JP5912417B2 - Solar power plant - Google Patents

Description

  The present invention belongs to a technical field of a photovoltaic power generation apparatus for efficiently obtaining power from a solar battery and charging the secondary battery or linking it to a power system.

  A solar cell element (cell) is a minimum unit of power generation in which an equivalent circuit is expressed by a current source and one diode (solar cell itself), but its output density is small, and usually a plurality of solar cell elements are included. The basic unit is a configuration in which they are arranged in series and connected in series or in series and parallel.

  In practical use, for example, as shown in the equivalent circuit of FIG. 18, a solar cell body SC in which a plurality of solar cell elements are connected in series (FIG. 18 is an example of seven solar cell elements in series. It is expressed as seven series diodes.) And a solar cell module having a configuration in which a bypass diode Db inserted as a countermeasure when an element that does not generate electricity appears is connected to a backflow prevention diode Da. ing.

  Furthermore, in a general solar power generation device, a plurality of the solar cell modules are used as a solar cell array or a solar cell panel connected in series and parallel.

  As a typical solar power generation device (or a solar power generation system having the same meaning) using the solar cell array, a plurality of solar cell arrays 21a, 21b, and 21c are provided as in the solar power generation device 30 shown in FIG. The solar cell arrays 21a, 21b, 21c,... Are formed by connecting the solar cell modules 22 in series and in parallel in a matrix shape. The box 23 collects the DC output output from each solar cell module 22 through the solar cell arrays 21a, 21b, 21c,..., And the power conversion device 26 collects the solar cell array 21a collected in the current collection box 23. , 21b, 21c,..., 21b, 21c,..., 21b, 21c,. , There is a configuration in which supply to the load 28 the converted AC output while linked to the power system 27.

  On the other hand, there are various types of solar cells in practical use, such as crystalline silicon solar cells, amorphous silicon solar cells, compound semiconductor solar cells, and organic semiconductor solar cells, all of which output characteristics (output current) of the solar cell. The I-output voltage V curve is generally an IV characteristic curve as shown in FIG. 20, and in order to efficiently extract the maximum power from the solar cell, the actual operating point P of the solar cell (operating current Iope × operating voltage Vope). ) At the maximum power point Pmax (optimum operating current Iop × optimum operating voltage Vop) as much as possible.

  In this respect, in the current solar power generation device (system) including the solar power generation device 30, so-called maximum power that controls the output voltage and output current so that the output of the solar cell array always operates at the maximum power point Pmax. Point tracking (Maximum Power Point Tracking: MPPT) control is often employed. Various methods have been devised for the MPPT control. For example, the output voltage of the solar cell array is decreased from the open circuit voltage, and during that time, the power value is scanned to measure the maximum power point Pmax, and the maximum power point is measured. There is a scanning method in which the operating point is moved to Pmax.

  By the way, in an actual photovoltaic power generation device (system), the entire solar cell is not always irradiated with sunlight under uniform conditions, and the output is partially weak due to shadows such as clouds and trees. It may become a state of partial shadow irradiation, or an operating state under so-called non-uniform solar radiation conditions where the solar radiation conditions differ depending on the orientation of the installation location and the temperature environment (this is also normal) ).

  Under the non-uniform solar radiation conditions as described above, efficient power extraction cannot be desired with a single MPPT control for the entire installed solar cell.

  In this regard, a number of solutions have been proposed in order to solve the inefficiency problem of the solar battery power generation device under the uneven solar radiation conditions (for example, under the partial shade conditions).

  For example, in [Patent Document 1] below, it is assumed that the output of a solar cell can be efficiently extracted by performing MPPT control with a DC-DC converter provided for each solar cell group (solar cell array). Is disclosed.

  [Patent Document 2] includes a solar cell module including a plurality of solar cell elements connected in series and parallel, and a converter for stepping down DC power generated by the plurality of solar cell elements of the solar cell module. There has been proposed a solar cell module provided on a substrate and configured so that the converter performs MPPT control.

  In [Patent Document 3] below, a step-up chopper circuit is provided for each of a plurality of blocks of a solar cell panel, and direct current voltage conversion is performed by MPPT control for each block, and these are integrated to flow into the system. A power generation device has been proposed.

  Furthermore, in [Patent Document 4] below, in a grid-connected inverter that is input by connecting a plurality of solar cell arrays in parallel, each solar cell array is independently subjected to MPPT control by a DC-DC converter to generate power. There has been proposed a power conversion device for photovoltaic power generation that is configured to improve efficiency.

  In addition, when a solar cell array in which a plurality of solar cell modules are connected in series and parallel is operated under non-uniform solar radiation conditions, it has recently been reported that there is a so-called bimodality in which multiple power maximum points appear in its output characteristics. (IEEE Trans. IA. Vol. 124, No. 8, 2004, Ichiro Takano et al.).

  That is, as shown in FIG. 21, when the vertical axis represents the solar cell current I or power P and the horizontal axis represents the solar cell voltage V, a plurality of solar cell modules shown in FIG. A plurality (two in FIG. 21) of power maximum points P1 and P2 appear in the current-voltage characteristics and power-voltage characteristics of the battery array. This bimodality also appears in the case of series connection, and their characteristic curves vary depending on the uneven solar radiation conditions. For example, under partial shading conditions, the shading area changes, and there are many possibilities that power maximum points are not limited to two.

  The present inventor connects two solar cell modules as shown in FIG. 18 in series, and when a current difference (difference in light intensity) occurs in each current source, the solar cell module with the smaller current As a result, it has been clarified that a remarkable bimodality appears in the output characteristics due to the fact that the current does not flow completely through the bypass diode Db provided for each solar cell module. In addition, when two solar cell modules are connected in parallel and a voltage difference appears due to a temperature difference between the two modules, a double peak appears, and the cause is the influence of the backflow prevention diode Da. Investigated.

