Solar panel power generation system

Abstract

To provide a solar panel power generation system that allows solar panels to generate power efficiently while detecting the total current generated by multiple solar panels using fewer current detection means than the number of solar panels. [Solution] The current detection means 40 of the solar panel power generation system 1 detects the total current output by multiple solar panels 20 regardless of the operating state of the power converter 13. The control circuit 100 of the solar panel power generation system 1 controls the power converter 13 to track its maximum power point based on the detection result of the voltage detection means 12 corresponding to the power converter 13 that is subject to maximum power point tracking control, and the detection result of the current detection means 40, while controlling the other power converters 13 by an arbitrary voltage command value without performing maximum power point tracking control. The control circuit 100 switches the power converter 13 subject to maximum power point tracking control at predetermined time intervals.

Description

Technical Field

[0001] The present invention relates to a solar panel power generation system.

Background Art

[0002] Conventionally, a solar power generation system is known that includes a plurality of solar panels connected in parallel to each other, a capacitor that stores the power generated by the solar panels, a number of power converters corresponding to the number of solar panels, and a switching element that switches the electrical connection between the capacitor and the power converter (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, for a plurality of solar panels connected in parallel to each other, in order to perform maximum power point tracking control, it may be necessary to provide current detection means for detecting the current output by each of the plurality of solar panels. However, when the current detection means is provided for each of the plurality of solar panels, the cost of the solar power generation system may increase. Further, in the solar power generation system disclosed in Patent Document 1, maximum power tracking control is performed based on the detection result of one current detection means that detects the total current output by the solar panels. On the other hand, in the solar power generation system disclosed in Patent Document 1, due to the noise of the detection result accompanying the switching of the electrical connection between the capacitor and the power converter, the swing width of the voltage operating point becomes large, and the solar panels may not be able to generate power efficiently.

Means for Solving the Problems

[0005] A solar panel power generation system that solves the above problems comprises a plurality of solar panels connected in parallel with each other, a power converter that converts the power generated by the solar panels into a predetermined power, wherein the power converters are a plurality of the same as the number of solar panels, an electrical load or battery that receives the predetermined power converted by the power converters, a plurality of voltage detection means for detecting the voltages output by the plurality of solar panels or the voltages output by the plurality of power converters, a current detection means for detecting the current output by the solar panels or the current output by the power converters, and the voltage detection means and the current detection means The system includes a control circuit that controls the power converter based on the detection results of the means, wherein the current detection means detects the total current output by the multiple solar panels regardless of the operating state of the power converter, and the control circuit performs the following actions based on the detection results of the voltage detection means corresponding to the power converter to be controlled for maximum power point tracking and the detection results of the current detection means, while controlling the other power converters by an arbitrary voltage command value without performing maximum power point tracking, and switching the power converter to be controlled for maximum power point tracking at predetermined time intervals. [Effects of the Invention]

[0006] According to the above configuration, the total current generated by the power generation of multiple solar panels can be detected by a number of current detection means that is fewer than the number of solar panels, while the solar panels can generate power efficiently. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a diagram used to explain a solar panel power generation system. [Figure 2] Figure 2 is a graph showing an example of the characteristics of a solar panel. [Figure 3] Figure 3 is a diagram used to explain MPPT control. [Figure 4]Figure 4 is a flowchart showing an example of the processing in a solar panel power generation system. [Figure 5] Figure 5 is a flowchart showing an example of the switching process for MPPT control. [Figure 6] Figure 6 shows an example of a modification to a solar panel power generation system. [Modes for carrying out the invention]

[0008] [Embodiment] An embodiment of the solar panel power generation system 1 will be described below with reference to the drawings. <Overall Structure> As shown in Figure 1, the solar panel power generation system 1 comprises a plurality of power conversion circuits 10, a plurality of solar panels 20, a battery 30, a current detection means 40, a capacitor 50, a voltage detection means 60, and a control circuit 100. The solar panel 20 comprises, for example, an upper solar panel 21 and a lower solar panel 22 connected in parallel to each other. The upper solar panel 21 and the lower solar panel 22 are stacked vertically on each other. Specifically, the upper solar panel 21 is stacked on the upper surface of the lower solar panel 22. The upper solar panel 21 and the lower solar panel 22 have the same transmittance, or the upper solar panel 21 has a structure in which the transmittance is higher than that of the lower solar panel 22. In other words, the solar panel 20 is a laminated solar panel in which a plurality of solar panels are stacked. In the following description, the case in which the upper solar panel 21 has a structure in which the transmittance is higher than that of the lower solar panel 22 will be described. Specifically, the solar panel 20 is a perovskite / silicon tandem solar panel in which the upper solar panel 21 is made of perovskite and the lower solar panel 22 is made of silicon. In this embodiment, the upper solar panel 21 is an example of a solar panel other than the bottom layer, and the lower solar panel 22 is an example of a solar panel for the bottom layer.

