Solar panel power generation system

Abstract

To provide a solar panel power generation system that can suppress the decrease in power generation efficiency of solar panels while identifying an appropriate voltage operating point with high power generation efficiency through scan control. [Solution] The control unit 110 controls the power converter 13a corresponding to the upper solar panel 21 to perform scan control to estimate the third voltage operating point, which is the voltage operating point with high power generation efficiency, for the upper solar panel 21, among the multiple solar panels of the upper solar panel 21 and the lower solar panel 22. The control unit 110 also estimates the fourth voltage operating point, which has high power generation efficiency, for the lower solar panel 22, taking into account the third voltage operating point and the transmittance. The control unit 110 also controls the power converters 13a and 13b to perform MPPT control based on the estimated third and fourth voltage operating points.

Description

Technical Field

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

Background Art

[0002] Conventionally, for a plurality of solar panels connected in parallel to each other, in order to estimate an appropriate voltage operating point with high power generation efficiency, a technique of sequentially performing scan control for each solar panel is known (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] However, in the technique disclosed in Patent Document 1, while performing scan control for each solar panel, power generation of the solar panel at an appropriate voltage operating point with high power generation efficiency cannot be executed. For this reason, the power generation efficiency of the solar panel may decrease.

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 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; a current detection means for detecting the current output by the solar panels or the current output by the power converters; and a control unit that controls the power converters based on the detection results of the voltage detection means and the current detection means, wherein the plurality of solar panels constitute a plurality of stacked solar panels stacked vertically on each other, and among the solar panels constituting the stacked solar panels, the bottom The solar panels other than the layer have the same transmittance as the bottom layer solar panel, or a structure with higher transmittance than the bottom layer solar panel. The control unit performs the following actions: it controls the power converter corresponding to the solar panels to be controlled to perform scan control to estimate the voltage operating point with high power generation efficiency for some of the solar panels to be controlled other than the bottom layer among the plurality of solar panels; it estimates the voltage operating point for other solar panels other than the solar panels to be controlled among the stacked solar panels including the solar panels to be controlled, reflecting the estimation result of the voltage operating point of the solar panels to be controlled and the transmittance; and it controls the power converter corresponding to the solar panels to perform maximum power point tracking control based on the estimation result of the voltage operating point. [Effects of the Invention]

[0006] According to the above configuration, it is possible to identify an appropriate voltage operating point with high power generation efficiency through scan control while suppressing a decrease in the power generation efficiency of the solar panel. [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 flowchart showing an example of a series of processes performed by the control unit. [Figure 4] Figure 4 is a flowchart showing an example of the scan control process of the control unit. [Figure 5] Figure 5 is a flowchart showing an example of the scan control process of the control unit. [Figure 6] Figure 6 is a graph showing the first solar radiation intensity. [Figure 7] Figure 7 is a graph showing the second solar radiation intensity. [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 power conversion circuit 10, a solar panel 20, a battery 30, a current detection means 40, a capacitor 50, a voltage detection means 60, and a control device 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 top of 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 multiple solar panels are stacked. In the following description, the case in which the upper solar panel 21 and the lower solar panel 22 have a structure in which the transmittance is the same will be described. Specifically, the solar panel 20 is a tandem solar panel in which the upper solar panel 21 and the lower solar panel 22 are made of silicon, or the upper solar panel 21 and the lower solar panel 22 are made of perovskite. 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 of the bottom layer.

[0009] The solar panel power generation system 1 includes 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 assumed to have one solar panel 20. In this case, the solar panel power generation system 1 includes one power conversion circuit 10 corresponding to the solar panel 20.

[0010] The power conversion circuit 10 has configurations corresponding to the number of solar panels that make up 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 has 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 busbar LN1 and the negative busbar LN2. Specifically, one end of the voltage detection means 12 is connected to the positive busbar LN1, and the other end of the voltage detection means 12 is connected to the negative 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 bus LN1. When the side of the positive bus LN1 closer to the solar panel 20 is considered upstream and the side further away is considered downstream, the drain terminal of the switching element 14 is connected to the upstream side of the positive bus LN1, and the source terminal of the switching element 14 is connected to the downstream side of the positive bus LN1. The cathode of the diode 15 is connected to the drain terminal of the switching element 14, and the anode is connected to the source terminal of the switching element 14.

