycle of at least ninety percent.
• (C4) In each of the two MPPT controllers designated as (C1) or (C2), the fixed duty cycle can be a duty cycle of one hundred percent.
• (C5) In each of the MPPT controllers referred to as (C1) to (C4), the control subsystem can be further designed: (a) Before the operation of the circuit, when the MPPT controller starts up, an amount of a signal that the voltage above represents the output terminal to compare with a first threshold value; and (b) operate the MPPT controller in its first mode of operation in response to determining that the magnitude of the signal is Voltage across the output terminal is greater than the first threshold value.
• (C6) In each of the MPPT controllers identified as (C1) through (C5), the control subsystem can be further configured to cause the circuit to operate in its non-conductive state until an amount of voltage is present on a power supply rail of the MPPT- Controller exceeds a specified value.
• (C7) In the MPPT controller referred to as (C6), the MPPT controller can further be designed such that, in the first operating mode of the MPPT controller, the power supply rail of the MPPT controller is supplied from the output connection.
• (C8) In each of the MPPT controllers referred to as (C1) to (C7): (a) the control switching device may be electrically connected between a first terminal of the input terminal and a first terminal of the output terminal; (b) the circuit may further include a free wheeling device electrically connected between the first terminal of the output port and a second terminal of the output port, the free wheeling device configured to provide a path for current flowing between the first and second terminals of the output port to provide when the control switching device is in its non-conductive state; (c) the first switching device may be the control switching device; and (d) the first terminal of the output terminal may be electrically connected to a switching node.
• (C9) In the MPPT controller referred to as (C8), the control switching device can be a control transistor, the control transistor containing a body diode with an anode electrically connected to the switching node and a cathode connected to the first terminal of the input connection .
• (C10) In each of the MPPT controllers designated as (C1) to (C9), the control subsystem can further be designed: (a) to compare a signal representing current flowing out of the output connection with a second threshold value; and (b) operate the MPPT controller in its first mode of operation in response to determining that the signal representing current flowing from the output port is less than or equal to the second threshold.
• (C11) In the method referred to as (C10), the second threshold value may represent that current flows from the output terminal in a negative direction.
• (C12) In the MPPT controller referred to as (C11), the control subsystem can further be designed to continue to operate the MPPT controller in its first operating mode after an amount of current flowing out of the output connection has fallen to zero.
• (C13) In each of the MPPT controllers designated as (C1) to (C12), the control subsystem can further be designed to operate the MPPT controller in its first operating mode in response to an external signal.
• (C14) In each of the MPPT controllers referred to as (C1) to (C13), the control subsystem can further be designed to operate the MPPT controller in its first operating mode each time the MPPT controller starts up.
• (C15) In each of the MPPT controllers referred to as (C1) to (C14), the control subsystem can further be designed to cause a duty cycle of the first switching device to run up to the fixed duty cycle when the MPPT controller starts in its first Working mode of operation.
• (C16) In each of the MPPT controllers designated as (C1) to (C15), the control subsystem can further be designed to cause the MPPT controller to switch from its first operating mode to another operating mode after a predetermined period of time.
• (C17) In each of the MPPT controllers referred to as (C1) to (C16), the control subsystem can further be designed: (a) to compare a first voltage signal with a third threshold value, the first voltage signal being a function of a voltage above the Input port is; and (b) to cause the MPPT controller to switch from its first operating mode to another operating mode of the MPPT controller when the first voltage signal falls below the third threshold value.
• (C18) In either of the two methods designated as (C16) or (C17), the other operating mode can be the second operating mode of the MPPT controller.
• (C19) In each of the MPPT controllers referred to as (C1) to (C18), the control subsystem can be further designed to cause the control switching device to repeatedly switch between its conductive and non-conductive state in a third operating mode of the MPPT controller to switch to a pulse duty factor that maintains a predetermined output current-voltage characteristic of the MPPT controller.
• (C20) In the MPPT controller referred to as (C19), the control subsystem can be further designed: (a) to compare a signal representing current flowing out of the output connection with a fourth threshold value; and (b) operate the MPPT controller in its third mode of operation in response to determining that the signal representing current flowing from the output port is less than or equal to the fourth threshold.
