RU2811080C1 - Power supply device based on photovoltaic panels - Google Patents

Abstract

FIELD: electrical engineering.

SUBSTANCE: invention can be used for efficient power extraction from solar panels, conversion and transmission of the resulting energy to the industrial network and consumer load. A power supply device based on photovoltaic panels consists of a block of solar panels, a block of current and voltage sensors of a block of solar panels, a DC/DC voltage converter, a DC bus, a reversible inverter, a block of current and voltage sensors at the output of the converter, a control unit for the DC/DC voltage converter , inverter control unit, control and switching microcontroller, DC bus current and voltage sensor unit, LC filter, radio interference filter, load current and voltage sensor unit, differs in that it additionally includes a voltage pulse unit installed between the solar unit panels and a DC/DC voltage converter, while the control unit of the DC/DC voltage converter is made with an additional function of controlling a block of voltage pulses, with the ability to adjust voltage pulses by amplitude, frequency, duration, polarity, as well as by the rise and fall time of the pulses.

EFFECT: increased energy generation in the solar panel block.

3 cl, 6 dwg

Description

Field of technology to which the invention relates

The invention relates to converter technology and can be used for efficient power extraction from solar panels, conversion and transmission of the resulting energy to the industrial network and consumer load. It is also possible to charge with energy received from photovoltaic panels or the network, batteries and supercapacitors with further conversion, if necessary, into alternating voltage of industrial frequency to provide the consumer's load with guaranteed uninterrupted power supply.

State of the art

A solar-powered device is known, containing a solar module, a first DC-DC converter, a battery, a second DC-DC converter, a controller and a load. (RF patent for invention No. 2503120 “Device on solar batteries”, IPC N02M 3/156, 12/27/2013).

The disadvantages of this device are:

1. Tracking the point of maximum power under uniform illumination using one of the classical methods;

2. Lack of connection with the industrial network in order to ensure the battery is charged in bad weather conditions, inability to supply energy to the network.

A power plant is known that contains batteries of solar cells, energy storage devices, a DC/DC voltage converter, a DC/AC voltage converter, and automatic switches (RF Patent for invention No. 2397593 “Power plant and method for its control”, IPC H02J 7/35, H01L 31/00 , 08/20/2010).

The disadvantages of this device are:

1. Inability to transfer energy received from solar panels to the industrial network;

2. Tracking the point of maximum power under uniform illumination using one of the classical methods.

A device and method for tracking the maximum power point for an inverter when using solar panels is known, consisting of solar panels, an inverter, a system controller and a load. (Patent US 7158395 B2 “Method and apparatus for tracking maximum power point for inverters, for example, in photovoltaic applications”, IPC H02M 7/44, 01/02/2007).

The disadvantages of this device are:

1. Tracking the classic maximum on the current-voltage characteristic of the panel block and its drift with temperature changes and uniform changes in illumination, as a result - ineffective power take-off from the solar panel block;

2. It is not possible to use this device as a backup power source in the event of a power failure.

An energy conversion system with maximum power point tracking is also known, consisting of a maximum power point tracking (MPPT) unit, a DC bus, a power converter, and a converter controller. (Patent US 20130027997 A1 “Maximum power point tracking for power conversion system and method thereof”), IPC H02M 7/44, 01/31/2013).

The disadvantages of this device are:

Tracking the classic maximum on the current-voltage characteristic of the panel block and its drift with temperature changes and uniform changes in illumination, resulting in a lack of power from the solar panel block;

The absence of an energy storage device (battery or supercapacitor), and, therefore, the inability to power the load with this system in the event of a power outage or low energy production from solar panels.

A known system and method for controlling the output power of a photovoltaic cell, consisting of solar panels, an inverter, a control unit, a switching power supply and a load. (Patent US 2015244313 A1 “System and Method for Managing the Power Output of a Photovoltaic Cell”, IPC G01R 31/40, 08/27/2015).