[0009] The solar panel power generation system 1 is equipped with a number of power conversion circuits 10 corresponding to the number of solar panels 20 installed in the solar panel power generation system 1. In the example shown in Figure 1, the solar panel power generation system 1 is equipped with two solar panels, solar panel 20-1 and 20-2. In this case, the solar panel power generation system 1 is equipped with two power conversion circuits 10: power conversion circuit 10-1 corresponding to solar panel 20-1 and power conversion circuit 10-2 corresponding to solar panel 20-2. In the following explanation, when solar panels 20-1 and 20-2 are not distinguished from each other, the part after the hyphen is omitted and they are simply referred to as solar panel 20. Similarly, when power conversion circuits 10-1 and 10-2 are not distinguished from each other, the part after the hyphen is omitted and they are simply referred to as power conversion circuits 10.

[0010] The power conversion circuit 10 comprises a number of configurations corresponding to the number of solar panels constituting the solar panel 20. As described above, in this example, the solar panel 20 comprises an upper solar panel 21 and a lower solar panel 22. Therefore, the power conversion circuit 10 comprises the same configuration for the corresponding upper solar panel 21 and lower solar panel 22. Specifically, the power conversion circuit 10 comprises capacitors 11a, 11b, voltage detection means 12a, 12b, and power converters 13a, 13b. The power converters 13a, 13b are, for example, step-down circuits that step down the voltage output by the solar panel 20 to a predetermined voltage. The power converter 13a comprises, for example, a switching element 14a, a diode 15a connected in antiparallel to the switching element 14a, a switching element 16a, a diode 17a connected in antiparallel to the switching element 16a, and a coil 18a. Furthermore, the power converter 13b includes, for example, a switching element 14b, a diode 15b connected in antiparallel to the switching element 14b, a switching element 16b, a diode 17b connected in antiparallel to the switching element 16b, and a coil 18b. The switching elements 14 and 16 are implemented, for example, by MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors).

[0011] The upper solar panel 21 and the lower solar panel 22 each have a positive terminal and a negative terminal, and generate electricity between the positive and negative terminals. The positive terminal of the upper solar panel 21 and the power converter 13a are connected by a positive busbar LN1a. The negative terminal of the upper solar panel 21 and the power converter 13a are connected by a negative busbar LN2a. The positive terminal of the lower solar panel 22 and the power converter 13b are connected by a positive busbar LN1b. The negative terminal of the lower solar panel 22 and the power converter 13b are connected by a negative busbar LN2b.

[0012] In this embodiment, the upper solar panel 21 of the solar panel 20 is denoted by the letter "a" at the end of its reference numeral, and the lower solar panel 22 is denoted by the letter "b" at the end of its reference numeral. In the following description, when the configuration of the upper solar panel 21 and the configuration of the lower solar panel 22 are not distinguished from each other, the reference numeral at the end will be omitted.

[0013] Capacitor 11 is connected between the positive busbar LN1 and the negative busbar LN2. Specifically, one end of capacitor 11 is connected to the positive busbar LN1, and the other end of capacitor 11 is connected to the negative busbar LN2. When switching element 14a is open, the power generated by the upper solar panel 21 charges capacitor 11a. When switching element 14a is closed, capacitor 11a discharges the stored power. When switching element 14b is open, the power generated by the lower solar panel 22 charges capacitor 11b. When switching element 14b is closed, capacitor 11b discharges the stored power.

[0014] The voltage detection means 12 is connected between the positive electrode busbar LN1 and the negative electrode busbar LN2. Specifically, one end of the voltage detection means 12 is connected to the positive electrode busbar LN1, and the other end of the voltage detection means 12 is connected to the negative electrode busbar LN2. The voltage detection means 12 detects the voltage generated across the capacitor 11. In other words, the voltage detection means 12 detects the voltage generated and output by the corresponding upper solar panel 21 or lower solar panel 22.

[0015] The switching element 14 is provided on the positive electrode busbar LN1. When the side of the positive electrode busbar LN1 closer to the solar panel 20 is defined as the upstream and the farther side as the downstream, the drain terminal of the switching element 14 is connected to the upstream side of the positive electrode busbar LN1, and the source terminal of the switching element 14 is connected to the downstream side of the positive electrode busbar LN1. The diode 15 has its cathode connected to the drain terminal of the switching element 14 and its anode connected to the source terminal of the switching element 14.

[0016] The switching element 16 is connected between the positive electrode busbar LN1 and the negative electrode busbar LN2. Specifically, the drain terminal of the switching element 16 is connected to the positive electrode busbar LN1, and the source terminal of the switching element 16 is connected to the negative electrode busbar LN2. The diode 15 has its cathode connected to the drain terminal of the switching element 16 and its anode connected to the source terminal of the switching element 16.

[0017] The coil 18 is provided on the positive electrode busbar LN1. Specifically, one end of the coil 18 is connected to the upstream side of the positive electrode busbar LN1, and the other end of the coil 18 is connected to the downstream side of the positive electrode busbar LN1.