[0016] The switching element 16 is connected between the positive bus bar LN1 and the negative bus bar LN2. Specifically, the drain terminal of the switching element 16 is connected to the positive bus bar LN1, and the source terminal of the switching element 16 is connected to the negative bus bar 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 bus bar LN1. Specifically, one end of the coil 18 is connected to the upstream side of the positive bus bar LN1, and the other end of the coil 18 is connected to the downstream side of the positive bus bar LN1.

[0018] The positive bus bars LN1a and LN1b 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 and the positive bus bar LN3 are connected. Also, the negative bus bars LN2a and LN2b are connected downstream of the power conversion circuit 10. Specifically, the source terminals of the switching elements 16a and 16b included in the power conversion circuit 10 and the negative bus bar LN4 are connected.

[0019] One end of the battery 30 is connected to the positive bus bar LN3, and the other end of the battery 30 is connected to the negative bus bar LN4. The battery 30 is charged by receiving 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 bus bar LN3. The current detection means 40 detects the total current generated and output by the solar panel 20 included in the solar panel power generation system 1. In the following description, the total current generated and 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] Capacitor 50 is connected between the positive busbar LN3 and the negative busbar LN4. Specifically, one end of capacitor 50 is connected to the positive busbar LN3, and the other end of capacitor 50 is connected to the negative busbar LN4. Capacitor 50 smooths out fluctuations in the power output from the power conversion circuit 10 of 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 device 100 comprises a control unit 110 and a storage unit 150. The control unit 110 is implemented, for example, by a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Some or all of the components of the control unit 110 may be implemented by hardware (including circuits) such as an LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), or GPU (Graphics Processing Unit), or by the cooperation of software and hardware. The program may be stored in advance in a storage device (not shown) equipped with a non-transient storage medium such as an HDD (Hard Disk Drive) or flash memory provided by the storage unit 150.

[0024] The control device 100 controls the open / closed state of switching elements 14 and 16 so as to increase the power generation efficiency of the solar panel 20. Specifically, the control device 100 is connected to the gate terminals of switching elements 14 and 16 via a driver (not shown). The control device 100 controls the open / closed state by driving switching elements 14 and 16. In order to effectively extract power from the solar panel 20, the control device 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 (maximum power point) where the output power is maximum. The details of the control of the control device 100 will be described below.

[0025] <Regarding the control of the control unit 110> The control unit 110 performs hill climbing control on the solar panel 20 at predetermined time intervals. The control unit 110 also performs scan control on the solar panels 20 other than the lower solar panel 22 (i.e., the upper solar panel 21) at predetermined time intervals. The control unit 110 does not perform scan control on the lower solar panel 22. Based on the maximum power point identified by the scan control performed on the upper solar panel 21 and the transmittance of the upper solar panel 21, the control unit 110 estimates the maximum power point of the lower solar panel 22, which is not subjected to scan 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] In Figure 2, Vu' represents the voltage operating point of the upper solar panel 21 at its maximum power point when mountain climbing control has been performed in advance (hereinafter referred to as the first voltage operating point Vu'), and Vd' represents the voltage operating point of the lower solar panel 22 at its maximum power point when mountain climbing control has been performed in advance (hereinafter referred to as the second voltage operating point Vd'). The information indicating the first voltage operating point Vu' and the second voltage operating point Vd' is stored in the storage unit 150 in advance.

[0028] The control unit 110 estimates the voltage operating point of the maximum power point of the lower solar panel 22 (hereinafter referred to as the fourth voltage operating point Vd) when scan control is not performed, based on the voltage operating point of the upper solar panel 21 (hereinafter referred to as the third voltage operating point Vu) when scan control is performed. Specifically, the control unit 110 estimates the value obtained by multiplying the third voltage operating point Vu by a coefficient λu as the fourth voltage operating point Vd. In this case, the fourth voltage operating point Vd is expressed by the following equation (1).

[0029] Vd = Vu × λu ... (1) The coefficient λu is a coefficient used to reflect the transmittance of the upper solar panel 21, based on its relationship with the waveforms W11 and W12 described above. The coefficient λu is expressed by the following equation (2).