The disadvantages of this device are:

1. Application of voltage pulses to solar panels, with adjustment of the pulse repetition rate, amplitude, pulse duration (duty factor), but the inability to adjust the rising and falling edges of these pulses, as well as the inability to apply aperiodic alternating voltage pulses to solar panels, as a consequence - inefficient power take-off from the solar panel unit;

2. It is not possible to use this device as a backup power source in the event of a power failure.

The closest in technical essence to the proposed solution is a guaranteed power supply device based on renewable energy sources (RU 207387 U1, 10.26.2021). In this patent, all zones on the current-voltage characteristic are monitored in case partial shading occurs and a power peak appears on the “left” of the current-voltage characteristic. When this point is found, energy is taken from the SP using the classical method.

For example, there is a boost converter that takes current from the panel so that the product of the current and voltage from the panel has a maximum value. This is an analogue of a rheostat, when the position of the rheostat handle (resistance) is selected, at which maximum energy flows from the joint venture.

The disadvantage of this device is the tracking of several local zones on the current-voltage characteristic of the panel block and its drift with temperature changes and changes in illumination, as well as tracking the appearance of the maximum power point in partial shading and power take-off at this point using the classical method, as a result - ineffective power take-off from the solar unit panels.

Disclosure of the Invention

The technical problem of the invention is to increase the efficiency of a device consisting of a block of solar panels (SP) and a converter, tracking the true point of maximum power under real operating conditions; transmission of the received energy to the network and load, as well as charging the electricity storage device from the solar panel unit and from the network. As a result, the efficiency (efficiency) of power take-off from a block of solar panels increases, and the reliability of providing power to the electricity consumer increases.

The technical result achieved when using the proposed device is an increase in the energy received from a block of solar panels.

It also provides an additional increase in the reliability of the guaranteed power supply to the consumer, which occurs, inter alia, through the use of energy storage devices, which receive energy from solar panels and the network according to a given algorithm, and in the event of a loss of mains voltage or a decrease in the energy received from solar panels, they provide uninterrupted power supply consumer, by mixing energy from the storage device with energy received from solar panels on a common DC bus, with further conversion to alternating voltage and powering the consumer’s load.

The technical problem is solved and the technical result is achieved due to the fact that the power supply device based on photovoltaic panels consists of a block of solar panels, a block of current and voltage sensors of the solar panel block, a DC/DC voltage converter, a DC bus, an inverter, a block of current and voltage sensors at the output of the converter, the DC/DC voltage converter control unit, the inverter control unit, the control and switching microcontroller, the DC bus current and voltage sensor unit, the LC filter and radio interference filter, the load current and voltage sensor unit, and the device is additionally introduced voltage pulse block installed between the solar panel and the DC/DC voltage converter, while the DC/DC voltage converter control unit is made with an additional function of controlling the voltage pulse block, with the ability to adjust voltage pulses by amplitude, frequency, duration, polarity, as well as by rise time and fall time of pulses.

In addition, the device includes a bidirectional DC/DC voltage converter for charging/discharging the battery and a rechargeable battery.

In addition, the device includes a bidirectional DC/DC voltage converter for charging/discharging a block of supercapacitors, a block of supercapacitors.

Brief description of drawings

Fig. 1 - Block diagram of a power supply device based on photovoltaic panels;

Fig. 2 - Family of current-voltage characteristics of a solar panel depending on temperature and changes in uniform illumination of the panel;

Fig. 3 - The essence of the method of disturbance and observation when tracking the point of maximum power;

Fig. 4 - Simplified diagram of the solar panel operation;

Fig. 5 - One of the possible implementation options;

Fig. 6 - Scheme of possible serial (a) and parallel (b) connection of solar panels.

Carrying out the invention

A power supply device based on photovoltaic panels consists of an interconnected solar panel unit, a voltage pulse unit, a solar panel unit current and voltage sensor unit, a DC/DC voltage converter, a DC bus, a DC bus current and voltage sensor unit, a reversible inverter, LC filter, block of current and voltage sensors at the output of the converter, radio interference filter, block of current and voltage sensors at the load, load, controlled network switch, block of current and voltage sensors of the network, network, control unit of the DC/DC voltage converter and voltage pulse block , reversible inverter control unit, microprocessor control and switching unit.