[0018] The positive busbars LN1a-1, LN1b-1, LN1a-2, LN1b-2 are connected downstream of the power conversion circuit 10. Specifically, the other ends of the coils 18a and 18b included in the power conversion circuit 10-1 and the other ends of the coils 18a and 18b included in the power conversion circuit 10-2 are connected to the positive busbar LN3. Also, the negative busbars LN2a-1, LN2b-1, LN2a-2, LN2b-2 are connected downstream of the power conversion circuit 10. Specifically, the source terminals of the switching elements 16a, 16b included in the power conversion circuit 10-1 and the source terminals of the switching elements 16a, 16b included in the power conversion circuit 10-2 are connected to the negative busbar LN4.

[0019] One end of the battery 30 is connected to the positive busbar LN3, and the other end of the battery 30 is connected to the negative busbar LN4. The battery 30 is charged by the power generated and output by the solar panel 20 included in the solar panel power generation system 1. Also, the power charged in the battery 30 is supplied to a power supply destination not shown.

[0020] The current detection means 40 is provided on the positive busbar LN3. The current detection means 40 detects the total sum of the currents generated and output by the solar panel 20 included in the solar panel power generation system 1. In the following description, the total sum of the currents output by the solar panel 20 included in the solar panel power generation system 1 is also referred to as the total current. The current detection means 40 is realized by, for example, a shunt resistance type sensor using a resistor.

[0021] The capacitor 50 is connected between the positive busbar LN3 and the negative busbar LN4. Specifically, one end of the capacitor 50 is connected to the positive busbar LN3, and the other end of the capacitor 50 is connected to the negative busbar LN4. The capacitor 50 levels out the fluctuations in the power output from the power conversion circuit 10 included in the solar panel power generation system 1.

[0022] The voltage detection means 60 is connected between the positive busbar LN3 and the negative busbar LN4. Specifically, one end of the voltage detection means 60 is connected to the positive busbar LN3, and the other end of the voltage detection means 60 is connected to the negative busbar LN4. The voltage detection means 60 detects the voltage generated across the capacitor 50. In other words, the voltage detection means 60 detects the voltage generated and output by the solar panel 20 of the solar panel power generation system 1.

[0023] The control circuit 100 is implemented by hardware (including circuitry) such as an LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), or GPU (Graphics Processing Unit). Furthermore, some or all of the components of the control circuit 100 may be implemented by a hardware processor such as a CPU (Central Processing Unit) executing a program (software), or by the collaboration of software and hardware. The program may be pre-stored in a memory device (not shown) equipped with an SSD (Solid State Drive) or a non-transient storage medium such as an EEPROM (Electrically Erasable Programmable Read Only Memory), ROM (Read Only Memory), or RAM (Random Access Memory) provided by the control circuit 100.

[0024] The control circuit 100 controls the open / closed states of switching elements 14 and 16 to increase the power generation efficiency of the solar panel 20. Specifically, the control circuit 100 is connected to the gate terminals of switching elements 14 and 16 via a driver (not shown). The control circuit 100 controls the open / closed states by driving switching elements 14 and 16. In order to effectively extract power from the solar panel 20, the control circuit 100 performs Maximum Power Point Tracking (MPPT control) to operate the target solar panel among the upper solar panel 21 and lower solar panel 22 of the solar panel 20 at the operating point where the output power is maximum. The details of the control of the control circuit 100 will be described below.

[0025] <Regarding the control of control circuit 100> The control circuit 100 calculates the power to be charged to the battery 30 based on the detection results of the current detection means 40 and the detection results of the voltage detection means 60. The control circuit 100 calculates the voltage command values ​​for each upper solar panel 21 and each lower solar panel 22 so that the power charged to the battery 30 increases. The control circuit 100 performs PI control on the power conversion circuit 10 so that the detection result of the voltage detection means 12 matches the voltage of the voltage command value. Specifically, the control circuit 100 controls the open / closed state of the gates of the switching elements 14 and 16 by outputting gate signals for the switching elements 14 and 16 identified in conjunction with the PI control.

[0026] Figure 2 shows the output characteristics of the upper solar panel 21 and the lower solar panel 22. Specifically, waveform W11 is a PV curve showing the correspondence between the output voltage and generated power of the upper solar panel 21. Waveform W12 is a PV curve showing the correspondence between the output voltage and generated power of the lower solar panel 22. Both waveforms W11 and W12 show the output characteristics at the same predetermined solar irradiance. As shown in waveforms W11 and W12, the upper solar panel 21 has a higher maximum power point than the lower solar panel 22.

[0027] The control circuit 100 performs MPPT control on each upper solar panel 21 and each lower solar panel 22 by switching the control target at predetermined time intervals using a time-division method. Specifically, the control circuit 100 performs mountain climbing control on each upper solar panel 21 and each lower solar panel 22 using a time-division method.

[0028] Figure 3 shows the time-dependent changes in the power generated by each upper solar panel 21 and each lower solar panel 22 when mountain climbing control is performed by time-division multiplexing. Specifically, waveform W21 shows the time-dependent changes in the power generated by the upper solar panel 21-1. Waveform W24 shows the time-dependent changes in the power generated by the lower solar panel 22-1. Waveform W22 shows the time-dependent changes in the power generated by the upper solar panel 21-2. Waveform W23 shows the time-dependent changes in the power generated by the lower solar panel 22-2.

