JP2012208725A - Photovoltaic power generation system - Google Patents

Abstract

The present invention provides a photovoltaic power generation system that improves the power extraction efficiency when the maximum output operating voltages of individual solar cell modules are different and does not require a measuring instrument or the like to be installed for each solar cell module.
SOLUTION: A plurality of solar cell modules 11, first and second DCDC converters 31, 32, a common power line 16, a main power line 14, a sub power line 15, a plurality of diode elements, and a plurality of switching elements. A photovoltaic power generation system including an element, an electronic load device 33 for measuring voltage-current characteristics of a solar cell module, and a control device. The controller detects the array maximum output operating voltage when all of the plurality of solar cell modules are connected in parallel, and sequentially obtains the power differential value near the array maximum output operating voltage with the electronic load device connected to the sub power line. Based on the power differential value, a group of modules having a high maximum output operating voltage value and a group of modules having a low maximum output operating voltage value are determined.
[Selection] Figure 1

Description

  The present invention relates to a photovoltaic power generation system for maximizing electric power extracted from a solar cell module. In particular, the present invention relates to an improvement in power extraction efficiency when the maximum output operating voltage of each solar cell module differs due to environmental changes and individual characteristic variations.

  A photovoltaic power generation system generally includes a large number of solar cell modules that convert solar energy into electric power, and a power conditioner (PCS) that collects the electric power output from the module and supplies it to a commercial power source or a storage battery. Consists of.

  FIG. 15 shows an example of the configuration of a conventional solar power generation system. As shown in FIG. 15, the photovoltaic power generation system includes a solar cell array 200 and a power conditioner 203. The solar cell array 200 is configured by connecting a plurality of solar cell modules 201 in parallel. In order to increase the output voltage of the solar cell module 201, a plurality of solar cell modules 201 are often connected in series. In addition, a diode 202 for preventing reverse current is connected to the output portion of the solar cell module 201. The power conditioner 203 mainly includes a DCDC converter 204, an inverter 205, and a control device 206 for controlling them.

  The DCDC converter 204 includes a step-up chopper circuit including a coil 207, a diode 208, a capacitor 209, and a switching element 210. The direct current boosted by the DCDC converter 204 is converted into an alternating current by the inverter 205 and supplied to the commercial system power supply 211.

  The control device 206 estimates the power value extracted from the solar cell array 200 from the product of the voltage value measured by the voltmeter 212 and the current value measured by the ammeter 213, and switches the switching element so that the power value becomes maximum. By performing 210 PWM control, the DCDC converter performs maximum power point tracking (MPPT) control.

  When approximately uniform sunlight is irradiated on the surface of the solar cell module, the power-voltage characteristic (P-V characteristic) of the solar cell module generally shows a tendency as shown in FIG. As a typical method of MPPT control, the hill-climbing method is known. This is because the DCDC converter sequentially changes the voltage of the solar cell module in the direction in which the electric power extracted from the solar cell array increases. This is a method for tracking the operating point of the power peak. The voltage of the solar cell array when maximum power is obtained from the solar cell array is referred to as the maximum output operating voltage of the array. Each solar cell module has the same characteristics as in FIG. 16, and the voltage of the solar cell module when the maximum power is obtained from the solar cell module can also be referred to as the maximum output operating voltage of the module.

  By the way, the maximum output operating voltage of the solar cell module may be different for each module due to various factors. Examples of the cause include the amount of solar radiation to the solar cell module (irradiation intensity of sunlight), module temperature, or variations in voltage-current characteristics of individual modules. If the maximum output operating voltage differs greatly among the solar cell modules that make up the solar cell array, it is not possible to simultaneously follow the different maximum output operating voltages with a single DCDC converter. Cannot be demonstrated.

  Therefore, a photovoltaic power generation system that tracks a plurality of maximum output operating voltages with a plurality of DCDC converters is known (see Patent Document 1). FIG. 17 shows the solar power generation system. 17 includes a plurality of ammeters 225, a plurality of switching elements 226, and a control circuit 227 in addition to a plurality of solar cell modules 221, DCDC converters 222 and 223, and an inverter 224. The plurality of ammeters 225 are connected to the output of each solar cell module, and the control circuit 227 can measure the current value of each output. Based on these current values, the control circuit 227 estimates the maximum output operating voltage of each module and switches the switching element 226 to divide it into two groups that are close in maximum output operating voltage. By performing MPPT control, the loss due to the operating voltage deviating from the maximum output operating voltage is further reduced.