In addition, the device may additionally contain a rechargeable battery (AB) and a bidirectional DC/DC voltage converter for charging/discharging the battery, a supercapacitor unit (SUB) and a bidirectional DC/DC voltage converter for charging/discharging the supercapacitor unit, as well as a battery control unit and BSK.

The claimed solution is illustrated by graphic materials, where Fig. 1 shows a block diagram of a power supply device based on photovoltaic panels.

The diagram shows: a block of solar panels (1), a block of current and voltage sensors of a block of solar panels (2), a DC/DC voltage converter (3), a DC bus (4), a block of current and voltage sensors of a DC bus (5) , reversible inverter (6), LC filter (7), block of current and voltage sensors at the output of the converter (8), radio interference filter (9), block of current and voltage sensors at the load (10), load (11), controlled switch network (12), network current and voltage sensor unit (13), network (14), control unit DC/DC voltage converter and voltage pulse unit (15), reversible inverter control unit (16), microprocessor control and switching unit (17 ), bidirectional DC/DC voltage converter for charging/discharging the battery (18), rechargeable battery (AB) (19), bidirectional DC/DC voltage converter for charging/discharging the supercapacitor unit (20), supercapacitor unit (BSC) (21 ), voltage pulse block (22), control unit AB, BSK (23).

The device works as follows.

The voltage and current from the block of solar panels (1) through the block of voltage pulses (22) and the block of current and voltage sensors from the solar panels (2) are supplied to the DC/DC voltage converter (3). Information about voltage and current from the solar panels is supplied to the control unit of the DC/DC voltage converter and the voltage pulse unit (15), in accordance with a given algorithm, the unit generates control signals for the operation of the DC/DC converter and the voltage pulse unit, as a result, The maximum possible power is taken from solar panels at a given temperature and illumination. In this case, the voltage pulse block can be controlled both together with the DCYDC converter by one control unit, and inside the voltage pulse block itself it can be controlled, provided that current and voltage sensors are present and data is received from them. The resulting electricity is supplied to the DC bus (4). From the DC bus, through a block of DC bus current and voltage sensors, voltage and current are supplied to a reversible inverter (6), which, in direct conversion mode, converts DC voltage and current into alternating voltage and current, for example, using pulse-width modulation. Next, the power PWM signal is supplied to the input of the LC filter (7), after which the filtered low-frequency network signal is supplied to the input of the current and voltage sensor block at the output of the converter (8). After which the signal is sent to the input of the radio interference filter (9). Next, the output current and voltage are supplied to the load (11) through a block of current and voltage sensors on the load (10), as well as to the network (14) through a controlled network switch (12) and a block of current and voltage sensors (13). The reversible inverter is controlled by the reversible inverter control unit (16), which receives information about the current and voltage on the DC bus, as well as on the output of the converter. The complete operation of the device is controlled by a microprocessor control and switching unit (17), which receives information from the control unit of the DC/DC voltage converter and the voltage pulse unit (15), the inverter control unit (16), and from the current and voltage sensor units at the output of the converter , on load and network.

By introducing an additional block of voltage pulses between the SP and the DC/DC voltage converter and implementing a control block of the DC/DC voltage converter with the ability to control the block of voltage pulses, effective power extraction from the solar panel block is ensured, and the energy received from the solar panel block increases. The voltage pulse block (22), regularly applying voltage pulses to the SP, seems to “pull out” additional electrons from the SP, which, with all the usual classical methods of power take-off, do not reach the conductor and recombine with holes in the SP itself. As a result, we obtain more energy from the joint venture than with any classical power take-off methods.

It is also possible that the system contains a battery (19) and a bidirectional DC/DC voltage converter unit for charging/discharging the battery (18).

It is also possible that the system contains a supercapacitor unit (SCB) (21) and a bidirectional DC/DC voltage converter for charging/discharging the supercapacitor unit (20).

When connected to the AB, BSK system, the guaranteed power supply system contains the AB, BSK control unit (23).

Due to this, an additional increase in the reliability of the guaranteed power supply to the consumer is ensured, which occurs, inter alia, through the use of energy storage devices, which receive energy from solar panels and the network according to a given algorithm, and in the event of a loss of mains voltage, a decrease in the energy received from solar panels - provide uninterrupted power supply to the consumer by mixing energy from the storage device with the energy received from solar panels on a common DC bus, with further conversion to alternating voltage and powering the consumer’s load.