  However, in the case of a solar cell array in which a plurality of conventional solar cell modules are connected in series and parallel, a large number of power maximum points may appear due to the influence of changes in the current and voltage of each module.

  In the conventional photovoltaic power generation apparatus (system) in which bimodality inevitably appears under the non-uniform conditions as described above, a simple maximum power point tracking (MPPT) control for a solar cell array or a solar cell module, or Even if the control is converged at the power maximum point P2 of FIG. 21 with the improved and accurate MPPT control considering the bimodality, a loss occurs in the solar cell array or the solar cell module, and the true maximum Inventor's research has revealed that no power can be obtained and about 60% of the loss may occur under worst-case conditions.

  As described above, the bimodality appearing in the output characteristics of the solar cell array under non-uniform conditions such as partial shading is caused by the backflow prevention diode Da and the bypass diode Db in the solar cell module as shown in FIG. However, in order to always extract the maximum electric power from the solar cell even under such partial shadow conditions where the multi-peaks appear, a solar cell array or solar cell composed of a plurality of conventional solar cell modules It is considered difficult to use a means for maximum power point tracking (MPPT) control for the module or a means for improving its accuracy.

  For this reason, installing a charge transfer circuit for each solar cell body and performing tracking control of the output to the maximum power point for each solar cell body is considered to be an effective means for improving power generation efficiency.

JP 2000-112545 A JP 2003-124492 A JP 2003-134667 A JP 2004-194500 A

  However, when a charge transfer circuit is installed for each solar cell body, when some of the charge transfer circuits stop operating due to a failure or the like, the output power from the normal solar cell module is stopped. Will flow down through. When the output power flows down the flywheel diode, a power loss that cannot be ignored occurs.

  The present invention has been made in view of the above circumstances, and has a charge transfer circuit for each solar cell body, and even when some of the charge transfer circuits are stopped, power loss due to the charge transfer circuit being stopped is small. It aims at providing a solar power generation device.

The present invention
(1) In a solar power generation apparatus including a string PVS in which module output ends 48a and 48b of a plurality of solar cell modules PVM are connected in series,
The solar cell module PVM includes a solar cell body SC to which one or more solar cell elements are connected, and a follow-up control to the maximum power point Pmax of the output to the solar cell body SC provided for each solar cell body SC. A charge transfer circuit CONV to perform ,
The charge transfer circuit CONV includes a first semiconductor switching element SW1 connected in series to the solar cell body SC, between the output terminal 47 of the charge transfer circuit CONV to the closed state connected in parallel to the solar cell body SC A second semiconductor switch element SW2 to be short-circuited, detection means (voltmeter 46, ammeter 52) for monitoring the output of the solar cell main body SC, and the first semiconductor switch element SW1 according to output information from the detection means, A control unit 44 that performs switching control of the second semiconductor switch element SW2 ,
The second semiconductor switch element SW2 of the charge transfer circuit CONV is a normally-on type semiconductor switch element, and when the operation of the charge transfer circuit CONV is stopped, the second semiconductor switch element of the charge transfer circuit CONV is stopped. SW2 is maintained in a closed state, and the electric power output from the other solar cell module CONV that has not stopped operation in the string PVS is caused to flow down through the second semiconductor switch element SW2. The above problem is solved by providing the device 40.
(2) The charge transfer circuit CONVh includes a coil L1 connected in series with the solar cell body SC, semiconductor switch elements SW (a) and SW (c) connected in series to both ends of the coil L1, respectively, A semiconductor switch element SW (b) and a semiconductor switch element SW (d) connected in parallel to the solar cell body SC at both ends of the coil L1, respectively.
During the step-down operation, the semiconductor switch element SW (c) is normally closed and the semiconductor switch element SW (d) is normally open. The semiconductor switch element SW (b) is connected to the second semiconductor switch element SW2. The semiconductor switching element SW (a) is controlled in the opposite phase and functions as the first semiconductor switching element SW1, and the semiconductor switching element SW (a) is controlled in the same phase as the second semiconductor switching element SW2,
During the boosting operation, the semiconductor switch element SW (a) is normally closed and the semiconductor switch element SW (b) is normally open. The semiconductor switch element SW (c) is connected to the second semiconductor switch element SW2. The switching control is performed in the opposite phase and functions as the first semiconductor switching element SW1, and the switching operation of the semiconductor switching element SW (d) is controlled in the same phase as the second semiconductor switching element SW2. By providing the described solar power generation device 40, the above-described problems are solved.

  Since the photovoltaic power generation apparatus according to the present invention has the above-described configuration, even if a part of the charge transfer circuit is stopped, power loss due to the charge transfer circuit being stopped can be minimized.