[0029] As shown in Figure 3, the control circuit 100 performs hill climbing control on the upper solar panel 21 that is being controlled. While the control circuit 100 is performing hill climbing control on the upper solar panel 21 that is being controlled, it does not perform MPPT control, including hill climbing control, on solar panels other than the one being controlled, while maintaining arbitrary voltage command values. The arbitrary voltage command value is, for example, a value that has been maintained up to that point. Specifically, as shown in waveform W21, during the period T1 in which hill climbing control is being performed on the upper solar panel 21-1, the control circuit 100 changes the voltage command value of the upper solar panel 21-1 at the timings of times ta, tb, tc, and td. More specifically, as shown in Figure 2, the control circuit 100 changes the voltage command value of the upper solar panel 21-1 to the voltage command value corresponding to point p12 at time ta, to the voltage command value corresponding to point p11 at time tb, and to the voltage command value corresponding to point p13 at time tc. The control circuit 100 then determines that the voltage command value of the maximum power point corresponds to the voltage command value of point p11, and changes it to the voltage command value corresponding to point p11 at time td. On the other hand, as shown by waveforms W22 to W24, the control circuit 100 does not change the voltage command values ​​of the solar panels other than the upper solar panel 21-1 that is being controlled during the period T1.

[0030] Similarly, as shown by waveform W24, the control circuit 100 changes the voltage command value only for the lower solar panel 22-1 during the period T2 in which it performs hill climbing control for the lower solar panel 22-1. Also, as shown by waveform W22, the control circuit 100 changes the voltage command value only for the upper solar panel 21-2 during the period T3 in which it performs hill climbing control for the upper solar panel 21-2. Furthermore, as shown by waveform W23, the control circuit 100 changes the voltage command value only for the lower solar panel 22-2 during the period T4 in which it performs hill climbing control for the lower solar panel 22-2.

[0031] Furthermore, when the control circuit 100 performs hill climbing control by time division, the current detection means 40 detects the total current output by the other solar panels 20, regardless of the operating state of the power converter 13 corresponding to the solar panel 20 being controlled. The total current detected by the current detection means 40 includes a current value corresponding to the operating state of the power converter 13 being controlled, and a current value corresponding to the fact that the solar panels 20 other than the controlled one are controlled by a predetermined voltage command value.

[0032] <Processing of control circuit 100> Figure 4 is a flowchart showing an example of the processing of the control circuit 100. The processing shown in Figure 4 is repeatedly executed at predetermined time intervals. First, the control circuit 100 determines which solar panels 20 of the solar panel power generation system 1 are to be controlled by MPPT (step S100). The control circuit 100 executes MPPT control in the order of, for example, upper solar panel 21-1, lower solar panel 22-1, upper solar panel 21-2, and lower solar panel 22-2. Note that the order of MPPT control is just an example and is not limited to this. Next, the control circuit 100 determines the voltage command value by executing hill climbing control for the solar panels 20 to be controlled by MPPT determined in step S100 (step S102). Details of the processing in step S102 will be described later.

[0033] The control circuit 100 performs PI control on the power converter 13 corresponding to the solar panel 20 to be controlled by MPPT, based on the determined voltage command value (step S104). The control circuit 100 determines whether the output power of the solar panel 20 controlled by the determined voltage command value is greater than the previous output power (step S106). The previous output power is the output power from the start of the series of processes in Figure 4 until the processing of the solar panel 20 to be controlled by MPPT, specifically steps S102 to S108. If the control circuit 100 determines that the output power has not increased (step S106; NO), it proceeds to step S110. If the control circuit 100 determines that the output power has increased (i.e., the output power is at its maximum) (step S106; YES), it stores the voltage command value determined in step S202 (step S108).

[0034] The control circuit 100 determines whether all steps of MPPT control have been completed for the solar panel 20 subject to MPPT control (step S110). For example, for the power converter 13 of a solar panel 20 subject to MPPT control, the control circuit 100 determines that all steps have been completed if the process of determining the voltage command value has been executed a predetermined number of times in step S102. The predetermined number of times is, for example, several times (specifically, about 5 times). The control circuit 100 repeatedly executes the processes from step S102 to step S110 until all steps of MPPT control have been completed (step S110; NO). If the control circuit 100 determines that all steps of MPPT control have been completed (step S110; YES), it determines the voltage command value of the power converter 13 of the solar panel 20 subject to MPPT control to the voltage command value stored in the process of step S108 (step S112). As a result, the control circuit 100 performs PI control on the power converter 13 of the solar panel 20 subject to MPPT control, based on the determined voltage command value.

[0035] Next, the control circuit 100 determines whether or not MPPT control has been performed on all of the solar panels 20 of the solar panel power generation system 1 (step S114). If the control circuit 100 determines that MPPT control has not been performed on any of the solar panels 20 (step S114; NO), it proceeds to step S100 and performs the processes in steps S100 to S112 for the next solar panel 20 to be MPPT controlled. If the control circuit 100 determines that MPPT control has been performed on all of the solar panels 20 (step S114; YES), it terminates the series of processes.