The power supply device can act as a source of microgeneration of energy received from renewable energy sources into the network; as a power source from renewable energy sources for consumer loads; as a guaranteed source of power supply to the consumer in the event of a power outage from the network.

Let's look at how the device operates under different configurations.

1. Without AB, BSK.

Energy from solar panels is taken at the point of maximum power, taking into account the reduction of parasitic recombination, and is converted into alternating network voltage. Next, the microcontroller analyzes the current and voltage on the load and network. If the energy received from the solar panels is sufficient to power the load, the converter disconnects the network from the load and power comes only from the solar panels. If the load consumes less than the solar panel unit (SPS) produces, then the converter directs part of the energy received from the SPS to the load, and part to the network. If the energy consumed by the load exceeds the energy generated by the BSP, then the converter supplies all the energy received from the BSP to the load, and consumes the missing energy for the load from the network. When there is no load, all the energy received from the BSP goes to the network.

2. With AB and (or) BSK.

If there is an AB and (or) BSK in the system, the general operating algorithm described above does not change, however, additional options for the system operation appear. If there is energy from the BSP and part of it is spent on the load, the rest of the energy goes to charging the battery and (or) the BSC. After they are fully charged, the energy goes into the network. When the network voltage fails, the control and switching microcontroller disconnects the network from the system and the load, and the consumer load is powered from the BSP. If there is a lack of energy received from the BSP, the stored energy from the battery and (or) BSK is supplied to the DC bus, which is further converted into alternating voltage of industrial frequency to power the consumer load. If the energy received from the BSP is not enough to load and maintain the charge of the battery and (or) BSC in a charged state in a certain time interval, then according to a given algorithm (for example, at night), the inverter operates in the reverse mode - charging the DC bus from the industrial network, and then the voltage converters charge the battery and BSK to a given level.

Let's consider the operation of a solar panel unit under various operating conditions. Figure 2 shows a family of current-voltage characteristics of a solar panel depending on temperature and changes in uniform illumination of the panel. The current-voltage characteristic (volt-ampere characteristic) has a classic form: at the initial stage there is a linear increase in power with increasing voltage, then an extremum is reached, after which there is a decrease in the received power with increasing voltage on the solar panel. We see that in this case there is only one extremum on the current-voltage characteristic of the panel, which, with a change in temperature and a uniform change in radiation, drifts along the current-voltage characteristic in a limited region.

As the temperature rises, the voltage at the maximum power point drops. The extremum of the power function on the current-voltage characteristic shifts down and to the left. As the temperature decreases: the voltage increases at the extremum point, the point of maximum power shifts along the I-V characteristic upward and to the right. As the uniform illumination of the panel decreases, the current at the point of maximum power drops and the power extremum shifts downward. As the uniform illumination of the panel increases, the current increases, therefore, the point of maximum power shifts upward.

Various algorithms for tracking the maximum power point are known. For example, perturbations and observations or the method of increasing conductivity. The essence of the perturbation and observation method is shown in Fig. 3. The voltage and current on the solar panel unit (PSB) are measured. Power P0 is calculated. Next, the output voltage of the BSP changes by controlling the converter (positive voltage increment). Current and voltage are measured. As a result, power point P1 appears. P1 and P0 are compared, if P1 is greater, then the voltage increment remains and then the next step occurs. The voltage on the panel block increases. The current is measured. The power P2 is calculated.

Further also P3 and P4. If the new power is lower than the previous one, then the sign of the increment changes. There are also adaptive algorithms in which the increment step is not constant, but changes depending on the approach to the extremum. The step is reduced in the extreme region to reduce the ripple of power removed from the solar panel block.

As a result, we have, with a smooth change in temperature and a uniform change in panel illumination, the classic algorithm for finding the point of maximum power tracks how the extremum drifts along the I-V characteristic of the solar panel in a given area.

In fact, all existing methods of power take-off from a joint venture are equivalent to connecting a rheostat to a solar panel and, automatically adjusting “its resistance”, ensure the selection of direct current from a joint venture at the point of the current-voltage characteristic where the power is maximum.