It is a block diagram of the solar power generation device concerning the present invention. It is a block diagram which shows 1st Embodiment of the solar cell module which comprises the solar power generation device which concerns on this invention. It is a figure which shows the relationship between the operating voltage of a solar cell main body, and output electric power. It is a block diagram which shows 2nd Embodiment of the solar cell module which comprises the solar power generation device which concerns on this invention. It is a block diagram which shows 3rd Embodiment of the solar cell module which comprises the solar power generation device which concerns on this invention. It is a block diagram which shows the example which provided the temperature detection element in 1st Embodiment of the solar cell module which concerns on this invention. It is a figure which shows the relationship between the operating voltage and output electric power of a solar cell main body when temperature changes. It is a block diagram which shows the example which provided the temperature detection element in 2nd Embodiment of the solar cell module which concerns on this invention. It is a figure which shows the example which applied this invention to the pressure | voltage rise type converter provided with three semiconductor switch elements. It is a figure which shows the example which applied this invention to the inverting converter. It is a figure which shows the example which applied this invention to the bridge converter. It is a block diagram which shows the structure which performs switching control of each solar cell module which forms the solar power generation device which concerns on this invention in the independent period. It is a block diagram which shows the structure which synchronizes switching control of each solar cell module which forms the solar power generation device which concerns on this invention. It is a block diagram which shows the structure which performs the switching control of each solar cell module which forms the solar power generation device which concerns on this invention for every string, and gives a phase difference to the period of each string. It is a block diagram which shows the structure which provided the backflow prevention diode in each string while performing switching control of each solar cell module which forms the solar power generation device which concerns on this invention in the independent period. It is a block diagram which shows the structure which provided the coil between the several solar cell module connected in series and the output terminal of the solar power generation device which concerns on this invention. It is a block diagram which shows the connection of the solar power generation device and load etc. which concern on this invention. It is a circuit diagram of the conventional solar cell module. It is a figure which shows the structure of the conventional typical solar power generation device. It is a figure for demonstrating the output characteristic (output current I-output voltage V curve) of a solar cell. It is a figure for demonstrating the bimodality of the output characteristic at the time of operating the solar cell array which consists of a several solar cell module on non-uniform solar radiation conditions.

  Embodiments of a photovoltaic power generation apparatus according to the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, the photovoltaic power generation apparatus 40 according to the present invention includes a solar cell module PVM mainly composed of a solar cell body SC and a charge transfer circuit CONV. A plurality of units are connected in series or in series and parallel via the negative module output end 48b. The positive output terminal 42a and the negative output terminal 42b, which are output terminals of the solar power generation device 40, are connected to the load 28 via a regulator, converter, power storage device, etc. (not shown), and supply power to the load 28. . Although FIG. 1 shows an example in which a plurality of series-connected solar cell modules PVM are connected in parallel in three rows, the number of parallel connections can be appropriately increased or decreased depending on the application, scale, etc. of the photovoltaic power generation apparatus. is there. Moreover, it is good also as only a serial connection without performing parallel connection.

  In the following description, the solar cell modules according to the present invention are collectively referred to as a solar cell module PVM, and individual solar cell modules having different configurations are described as solar cell modules PVMa to PVMh. The charge transfer circuits are collectively referred to as a charge transfer circuit CONV, and individual charge transfer circuits having different configurations are described as charge transfer circuits CONVa to CONVh.

  Next, FIG. 2 shows a first embodiment of the solar cell module PVM in the solar power generation device 40 according to the present invention. The solar cell module PVMa of the first embodiment includes a solar cell main body SC formed by connecting a single solar cell element or a plurality of solar cell elements in series or series-parallel, and an input terminal 43 having a positive electrode of each solar cell main body SC. The charge transfer circuit CONVa is connected to the terminal 41a and the negative terminal 41b, and the output end 47 is connected to the module output ends 48a and 48b.

  The charge transfer circuit CONVa of the battery module PVMa includes a first semiconductor switch element SW1 connected in series between the positive electrode terminal 41a of the solar cell body SC and the output terminal 47 on the positive electrode side of the charge transfer circuit CONVa, and a first semiconductor A second semiconductor switch element that is connected in parallel to the solar cell body SC on the output end 47 side of the switch element SW1 and short-circuits between the output terminals 47 when in the closed (on) state, and a positive terminal 41a and a negative terminal 41b of the solar cell body SC A voltmeter 46 as a detecting means connected in parallel, a control unit 44 for performing switching control of the first semiconductor switch element and the second semiconductor switch element, and a fly connected to the second semiconductor switch element SW2 in parallel. And a diode D functioning as a wheel diode. In particular, a depletion type semiconductor switching element made of a compound semiconductor such as GaN (gallium nitride) or GaAs (gallium arsenide), which is in a closed state (normally on) when there is no signal, is used as the second semiconductor switching element. . This is a common configuration in the charge transfer circuit CONV of the present invention.

  In addition, a coil L1 that accumulates or discharges electric energy from the solar cell main body SC is connected in series between the positive-side output terminal 47 and the positive-electrode output terminal 48a of the charge transfer circuit CONVa. Capacitors Ca and Cb are smoothing capacitors for reducing terminal voltage ripples between the solar cell body SC and the positive module output terminal 48a and the negative output terminal 48b.

  Here, FIG. 3 shows the relationship between the operating voltage generated in the solar cell main body SC and the output power when the intensity of the irradiated light is changed. Note that solid lines A, B, and C in FIG. 3 indicate the relationship between the operating voltage Vope and the output power when the light intensity is A> B> C. However, the temperature of the solar cell body SC is constant. As can be seen from FIG. 3, when the temperature of the solar cell body SC is constant, the optimum operating voltage Vop of the solar cell body SC that provides the maximum power point Pmax is constant regardless of the intensity of the irradiated light. . Therefore, the solar cell main body SC can always be operated at the maximum power point Pmax by controlling the operating voltage Vope of the solar cell main body SC to take the optimum operating voltage Vop.

  Next, the operation of the charge transfer circuit CONVa will be described. The control unit 44 of the charge transfer circuit CONVa has an oscillator 55. Based on a signal from the oscillator 55, the first semiconductor switch element SW1 and the second semiconductor switch element SW2 are alternately pulse width modulated (PWM). Switching control and synchronous rectification. The signal for performing the switching control is not necessarily obtained from the control unit 44, and may be obtained from the oscillator 55 provided outside. The same applies to each charge transfer circuit CONV described later.