[0036] Figure 5 is a flowchart showing an example of the process in step S102 shown in Figure 4. First, the control circuit 100 updates various values ​​to be used in subsequent processes (step S200). For example, the control circuit 100 reads and updates the previous power generation value Pold, the previous voltage command value Vcmdold, and the current voltage command value Vcmd. The previous power generation value Pold and the previous voltage command value Vcmdold are values ​​that are stored and updated in the memory device through the process in step S210 or step S216, which will be described later. The current voltage command value Vcmd is updated through the process in step S212 or step S218, which will be described later, and is a value that is output in the process in step S220, which will be described later. In the series of processes in Figure 4, in the first step S200 after the process in Figure 5 for the solar panel 20 that is the target of MPPT control has started, these values ​​are not stored in the memory device. Therefore, in the first step S200 of the series of processes in Figure 4, after the processing in Figure 5 for the solar panel 20 to be MPPT controlled has started, the control circuit 100 updates the value obtained by multiplying the voltage value detected by the voltage detection means 60 and the current value detected by the current detection means 40 as the previous power generation power Pold. Also, in the first step S200 of the series of processes in Figure 4, after the processing in Figure 5 for the solar panel 20 to be MPPT controlled has started, the control circuit 100 updates the current voltage command value at the power converter 13 of the solar panel 20 to be MPPT controlled as the previous voltage command value Vcmdold and the current voltage command value Vcmd.

[0037] Next, the control circuit 100 acquires the voltage value detected by the voltage detection means 60 and the current value detected by the current detection means 40 (step S202). Based on the voltage value and current value acquired in step S202, the control circuit 100 calculates the power generation P of the solar panel 20 to be controlled by MPPT (step S204). Specifically, the control circuit 100 calculates the power generation P as the product of the voltage value and current value acquired in step S202. Next, the control circuit 100 compares the current voltage command value Vcmd, which was updated in step S200, with the previous voltage command value Vcmdold to determine whether the current voltage command value Vcmd has increased (step S206). If the current voltage command value Vcmd is greater than or equal to the previous voltage command value Vcmdold, the control circuit 100 determines that the current voltage command value Vcmd has increased.

[0038] If the control circuit 100 determines that the voltage command value Vcmd has not increased this time (step S206; NO), it determines whether the generated power P has increased or not (step S208). The control circuit 100 determines that the generated power P has increased if the generated power P is equal to or greater than the previous generated power Pold. If the control circuit 100 determines that the voltage command value Vcmd has not increased this time and that the generated power P has increased (step S208; YES), it stores the value of the current voltage command value Vcmd as the previous voltage command value Vcmdold in the memory device, and also stores the value of the generated power P as the previous generated power Pold in the memory device (step S210). Next, the control circuit 100 determines the value obtained by subtracting a predetermined voltage ΔV from the previous voltage command value Vcmdold as the current voltage command value Vcmd (step S212), and proceeds to step S220. The predetermined voltage ΔV is, for example, a voltage of a few volts, which is a voltage appropriate for the degree of change required to modify the voltage command value in order to identify the maximum power point. If the control circuit 100 determines that the voltage command value Vcmd has increased (step S206; YES), it determines whether the generated power P has increased (step S214). If the control circuit 100 determines that the voltage command value Vcmd has increased and that the generated power P has not increased (step S214; NO), it proceeds to step S210.

[0039] If the control circuit 100 determines that the voltage command value Vcmd has not increased and that the generated power P has not increased (step S208; NO), it stores the current voltage command value Vcmd in the memory as the previous voltage command value Vcmdold and the generated power P as the previous generated power Pold (step S216). Next, the control circuit 100 determines the current voltage command value Vcmd by adding a predetermined voltage ΔV to the previous voltage command value Vcmdold (step S218) and proceeds to step S220. If the control circuit 100 determines that the current voltage command value Vcmd has increased and that the generated power P has increased (step S214; YES), it proceeds to step S216. The control circuit 100 outputs the determined value (step S220). Specifically, the control circuit 100 outputs the current voltage command value Vcmd determined in step S212 or step S218 (step S220), and terminates the series of processes. The control circuit 100 performs PI control on the power conversion circuit 10 so that the detection result of the voltage detection means 12 matches the voltage of the output current voltage command value Vcmd.

[0040] [Effect of the Embodiment] The operation of the solar panel power generation system 1 will be explained below. The control circuit 100 identifies the voltage command value that results in the maximum power point by repeatedly changing the voltage command value of the power converter 13 of the solar panel 20 subject to MPPT control a predetermined number of times, as shown in the processes of Figures 4 and 5. For example, in the first step S200 after the processing of the upper solar panel 21-1 subject to MPPT control in Figure 5 has started, the control circuit 100 sets the voltage command value Vcmd to correspond to point p11 shown in waveform W11 of Figure 2. In this case, as a result of the first series of processes in Figure 5, the control circuit 100 outputs the voltage command value Vcmd to correspond to point p12 in the process of step S220. As shown in Figure 2, the output power of the upper solar panel 21-1 corresponding to point p12 is lower than the output power corresponding to point p11. As a result, the generated power P, which is the product of the voltage value detected by the voltage detection means 60 and the current value detected by the current detection means 40, becomes lower. Furthermore, as described above, the control circuit 100 does not change the voltage command value for solar panels 20 other than the upper solar panel 21-1 that is subject to MPPT control. Therefore, the change in generated power P, which is the product of the voltage value detected by the voltage detection means 60 and the current value detected by the current detection means 40, can be said to be a change in generated power P due to the output characteristics of the upper solar panel 21-1 that is subject to MPPT control.