• (C21) In the MPPT controller referred to as (C20), the fourth threshold value may represent that current flows from the output terminal in a negative direction.
• (C22) In each of the MPPT controllers designated as (C19) to (C21), the predetermined output current-voltage characteristic curve of the MPPT controller can be linear, so that the magnitude of the mean voltage across the output terminal changes linearly with a change in the The amount of an average current flowing into the input terminal changes.
• (C23) In each of the MPPT controllers designated as (C19) to (C21), the specified output current-voltage characteristic curve of the MPPT controller can be non-linear, so that the amount of the mean voltage across the output connection changes non-linearly with a change in the The amount of an average current flowing into the input terminal changes.

Changes can be made to the above procedures and systems without departing from the present scope. For example, with appropriate changes to the associated circuitry, N-channel field effect transistors could be replaced by P-channel field effect transistors, or vice versa. As a further example, with appropriate changes to the associated circuitry, field effect transistors could be replaced by bipolar junction transistors. It should therefore be noted that the subject matter contained in the above description and shown in the accompanying drawings should be construed as illustrative and not in a restrictive sense. The following claims are intended to cover generic and specific features described here as well as all information about the scope of the present method and system which could be said linguistically to fall in between.

Claims (56)

Method for operating a controller (302; 1202) for maximum power point tracking (MPPT controller), which contains a switching circuit (326; 1226) with switching devices (328, 330; 1228, 1230), designed to deliver power between an input connection ( 308; 1208) and an output port (314; 1214), the MPPT controller (302; 1202) including at least one MPPT operating mode and one operating mode with a fixed duty cycle, the method comprising the steps of: Determine that a magnitude of a voltage across the output terminal (314; 1214) upon startup of the MPPT controller (302; 1202) prior to operation of the circuit (326; 1226) while the switching devices (328, 330; 1228, 1230) are in their non-conductive states is greater than a threshold value; in response to determining that the magnitude of the voltage across the output terminal (314; 1214) upon startup of the MPPT controller (302; 1202) prior to operation of the circuit (326, 1226) while the switching devices (328, 330; 1228, 1230) are in their non-conductive states, is greater than the threshold value, operating the MPPT controller (302; 1202) in its operating mode with a fixed duty cycle. Procedure according to Claim 1 , wherein the operation of the MPPT controller (302; 1202) in the operating mode with a fixed duty cycle comprises that a first switching device of said switching devices (328, 330; 1228, 1230) is operated at a fixed duty cycle, the first switching device being a control Switching device (328; 1228) of said switching devices (328, 330; 1228, 1230) of the switching circuit (326; 1226) and / or a free-running switching device (330; 1230) of said switching devices (328, 330; 1228, 1230) of the switching circuit (326; 1226) contains. Procedure according to Claim 2 , wherein the fixed duty cycle is a duty cycle of at least ninety percent. Procedure according to Claim 3 , where the fixed duty cycle is a one hundred percent duty cycle. Procedure according to Claim 2 further comprising causing the circuit (326; 1226) to operate in its non-conductive state until an amount of voltage on a power rail of the MPPT controller (302; 1202) exceeds a predetermined value. Procedure according to Claim 5 , further comprising supplying the power supply rail of the MPPT controller (302; 1202) from the output connection (314; 1214) in the operating mode with a fixed duty cycle of the MPPT controller (302; 1202). Procedure according to Claim 5 , wherein the first switching device includes a first transistor and the method further electrically feeding current into the power supply rail of the MPPT- Regulator (302; 1202) using a body diode (344) of the first transistor. Procedure according to Claim 2 further comprising operating the MPPT controller (302; 1202) in its fixed duty cycle mode of operation in response to an external signal. Procedure according to Claim 2 , further comprising causing a duty cycle of the first switching device to ramp up to the fixed duty cycle when the MPPT controller (302; 1202) begins to operate in its fixed duty cycle mode of operation. Procedure according to Claim 2 , further comprising switching from the operating mode with a fixed duty cycle to another operating mode of the MPPT controller (302; 