  Here, when the first semiconductor switch element SW1 is closed and the second semiconductor switch element SW2 is opened, the output power generated in the solar cell body SC is stored as electric energy in the coil L1 through the first semiconductor switch element SW1. And output from the positive terminal 48a to the load side. When the output power generated in the solar cell body SC is output to the load side, the operating voltage Vope of the solar cell body SC decreases. On the other hand, when the second semiconductor switch element SW2 is closed and the first semiconductor switch element SW1 is open, the coil L1 releases the stored electrical energy to the load side. At this time, the electric power generated in the solar cell main body SC is not output to the load side, thereby increasing the operating voltage Vope of the solar cell main body SC. When the second semiconductor switch element SW2 is closed and the first semiconductor switch element SW1 is open, the output power from the other solar cell modules PVMa connected in series is loaded through the second semiconductor switch element SW2. Output to the side.

  The voltmeter 46 constantly monitors the operating voltage Vope of the solar cell main body SC, and outputs this to the control unit 44 as output information. As described above, since the optimum operating voltage Vop when taking the maximum power point Pmax is constant regardless of the light intensity, the optimum operating voltage Vop of the solar cell body SC can be preset in the control unit 44. . The control unit 44 receives the operation voltage Vope from the voltmeter 46, and when the operation voltage Vope is higher than the preset optimum operation voltage Vop, the PWM is performed so as to widen the time interval at which the first semiconductor switch element SW1 is closed. Change the duty ratio of the signal. By this switching control, the time interval of the closed state of the first semiconductor switch element SW1 becomes longer. If the time interval of the closed state of the first semiconductor switch element SW1 becomes longer, the time interval for outputting the output power generated in the solar cell main body SC to the load side becomes longer, and the operating voltage Vope of the solar cell main body SC decreases. On the other hand, when the operating voltage Vope is lower than the optimum operating voltage Vop, the control unit 44 performs switching control so as to widen the time interval at which the first semiconductor switch element SW1 is opened. If the time interval of the open state of 1st semiconductor switch element SW1 becomes long, the time interval which outputs the output electric power which generate | occur | produced in the solar cell main body SC to the load side will become short, and the operating voltage Vope of the solar cell main body SC will increase.

  Under the control of the control unit 44, the operation voltage Vope of the solar cell main body SC is controlled so as to always take the optimum operation voltage Vop. As described above, if the operating voltage Vope is the optimum operating voltage Vop, the solar cell body SC operates at the maximum power point Pmax. Therefore, the solar cell module PVMa always outputs the maximum power under the sunshine conditions. can do.

  Next, a second embodiment of the solar cell module PVM according to the present invention is shown in FIG. The charge transfer circuit CONVb of the solar cell module PVMb of the second embodiment replaces the voltmeter 46 of the charge transfer circuit CONVa of the first embodiment, and the positive terminal 41a of the solar cell body SC and the first semiconductor switch It has an ammeter 52 as detection means connected in series with the element SW1.

  Here, reference is made to the output characteristics (output current I-output voltage V curve) of the solar cell of FIG. From FIG. 20, the optimum operating current Iop of the solar cell body SC at which the maximum power point Pmax of the solar cell body SC is obtained is the short-circuit current Isc of the solar cell body SC (the solar cell body SC when the operating voltage Vope = 0V). It is known that the current value is reduced by a certain ratio. That is, if the fixed ratio is 90%, the optimum operating current Iop is Isc × 0.9. Note that the output characteristics in FIG. 20 change depending on the sunlight irradiation conditions and the like, but the relationship between the optimum operating current Iop and the short-circuit current Isc always holds even if the output characteristics change. Therefore, if the short-circuit current Isc is found, the optimum operating current Iop is obtained, and the solar cell body SC is always kept at the maximum power point Pmax by controlling so that the operating current Iope of the solar cell body SC takes the optimum operating current Iop. It becomes possible to operate.

  Next, the operation of the charge transfer circuit CONVb will be described. Similarly to the charge transfer circuit CONVa, the control unit 44 of the charge transfer circuit CONVb performs switching control of the first semiconductor switch element SW1 and the second semiconductor switch element SW2 based on a signal from the oscillator 55. The ammeter 52 constantly monitors the operating current Iope of the solar cell main body SC, and outputs this to the control unit 44 as output information. The optimal operating current Iop of the solar cell main body SC obtained from the short-circuit current Isc of the solar cell main body SC is set in advance in the control unit 44, and the control unit 44 determines that the operating current Iope from the ammeter 52 is the optimal operating current Iop. If it is lower, switching control is performed so as to widen the time interval at which the first semiconductor switch element SW1 is closed. If the time interval of the closed state of the switch element SW1 becomes longer, the time interval for outputting the output power generated in the solar cell main body SC to the load side becomes longer, and the operating current Iope of the solar cell main body SC increases in the short-circuit current Isc direction. To do.

  On the other hand, when the operating current Iope is higher than the optimal operating current Iop, the control unit 44 performs switching control so as to widen the time interval at which the first semiconductor switch element SW1 is opened. If the time interval of the open state of the first semiconductor switch element SW1 is lengthened, the time interval for outputting the output power generated in the solar cell body SC to the load side is shortened, thereby reducing the operating current Iope of the solar cell body SC. To do.

  By the control of the control unit 44, the operation current Iope of the solar cell main body SC is follow-up controlled so as to always take the optimum operation current Iop. If the operating current Iope is the optimum operating current Iop as described above, the solar cell main body SC operates at the maximum power point Pmax, and therefore the solar cell module PVMb always outputs the maximum power under the sunshine conditions. can do.

  Next, 3rd Embodiment of the solar cell module PVM in the solar power generation device 40 which concerns on this invention is shown in FIG. The charge transfer circuit CONVc of the solar cell module PVMc of the third embodiment has a voltmeter 46 and an ammeter 52 as detection means.

