Solar power generation system

Abstract

Provided is a solar power generation system in which the operation point of each solar panel is suppressed from deviating from the maximum power point. The solar power generation system is configured by connecting a plurality of power generation systems in parallel, and includes a solar panel and a DCDC circuit unit that controls an operation point of power generation of the solar panel in accordance with a duty ratio of a drive signal of a DCDC converter, the solar power generation system being provided with: a first control unit that controls a main power generation system, which is one of the plurality of power generation systems, in response to the duty ratio of the drive signal of the DCDC converter; a maximum power point tracking control unit that performs maximum power point tracking control so as to drive the DCDC circuit unit at a duty ratio at which the maximum power of the solar panel is reached; and a second control unit that derives, for each of the slave power generation systems other than the master power generation system among the plurality of power generation systems, the variation ratio of the input voltage or the output voltage of the DCDC circuit unit before and after the implementation of the maximum power point following control by the first control unit, and corrects the duty ratio of the DCDC circuit unit on the basis of the variation ratio.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a solar power generation system that adopts a structure in which a plurality of solar panels are connected in parallel. BACKGROUND

[0002] In Patent Literature 1, a solar power generation system that adopts a structure in which a plurality of solar panels are connected in parallel is disclosed. For this solar power generation system, a method of improving the power generation efficiency of the entire solar power generation system by reducing the overlap of the periods in which maximum power point tracking (MPPT) control is implemented for each solar panel is described.

[0003] Patent Literature 1: Japanese Patent Application Publication No. 2020-141545

[0004] In a solar power generation system in which a plurality of solar panels are connected in parallel, in order to avoid overlap of the periods in which MPPT control is implemented, a method of independently implementing MPPT control for each of the plurality of solar panels in sequence is considered.

[0005] However, in this method, in a case where the structure of the solar power generation system is a structure in which the output sides of a plurality of DCDC converters that perform MPPT control for each of the plurality of solar panels are directly connected to a battery or the like, if the current and voltage of the output side that is common to the plurality of DCDC converters fluctuate due to MPPT control being implemented by the DCDC converter for any one of the solar panels, the voltage of the input side of the other DCDC converter that is not performing MPPT control is also affected. Such an effect is caused by factors such as the wiring resistance between devices, the pattern resistance within an ECU (Electronic Control Unit) that controls solar power generation, or the charge current-voltage characteristics of a battery.

[0006] If the current and voltage of the output side that is common to the plurality of DCDC converters fluctuate due to the effect of the fluctuation, the input voltage of the solar panel side connected to the other DCDC converter unexpectedly fluctuates, and the operating point of the solar panel deviates from the maximum power point, resulting in a decrease in power generation efficiency. Regarding such a decrease in power generation efficiency, the more the number of solar panels connected in parallel, the later the timing at which the operating point can be corrected (the longer the interval between the implementation of control), and the longer the time during which the solar panels operate in an inefficient state. Therefore, in a solar power generation system in which MPPT control is implemented for each of a plurality of solar panels in sequence, there is room for further exploration regarding the method of implementing MPPT control. SUMMARY

[0007] The present disclosure was made in view of the above-described problems, and aims to provide a solar power generation system capable of suppressing a case where an operating point of each solar panel deviates from a maximum power point in a case where MPPT control is implemented for a plurality of solar panels connected in parallel one by one.

[0008] To solve the above-described problems, one embodiment of the present disclosure is a solar power generation system configured by connecting a plurality of power generation systems in parallel, the power generation system including a solar panel and a DCDC circuit portion that controls an operating point of power generation of the solar panel according to a duty ratio of a drive signal of a DCDC converter, the solar power generation system including: a first control portion that implements maximum power point tracking control to drive the DCDC circuit portion at a duty ratio of a maximum power of the solar panel, for a master power generation system that is one of the plurality of power generation systems; and a second control portion that derives a variation ratio of an input voltage or an output voltage of the DCDC circuit portion before and after implementation of the maximum power point tracking control implemented by the first control portion, for each of slave power generation systems that are the power generation systems other than the master power generation system, and corrects the duty ratio of the DCDC circuit portion based on the variation ratio.