JP 2010-267106 A

  Conventionally, as in Patent Document 1, grouping is performed using the fact that there is a correlation between the absolute amount of current output from the solar cell module and the maximum output operating voltage. FIG. 18 shows an example of power-voltage characteristics (also referred to as PV characteristics) of two modules A and B having different characteristics. FIG. 18A is an example of PV characteristics of modules A and B having different solar radiation amounts (irradiation intensity of sunlight) to the solar cell module. In this case, since there is a certain degree of correlation between the absolute amount of current output from the solar cell module and the maximum output operating voltage, for example, as in Patent Document 1, an ammeter is provided for each solar cell module, and the current value It is possible to estimate the maximum output operating voltage from the group, group the solar cell modules for which the value of the maximum output operating voltage is close, and connect the solar cell modules of the group in parallel using a selection switch.

  However, if the maximum output operating voltage differs due to variations in module temperature or module voltage / current characteristics, the absolute amount of current output by the solar cell module and the maximum output operating voltage are set as shown in FIG. There may be no clear correlation. In this case, there is a problem that it is difficult to estimate the maximum output operating voltage of each solar cell module only by the current value of an ammeter provided for each solar cell module.

  On the other hand, providing a large number of circuit elements in the solar cell module leads to a decrease in reliability and an increase in cost. Therefore, it is desirable that the number of circuit elements provided for each solar cell module is small and simple. Therefore, it is preferable to install as few as possible measuring instruments for calculating the maximum output operating voltage of each solar cell module and switching elements for parallel connection.

  The present invention is intended to solve these problems, and it is an object of the present invention to improve the power extraction efficiency when the maximum output operating voltage of each solar cell module differs due to environmental changes and individual characteristic variations. To do. Another object of the present invention is to reduce the number of elements without having to install circuit elements such as measuring instruments for each solar cell module.

  In the present invention, the current value and the voltage value are measured by one electronic load device attached to the power supply line, so that it is not necessary to install a current sensor for each solar cell module, and a switching element is necessary. The number can be one element per module. In addition, according to the present invention, the electronic load device records the differential value of the voltage-current characteristic of each solar cell module, so that the absolute amount of current output from the solar cell module and the maximum output operation as shown in FIG. Even when a clear correlation does not appear in the voltage, the maximum output operating voltage can be estimated.

  The present invention has the following features in order to achieve the above object.

  The present invention is a photovoltaic power generation system for sending a plurality of solar cell modules, first and second DCDC converters, and electric power generated by the solar cell modules to the first or second DCDC converter. A common power line, a main power line, a sub power line, a plurality of diode elements, a plurality of switching elements, an electronic load device for measuring voltage-current characteristics of a solar cell module, and the first and second And a control device for controlling the DCDC converter, the switching element, and the electronic load device. The control device of the present invention sequentially obtains a power differential value in the vicinity of the array maximum output operating voltage of the solar cell module, and based on the power differential value, a group of modules having a high maximum output operating voltage value, and a maximum output A group of modules having a low operating voltage value is determined. More specifically, the control device of the present invention performs the following three-stage control. As a first step, the maximum DC operating voltage when the plurality of solar cell modules are all connected in parallel is detected by causing the first DCDC converter to perform a maximum power point search. As a second step, the sub-power supply lines are sequentially turned on one by one while causing the first DCDC converter to generate a voltage higher than the array maximum output operating voltage on the main power supply line one by one. In the electronic load device connected to the solar cell module, differential power values in the vicinity of the array maximum output operating voltage of the solar cell module are sequentially obtained. As a third step, a group of modules having a high maximum output operating voltage value and a group of modules having a low maximum output operating voltage value are determined based on the power differential value. The first stage corresponds to S102 (array maximum output operating voltage search) in the flowchart described later, the second stage corresponds to S103 (acquisition of power differential value), and the third stage corresponds to S104 (grouping) and S105 ( (Maximum power point tracking). According to the present invention, the first DCDC converter has a high maximum output operating voltage by turning on the switching element connected to the solar cell module determined to be a group of modules having a low maximum output operating voltage value. A DCDC conversion operation is performed, and the second DCDC converter performs a DCDC conversion operation at a low maximum output operation voltage. Specifically, a group of modules having a high maximum output operating voltage value has a voltage higher than the array maximum output operating voltage VPMA, and a group of modules having a low maximum output operating voltage value has a voltage lower than the array maximum output operating voltage VPMA. Operating point voltage.