  Next, the operation of the charge transfer circuit CONVc will be described. Similarly to the charge transfer circuit CONVa, the control unit 44 of the charge transfer circuit CONVc performs switching control of the first semiconductor switch element SW1 and the second semiconductor switch element SW2 based on a signal from the oscillator 55. The operating current Iope of the solar cell main body SC is constantly monitored by the ammeter 52, and the operating voltage Vope of the solar cell main body SC is constantly monitored by the voltmeter 46 and is output to the control unit 44, respectively. The control unit 44 obtains the output power of the solar cell main body SC from the operating current Iope obtained from the ammeter 52 and the operating voltage Vope obtained from the voltmeter 46, and performs switching control so that this output power follows the maximum power point Pmax. I do. Thus, the solar cell main body SC always operates at the maximum power point Pmax, and thus the solar cell module PVMc can always output the maximum power under the sunshine conditions.

  Further, the solar cell module PVM in the photovoltaic power generation apparatus 40 according to the present invention includes a temperature sensing element 54 in addition to the configuration of the charge transfer circuit CONVa, like the charge transfer circuit CONVd of the battery module PVMd shown in FIG. Also good.

  Here, FIG. 7 shows the relationship between the operating voltage and the output power generated in the solar cell main body SC when the temperature is changed. In addition, the solid line D, the solid line E, and the solid line F in FIG. 7 are the relationship between the operating voltage Vope and the output power when the temperature of the solar cell body SC is D <E <F, respectively. From FIG. 7, the optimum operating voltage Vop of the solar cell main body SC at which the maximum power point Pmax is obtained increases or decreases depending on the temperature of the solar cell main body SC, and is high when the temperature is a low solid line D (optimum operating voltage Vop (D)). On the contrary, when the solid line F has a high temperature, a low value (optimum operating voltage Vop (F)) is taken. When the solid line E is the temperature between the two, the optimum operating voltage Vop (E) between the two voltages is taken. I understand. It has been found that the temperature of the solar cell body SC and the optimum operating voltage Vop are in a proportional relationship. Therefore, if the temperature of the solar cell body SC is known, the optimum operating voltage Vop at that temperature can be obtained.

  Next, the operation of the charge transfer circuit CONVd will be described. However, since the operation of the charge transfer circuit CONVd is almost the same as that of the charge transfer circuit CONVa, the description of the overlapping parts is omitted. First, the temperature sensing element 54 measures the temperature around the solar cell body SC and outputs this to the control unit 44 as the temperature of the solar cell body SC. The controller 44 obtains the optimum operating voltage Vop of the solar cell body SC at the temperature from the temperature obtained from the temperature detecting element 54. Then, based on the determined optimum operating voltage Vop and the operating voltage Vope obtained from the voltmeter 46, switching control similar to that of the charge transfer circuit CONVa is performed. As a result, the solar cell body SC operates at the maximum power point Pmax at any temperature, so that the solar cell module PVMd can always output the maximum power under the sunshine conditions.

  Further, a temperature sensing element 54 may be added to the configuration of the charge transfer circuit CONVb like the charge transfer circuit CONVe of the battery module PVMe shown in FIG. In the charge transfer circuit CONVe of the battery module PVMe, the controller 44 corrects the optimum operating current Iop based on the temperature of the solar cell body SC obtained from the temperature sensing element 54, and based on the corrected optimum operating current Iop. Then, switching control similar to that of the charge transfer circuit CONVb is performed. As a result, the solar cell body SC operates at the maximum power point Pmax at any temperature, so that the solar cell module PVMd can always output the maximum power under the sunshine conditions.

  Various temperature detecting elements can be used as the temperature detecting element 54, and it is particularly preferable to use a thermistor or a diode. In this example, the temperature detecting element 54 measures the temperature around the solar cell body SC. However, if the temperature of the solar cell body SC itself is measured, the charge transfer circuits CONVd and CONVe The accuracy of the follow-up control is further improved.

  Further, the charge transfer circuit of the present invention may be applied to a step-up converter including three semiconductor switch elements, like the charge transfer circuit CONVf of the solar cell module PVMf shown in FIG. The charge transfer circuit CONVf includes a third semiconductor switch element SW3 connected in parallel with the second semiconductor switch element SW2 on the solar cell body SC side of the first semiconductor switch element SW1. The coil L1 is connected in series with the first semiconductor switch element SW1 between the solar cell body SC and the connection end of the third semiconductor switch element SW3. The third semiconductor switch element SW3 is subjected to switching control in the same phase as the second semiconductor switch element SW2.

  In the charge transfer circuit CONVf, when the first semiconductor switch element SW1 is opened and the second semiconductor switch element SW2 and the third semiconductor switch element SW3 are closed, the output power generated in the solar cell body SC is supplied as electric energy to the coil L1. Stored. At this time, output power from the other solar cell module PVMf is output to the load side through the second semiconductor switch element SW2. In addition, when the first semiconductor switch element SW1 is closed and the second semiconductor switch element SW2 and the third semiconductor switch element SW3 are open, the charge transfer circuit CONVf uses the electric energy stored in the coil L1 and the solar cell body SC. The generated output power is discharged to the load side.

  The switching control of the charge transfer circuit CONVf is performed so that the solar cell main body SC operates at the maximum power point Pmax based on the output information of the detection means, similarly to the charge transfer circuit CONVa to the charge transfer circuit CONVe. Thus, the solar cell body SC is controlled to follow at the maximum power point Pmax, and the solar cell module PVMf always outputs the maximum power under the sunshine condition.

  FIG. 9A shows an example in which a voltmeter 46 is used as detection means. FIG. 9B shows an example in which an ammeter 52 is used as detection means. Furthermore, the charge transfer circuit CONVf may include a voltmeter 46 and an ammeter 52 as detection means, like the charge transfer circuit CONVc. Further, a temperature sensing element 54 may be provided as in the charge transfer circuit CONVd and the charge transfer circuit CONVe.