1202) after a predetermined period of time. Procedure according to Claim 10 wherein the other mode of operation is the MPPT mode of operation of the MPPT controller (302; 1202), the switching device of the circuit (326; 1226) repeatedly switching between its conductive and non-conductive state, one of which is connected to the input terminal (308; 1208 ) electrically connected photovoltaic device (304; 1204; 1404) to maximize the decoupled amount of power. Procedure according to Claim 2 , further comprising switching from the operating mode with a fixed duty cycle to another operating mode of the MPPT controller (302; 1202) when a first voltage signal falls below a third threshold value. Procedure according to Claim 12 wherein the first voltage signal is a function of a voltage across the input terminal (308; 1208). Procedure according to Claim 12 wherein the other mode of operation is the MPPT mode of operation of the MPPT controller (302; 1202), the switching device of the circuit (326; 1226) repeatedly switching between its conductive and non-conductive state, one of which is connected to the input terminal (308; 1208 ) electrically connected photovoltaic device (304; 1204; 1404) to maximize the decoupled amount of power. Procedure according to Claim 2 , further comprising causing the control switching device (328; 1228), in a reverse current operating mode of the MPPT controller (302; 1202) to repeatedly switch between its conductive and non-conductive state at a duty cycle which is a predetermined output current-voltage Characteristic curve of the MPPT controller (302; 1202) maintains, so that the amount of the mean voltage across the output terminal (314; 1214) changes linearly with a change in the amount of an average current flowing into the output terminal (314; 1214). Procedure according to Claim 15 , further comprising operating the MPPT controller (302; 1202) in its reverse current mode of operation in response to determining that a signal representative of current flowing from the output port (314; 1214) is less than or equal to a second threshold value is. Procedure according to Claim 16 wherein the second threshold represents that current is flowing from the output terminal (314; 1214) in a negative direction. Procedure according to Claim 2 , further comprising causing the control switching device (328; 1228), in a reverse current operating mode of the MPPT controller (302; 1202) to repeatedly switch between its conductive and non-conductive state at a duty cycle which is a predetermined output current-voltage The characteristic curve of the MPPT controller (302; 1202) maintains, so that the amount of the mean voltage across the output terminal (314; 1214) changes non-linearly with a change in the amount of an average current flowing into the output terminal (314; 1214). Method for testing a photovoltaic device (304; 1204; 1404) electrically connected to an input connection (308; 1208) of a controller (302; 1202) for maximum power point tracking (MPPT controller), wherein the MPPT controller (302; 1202 ) contains a circuit (326; 1226) configured to transfer power between the input port (308; 1208) and an output port (314; 1214) of the MPPT controller (302; 1202), the method comprising the steps of: Driving a test current into the output port (314; 1214) of the MPPT controller (302; 1202); Detecting the presence of the test current; and in response to detecting the presence of the test current, causing the circuit (326; 1226) to provide a path for the test current from the output port (314; 1214) to the photovoltaic device (304; 1204; 1404), the step of causing the circuit (326; 1226), providing a path for the test current from the output terminal (314; 1214) to the photovoltaic device (304; 1204; 1404) comprises causing a switching device of the circuit (326; 1226) to operate at a fixed duty cycle. Procedure according to Claim 19 , wherein the fixed duty cycle is a duty cycle of at least ninety percent. Procedure according to Claim 20 , where the fixed duty cycle is a one hundred percent duty cycle. Procedure according to Claim 19 wherein the step of detecting the presence of the test current comprises detecting the presence of current flowing into the output port (314; 1214) from an external source. Controller (302; 1202) for maximum power point tracking (MPPT controller), comprising: an input (308; 1208) and an output port (314; 1214); a switching circuit (326; 1226) having switching devices (328, 330; 1228, 1230) adapted to transfer power between the input (308; 1208) and the output connection (314; 1214); and a rule subsystem (338; 1238) configured: to determine that an amount of a voltage across the output terminal (314; 1214) when the MPPT controller (302; 1202) starts up before the circuit (326; 1226) is operated is greater than a threshold value, operate the MPPT controller (302; 1202) in its fixed duty cycle operating mode in