  In the photovoltaic power generation system of the present invention, the output terminal of the solar cell module and the main power supply line are connected via the diode element, and the output terminal and the sub power supply line are connected via the switching element. The main power line is connected to the first DCDC converter, the sub power line is connected to the second DCDC converter and the electronic load device, and the common power line is the solar cell. It is preferably connected to the other output terminal of the module, the first and second DCDC converters.

  In the photovoltaic power generation system of the present invention, it is preferable to determine a group of modules having a high maximum output operating voltage value and a group of modules having a low maximum output operating voltage value based on the positive / negative polarity of the power differential value. In the photovoltaic power generation system of the present invention, it is preferable that a plurality of switch control circuits for driving the plurality of switching elements are provided, and wireless communication is used for communication between the switch control circuit and the control device. In the photovoltaic power generation system of the present invention, it is preferable that the output terminal of the solar cell module and the sub power line are connected via a series connection of the switching element and the diode element. In the photovoltaic power generation system of the present invention, it is preferable that the electronic load device is configured using a shunt regulator constant voltage circuit whose voltage can be set by the control device. In the photovoltaic power generation system of the present invention, it is preferable that the first and second DCDC converters are constituted by a step-up chopper circuit capable of controlling a conduction rate by the control device.

  Even if a clear correlation does not appear between the absolute amount of current output from the solar cell module and the maximum output operating voltage by measuring the differential value of the power voltage characteristics of each solar cell module by the electronic load device. The maximum output operating voltage of each module can be estimated, and the maximum output operating voltage can be divided into two groups close to each other accordingly. Further, in the present invention, the DCDC converter performs MPPT control on the two determined groups, so that the loss due to the operating voltage deviating from the maximum output operating voltage can be further reduced.

  Furthermore, according to the present invention, it is not necessary to install a current sensor for each solar cell module by measuring the current value and the voltage value with one electronic load device attached to the power line, and the switching element Since the required number is one element per module, the cost can be reduced and the reliability of the system can be improved.

  The present invention can improve the power generation efficiency when partial shade occurs in the solar cell module, when there is a variation in characteristics between the solar cell modules, and when there is a difference in temperature.

It is a block diagram of the solar power generation system of this invention. It is the figure which showed the DCDC converter in the photovoltaic power generation system of this invention, and the circuit structure of those periphery. It is the figure which showed the electronic load apparatus in the photovoltaic power generation system of this invention, and the circuit structure of the periphery. It is a block diagram of a switch control signal generation circuit in the photovoltaic power generation system of the present invention. It is the figure which showed the switch control circuit in the photovoltaic power generation system of this invention, and its peripheral circuit structure. It is a flowchart of the main program mounted in the control apparatus in the solar energy power generation system of this invention. It is a flowchart of array maximum output operation voltage VPMA search subroutine S102 in the photovoltaic power generation system of the present invention. It is a flowchart of the subroutine of the electric power measurement in the solar energy power generation system of this invention. It is a figure showing the maximum power point tracking operation | movement of the DCDC converter 31 by the array maximum output operation voltage VPMA search subroutine S102 in the solar energy power generation system of this invention. It is a flowchart of electric power differential value acquisition subroutine S103 in the solar energy power generation system of this invention. It is a flowchart of grouping subroutine S104 in the solar energy power generation system of this invention. It is the figure which showed the relationship between the power-voltage characteristic of the module in the solar energy power generation system of this invention, and the polarity of the power differential value P '[k] of the module in the vicinity of the array maximum output operating voltage VPMA. It is a flowchart of maximum electric power point tracking subroutine S105 in the solar energy power generation system of this invention. It is a timing chart of the state of the voltage of the main power supply line and sub power supply line which generate | occur | produce by the control operation of the main program in the photovoltaic power generation system of this invention, and switch control signal S [1] -S [n]. It is the figure which showed an example of the conventional solar power generation system structure. It is the figure which showed the power-voltage characteristic of the general solar cell module. It is the structure of the conventional photovoltaic power generation system which tracks several maximum output operating voltage with several DCDC converter. It is the figure which showed the example of the PV characteristic of two modules A and B from which a characteristic differs.