  Further, the charge transfer circuit of the present invention may be applied to an inverting converter provided with three semiconductor switch elements, like the charge transfer circuit CONVg of the solar cell module PMGg shown in FIG. The charge transfer circuit CONVg includes a third semiconductor switch element SW3 connected in series on the solar cell body SC side of the first semiconductor switch element SW1. The coil L1 is connected in parallel with the solar cell body SC between the first semiconductor switch element SW1 and the third semiconductor switch element SW3. The third semiconductor switch element SW3 is subjected to switching control in the same phase as the second semiconductor switch element SW2.

  Similarly to the charge transfer circuit CONVf, when the first semiconductor switch element SW1 is opened and the second semiconductor switch element SW2 and the third semiconductor switch element SW3 are closed, the charge transfer circuit CONVg generates output power generated in the solar cell body SC. Is stored as electrical energy in the coil L1. At this time, output power from the other solar cell module PVMf is output to the load side through the second semiconductor switch element SW2. However, the output direction is different from the charge transfer circuit CONVa to the charge transfer circuit CONVg, and the module output end 48a is a negative electrode and the module output end 48b is a positive electrode. Therefore, the output flows down from the module output end 48a to the module output end 48b. When the first semiconductor switch element SW1 is closed and the second semiconductor switch element SW2 and the third semiconductor switch element SW3 are open, the charge transfer circuit CONVf releases the electric energy stored in the coil L1 to the load side. .

  The switching control of the charge transfer circuit CONVg is performed so that the solar cell main body SC operates at the maximum power point Pmax based on the output information of the detection means, similarly to the charge transfer circuits CONVa to CONVf described above. Thereby, the solar cell main body SC is controlled to follow at the maximum power point Pmax, and the solar cell module PMGg always outputs the maximum power under the sunshine conditions.

  FIG. 10A shows an example in which a voltmeter 46 is used as detection means. FIG. 10B shows an example in which an ammeter 52 is used as detection means. Furthermore, the charge transfer circuit CONVg may include a voltmeter 46 and an ammeter 52 as detection means, like the charge transfer circuit CONVc. Further, a temperature sensing element 54 may be provided as in the charge transfer circuit CONVd and the charge transfer circuit CONVe.

  Further, the charge transfer circuit of the present invention may be applied to a bridge converter like the charge transfer circuit CONVh of the solar cell module PVMh shown in FIG. In the charge transfer circuit CONVh, a semiconductor switch element SW (a) and a semiconductor switch element SW (c) are respectively connected in series at both ends of a coil L1 connected in series with the solar cell body SC. Further, the semiconductor switch element SW (b) and the semiconductor switch element SW (d) are respectively connected in parallel with the solar cell body SC at both ends of the coil L1.

  During the step-down operation, the semiconductor switch element SW (c) is normally closed, and the semiconductor switch element SW (d) is normally open. Further, the semiconductor switch element SW (a) is controlled to be switched in phase with the second semiconductor switch element SW2, and the semiconductor switch element SW (b) is controlled to switch in phase opposite to the second semiconductor switch element SW2. Therefore, during the step-down operation of the load transfer circuit CONVh, the semiconductor switch element SW (a) connected in series with the solar cell body SC corresponds to the first semiconductor switch element SW1.

  During the step-down operation of the charge transfer circuit CONVh, the semiconductor switch element SW (b) (third semiconductor switch element SW3) is opened, and the semiconductor switch element SW (a) (first semiconductor switch element SW1) and second semiconductor switch element SW2 are opened. Is closed, the output power generated in the solar cell main body SC is stored in the coil L1 as electric energy and is output to the load side. Further, when the semiconductor switch element SW (b) (third semiconductor switch element SW3) is closed and the semiconductor switch element SW (a) (first semiconductor switch element SW1) and the second semiconductor switch element SW2 are opened, charge transfer is performed. The circuit CONVh releases the electric energy stored in the coil L1 to the load side.

  Further, during the boosting operation of the charge transfer circuit CONVh, the semiconductor switch element SW (a) is normally closed and the semiconductor switch element SW (b) is normally open. Further, the semiconductor switch element SW (d) is controlled to be switched in phase with the second semiconductor switch element SW2, and the semiconductor switch element SW (c) is controlled to switch in phase opposite to the second semiconductor switch element SW2. Therefore, during the boosting operation of the load transfer circuit CONVh, the semiconductor switch element SW (c) connected in series with the solar cell body SC corresponds to the first semiconductor switch element SW1.

  During the boosting operation of the charge transfer circuit CONVh, the semiconductor switch element SW (c) (first semiconductor switch element SW1) is opened, and the second semiconductor switch element SW2 and semiconductor switch element SW (d) (third semiconductor switch element SW3). Is closed, the output power generated in the solar cell main body SC is stored as electric energy in the coil L1. At this time, output power from the other solar cell module PVMh is output to the load side through the second semiconductor switch element SW2. Further, when the semiconductor switch element SW (c) (first semiconductor switch element SW1) is closed and the second semiconductor switch element SW2 and semiconductor switch element SW (d) (third semiconductor switch element SW3) are opened, charge transfer is performed. The circuit CONVh releases the electrical energy stored in the coil L1 and the output power generated in the solar cell body SC to the load side.

  The switching control of the charge transfer circuit CONVh is performed so that the solar cell main body SC operates at the maximum power point Pmax based on the output information of the detection means, similarly to the charge transfer circuits CONVa to CONVe described above. Thus, the solar cell body SC is controlled to follow at the maximum power point Pmax, and the solar cell module PVMh always outputs the maximum power under the sunshine condition.

  FIG. 11A shows an example in which a voltmeter 46 is used as detection means. FIG. 11B shows an example in which an ammeter 52 is used as detection means. Furthermore, the charge transfer circuit CONVh may include a voltmeter 46 and an ammeter 52 as detection means, like the charge transfer circuit CONVc. Further, a temperature sensing element 54 may be provided as in the charge transfer circuit CONVd and the charge transfer circuit CONVe.