[0009] According to the solar power generation system of the present disclosure described above, it is possible to suppress a case where an operating point of each solar panel deviates from a maximum power point, and thus it is possible to reduce a decrease in power generation efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a schematic configuration diagram of a solar power generation system according to an embodiment of the present disclosure.

[0011] Figure 2A is a processing flowchart of solar power generation control implemented by the solar power generation system.

[0012] Figure 2B is a processing flowchart of solar power generation control implemented by the solar power generation system.

[0013] BRIEF DESCRIPTION OF DRAWINGS

[0014] 1... solar power generation system; 11, 12, 1n... power generation system; 21, 22, 2n... solar panel; 31, 32, 3n... DCDC circuit portion; 50... battery; 70... control portion; 100... solar control ECU. DETAILED DESCRIPTION

[0015] In the disclosed solar power generation system, which comprises multiple systems connected in parallel to generate electricity using solar panels, the MPPT (Maximum Power Point Test) control of each system is implemented sequentially. However, the system does not refrain from any operation until the MPPT control sequence of its own system arrives. Instead, it continuously adjusts its operation based on the results of MPPT control from other systems, ensuring that the operating point of the solar panels in this system does not deviate from the maximum power point. This mitigates the reduction in the system's power generation efficiency.

[0016] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0017] <Implementation Method>

[0018] [structure]

[0019] Figure 1 This is a block diagram showing the schematic structure of a solar power generation system 1 according to one embodiment of the present disclosure. Figure 1 The illustrated solar power generation system 1 includes: a first power generation system 11, a second power generation system 12, and so on up to an nth power generation system 1n (n being an integer of 3 or more); a battery 50; and a control unit 70. Figure 1 In the diagram, thick solid lines represent wiring that carries electrical power, while dashed lines represent wiring that carries measurement values, control signals, etc.

[0020] This solar power generation system 1 can be installed in vehicles such as hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV), and battery electric vehicles (BEV).

[0021] The first power generation system 11 is configured to include a first solar panel 21 and a first DC-DC circuit unit 31. The first solar panel 21 is a solar cell module that generates electricity by receiving sunlight. The first solar panel 21 is connected to the first DC-DC circuit unit 31, and the power generated by the first solar panel 21 is output to the first DC-DC circuit unit 31. The first DC-DC circuit unit 31 is configured to independently control the power generated by the first solar panel 21. More specifically, the first DC-DC circuit unit 31 includes a DC-DC converter (not shown) and is capable of implementing MPPT control. This MPPT control increases or decreases the voltage based on the change in the duty cycle of the DC-DC converter's drive signal according to the instruction of the control unit 70, thereby searching for the operating point, i.e., the maximum power point, where the power generation efficiency of the first solar panel 21 is maximized. Furthermore, a known technique known as the so-called mountaineering method can be used in this MPPT control. The output of the first DC-DC circuit unit 31 is output to the battery 50.

[0022] Additionally, the first power generation system 11 includes a sensor (not shown) for acquiring information related to the power generation status of the first solar panel 21. This sensor acquires at least the voltage V1in and current I1in input from the first solar panel 21 to the first DC-DC circuit 31, and the voltage V1out and current I1out output from the first DC-DC circuit 31 to the battery 50. The information acquired by the sensor is output to the control unit 70.

[0023] The second power generation system 12 is configured to include a second solar panel 22 and a second DC-DC circuit section 32. The second solar panel 22, like the first solar panel 21, is a solar cell module that generates electricity by receiving sunlight. The second solar panel 22 is connected to the second DC-DC circuit section 32, and the power generated by the second solar panel 22 is output to the second DC-DC circuit section 32. The second DC-DC circuit section 32 is configured to independently control the power generated by the second solar panel 22. More specifically, the second DC-DC circuit section 32, like the first DC-DC circuit section 31, includes a DC-DC converter (not shown), and is capable of MPPT control to search for the maximum power point of the second solar panel 22 by increasing or decreasing the voltage according to changes in the duty cycle of the DC-DC converter's drive signal based on instructions from the control unit 70. The output of the second DC-DC circuit section 32 is connected in parallel with the output of the first DC-DC circuit section 31 and output to the battery 50.