[0041] Therefore, in step S106 of Figure 4, the control circuit 100 does not determine that the output power is increasing and does not store the voltage command value corresponding to point p12. Next, in the second series of processes shown in Figure 5, the control circuit 100 outputs the voltage command value corresponding to point p11 as the current voltage command value Vcmd in step S220. As shown in Figure 2, the output power of the upper solar panel 21-1 corresponding to point p11 is higher than the output power corresponding to point p12. Therefore, in step S106 of Figure 4, the control circuit 100 determines that the output power is increasing and stores the voltage command value corresponding to point p11. If this process is repeated a predetermined number of times (for example, 5 times), the changes in the voltage command value will be point p12 in the first time, point p11 in the second time, point p13 in the third time, point p11 in the fourth time, and point p12 in the fifth time. Therefore, the control circuit 100 identifies the voltage command value corresponding to point p11 as the voltage command value that will be the point of maximum power. The process by which the control circuit 100 identifies the voltage command value that results in the maximum power point for the lower solar panel 22 is a transition that occurs at points p21 to p23 shown in waveform W12 of Figure 2, and is the same as the transition at points p11 to p13 described above, so the explanation is omitted.

[0042] [Effects of the Embodiment] According to the above embodiment, the following effects can be obtained. (1) The solar panel power generation system 1 comprises a plurality of solar panels 20 connected in parallel to each other, a plurality of power converters 13 corresponding to the number of solar panels 20, a battery 30, a plurality of voltage detection means 12, a current detection means 40, and a control circuit 100. The power converters 13 convert the power generated by the solar panels 20 into predetermined power. The battery 30 receives the predetermined power converted by the power converters 13. The plurality of voltage detection means 12 each detect the voltage output by the plurality of solar panels 20. The current detection means 40 detects the current output by the power converters 13. Specifically, the current detection means 40 detects the total current output by the plurality of solar panels 20 regardless of the operating state of the power converters 13. The control circuit 100 controls the power converters 13 based on the detection results of the voltage detection means 12 and the current detection means 40.

[0043] The control circuit 100 controls the MPPT-controlled power converter 13 based on the detection result of the voltage detection means 12 corresponding to the MPPT-controlled power converter 13 among the multiple voltage detection means 12, and the detection result of the current detection means 40, while controlling the other power converters 13 by an arbitrary voltage command value without performing MPPT control. The control circuit 100 also switches the MPPT-controlled power converters 13 at predetermined time intervals.

[0044] In this case, to perform MPPT control on multiple solar panels connected in parallel, it may be necessary to equip each of the solar panels with a current sensor to detect the current output by each panel. However, equipping each solar panel with a current sensor can increase the cost of the solar power generation system. On the other hand, to suppress the increase in cost, a single current sensor that detects the total current output by the solar panels may be installed on the secondary side of the power converter. In this case, generally, solar panels other than those subject to MPPT control are not electrically connected to the power converter. As a result, only the solar panels subject to MPPT control are connected to the current sensor. Therefore, the current sensor detects only the current output by the solar panels subject to MPPT control.

[0045] However, while the MPPT-controlled solar panel is undergoing MPPT control, the electrical connection to the power converter is disconnected, causing the voltage of the capacitor connected in parallel with other solar panels to rise. Consequently, when the MPPT-controlled solar panel is next connected to the power converter, the apparent voltage output by that solar panel rises. In this case, the detection result of the increased voltage becomes noise, making it difficult to perform MPPT control properly.

[0046] According to the solar panel power generation system 1 of this embodiment, solar panels 20 other than those subject to MPPT control are not electrically disconnected from the power converter 13 regardless of the operating state of the power converter 13 of the solar panel 20 subject to MPPT control. Therefore, it is possible to suppress the voltage rise of the capacitor 11 corresponding to the solar panels 20 other than those subject to MPPT control. Accordingly, the solar panel power generation system 1 of this embodiment allows the solar panels 20 to generate power efficiently while detecting the total current generated by the multiple solar panels 20 using a number of current detection means 40 that is fewer than the number of solar panels 20 provided in the solar panel power generation system 1.

[0047] (2) The control circuit 100 performs MPPT control on each of the solar panels 20 of the solar panel power generation system 1. With this configuration, the solar panel power generation system 1 can determine an appropriate voltage command value for each solar panel 20, enabling the solar panels 20 to generate power efficiently.

[0048] (3) The current detection means 40 is provided between the multiple power converters 13 and the battery 30 and detects the total current output by the multiple power converters 13 as the total current output by the solar panel 20.