  Examples of the present invention will be described below.

(Example)
An embodiment of the present invention will be described with reference to FIGS. The block diagram of the solar energy power generation system of a present Example is shown in FIG. The solar power generation system according to this embodiment includes a solar cell module 11, a switch circuit 12 attached to the solar cell module, and a power conditioner 13. The solar cell module 11 and the switch circuit 12 are connected on a one-to-one basis, and the switch circuit 12 is connected in parallel by three power supply lines including a main power supply line 14, a sub power supply line 15, and a common power supply line 16. Further, the main power supply line 14, the sub power supply line 15, and the common power supply line 16 are also connected to the power conditioner 13. In FIG. 1, only three modules and three switch circuits are shown for simplicity, but in practice the number of parallels may be increased according to the required power generation amount. The current output from the positive electrode of the solar cell module 11 is supplied to the power conditioner 13 through the main power supply line 14 and the sub power supply line 15, and the returning current flows into the negative electrode of the solar cell module 11 through the common power supply line 16. Hereinafter, the description of the voltage will be described based on the potential of the common power supply line 16 unless otherwise specified.

  The switch circuit 12 functions to distribute the current output from the positive electrode of the solar cell module 11 to either the main power supply line 14 or the sub power supply line 15. The switch circuit 12 includes diode elements 21 and 22, a switching element 23, and a switch control circuit 24. The diode element 21 connects the positive electrode of the solar cell module 11 and the main power supply line 14, and the series circuit composed of the diode element 22 and the switching element 23 connects between the positive electrode of the solar cell module 11 and the sub power supply line 15. Connected. The plurality of switching elements 23 may be semiconductor transistors. The switch control circuit 24 controls opening and closing of the switching element 23. With the configuration of the switch circuit 12 as described above, the current output from the positive electrode of the solar cell module 11 is supplied to the main power supply line 14 when the switching element 23 is OFF, and to the sub power supply line 15 when the switching element 23 is ON. Flowing. Further, when the sub power supply line 15 is handled with the potential always lower than the positive electrode potential of the solar cell module 11, the diode element 22 is omitted and switching between the positive electrode of the solar cell module 11 and the sub power supply line 15 is performed. Even if only the element 23 is connected, the same control is possible.

  The power conditioner 13 includes DCDC converters 31 and 32, an electronic load device 33, a control device 34, a switch control signal generation circuit 35, and an inverter 36. The DCDC converter 31 boosts and outputs a direct current input from the main power supply line 14, and the DCDC converter 32 boosts and outputs a direct current input from the sub power supply line 15. The direct current boosted by the DC converters 31 and 32 is converted into an alternating current by an inverter 36 and supplied to a commercial power supply 17.

  The DCDC converters 31 and 32 and the electronic load device 33 are controlled by the control device 34.

  FIG. 2 shows the DCDC converters 31 and 32 and their peripheral circuit configurations. The DCDC converters 31 and 32 are composed of boost chopper circuits that can control the conduction rate by the control device 34. The DCDC converters 31 and 32 are constituted by a booster circuit using coils 41 and 42, diode elements 43 and 44, and switching elements 45 and 46. The PWM circuits 47 and 48 supply a PWM waveform corresponding to the conduction ratio to the switching elements 45 and 46 according to the data of the conduction ratios α1 and α2 transmitted from the control device 34, and the conduction ratio of the booster circuit. Is controlled to α1 and α2. A smoothing capacitor 49 for smoothing the DC voltage of the output unit, an ammeter 50 and a voltmeter 51 are installed at the output units of the DCDC converters 31 and 32. The DC current value Iout measured by the ammeter 50 and the DC voltage value Vout measured by the voltmeter 51 are digitized by the AD converters 52 and 53 and transmitted to the control device 34. These values are output power. And is used as feedback to the flow rates α1 and α2. Furthermore, a voltmeter 54 is installed at the input of the DCDC converter 31. The DC voltage value V1Mes measured by the voltmeter 54 is digitized by the AD converter 55 and transmitted to the control device 34, and the value is used for voltage measurement of the main power supply line 14.