[0030] λu = |Vu' - Vd'| / Vu' ... (2) Based on the estimation results of the scan control, the control unit 110 performs hill-climbing control on the upper solar panel 21 to identify the maximum power point near the third voltage operating point Vu. The control unit 110 also performs hill-climbing control on the lower solar panel 22 to identify the maximum power point near the estimated fourth voltage operating point Vd, based on the estimation results of the scan control. Based on the voltage command value at the maximum power point identified by the hill-climbing control and the detection results of the multiple voltage detection means 12, the control unit 110 performs PI control on the power conversion circuit 10. Specifically, the control unit 110 performs PI control on the power converter 13a so that the detection result of the voltage detection means 12a matches the identified voltage command value of the upper solar panel 21. The control unit 110 also performs PI control on the power converter 13b so that the detection result of the voltage detection means 12b matches the identified voltage command value of the lower solar panel 22. The control unit 110 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.

[0031] <Processing by control device 100> Figure 3 is a flowchart showing an example of the processing of the control device 100. The processing shown in Figure 3 is executed, for example, when the control device 100 is started up or when the maximum power point is identified. First, the control unit 110 starts counting a timer that measures the execution period of scan control (step S100). Next, the control unit 110 determines whether the timer count is greater than or equal to a predetermined count T0 (step S102). The predetermined count T0 is, for example, a value that indicates a typical period for which the solar panel 20 requires scan control, and is a value that indicates a time of, for example, several minutes to several tens of minutes.

[0032] If the control unit 110 determines that the timer count is not equal to or greater than a predetermined count T0 (step S102; NO), it performs hill climbing control of the solar panel 20 (step S104) and proceeds to step S100. Specifically, the control unit 110 performs hill climbing control on the upper solar panel 21 and the lower solar panel 22, respectively, to identify the voltage command value of the maximum power point. Based on the voltage command value near the maximum power point of the upper solar panel 21 identified by the scan control described later, the control unit 110 performs hill climbing control on the upper solar panel 21. Also, based on the voltage command value near the maximum power point of the lower solar panel 22 estimated by the scan control described later, the control unit 110 performs hill climbing control on the lower solar panel 22. Then, the control unit 110 performs PI control on the power conversion circuit 10 so that the detection result of the voltage detection means 12 matches the voltage command value identified by the hill climbing control.

[0033] If the control unit 110 determines that the timer count is equal to or greater than a predetermined count T0 (step S102; YES), it stores information indicating the current voltage command value of the upper solar panel 21 and the current voltage command value of the lower solar panel 22 in the storage unit 150 (step S106). Next, the control unit 110 performs scan control on the upper solar panel 21 (step S108). Details of the scan control will be described later. While the control unit 110 is performing scan control on the upper solar panel 21, it controls the power converter 13b to maintain the voltage command value of the lower solar panel 22 based on the information stored in the storage unit 150. In other words, while the control unit 110 is performing scan control on the upper solar panel 21, it does not perform scan control on the lower solar panel 22. Next, the control unit 110 clears (initializes) the timer count (step S110) and proceeds to step S104. The control unit 110 repeatedly executes the processes from steps S100 to S110.

[0034] Figure 4 is a flowchart showing an example of the process in step S108 shown in Figure 3. First, the control unit 110 determines whether or not it is the timing when scan control has started (step S200). In the series of processes shown in Figure 4, if it is the first step S200, the control unit 110 determines that it is the timing when scan control has started. If the control unit 110 determines that it is the timing when scan control has started (step S200; YES), it sets the duty cycle D of the switching element 14a to the initial duty cycle value D0 (step S202) and proceeds to step S204. The initial value D0 is, for example, the duty cycle D corresponding to the voltage command value of the upper solar panel 21 stored in the storage unit 150 in the process of step S106. If the control unit 110 determines that it is not the timing when scan control has started (step S200; NO), it acquires various values ​​(step S204). Specifically, the control unit 110 acquires the detection result of the voltage detection means 60 and the detection result of the current detection means 40. Next, the control unit 110 calculates the current power PP (step S206). The current power PP is, for example, the product of the voltage value detected by the voltage detection means 60 and the current value detected by the current detection means 40.