[0049] In contrast, a current detection means 40 may be provided between each capacitor 11 and the power converter 13. Specifically, the other end of each capacitor 11 and the source terminal of each switching element 16 are not electrically connected, the other ends of each capacitor 11 are shared, and the source terminals of each switching element 16 are shared. One end of the current detection means 40 is connected to the connection point where the other ends of each capacitor 11 are shared, and the other end of the current detection means 40 is connected to the connection point where the source terminals of each switching element 16 are shared. In this case, if the switching element 14 of each power converter 13 is controlled to the open state, a closed loop is formed between the solar panel 20 and the capacitor 11, causing the voltage of the capacitor 11 to rise.

[0050] The current detection means 40 in this embodiment is provided between the multiple power converters 13 and the battery 30, thereby suppressing an increase in the voltage of the capacitor 11 regardless of the operating state of the power converters 13. Therefore, the solar panel power generation system 1 of this embodiment allows the solar panel 20 to generate power efficiently.

[0051] Each of the above embodiments may be modified as follows. Furthermore, the above embodiments and the following alternative examples may be combined with each other to the extent that they do not contradict the technical standards. • The control circuit 100 has been described in the case where it performs MPPT control on each of the solar panels 20 of the solar panel power generation system 1, but it is not limited to this. The control circuit 100 may also perform MPPT control on other solar panels 20 based on the results of MPPT control for which the output characteristics match.

[0052] Specifically, the control circuit 100 controls the upper solar panel 21-1 and the lower solar panel 22-1 of solar panel 20, respectively, while switching the target of MPPT control at predetermined time intervals. In other words, the control circuit 100 controls the power converter 13a corresponding to the upper solar panel 21-1 and the power converter 13b corresponding to the lower solar panel 22-1, respectively, while switching the target of MPPT control at predetermined time intervals. Furthermore, based on the results of the upper solar panel 21-1, the control circuit 100 determines the voltage command value of the upper solar panel 21 (in this case, the upper solar panel 21-2) of the other solar panel 20, and based on the results of the lower solar panel 22-1, it determines the voltage command value of the lower solar panel 22 (in this case, the lower solar panel 22-2) of the other solar panel 20.

[0053] With this configuration, the solar panel power generation system 1 can perform MPPT control in a shorter time compared to the case where each of the solar panels 20 equipped with the solar panel power generation system 1 is subject to MPPT control.

[0054] • The above description explains the case where the current detection means 40 is provided between the power converter 13 and the capacitor 50, but it is not limited to this. The current detection means 40 may also be provided on the positive busbar LN3 between the capacitor 50 and the battery 30.

[0055] • The above description explains the case where the power converter 13 is a step-down circuit, but it is not limited to this. The power converter 13 may also be a step-up circuit. In this case, as shown in Figure 6, the power converter 13 has a coil 18 at the position of the switching element 14 and diode 15 shown in Figure 1. Also in this case, as shown in Figure 6, the power converter 13 has a diode at the position of the coil 18 shown in Figure 1. In this case, the anode of the diode is connected to the upstream side of the positive bus LN1, and the cathode is connected to the downstream side of the positive bus LN1. Also in this case, the other ends of each capacitor 11 are common, and the source terminals of each switching element 16 are common. Furthermore, the connection point where the other ends of each capacitor 11 are common is connected to the connection point where the source terminals of each switching element 16 are common.

[0056] In the configuration described above, the current detection means 40 may be implemented by a through-type sensor provided at a location where the positive terminals of each solar panel 20 are grouped together, as shown in Figure 6. In this case, the current detection means 40 detects the total current output by each solar panel 20. On the other hand, when the current detection means 40 is implemented by a shunt resistor, one end of the current detection means 40 is connected to a common connection point where the other ends of each capacitor 11 are shared, and the other end of the current detection means 40 is connected to a common connection point where the source terminals of each switching element 16 are shared. With this configuration, it is possible to suppress the voltage of the capacitor 11 corresponding to the solar panel 20 other than the solar panel 20 being controlled by MPPT. Therefore, the solar panel power generation system 1 can efficiently generate power while detecting the total current generated by the multiple solar panels 20 using fewer current detection means 40 than the number of solar panels 20 provided in the solar panel power generation system 1.

[0057] Furthermore, the current detection means 40 may be provided between the connection point where the cathodes of the diodes are shared and the connection point between the positive bus LN3 and one end of the capacitor 50. Also, even in the case of a boost circuit, the current detection means 40 may be provided on the positive bus LN3 between the capacitor 50 and the battery 30. In such a configuration, the same effects as described above can be obtained.

[0058] • As described above, in the first step S200 after the processing shown in Figure 5 for the solar panel 20 subject to MPPT control begins, the control circuit 100 updates the value obtained by multiplying the voltage value detected by the voltage detection means 60 and the current value detected by the current detection means 40 as the previous power generation Pold at the timing of step S200. However, it is not limited to this. The control circuit 100 may update the previous power generation Pold by, for example, a predetermined initial value of the previous power generation Pold. In this case, the initial value of the previous power generation Pold may be the average power generation of the solar panel 20 subject to MPPT control at a predetermined solar radiation intensity, and may be changed as appropriate depending on the timing of the MPPT control and the surrounding environment.