response to determining that the magnitude of the voltage across the output terminal (314; 1214) upon startup of the MPPT controller (302; 1202) prior to operation of the switching circuit (326; 1226), while the switching devices (328, 330; 1228, 1230) are in their non-conductive states, is greater than the threshold value, in the fixed duty cycle operating mode of the MPPT controller (302; 1202) causing a first switching device of said switching devices (328, 330; 1228, 1230) of the circuit (326; 1226) to operate at a fixed duty cycle, and in an MPPT operating mode of the MPPT controller (302; 1202) to cause a control switching device (328; 1228) of said switching devices (328, 330; 1228, 1230) of the circuit (326; 1226), repeatedly between their conducting and to switch the non-conductive state in order to maximize an amount of electrical power coupled out from a photovoltaic device (304; 1204; 1404) electrically connected to the input connection (308; 1208). MPPT controller (302; 1202) according to Claim 23 wherein the first switching device comprises at least one of the regulating switching device (328; 1228) of the switching circuit (326; 1226) and a free-running switching device (330; 1230) of said switching devices (328, 330; 1228, 1230) of the switching circuit (326; 1226) contains. MPPT controller (302; 1202) according to Claim 24 , wherein the fixed duty cycle is a duty cycle of at least ninety percent. MPPT controller (302; 1202) according to Claim 25 , where the fixed duty cycle is a one hundred percent duty cycle. MPPT controller (302; 1202) according to Claim 24 wherein the control subsystem (338; 1238) is further configured to cause the circuit (326; 1226) to operate in its non-conductive state until an amount of voltage on a power rail of the MPPT controller (302; 1202) becomes one exceeds the specified value. MPPT controller (302; 1202) according to Claim 27 , wherein the MPPT controller (302; 1202) is further designed so that in the fixed duty cycle operating mode of the MPPT controller (302; 1202) the power supply rail of the MPPT controller (302; 1202) from the output terminal (314; 1214) is supplied. MPPT controller (302; 1202) according to Claim 27 wherein the control switching device (328; 1228) is electrically connected between a first terminal (310; 1210) of the input terminal (308; 1208) and a first terminal (316; 1216) of the output terminal (314; 1214); the circuit (326; 1226) further comprises a free-running device (330; 1230) connected between the first terminal (316; 1216) of the output connection (314; 1214) and a second terminal (318; 1218) of the output connection (314; 1214 ) is electrically connected, the free-wheeling device (330; 1230) being configured to provide a path for current flowing between the first (316; 1216) and second terminals (318; 1218) of the output terminal (314; 1214) when the control switching device (328; 1228) is in its non-conductive state; the first switching device is the control switching device (328; 1228); and the first terminal (316; 1216) of the output terminal (314; 1214) is electrically connected to a switching node (Vx). MPPT controller (302; 1202) according to Claim 29 wherein the regulating switching device (328; 1228) comprises a regulating transistor, the regulating transistor being a body diode (344) having an anode electrically connected to the switching node (Vx) and one to the first terminal (316; 1216) of the Input terminal (308; 1208) connected cathode contains. MPPT controller (302; 1202) according to Claim 24 , wherein the control subsystem (338; 1238) is further configured to include the MPPT controller (302; 1202) as Response to an external signal to operate in its operating mode with a fixed duty cycle. MPPT controller (302; 1202) according to Claim 24 wherein the control subsystem (338; 1238) is further configured to cause a duty cycle of the first switching device to ramp up to the fixed duty cycle when the MPPT controller (302; 1202) begins to work in its operating mode with a fixed duty cycle. MPPT controller (302; 1202) according to Claim 24 , wherein the control subsystem (338; 1238) is further designed to cause the MPPT controller (302; 1202) to switch from its operating mode with a fixed duty cycle to another operating mode after a predetermined period of time. MPPT controller (302; 1202) according to Claim 33 wherein the other operating mode is the MPPT operating mode of the MPPT controller (302; 1202). MPPT controller (302; 1202) according to Claim 24 wherein the control subsystem (338; 1238) is further configured to: compare a first voltage signal to a third threshold, the first voltage signal being a function of a voltage across the input terminal (308; 1208); and causing the MPPT controller (302; 1202) to switch from its operating mode with a fixed duty cycle to another operating mode of the MPPT controller (302; 1202) when the first voltage signal falls