[0035] Next, the control unit 110 compares the current power PP calculated in step S206 with the maximum power MP to determine whether the current power PP is greater than the maximum power MP (step S208). The maximum power MP is updated in step S210, which will be described later. The value of the maximum power MP in the first step S208 (i.e., the initial value of the maximum power MP) is, for example, the current power PP calculated in the preceding step S206. If the control unit 110 determines that the current power PP is greater than the maximum power MP (step S208; YES), it updates the value of the current power PP as the maximum power MP (step S210). Next, the control unit 110 updates the current duty cycle D as the maximum power duty cycle MD (step S212) and proceeds to step S214.

[0036] If the control unit 110 determines that the current power PP is not greater than the maximum power MP (step S208; NO), it determines whether the value obtained by subtracting the current power PP from the previous power BP is greater than a predetermined power difference ΔP (step S214). The predetermined power difference ΔP is a value used, for example, to identify the maximum point of the PV curve that shows the correspondence between the output voltage and the generated power, and is a value corresponding to the slope of the curve near the maximum point of the PV curve. The previous power BP is updated in the process of step S228, which will be described later. In the first process of step S214, the value of the previous power BP (i.e., the initial value of the previous power BP) is the power value immediately before the start of scan control. If the control unit 110 determines that the value obtained by subtracting the current power PP from the previous power BP is not greater than a predetermined power difference ΔP (step S214; NO), it updates the duty cycle D to the value obtained by subtracting a predetermined duty cycle ΔD from the current duty cycle D (step S216). As a result, the duty cycle D becomes smaller than the current duty cycle D, and the voltage command value for the switching element 14a increases.

[0037] If the control unit 110 determines that the value obtained by subtracting the current power PP from the previous power BP is greater than a predetermined power difference ΔP (step S214; YES), it determines whether the value of the flag is 0 (step S218). The value of the flag can be 0 or 1. The flag is set to 0 at the start of the series of processes shown in Figure 4 and updated to 1 in step S224, which will be described later. If the control unit 110 determines that the value of the flag is 0 (step S218; YES), it determines whether the duty cycle D is 0 [%] (step S220). If the control unit 110 determines that the duty cycle D is 0 [%] (step S220; YES), it updates the duty cycle D to the maximum duty cycle Dmx (step S222). The maximum duty cycle Dmx is a value that represents 100 [%]. When the duty cycle D is set to the maximum duty cycle Dmx, the switching element 14a is closed, and the detection result of the voltage detection means 60 matches the voltage across the battery 30 (i.e., the battery voltage). Next, the control unit 110 updates the value of the flag to 1 (step S224) and proceeds to step S226.

[0038] If the control unit 110 determines that the flag value is not 0 (step S218; NO), or if it determines that the duty cycle D is not 0 [%] (step S220; NO), it proceeds to step S226. The control unit 110 updates the duty cycle D by subtracting twice the predetermined duty cycle ΔD from the current duty cycle D (step S226). As a result, the duty cycle D becomes smaller than the current duty cycle D, and the voltage command value of the switching element 14a increases. The degree of increase in the voltage command value of the switching element 14a that occurs with the processing in step S226 is twice the degree of increase that occurs with the processing in step S216. Next, the control unit 110 updates the current power PP as the previous power BP (step S228).

[0039] Next, the control unit 110 determines whether the value of the flag is 1 or not (step S230). If the value of the flag is not 1 but 0 (step S230; NO), the control unit 110 proceeds to step S200. The control unit 110 repeatedly executes the processes from steps S200 to S228 until the value of the flag becomes 1. If the value of the flag is 1 (step S230; YES), the control unit 110 determines whether the duty cycle D is greater than the initial value D0 (step S232). If the duty cycle D is greater than the initial value D0 (step S232; YES), the control unit 110 proceeds to step S200. The control unit 110 repeatedly executes the processes from steps S200 to S228 until the duty cycle D matches the initial value D0 or the duty cycle D becomes less than the initial value D0.