[0059] • In the above description, the control circuit 100 updates the current voltage command value at the power converter 13 of the solar panel 20 subject to MPPT control as the previous voltage command value Vcmdold and the current voltage command value Vcmd in the first step S200 after the processing of the solar panel 20 subject to MPPT control begins. However, it is not limited to this. The control circuit 100 may update the previous voltage command value Vcmdold using predetermined initial values ​​for the previous voltage command value Vcmdold and the current voltage command value Vcmd. In this case, the initial value of the previous voltage command value Vcmdold may be a voltage command value such that the solar panel 20 subject to MPPT control generates power at the maximum power point at a predetermined solar irradiance, and may be changed as appropriate depending on the timing of MPPT control and the surrounding environment.

[0060] The current detection means 40 may be implemented by a through-hole method using electromagnetics or light. The voltage detection means 12 may be located furthest downstream of the power converter 13. In this case, the voltage detection means 12 detects the voltage output by each of the multiple power converters 13.

[0061] The solar panel 20 may consist of multiple upper solar panels 21 and lower solar panels 22 stacked vertically on top of each other. In this case, the multiple upper solar panels 21 are examples of solar panels other than the bottom layer, and the lower solar panels 22 are examples of the bottom layer solar panels. Furthermore, the multiple upper solar panels 21 of the solar panel 20 may be realized with structures that have different transmittances, as long as each has a higher transmittance than the lower solar panels 22. In this case, it is preferable that the upper solar panels 21 with higher transmittances are stacked higher vertically.

[0062] Furthermore, the control circuit 100 may perform MPPT control on one of the multiple upper solar panels 21 stacked as the solar panel 20, or it may perform MPPT control on each of the upper solar panels 21. When the control circuit 100 performs MPPT control on one upper solar panel 21, it performs MPPT control on the upper solar panel 21 among the multiple upper solar panels 21 that has the smallest difference in output characteristics from the other upper solar panels 21. The control circuit 100 then applies the voltage command value specified for the upper solar panel 21 to the other upper solar panels 21. On the other hand, when the control circuit 100 performs MPPT control on each of the upper solar panels 21, it executes MPPT control based on the output characteristics of each upper solar panel 21.

[0063] The solar panel power generation system 1 was equipped with a battery 30 that received power converted by the power converter 13. The solar panel power generation system 1 may also be equipped with an electrical load such as a capacitor instead of the battery 30. [Explanation of symbols]

[0064] 1...Solar panel power generation system, 10, 10-1, 10-2...Power conversion circuit, 11, 11a, 11b, 50...Capacitor, 12, 12a, 12b, 60...Voltage detection means, 13, 13a, 13b...Power converter, 20, 20-1, 20-2...Solar panel, 21, 21-1, 21-2...Upper solar panel, 22, 22-1, 22-2...Lower solar panel, 30...Battery, 40...Current detection means, 100...Control circuit.

Claims

1. A solar panel power generation system comprising: a plurality of solar panels connected in parallel to each other; a power converter that converts the power generated by the solar panels into a predetermined power, wherein the power converters correspond to the number of solar panels; an electrical load or battery that receives the predetermined power converted by the power converters; a plurality of voltage detection means for detecting the voltages output by the plurality of solar panels or the voltages output by the plurality of power converters; current detection means for detecting the current output by the solar panels or the current output by the power converters; and a control circuit that controls the power converters based on the detection results of the voltage detection means and the current detection means, The current detection means detects the total current output by the multiple solar panels, regardless of the operating state of the power converter. The aforementioned control circuit is Based on the detection result of the voltage detection means corresponding to the power converter to be controlled for maximum power point tracking, and the detection result of the current detection means, the power converter is controlled for maximum power point tracking, while other power converters are not controlled for maximum power point tracking and are controlled by an arbitrary voltage command value. The power converter subject to maximum power point tracking control is switched at predetermined time intervals. Solar panel power generation system.

2. The multiple solar panels constitute a stacked solar panel arranged vertically on top of each other, and among the solar panels constituting the stacked solar panel, the solar panels other than the bottom layer have a structure with a transmittance equivalent to or higher than that of the bottom layer solar panel. The aforementioned control circuit is The power converter is switched at predetermined time intervals, with the solar panels other than the bottommost layer and the bottommost layer of the aforementioned plurality of stacked solar panels being the targets for the maximum power point tracking control, respectively. The solar panel power generation system according to claim 1.

3. The aforementioned control circuit is The power converter is switched at predetermined time intervals, with each of the multiple solar panels being the target of the maximum power point tracking control. The solar panel power generation system according to claim 1.

4. The current detection means is provided between the power converter and the electrical load or the battery, and detects the total current output by the multiple power converters as the total current output by the solar panel. The solar panel power generation system according to claim 1.

5. The power converter is a voltage boosting circuit, The current detection means is a through-type current detection means provided between the solar panel and the power converter, and detects the total current output by the multiple solar panels. The solar panel power generation system according to claim 1.

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