below the third threshold value. MPPT controller (302; 1202) according to Claim 35 wherein the other operating mode is the MPPT operating mode of the MPPT controller (302; 1202). MPPT controller (302; 1202) according to Claim 24 wherein the control subsystem (338; 1238) is further configured to cause the control switching device (328; 1228) to repeatedly switch between its conductive and non-conductive states in a reverse flow mode of operation of the MPPT controller (302; 1202) To switch duty cycle that maintains a predetermined output current-voltage characteristic of the MPPT controller (302; 1202), so that the amount of the average voltage across the output terminal (314; 1214) changes linearly with a change in the amount of a in the output terminal ( 314; 1214) of the flowing mean current changes. MPPT controller (302; 1202) according to Claim 37 wherein the control subsystem (338; 1238) is further configured to: compare a signal representing current flowing from the output port (314; 1214) with a second threshold value; and operating the MPPT controller (302; 1202) in its reverse current mode of operation in response to determining that the signal representing current flowing from the output port (314; 1214) is less than or equal to the second threshold. MPPT controller (302; 1202) according to Claim 38 wherein the second threshold represents that current is flowing from the output terminal (314; 1214) in a negative direction. MPPT controller (302; 1202) according to Claim 24 wherein the control subsystem (338; 1238) is further configured to cause the control switching device (328; 1228) to repeatedly switch between its conductive and non-conductive states in a reverse flow mode of operation of the MPPT controller (302; 1202) To switch duty cycle, which maintains a predetermined output current-voltage characteristic curve of the MPPT controller (302; 1202), so that the amount of the average voltage across the output terminal (314; 1214) changes non-linearly with a change in the amount of a in the output terminal ( 314; 1214) of the flowing mean current changes. A method for operating a controller (302; 1202) for the maximum power point tracking (MPPT controller), which contains a circuit (326; 1226), designed, power between an input connection (308; 1208) and an output connection (314; 1214 ), the MPPT controller (302; 1202) including at least one MPPT operating mode and one operating mode with a fixed duty cycle, the method comprising the following steps: Determining that current flows out of the output terminal (314; 1214) in a negative direction; and in response to determining that current is flowing out of the output terminal (314; 1214) in a negative direction, operating the MPPT controller (302; 1202) in the fixed duty cycle mode of operation. Procedure according to Claim 41 , wherein operating the MPPT controller (302; 1202) in the operating mode with a fixed duty cycle comprises that a first switching device is operated at a fixed duty cycle, the first switching device being a control switching device (328; 1228) of the circuit (326; 1226 ) and / or a free-running switching device (330; 1230) of the circuit (326; 1226). Procedure according to Claim 42 , further comprising causing the circuit (326; 1226) to operate in its non-conductive state until an amount of voltage reaches a Power supply rail of the MPPT controller (302; 1202) exceeds a predetermined value. Procedure according to Claim 43 , further comprising supplying the power supply rail of the MPPT controller (302; 1202) from the output connection (314; 1214) in the operating mode with a fixed duty cycle of the MPPT controller (302; 1202). Procedure according to Claim 44 wherein the first switching device includes a first transistor and the method further comprises electrically injecting current into the power supply rail of the MPPT controller (302; 1202) using a body diode (344) of the first transistor. Procedure according to Claim 42 further comprising continuing to operate the MPPT controller (302; 1202) in its fixed duty cycle mode of operation after an amount of current flowing from the output port (314; 1214) has fallen to zero. Procedure according to Claim 42 , further comprising causing the control switching device (328; 1228), in a reverse current operating mode of the MPPT controller (302; 1202) to repeatedly switch between its conductive and non-conductive state at a pulse duty factor that is a predetermined output current-voltage Characteristic curve of the MPPT controller (302; 1202) maintains, so that the amount of the mean voltage across the output terminal (314; 1214) changes linearly with a change in the amount of an average current flowing into the output terminal (314; 1214). Procedure according to Claim 47 , further comprising causing the control switching device (328; 1228), in a reverse current operating mode of the MPPT controller (302; 1202) to repeatedly