  Thus, the solar cell main body SC of the solar power generation device 40 is individually controlled to follow the maximum power point Pmax by the charge transfer circuit CONV provided for each solar cell main body SC. For this reason, it is possible to always output the maximum power under the sunshine conditions. As a result, the solar power generation device 40 constituted by a plurality of solar cell modules PVM can always output the maximum power to the load side.

  In addition, the charge transfer circuit CONV of the solar power generation device 40 includes a second semiconductor switch element SW2 that opens and closes between the output ends 47 of the charge transfer circuit CONV. Therefore, when the second semiconductor switch element SW2 is in the closed state, the power output from the other solar cell modules PVM flows down through the second semiconductor switch element SW2 instead of the diode D. In general, the semiconductor switch element (in a closed state) has much lower power loss than the diode D. For this reason, the solar power generation device 40 can suppress the power loss of each solar cell module PVM when the first semiconductor switch element SW1 is in the open state. In particular, when the first semiconductor switch element SW1 of each solar cell module PVM is in a relatively long open state due to lack of sunlight, this effect becomes significant.

  Further, for example, when the second semiconductor switch element SW2 does not exist and there is one solar cell element constituting the solar cell body SC, and the electromotive force of this solar cell element is equal to or smaller than the forward voltage of the diode D There is a possibility that the loss is larger than the electromotive force and the circuit itself does not operate. However, the charge transfer circuit CONV of the present invention includes the second semiconductor switch element SW2 that short-circuits between the output terminals 47 of the charge transfer circuit CONV with a low loss in the closed state. For this reason, even if the number of solar cell elements constituting the solar cell body SC is one, it can be operated without any problem.

  Furthermore, a normally-on semiconductor switch element that is closed when there is no signal is used as the second semiconductor switch element SW2 used in the charge transfer circuit CONV of the present invention. For this reason, even when some of the charge transfer circuits CONV of the photovoltaic power generation apparatus 40 are stopped for some reason, the second semiconductor switch element SW2 of the charge transfer circuit CONV is maintained in the closed state. Accordingly, as described above, the electric power output from the normal solar cell module PVM that has not stopped operating flows down through the second semiconductor switch element SW2 instead of the diode D. Therefore, the solar power generation device 40 according to the present invention can minimize power loss when passing through the solar cell module PVM whose operation is stopped even when some of the solar cell modules PVM are stopped. .

  Next, description will be made regarding connection of each solar cell module PVM of the photovoltaic power generation apparatus according to the present invention, signal synchronization of switching control, and the like.

  The solar power generation device 40a illustrated in FIG. 12 has a configuration in which a signal used for switching control of the control unit 44 is obtained from an oscillator 55 having an independent period for each solar cell module PVM. According to the configuration of the solar power generation device 40a, since switching control is performed for each solar cell module PVM, one of the solar cell modules PVM is always operating, and the solar power generation device 40a has more stable power. Can be output to the load side. Although FIG. 12 shows an example in which the oscillator 55 is provided in the control unit 44 of the charge transfer circuit CONV, the oscillator 55 can also be provided outside.

  Moreover, the solar power generation device 40b shown in FIG. 13 is the structure which synchronizes the switching control period of each solar cell module PVM by providing the sync terminal 59 in the control part 44, and connecting this. According to the configuration of the solar power generation device 40b, each solar cell module PVM performs switching control based on a signal having a synchronized period. Therefore, even if the duty ratios of the individual solar cell modules PVM are different, they are synchronized. There is always a section where all the first semiconductor switch elements SW1 of the solar cell module PVM are simultaneously closed. In the section where all the first semiconductor switch elements SW1 are simultaneously closed, all the synchronized solar cell modules PVM output power all at once, so that the maximum power in the photovoltaic power generation device 40b is on the load side. Can be output. As a means for synchronizing each solar cell module PVM, one oscillator and a control unit 44 of each solar cell module PVM are connected, and the switching control of each solar cell module PVM is synchronized based on a signal from the oscillator. May be performed.

  In FIGS. 12 and 13, an example in which the solar cell modules PVM connected in series are arranged in one row is used. However, the present invention can also be applied to a configuration in which a plurality of solar cell modules PVM as shown in FIG. Is possible.

  Moreover, the photovoltaic power generation device 40c shown in FIG. 14 connects a plurality of strings PVS composed of a plurality of series-connected solar cell modules PVM in parallel to the control unit 44 of the solar cell module PVM that configures each string PVS. By providing the sync terminal 59 and connecting it, the switching control cycle of the solar cell module PVM is synchronized for each string PVS, and the switching control cycle of each string PVS is set by the oscillator controller 50 at a constant phase difference. Provided.

  According to this solar power generation device 40c, since the switching control signals of the solar cell modules PVM constituting one string PVS are synchronized, all the first semiconductor switch elements SW1 of the solar cell modules PVM in the string PVS are synchronized. There are sections in which are simultaneously closed. At this time, the string PVS outputs the maximum power to the load side. Further, the switching control cycle of each string PVS has a phase difference of a constant interval by the oscillator controller 50. For this reason, even if one string PVS outputs the maximum power to the load side and the output power decreases, another string PVS can sequentially output the maximum power to the load side. Therefore, the solar power generation device 40c can stably output high power to the load side.

  Moreover, the solar power generation device 40d shown in FIG. 15 has a configuration in which a plurality of string PVSs are connected in parallel, and a signal cycle serving as a basis for switching control is performed independently for each solar cell module PVM. According to this configuration, since all the solar cell modules PVM are subjected to switching control at an independent cycle, the solar power generation device 40d can output extremely stable power to the load side. However, in the solar power generation device 40d, there is a possibility that a certain string PVS does not output any power at all depending on the timing of the switching control. For this reason, it is preferable to connect the diode D1 which prevents the backflow of an electric current between each string PVS and the positive electrode output terminal 42a of the solar power generation device 40d.