[0040] If the duty cycle D matches the initial value D0, or if the duty cycle D is less than or equal to the initial value D0 (step S232; NO), the control unit 110 estimates the voltage command value corresponding to the duty cycle D as the voltage command value for the switching element 14a at the maximum power point of the upper solar panel 21 (step S234). Next, the control unit 110 estimates the fourth voltage operating point Vd based on the third voltage operating point Vu (step S236). In this case, the third voltage operating point Vu is the voltage operating point when the switching element 14a is driven by the voltage command value converted in step S234, and is a voltage operating point with high power generation efficiency. As described above, the fourth voltage operating point Vd is calculated based on the information indicating the first voltage operating point Vu' and the second voltage operating point Vd' stored in the storage unit 150, and the third voltage operating point Vu. The control unit 110 estimates the voltage command value based on the calculated fourth voltage operating point Vd as the voltage operating point of the switching element 14b at the maximum power point of the lower solar panel 22. Based on the estimated fourth voltage operating point Vd, the control unit 110 estimates the voltage command value of the lower solar panel 22 at the maximum power point (step S238) and completes the series of processes.

[0041] [Effect of the Embodiment] The operation of the solar panel power generation system 1 will be explained below. The control unit 110 performs scan control on the upper solar panel 21 through the processes shown in Figures 4 and 5. Specifically, the control unit 110 performs control in four stages, from the first to the fourth stage. The first stage is the process of gradually decreasing the duty cycle D from the duty cycle D corresponding to the voltage command value immediately before performing the scan control until the duty cycle D becomes 0[%], while bringing the upper solar panel 21 to open potential. The first stage is the process of steps S200~S216, S228, S230~S232 in the processes shown in Figures 4 and 5. The second stage is the process of setting the duty cycle D to 100[%] when the duty cycle D becomes 0[%], bringing the upper solar panel 21 to battery potential. The second stage is the process of steps S200~S214, S218~S232 in the processes shown in Figures 4 and 5.

[0042] The third stage is the process of gradually increasing the duty cycle D from 100% to the duty cycle D corresponding to the voltage command value immediately before executing the scan control, until the scan control is terminated. The third stage corresponds to steps SS200~S214, S218~S220, and S226~S232 in the processes shown in Figures 4 and 5. The fourth stage is the process of converting the duty cycle D that maximizes the identified generated power into the voltage command value of the switching element 14a, and estimating the voltage command value of the lower solar panel 22 using a correction value. The fourth stage corresponds to steps S234~S238 in the processes shown in Figures 4 and 5.

[0043] As a result, the control unit 110 performs scan control only on the upper solar panel 21. On the other hand, the control unit 110 also determines a voltage command value for the lower solar panel 22, taking into account the results of the scan control.

[0044] [Effects of the Embodiment] According to the above embodiment, the following effects can be obtained. (1) The control unit 110 controls the power converter 13a corresponding to the upper solar panel 21 to perform scan control to estimate the third voltage operating point Vu, which is the voltage operating point with high power generation efficiency, for the upper solar panel 21, among the multiple solar panels of the upper solar panel 21 and the lower solar panel 22. The control unit 110 also estimates the fourth voltage operating point Vd, which has high power generation efficiency, for the lower solar panel 22, taking into account the third voltage operating point Vu and the transmittance. The control unit 110 also controls the power converters 13a and 13b to perform MPPT control (specifically, hill climbing control) based on the estimated third voltage operating point Vu and fourth voltage operating point Vd.

[0045] In this process, the solar panel being scanned identifies its maximum power point by shifting its voltage operating point from the voltage operating point of the maximum power point. Therefore, while the scan control is running, the solar panel being scanned cannot generate power at the appropriate voltage operating point for high power generation efficiency.

[0046] In this embodiment of the solar panel power generation system 1, scan control is performed only on the upper solar panel 21 of the solar panel 20. This allows the solar panel power generation system 1 to identify an appropriate third voltage operating point Vu for the upper solar panel 21 that has high power generation efficiency. Furthermore, based on the results of the scan control of the upper solar panel 21, the solar panel power generation system 1 can estimate an appropriate fourth voltage operating point Vd for the lower solar panel 22 that has high power generation efficiency. As a result, the solar panel power generation system 1 performs scan control only on the upper solar panel 21 of the solar panel 20, while not performing scan control on the lower solar panel 22. Therefore, by shortening the time required for scan control of the solar panel 20, the solar panel power generation system 1 can ensure a longer period of time during which the solar panel 20 generates power using the appropriate third voltage operating point Vu and fourth voltage operating point Vd that have high power generation efficiency.