switch between its conductive and non-conductive state at a duty cycle which is a predetermined output current-voltage The characteristic curve of the MPPT controller (302; 1202) maintains, so that the amount of the mean voltage across the output terminal (314; 1214) changes non-linearly with a change in the amount of an average current flowing into the output terminal (314; 1214). Controller for Maximum Power Point Tracking (MPPT controller), comprising: an input (308; 1208) and an output port (314; 1214); a circuit (326; 1226) configured to transfer power between the input and output ports (314; 1214); and a rule subsystem (338; 1238) designed: determine that current flows out of the output terminal (314; 1214) in a negative direction; in response to determining that current is flowing out of the output terminal (314; 1214) in a negative direction, operating the MPPT controller (302; 1202) in a fixed duty cycle mode of operation; in the operating mode with a fixed duty cycle of the MPPT controller (302; 1202) to cause a first switching device of the circuit (326; 1226) to operate at a fixed duty cycle, and in an MPPT operating mode of the MPPT controller (302; 1202) to cause a control switching device (328; 1228) of the circuit (326; 1226) to repeatedly switch between its conductive and non-conductive state in order to select one of the input terminals ( 308; 1208) electrically connected photovoltaic device (304; 1204; 1404) to maximize decoupled amount of electrical power. MPPT controller (302; 1202) according to Claim 49 wherein the control subsystem (338; 1238) is further configured to cause the circuit (326; 1226) to operate in its non-conductive state until an amount of voltage on a power rail of the MPPT controller (302; 1202) becomes one exceeds the specified value. MPPT controller (302; 1202) according to Claim 50 , wherein the MPPT controller (302; 1202) is further designed so that in the fixed duty cycle operating mode of the MPPT controller (302; 1202) the power supply rail of the MPPT controller (302; 1202) from the output terminal (314; 1214) is supplied. MPPT controller (302; 1202) according to Claim 49 wherein the control switching device (328; 1228) is electrically connected between a first terminal (310; 1210) of the input terminal (308; 1208) and a first terminal (316; 1216) of the output terminal (314; 1214); the circuit (326; 1226) further comprises a free-running device (330; 1230) connected between the first terminal (316; 1216) of the output connection (314; 1214) and a second terminal (318; 1218) of the output connection (314; 1214 ) is electrically connected, the free-wheeling device (330; 1230) being configured to provide a path for current flowing between the first (316; 1216) and second terminals (318; 1218) of the output terminal (314; 1214) when the control switching device (328; 1228) is in its non-conductive state; and the first switching device is the control switching device (328; 1228). MPPT controller (302; 1202) according to Claim 52 , wherein the control switching device (328; 1228) comprises a control transistor, the control transistor having a body diode (344) with a Switching node electrically connected anode and a cathode connected to the first terminal of the input terminal (308; 1208). MPPT controller (302; 1202) according to Claim 49 wherein the control subsystem (338; 1238) is further configured to continue to operate the MPPT controller (302; 1202) in its fixed duty cycle operating mode after an amount of current flowing from the output terminal (314; 1214) has decreased to zero has fallen. MPPT controller (302; 1202) according to Claim 49 wherein the control subsystem (338; 1238) is further configured to cause the control switching device (328; 1228) to repeatedly switch between its conductive and non-conductive states in a reverse flow mode of operation of the MPPT controller (302; 1202) To switch duty cycle that maintains a predetermined output current-voltage characteristic of the MPPT controller (302; 1202), so that the amount of the average voltage across the output terminal (314; 1214) changes linearly with a change in the amount of a in the output terminal ( 314; 1214) of the flowing mean current changes. MPPT controller (302; 1202) according to Claim 49 wherein the control subsystem (338; 1238) is further configured to cause the control switching device (328; 1228) to repeatedly switch between its conductive and non-conductive states in a reverse flow mode of operation of the MPPT controller (302; 1202) To switch duty cycle, which maintains a predetermined output current-voltage characteristic curve of the MPPT controller (302; 1202), so that the amount of the average voltage across the output terminal (314; 1214) changes non-linearly with a change in the amount of a in the output terminal ( 314; 1214) of the flowing mean current changes.

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