  FIG. 3 shows a circuit configuration of the electronic load device 33 and its periphery. The electronic load device 33 is configured using a shunt regulator constant voltage circuit whose voltage can be set by the control device. As shown in FIG. 3, the electronic load device 33 includes a field effect transistor 61, a shunt resistor 62, voltage dividing resistors 63 and 64, and an OP amplifier 65. The voltage set value V2AL sent from the control device 34 is converted into an analog voltage by the DA converter 66. The field effect transistor (FET) 61, the voltage dividing resistors 63 and 64, and the OP amplifier 65 form a constant voltage circuit, and generate a voltage proportional to the voltage setting value V2AL on the sub power supply line 15. At this time, a voltage proportional to the current flowing from the sub power supply line 15 to the common power supply line 16 is generated at both ends of the shunt resistor 62, and the voltage is digitized by the AD converter 67 to the control device 34 as a measured current value I2AL. Send.

  FIG. 4 is a block diagram of the switch control signal generation circuit 35. As shown in FIG. The switch status signals S [1] to S [n] transmitted from the control device 34 are encoded by the encoder 72, further modulated by the wireless transmitter 73, and then wirelessly transmitted to each switch control circuit 24 through the antenna 74. The

  FIG. 5 shows the circuit configuration of the switch control circuit 24 and its periphery. The switch control circuit 24 performs switching based on a receiver 76 that demodulates a radio signal from the switch control signal generation circuit 35 received through the antenna 75, an encoder 77 that decodes only a valid signal from the received signal, and an output signal of the encoder 77. The drive circuit 78 is configured to control ON / OFF of the element 23. Further, the switch control circuit 24 incorporates an insulation type DCDC converter 79, and drives a receiver 76, an encoder 77, and a drive circuit 78 with a small part of the power generated by the solar cell module 11. It is converted into electric power and supplied. The relationship between the switch state signals S [1] to S [n] and the ON / OFF of the switching element 23 is ON when S [1] to S [n] is 1, and the switch states S [1] to S [ When n] is 0, the relationship is OFF.

  FIG. 6 shows a flowchart of the main program installed in the control device 34. When the program is started, initial setting S101 is performed, and the continuity α1 and α2 of the DCDC converters 31 and 32 are set to 0%, and the switching elements 23 of all the switch circuits 12 are turned OFF.

  After the initial setting S101, four subroutines of an array maximum output operating voltage VPMA search subroutine S102, a power differential value acquisition subroutine S103, a grouping subroutine S104, and a maximum power point tracking subroutine S105 are repeatedly performed. A maximum output operating voltage of a solar cell array configured by connecting a plurality of solar modules in parallel is referred to as an array maximum output operating voltage VPMA.

  FIG. 7 shows a flowchart of the array maximum output operating voltage VPMA search subroutine S102. In S111, the power measurement subroutine shown in FIG. 8 is executed. In the power measurement subroutine, global variables P1, P2, V2, and I2 are used, which can be referred to from the calling program. In S121, the value of the variable P2 is moved to the variable P1, and in S122, the voltage measurement value Vout of the voltmeter 51 of the DCDC converter output unit is substituted for V2, and the current measurement value Iout of the ammeter 50 is substituted for I2, and in S123 The result of multiplying the variable V2 and the variable I2 is substituted into P2. Therefore, at the time of return, P1 is the power value measured once before, P2 is the power value measured this time, the voltage value measured this time is substituted for V2, and the current value measured this time is substituted for I2.

  In FIG. 7, after the power measurement S111 ends, the flow rate α1 is increased in S112, and the power measurement is performed again in S113. In S114, P1 and P2 are compared. If P2 is larger than P1, the process returns to S112 to repeat increasing the flow rate α1. If P1 is greater than P2, the flow rate α1 is decreased in S115, and power measurement is performed again in S116. In SS17, P1 and P2 are compared. If P2 is larger than P1, the process returns to S115, and the flow rate α1 is further decreased.