The efficiency of modern industrially produced SPs, from which energy is extracted using the classical (“rheostat”) method, is in the range of 18-23%. Those. from 1 kW of solar photon energy on an equivalent load rheostat there will be 180-230 W of electricity.

The rest of the energy received from solar radiation goes to losses in the solar power plant. The main processes leading to low SC efficiency include: reflection of part of the radiation from the surface of the semiconductor, inactive absorption of light quanta, parasitic recombination of nonequilibrium carriers, etc.

Let us consider in a simplified form the operation of the joint venture, see Fig.4. In Fig.4: light falls on the SP and passes to the n, p regions and the depletion region. In the depletion region, photon energy transfers to the electron-hole pair. They are separated. Due to the presence of an internal field, electrons move up through the n region to the conductor, and then into the load. After the load, the electrons return through the conductor to the SC from the p side of the region and recombine with holes.

In the described manner, the energy of photons is converted into electrical energy.

After the separation of electrons and holes under the influence of sunlight, some of the electrons do not reach the conductor, and therefore the load. During the movement of electrons and holes in the depletion region, as well as partially in the n and p regions, parasitic recombination of electrons and holes occurs. As a result, most of the energy received by the SP from the sun does not reach the load due to the process of parasitic recombination.

To reduce energy losses due to parasitic recombination, we introduce a pulse voltage block between the SP and the load. The purpose of which is to apply, in short pulses of a certain amplitude, frequency (period), duration, with certain rising and falling fronts, either a unipolar positive voltage pulse to the n region and a negative one to the p region of the SP, or an aperiodic alternating voltage pulse.

Voltage pulses are applied to the solar panel to give the electrons and holes that have received energy from the photons an additional impulse as they move from the depletion region to the conductor. As a result of the action of these voltage pulses, the probability of parasitic recombination decreases, the number of electrons reaching the conductor and load increases, therefore, the amount of energy received from the solar panel and the efficiency of the SP-converter system increases.

In the general case, voltage pulses are controlled by amplitude, frequency (f), duration (ti), polarity, as well as by the duration of rise (tr) and fall (tf) of the fronts of voltage pulses (dU/dt). It is also possible to apply an aperiodic alternating signal to an array of solar panels. It should be noted that the voltage amplitude, frequency and pulse duration are parameters that are set for a given package and type of panels, and then practically do not change (such an implementation is possible) or change quite slowly during the automatic adjustment process. When changing the illumination and temperature of solar panels, the main adjustment parameters are the rising and falling edges of voltage pulses.

For this reason, the control system for a pulsed voltage source and the implementation of a pulsed voltage source itself installed between solar panels and a DC-DC converter, or a load, or an inverter must necessarily have the ability to create and adjust voltage pulses in amplitude, frequency, duration (duty cycle). ), polarity and time of rise and fall of voltage pulses. Only by controlling all these parameters is the maximum increase in the energy received from solar panels achieved.

It should be noted that voltage pulses have a duration of a few microseconds, so the energy consumption for their creation is an order of magnitude less than the energy of electrons, which do not lose it during parasitic recombination and are supplied to the load.

When exposed to this “control” voltage, a large number of electrons, which received energy from light quanta, which previously recombined with holes and did not reach the load, leave the n layer of the SP, thereby increasing the useful energy and efficiency of the SP by 1.5-1.7 times under intense illumination, relative to classical (“rheostatic”) methods of power take-off with a joint venture.

To some extent, this principle figuratively corresponds to the operation of a field-effect transistor, when we use the electric field of the gate, practically without wasting current, to control the opening of the channel and the passage of power current through the p-n junctions of the field-effect transistor.

From the analysis of patent US 2015244313 A1 “Method and apparatus for tracking maximum power point for inverters, for example, in photovoltaic applications”, IPC G01R 31/40, 08/27/2015 - we see that it does not implement the control system and the pulse source device itself with the function of adjusting the rising and falling fronts of voltage pulses depending on the illumination and temperature of the solar panels. The result is less energy received from solar panels. The authors of this patent indicate an increase in energy from solar panels of 1.2 at full illumination.