[0047] (2) The transmittance is used to estimate the fourth voltage operating point Vd by using the difference between the first voltage operating point Vu' obtained when mountain climbing control is performed in advance for the upper solar panel 21 and the second voltage operating point Vd' obtained when mountain climbing control is performed in advance for the lower solar panel 22. With this configuration, the control unit 110 can easily estimate the fourth voltage operating point Vd, taking transmittance into consideration, by predetermined processing.

[0048] (3) When the upper solar panel 21 and the lower solar panel 22 have the same characteristics, the control unit 110 estimates the fourth voltage operating point Vd of the lower solar panel 22 at the same solar irradiance intensity by multiplying the difference between the voltage operating point of the maximum power point when the upper solar panel 21 is pre-controlled with hill climbing (i.e., the first voltage operating point Vu') and the voltage operating point of the maximum power point when the lower solar panel 22 is pre-controlled with hill climbing (i.e., the second voltage operating point Vd') by the first voltage operating point Vu' (i.e., the coefficient λu), and the third voltage operating point Vu of the upper solar panel 21 at a predetermined solar irradiance intensity identified by scan control. With this configuration, the control unit 110 can easily estimate the fourth voltage operating point Vd by a predetermined process.

[0049] 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 above description explains the case where the upper solar panel 21 and the lower solar panel 22 have structures with the same transmittance, but the case is not limited to this. The upper solar panel 21 and the lower solar panel 22 may have structures with different transmittances. It is preferable that the upper solar panel 21 has a structure with the same or higher transmittance than the lower solar panel 22. The following describes various processes when 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.

[0050] If the upper solar panel 21 and the lower solar panel 22 have structures with different transmittances, the output characteristics of the upper solar panel 21 and the lower solar panel 22 will be different. The control unit 110 determines a coefficient λu to reflect the transmittance for the upper solar panel 21 and the lower solar panel 22, based on the voltage operating point of the maximum power point when mountain climbing control is performed in advance for each.

[0051] Figure 6 shows a graph illustrating the relationship between the voltage operating point at the maximum power point of the upper solar panel 21 and the solar irradiance. Specifically, waveform W21 represents the result of measuring a certain solar irradiance and the voltage operating point at the maximum power point at that solar irradiance at multiple solar irradiance levels. Waveform W22 is an approximate waveform of waveform W21. Information showing waveform W22 related to the upper solar panel 21 is pre-stored in the memory unit 150 as first solar irradiance information.

[0052] Figure 7 shows a graph illustrating the relationship between solar irradiance and the voltage operating point at the maximum power point of the lower solar panel 22. Specifically, waveform W31 represents the result of measuring the relationship between a given solar irradiance and the voltage operating point at the maximum power point at that solar irradiance at multiple solar irradiance levels. Waveform W32 is an approximate waveform of waveform W31. Information showing waveform W32 related to the lower solar panel 22 is pre-stored in the memory unit 150 as second solar irradiance information.

[0053] The control unit 110 estimates the third voltage operating point Vu of the upper solar panel 21 by processing steps S200 to S234 shown in Figures 4 and 5 above. Based on the estimated third voltage operating point Vu and the first solar radiation intensity information, the control unit 110 identifies the first solar radiation intensity Pmu irradiated onto the solar panel 20. For example, the control unit 110 estimates that the third voltage operating point Vu is approximately V1[V] by the processing described above. As shown in Figure 6, based on the first solar radiation intensity information, the control unit 110 determines that the first solar radiation intensity Pmu corresponding to the third voltage operating point Vu being V1[V] is P1[W / m 2 To determine that it is to a certain extent.