  FIG. 9 shows the maximum power point operation of the DCDC converter 31 by the array maximum output operation voltage VPMA search subroutine S102 described above. The vertical axis represents power P, the horizontal axis represents voltage V, and the curve represents power-voltage (P-V) characteristics of the solar cell module. In the initial state, the operating point is at the position of Qst, the power is 0, and the voltage is the open circuit voltage VOC. The operating point moves in the direction of the arrow due to the increase in the conduction rate in S112 to S114, and eventually reaches the maximum power point QPMA. At this time, since the voltage of the main power supply line 14 is the maximum output voltage VPMA of the array, the voltage VPMA is obtained by measuring the voltage V1Mes in S118, and the voltage V1Mes is set as the return value VPMA in S119. .

  FIG. 10 shows a flowchart of the power differential value acquisition subroutine S103. In the subroutine S103, the flow from S131 to S143 is repeated k times using the counter variable k. Here, n is the number of the switch circuits 12, and n = 3 in FIG. In S131, the switch control signal S [k] is set to 1, so that the switching element 23 of the kth switch circuit 12 is turned ON. In S132, the operating voltage V2AL of the electronic load device is set to VPMA. Then, the k-th solar cell module 11 is connected to the sub power supply line 15, and the voltage VPMA of the sub power supply line 15 is lower than the voltage VPMA + ΔV1 of the main power supply line 14, so that the rectifying action of the diode elements 21 and 22 All of the current output from the positive electrode of the solar cell module 11 flows to the sub power line 15 and the electronic load device 33, and the value of the current is measured as the current value I2AL from the voltage drop of the shunt resistor 62 in the electronic load device 33. be able to.

  Further, since the amount of current flowing through the main power supply line 14 and the DCDC converter 31 is changed by turning on the switching element 23 of the k-th switch circuit 12, it is necessary to adjust the conduction ratio α1. In S133 to S137, while monitoring the voltage of the voltmeter 54, the conduction ratio α1 is adjusted so that the voltage of the main power supply line 14 after the change in the current amount becomes VPMA + ΔV1.

  In S139, the current value I2AL is measured and substituted into the variable IMes1 [k]. In S140, the voltage V2AL of the electronic load device 33 is set to a voltage VPMA-ΔV2 slightly lower than the array maximum output operating voltage VPMA. In S141, the electronic load device 33 measures the current I2AL again and assigns it to the variable IMes2 [k]. To do. In S142, the switch control signal S [k] is set to Low, and the switching element 23 of the kth switch circuit 12 is turned OFF.

  In S143, the power differential value P '[k] in the vicinity of the array maximum output operating voltage VPMA is calculated. P ′ [k] is calculated by the following equation.

P ′ [k]
= {IMes1 [k] × VPMA−IMes2 [k] × (VPMA−ΔV2)} / ΔV

  The power differential value P ′ [k] in the vicinity of the array maximum output operating voltage VPMA can be acquired for each solar cell module 11 by the operation of the power differential value acquisition subroutine S103 described above.

  FIG. 11 shows a flowchart of the grouping subroutine S104. In S104 as well as in the subroutine S103, S153 to S155 are repeated n times using the counter variable k. In S153, the process branches depending on the polarity of the obtained differential value P '[k]. If P ′ [k] is negative, the switch control signal S [k] is set to 1 and the switching element 23 of the kth switch circuit 12 is turned ON in S154. Otherwise, in S155, the switch control signal S [k] is set to 0, and the switching element 23 of the kth switch circuit 12 is turned OFF. The above operation is performed for all switch control signals S [k] by the iterative loop described in S156 and S157.