In all classic converters, the DC/DC voltage converter control unit provides, by adjusting the duty cycle of the switch, an increase in the voltage received from the solar panels to the level of the DC bus voltage, from which the inverter is then powered. In our case, this control unit also has a built-in control function for a voltage pulse block, the target control function of which is to obtain more energy from solar panels. Those. Now it not only increases the voltage, but also regulates the flow of energy from the solar panels, also providing the output voltage on the DC bus. And then, the inverter control unit takes energy from the bus in the amount that the control unit and solar panels can provide at a given time.

There are a large number of circuit engineering methods for implementing the described method of increasing the efficiency of the SP-converter system. Figure 5 shows one of the possible options.

Figure 5 shows the solar panel SP1, storage capacitor C1, a step-up voltage converter consisting of capacitors C2, inductor L1, diode D1, switch K1, a pulse source consisting of transformer Tp1, capacitor C3, switch K2, power supply U1 and general control device УУ1.

The control device УУ1 generates control signals for keys K1 and K2. When switch K2 briefly transitions to the open state, a current pulse passes through the primary winding 1 of transformer Tp1. A voltage pulse is formed on the secondary winding of transformer Tp1. The positive polarity is applied to the n region of the solar panel SP1, and the negative polarity is applied to the p region of the solar panel SP1 through capacitor C1. At the same time, in accordance with the given operating algorithm, key K1 is periodically opened, resulting in the formation of voltage on capacitor C2. The voltage on capacitor C2 is then supplied either to the load or to the voltage inverter.

Light falling on the SP1 solar panel separates electrons and holes. Electrons move along the circuit and charge capacitance C1. At the same time, through the pulse transformer Tp1, voltage pulses with a given frequency, duration, amplitude, rising and falling fronts are applied to the n region of the solar panel; as a result, the probability of parasitic recombination of electrons and holes decreases, and an additional number of electrons that have received energy from light photons reaches the conductor and charges the storage capacitance C1. Then, using a boost converter (L1, K1, D1, C2), the voltage is increased to the level required for the load or for the inverter voltage.

Transformer Tp1 can be made with or without a ferromagnetic core.

Figure 6 shows a diagram of a possible series (a) and parallel (b) connection of solar panels using an example of two panels. When connecting the SP into blocks, diodes are switched on parallel to the SP, which serve to bypass the current when the SP in the panel block is partially shaded. To prevent these diodes from shunting pulse signals that are applied to the solar panels, chokes (L2-L4) are installed in series with each of the diodes (D2-D4). These DC chokes offer virtually no resistance, and when partially shaded, DC flows through the diodes. Moreover, when exposed to voltage pulses from the transformer Tp1 (Fig. 5) lasting a few microseconds or less, the chokes D2-D4 have a high characteristic impedance and do not shunt these pulses.

The declared solution allows you to increase the amount of energy received from an array of solar panels under real operating conditions. This is of paramount importance both for autonomous power supply systems without a network, and for systems with a network, because ultimately affects the amount of energy received from solar panels and the payback of the system as a whole.

Claims (3)

1. A power supply device based on photovoltaic panels, consisting of a solar panel unit, a current and voltage sensor unit of a solar panel unit, a DC/DC voltage converter, a DC bus, a reversible inverter, a current and voltage sensor unit at the output of the converter, a DC/DC control unit. DC voltage converter, inverter control unit, control and switching microcontroller, DC bus current and voltage sensor unit, LC filter, radio interference filter, load current and voltage sensor unit, characterized in that it additionally includes a voltage pulse unit installed between the block of solar panels and the DC/DC voltage converter, while the control unit of the DC/DC voltage converter is made with an additional function of controlling the block of voltage pulses, with the ability to adjust the voltage pulses by amplitude, frequency, duration, polarity, as well as by rise time and time decline in impulses. 2. A power supply device based on photovoltaic panels according to claim 1, characterized in that it contains a bidirectional DC/DC voltage converter for charging/discharging the battery and a battery. 3. A power supply device based on photovoltaic panels according to claim 1, characterized in that it contains a bidirectional DC/DC voltage converter for charging/discharging a block of supercapacitors, a block of supercapacitors.