[0054] Next, the control unit 110 calculates the solar radiation intensity of the lower solar panel 22 (hereinafter referred to as the second solar radiation intensity Pmd) taking the coefficient λu into consideration, based on the identified first solar radiation intensity Pmu and the coefficient λu. The second solar radiation intensity Pmd is expressed by the following equation (3). In equation (3), Pmd represents the second solar radiation intensity Pmd, Pmu represents the first solar radiation intensity Pmu, and λu represents the coefficient λu.

[0055] Pmd = Pmu × λu ... (3) As shown in Figure 7, the control unit 110 controls P1[W / m 2 If the value is approximately λu, then considering the coefficient λu, the second solar radiation intensity Pmd is P2[W / m 2 The control unit 110 calculates that the second solar radiation intensity Pmd is approximately [W / m²]. Based on the calculated second solar radiation intensity Pmd and the solar radiation intensity information related to the lower solar panel 22, the control unit 110 estimates the fourth voltage operating point Vd. Specifically, it estimates the voltage operating point associated with the calculated second solar radiation intensity Pmd from the solar radiation intensity information of the lower solar panel 22 as the fourth voltage operating point Vd. As shown in Figure 7, the control unit 110 calculates that the second solar radiation intensity Pmd is approximately P2 [W / m²] based on the second solar radiation intensity information. 2 The fourth voltage operating point Vd corresponding to [ ] is estimated to be around V2[V].

[0056] In this configuration, the control unit 110 identifies a coefficient λu that reflects the transmittance of the upper solar panel 21 by dividing the difference between the first voltage operating point Vu' when the upper solar panel 21 is pre-controlled to climb a hill and the second voltage operating point Vd' when the lower solar panel 22 is pre-controlled to climb a hill by the first voltage operating point Vu'.

[0057] Furthermore, the control unit 110 identifies the first solar radiation intensity Pmu based on the third voltage operating point Vu of the upper solar panel 21 at a predetermined solar radiation intensity identified by scan control, and the solar radiation intensity information of the upper solar panel 21. The control unit 110 also calculates the second solar radiation intensity Pmd based on the first solar radiation intensity Pmu and the coefficient λu. The control unit 110 estimates the fourth voltage operating point Vd of the lower solar panel 22 based on the calculated second solar radiation intensity Pmd and the solar radiation intensity information.

[0058] As a result, the solar panel power generation system 1 can ensure a longer period of time for the solar panel 20 to generate power at an appropriate third voltage operating point Vu and fourth voltage operating point Vd, which have high power generation efficiency, by reducing the time required for scan control of the solar panel 20, which has an upper solar panel 21 and a lower solar panel 22 having different characteristics.

[0059] • As described above, the coefficient λu is the value obtained by dividing the difference between the first voltage operating point Vu' when the upper solar panel 21 is pre-controlled with hill climbing and the second voltage operating point Vd' when the lower solar panel 22 is pre-controlled with hill climbing by the first voltage operating point Vu', but it is not limited to this. The coefficient λu may be calculated, for example, based on the second voltage operating point Vd' and the fifth voltage operating point Vs'. The fifth voltage operating point Vs' is the voltage operating point of the maximum power point when the lower solar panel 22 is pre-controlled with hill climbing when the lower solar panel 22 is used without being stacked.

[0060] In this case, the coefficient λu is expressed by equation (4). In equation (4), λu represents the coefficient λu, Vs' represents the fifth voltage operating point Vs', and Vd' represents the second voltage operating point Vd'.

[0061] λu = |Vs' - Vd'| / Vs' ... (4) With this configuration, the control unit 110 can calculate the coefficient λu based only on the information obtained when mountain climbing control is performed on the lower solar panel 22.

[0062] The control unit 110 may, instead of (or in addition to) performing scan control on the upper solar panel 21 at predetermined time intervals, perform scan control based on predetermined conditions. The predetermined conditions are, for example, conditions that identify that partial shading occurs on the solar panel 20, such as the detection results of the solar radiation sensor or weather forecasts. The control unit 110 may perform scan control when it is estimated that partial shading occurs on the solar panel 20 based on the predetermined conditions.

[0063] The information indicating the coefficient λu may be stored in the memory unit 150 beforehand. 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.