  FIG. 12 shows the relationship between the power-voltage (P-V) characteristics of the solar cell module and the polarity of the power differential value P ′ [k] of the solar cell module in the vicinity of the array maximum output operating voltage VPMA. FIG. 12A shows the PV characteristics when the value of P ′ [k] is negative. In this case, the maximum power point QPM of the solar cell module is on the left side of the line of the array maximum output operating voltage VPMA. That is, the maximum output operating voltage VPM of the solar cell module is lower than the array maximum output operating voltage VPMA. On the other hand, FIG. 12B shows the PV characteristic when the value of P ′ [k] is positive. In this case, the maximum power point QPM of the solar cell module is on the right side of the array maximum output operating voltage VPMA. That is, the maximum output operating voltage VPM of the solar cell module is higher than the array maximum output operating voltage VPMA.

  Therefore, in the grouping subroutine S104 shown in FIG. 11, the maximum output operating voltage VPM of the kth solar cell module depends on whether or not the power differential value P ′ [k] in the vicinity of the array maximum output operating voltage VPMA is negative. Is lower than VPMA, and grouping is performed based on the 0/1 logical value of the switch control signal S [k].

  FIG. 13 shows a flowchart of the maximum power point tracking subroutine S105. In S161, the conduction ratio α2 of the transistor 46 in the DCDC converter 32 is set to 100%. Alternatively, a value close to 100% may be used. Then, since the voltage of the sub power supply line 15 decreases to near 0 V, the output current of the solar cell module 11 grouped into S [k] = 1 flows to the auxiliary power supply line 15 through the diode 22 and the switching element 23. become. On the other hand, the output current of the solar cell module 11 grouped into S [k] = 0 flows to the main power supply line 14 because the switching element 23 is OFF. In this state, the output current of the solar cell module 11 grouped into S [k] = 0 is sent to the DCDC converter 31, and the output current of the solar cell module 11 grouped into S [k] = 1 is fed to the DCDC converter 32. Began to flow.

  Subsequently, the DCDC converters 31 and 32 perform a maximum power point search for the respective groups of S [k] = 0 and 1. In S162 and S163 to S168, as in the array maximum output operating voltage VPMA search subroutine S102, α1 is adjusted to search for the maximum power point of the DCDC converter 31. In steps S169 to S174, the maximum power point of the DCDC converter 32 is searched by adjusting α2 as in the array maximum output operation voltage VPMA search subroutine S102. Thereafter, the maximum power point search of the DCDC converter 31 by S163 to S168 and the maximum power point search of the DCDC converter 32 by 169 to S174 are repeated.

  The state of repeating the loop of S163 to S174 realizes maximum power point tracking for a group of solar cell modules with a high VPM by the DCDC converter 31 and maximum power point tracking for a group of solar cell modules with a low VPM by the DCDC converter 32. is made of. As a result, it is possible to drive at a voltage closer to the maximum output operating voltage VMP of an individual solar cell module, compared with the case where the entire array is driven by one voltage VMPA, so that the efficiency can be improved.

  As time passes, the environment changes, such as sunlight and temperature, so it is necessary to review the grouping. Therefore, after a predetermined time elapses, the process exits from the loop of S163 to S174 by the branch of S175 and ends.

  After that, the main program loop returns to the array maximum output operating voltage VPMA search subroutine S102 shown in FIG.

  FIG. 14 shows a timing chart of the voltages of the main power supply line 14 and the sub power supply line 15 generated by the control operation of the main program and the states of the switch control signals S [1] to S [n]. In the array maximum output operating voltage VPMA search subroutine S102, since the DCDC converter 31 searches for the maximum power point of the entire array, the potential VA of the main power supply line 14 gradually decreases starting from VOC and the array maximum output operating voltage VPMA. To reach. In the power differential value acquisition subroutine S103, first, the potential VA of the main power supply line 14 is increased by the voltage ΔV1. The switch control signals S [1] to S [n] sequentially become 1 in the form of pulses, during which the potential VB of the sub power supply line 15 reciprocates between the voltage VPMA and VPMA-ΔV, and timings t11 and t12. , T21, t22 ... tn1, tn2, current measurement is performed. Grouping is performed in the grouping subroutine S104. In FIG. 14, S [1] and S [n] are set to 1 as an example. In the maximum power point tracking subroutine S105, a group of solar cell modules 11 having a high maximum output operating voltage VMP is connected to the main power line 14, and a group of solar cell modules 11 having a low maximum output operating voltage VMP is connected to the sub power line 15. Since the maximum power point tracking is performed by the DCDC converters 31 and 32, respectively, the voltage of the main power line 14 is higher than VPMA, and the voltage of the sub power line 15 is lower than VPMA as the operating point voltage. After a predetermined time has elapsed, the process returns to the array maximum output operating voltage VPMA search subroutine S102, and is repeated thereafter.