  14 and 15 show an example in which three strings PVS are connected in parallel, but the number of parallel connections can be appropriately increased or decreased depending on the use, scale, etc. of the photovoltaic power generation apparatus.

  Moreover, as shown in FIG. 16, the solar power generation devices 40a, 40b, 40c, and 40d are a string PVS and the solar power generation device 40a except for the coil L1 provided in each solar cell module PVM (PVMa to PVMe). , 40b, 40c, and 40d, the coil L2 may be provided between the positive electrode output end 42a. According to this configuration, it is possible to save space by installing the coil L1 provided in each solar cell module PVM. Further, by removing the coil L1 from the configuration of the solar cell module PVM, the solar cell modules PVMa to PVMe can be made into one IC package, and further space saving can be achieved. In FIG. 16, one string PVS is used as an example, but a plurality of strings PVS are connected in parallel, and between each string PVS and the positive output terminal 42a of the solar power generation devices 40a, 40b, 40c, and 40d. The coil L2 may be provided in the. In addition, when an inductive load such as a motor is connected to the solar power generation devices 40a, 40b, 40c, and 40d, the inductive load may be used as the coil L2.

  Also in the configuration of these photovoltaic power generation devices 40a, 40b, 40c, and 40d, the solar cell main body SC of each solar cell module PVM is controlled by switching control of the charge transfer circuit CONV provided for each solar cell module PVM as described above. Since the follow-up control is always performed so as to operate at the maximum power point Pmax, the maximum power is always output under the sunshine condition. As a result, the solar power generation devices 40a, 40b, 40c, and 40d can always output the maximum power to the load side.

  Moreover, the solar power generation devices 40, 40a, 40b, 40c, and 40d are each provided with a charge transfer circuit CONV in each solar cell body SC, and MPPT control is performed for each solar cell body SC to follow the maximum power point Pmax. Therefore, since there is no bypass diode Db or backflow prevention diode Da provided in the conventional solar cell module, there is no principle of bimodality. Therefore, MTTP control for extracting the true maximum power without loss is performed for each solar cell body SC.

  In addition, since the solar power generation devices 40, 40a, 40b, 40c, and 40d are configured to extract and output the power of each solar cell module PVM to the maximum, the solar power generation devices 40, 40a, 40b, 40c, and 40d When connecting the load 28 or the power system 27, as shown in FIG. 17, a regulator 60, a converter 61, etc. are provided between the photovoltaic power generation devices 40, 40a, 40b, 40c, 40d and the load 28 or the power system 27. Therefore, it is necessary to convert to a predetermined voltage value and current value. Further, a power storage device 62 may be provided between the solar power generation devices 40, 40 a, 40 b, 40 c, and 40 d and the regulator 60 and the converter 61 as necessary.

  In addition, the photovoltaic power generation devices 40, 40a, 40b, 40c, and 40d according to the present invention can be used to charge the extracted battery to the secondary battery via a regulator, a converter, or the like at the output end. It can also be linked. Furthermore, the range of application ranges from a small-scale photovoltaic power generation system for indoor use to a large-scale photovoltaic power generation system for outdoor use.

40, 40a-40d Photovoltaic power generation device
44 Control unit
46 Voltmeter (detection means)
47 Output terminal
52 Ammeter (detection means)
CONV, CONVa to CONVh Charge transfer circuit
SC solar cell body
SW1 First semiconductor switch element
SW2 Second semiconductor switch element
Pmax maximum power point

Claims (2)

In the solar power generation apparatus provided with a string in which module output ends of a plurality of solar cell modules are connected in series,
The solar cell module includes a solar cell main body to which one or a plurality of solar cell elements are connected, a charge transfer circuit that is provided for each solar cell main body and performs follow-up control to the maximum power point of the output with respect to the solar cell main body, Have
The charge transfer circuit, a second semiconductor switch for short-circuiting the first semiconductor switching element connected in series to the solar cell body, between an output terminal of said charge transfer circuit in the closed state connected in parallel with the solar cell body An element, a detection unit that monitors the output of the solar cell body, and a control unit that performs switching control of the first semiconductor switch element and the second semiconductor switch element according to output information from the detection unit ,
The second semiconductor switch element of the charge transfer circuit is a normally-on type semiconductor switch element, and when the charge transfer circuit stops operating, the second semiconductor switch element of the stopped charge transfer circuit is in a closed state. The photovoltaic power generation apparatus characterized in that the power output from the other solar cell module that is maintained as it is and has not stopped operating is caused to flow through the second semiconductor switch element . The charge transfer circuit includes a coil connected in series to the solar cell body, semiconductor switch elements SW (a) and SW (c) connected in series to both ends of the coil, and solar cells respectively connected to both ends of the coil. A semiconductor switch element SW (b) and a semiconductor switch element SW (d) connected in parallel with the main body;
During the step-down operation, the semiconductor switch element SW (c) is normally closed and the semiconductor switch element SW (d) is normally open, and the semiconductor switch element SW (b) is opposite to the second semiconductor switch element. The semiconductor switching element SW (a) is controlled to be in phase with the second semiconductor switching element, while being controlled to be switched to the phase and functioning as the first semiconductor switching element.
During the boosting operation, the semiconductor switch element SW (a) is normally closed and the semiconductor switch element SW (b) is normally open, and the semiconductor switch element SW (c) is opposite to the second semiconductor switch element. 2. The sunlight according to claim 1, wherein the semiconductor switch element SW (d) is controlled to be in phase with the second semiconductor switch element while being controlled to be switched in phase and functioning as a first semiconductor switch element. Power generation device.

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