[0064] Furthermore, the control unit 110 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 unit 110 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 little difference in output characteristics from the other upper solar panels 21. The control unit 110 then applies the voltage command value specified for the upper solar panel 21 to the other upper solar panels 21. The one upper solar panel 21 to be controlled by MPPT is, for example, the topmost upper solar panel 21. On the other hand, when the control unit 110 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.

[0065] 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]

[0066] 1...Solar panel power generation system, 10...Power conversion circuit, 11,11a,11b...Capacitors, 12,12a,12b,60...Voltage detection means, 13a,13b...Power converter, 14,14a,14b,16,16a,16b...Switching elements, 15,15a,15b,17a,17b...Diodes, 18,18a,18b...Coils, 20...Solar panel, 21...Upper solar panel, 22...Lower solar panel, 30...Battery, 40...Current detection means, 50...Capacitor, 100...Control device, 110...Control unit, 150...Storage unit, Pmd...Second solar irradiance, Pmu...First solar irradiance, Vd...Fourth voltage operating point, Vd'...Second voltage operating point, Vs'...Fifth voltage operating point, Vu...Third voltage operating point, Vu'...First voltage operating point, λu...Coefficient.

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; a current detection means for detecting the current output by the solar panels or the current output by the power converters; and a control unit that controls the power converters based on the detection results of the voltage detection means and the current detection means, wherein the plurality of solar panels constitute a plurality of stacked solar panels stacked vertically, and among the solar panels constituting the stacked solar panels, the solar panels other than the bottom layer have the same transmittance as the bottom layer solar panel, or a structure with higher transmittance than the bottom layer solar panel, The control unit, Controlling the power converter corresponding to the solar panels to be controlled so that, for some of the solar panels to be controlled, excluding the bottom layer, a scan control is performed to estimate the voltage operating point with high power generation efficiency. The estimated voltage operating point of the solar panel to be controlled, and the transmittance, are used to estimate the voltage operating point of other solar panels in the stacked solar panel, including the solar panel to be controlled, other than the solar panel to be controlled. With respect to the solar panel, the power converter corresponding to the solar panel is controlled to perform maximum power point tracking control based on the estimated voltage operating point. Solar panel power generation system.

2. The aforementioned transmittance is used to estimate the voltage operating point for other solar panels other than the solar panel being controlled, by using the difference in voltage operating points when mountain climbing control is performed for each of the solar panels constituting the stacked solar panel. The solar panel power generation system according to claim 1.

3. Some of the solar panels that are subject to control, other than the bottom layer, and the solar panel on the bottom layer have the same characteristics. The control unit estimates the voltage operating point of the solar panel on the lowest layer at the predetermined solar irradiance by multiplying the value obtained by dividing the difference between the first voltage operating point obtained when mountain climbing control is performed in advance on some of the solar panels other than the lowest layer that are subject to control by mountain climbing control in advance on the solar panel on the lowest layer by the third voltage operating point of some of the solar panels other than the lowest layer that are subject to control at a predetermined solar irradiance, which is identified by scan control. The solar panel power generation system according to claim 1.

4. Some of the solar panels that are subject to control, other than the bottom layer, and the solar panel on the bottom layer have different characteristics. The control unit identifies a coefficient that reflects the transmittance of some of the solar panels other than the lowest layer, obtained by dividing the difference between the first voltage operating point when the uppermost solar panel to be controlled is pre-controlled and the second voltage operating point when the lowermost solar panel to be controlled is pre-controlled by the first voltage operating point. Based on the third voltage operating point of some of the solar panels other than the bottom layer that are subject to control at a predetermined solar radiation intensity identified by scan control, and the characteristics of some of the solar panels other than the bottom layer that are subject to control, a predetermined solar radiation intensity is determined. Based on the predetermined solar radiation intensity and the coefficient, the voltage operating point of the lowest layer solar panel at the predetermined solar radiation intensity is estimated. The solar panel power generation system according to claim 1.

5. Some of the solar panels that are subject to control, other than the bottom layer, and the solar panel on the bottom layer have different characteristics. The aforementioned transmittance is used to estimate the voltage operating point by dividing the difference between the voltage operating point of the bottommost solar panel (when it is not stacked) and the voltage operating point of the bottommost solar panel by the voltage operating point of the bottommost solar panel. The solar panel power generation system according to claim 1.

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