  In addition, the example shown by the said Example was described in order to make invention easy to understand, and is not limited to this.

  The solar power generation system of the present invention is useful as a solar power generation system with high power generation efficiency, high reliability, and downsizing.

11, 201, 221 Solar cell module 12 Switch circuit 13, 203 Power conditioner 14 Main power supply line 15 Sub power supply line 16 Common power supply line 17, 211 Commercial system power supply 21, 22, 43, 44, 202, 208 Diode element 23 , 45, 46, 210, 226 Switching element 24 Switch control circuit 31, 32, 79, 204, 222, 223, DCDC converter 33 Electronic load device 34, 206, 227 Control device 35 Switch control signal generation circuit 36, 205, 224 Inverter 47, 48 PWM circuit 49 Smoothing capacitor 50, 213, 225 Ammeter 51, 54, 212 Voltmeter 62 Shunt resistor 63, 64 Voltage divider resistor 65 OP amplifier 72, 77 Encoder 78 Drive circuit 200 Solar cell array

Claims (8)

A plurality of solar cell modules; first and second DCDC converters;
A common power line, a main power line, and a sub power line for sending the power generated by the solar cell module to the first or second DCDC converter;
A plurality of diode elements, a plurality of switching elements, and an electronic load device for measuring voltage-current characteristics of the solar cell module;
A controller for controlling the first and second DCDC converters, the switching element, and the electronic load device;
The control device sequentially obtains a power differential value in the vicinity of the array maximum output operating voltage of the solar cell module, and based on the power differential value, a group of modules having a high maximum output operating voltage value, and a maximum output operating voltage value A photovoltaic system characterized by determining a group of low modules. The controller is
As a first step, by causing the first DCDC converter to perform a maximum power point search, an array maximum output operating voltage when all of the plurality of solar cell modules are connected in parallel is detected,
As a second step, the sub power supply line is sequentially turned on one by one while causing the first DCDC converter to generate a voltage higher than the array maximum output operating voltage on the main power supply line. In the electronic load device connected to the solar battery module, sequentially obtaining a power differential value in the vicinity of the array maximum output operating voltage of the solar cell module,
As a third step, based on the power differential value, determine a group of modules having a high maximum output operating voltage value and a group of modules having a low maximum output operating voltage value, and a group of modules having a low maximum output operating voltage value; By turning on the switching element connected to the determined solar cell module, the first DCDC converter performs a DCDC conversion operation at a high maximum output operating voltage, and the second DCDC converter is low 2. The photovoltaic power generation system according to claim 1, wherein the DCDC conversion operation is performed at the maximum output operating voltage. The output terminal of the solar cell module and the main power line are connected via the diode element, and the output terminal and the sub power line are connected via the switching element,
The main power line is connected to the first DCDC converter,
The sub power line is connected to the second DCDC converter and the electronic load device,
The photovoltaic power generation system according to claim 1 or 2, wherein the common power line is connected to the other output terminal of the solar cell module, and first and second DCDC converters. 4. The group of modules having a high maximum output operating voltage value and a group of modules having a low maximum output operating voltage value are determined according to the positive / negative polarity of the power differential value. A photovoltaic power generation system according to item 1. 5. The apparatus according to claim 1, further comprising a plurality of switch control circuits for driving the plurality of switching elements, wherein wireless communication is used for communication between the switch control circuit and the control device. The described solar power generation system. 6. The sunlight according to claim 1, wherein the output terminal of the solar cell module and the sub power line are connected via a series connection of the switching element and the diode element. Power generation system. The solar power generation system according to any one of claims 1 to 6, wherein the electronic load device is configured using a shunt regulator constant voltage circuit whose voltage can be set by the control device. The sunlight according to any one of claims 1 to 7, wherein the first and second DC / DC converters are configured by a step-up chopper circuit capable of controlling a conduction rate by the control device. Power generation system.