[0024] Additionally, the second power generation system 12 includes a sensor (not shown) for acquiring information related to the power generation status of the second solar panel 22. This sensor acquires at least the voltage V2in and current I2in input from the second solar panel 22 to the second DC-DC circuit 32, and the voltage V2out and current I2out output from the second DC-DC circuit 32 to the battery 50. The information acquired by the sensor is output to the control unit 70.

[0025] The structures of the third power generation system 13 to the nth power generation system 1n are the same as those of the first power generation system 11 and the second power generation system 12 described above, therefore their description is omitted. Furthermore, the performance, capacity, size, and shape of the first solar panel 21, the second solar panel 22, and the nth solar panels 2n can be completely identical, or partially or completely different. Additionally, the type, function, and performance of the step-up / step-down voltage of the first DC-DC circuit section 31, the second DC-DC circuit section 32, and the nth DC-DC circuit sections 3n can be completely identical, or partially or completely different.

[0026] The battery 50 is configured as a rechargeable battery, such as a lithium-ion battery. This battery 50 is connected to the outputs of the first DC-DC circuit section 31, the second DC-DC circuit section 32, and so on, up to the nth DC-DC circuit section 3n, and is configured to receive power from the first power generation system 11, the second power generation system 12, and so on, up to the nth power generation system 1n. When the solar power generation system 1 is mounted in a vehicle, the battery 50 can serve as an auxiliary battery. Furthermore, devices (auxiliary loads) that receive power from the battery 50 and operate can also be connected to the battery 50.

[0027] The control unit 70 can control the first DC-DC circuit unit 31, the second DC-DC circuit unit 32, and so on, up to the nth DC-DC circuit unit 3n, thereby controlling the power generated by the first solar panel 21, the second solar panel 22, and so on, up to the nth solar panel 2n. Specifically, the control unit 70 obtains information on the input voltages V1in, V2in, and so on, the input currents I1in, I2in, and so on, the output voltages V1out, V2out, and so on, and the output currents I1out, I2out, and so on, up to the nth power generation system 11, the second power generation system 12, and so on, up to the nth power generation system 1n, and based on this information, appropriately controls the duty cycle of the drive signal of the DC-DC converter, which is the indication value provided to the first DC-DC circuit unit 31, the second DC-DC circuit unit 32, and so on, up to the nth DC-DC circuit unit 3n. Furthermore, the control performed by this control unit 70 will be described later.

[0028] All or part of the aforementioned control unit 70 can typically be configured as an electronic control unit (ECU) including a processor such as a CPU, a memory, and input / output interfaces. For example, the control unit 70, which functions as a CPU, the first DC-DC circuit unit 31, the second DC-DC circuit unit 32, and up to the nth DC-DC circuit units 3n can be configured as a solar control ECU 100. In such an electronic control unit, the processor reads and executes a program stored in the memory to achieve the specified function.

[0029] [control]

[0030] Next, further reference Figure 2A and Figure 2B This describes the control performed by a solar power generation system 1 according to one embodiment of the present disclosure. Figure 2A and Figure 2B This is a flowchart illustrating the processing steps of solar power generation control executed by the control unit 70 of the solar power generation system 1. Figure 2A processing and Figure 2B The processing is done through the connector Z.

[0031] existFigure 2A as well as Figure 2B In the illustrated solar power generation control, for example, it starts when solar power generation system 1 is turned on (wakes up) and ends when solar power generation system 1 is turned off (goes into hibernation).

[0032] (Step S201)

[0033] The control unit 70 implements MPPT control on the first power generation system 11, the second power generation system 12, and so on up to the nth power generation system 1n, thereby detecting the maximum power point of the first solar panel 21, the second solar panel 22, and so on up to the nth solar panel 2n. Specifically, the control unit 70 implements MPPT control on the first power generation system 11 to detect the initial value of the maximum power point of the first solar panel 21, implements MPPT control on the second power generation system 12 to detect the initial value of the maximum power point of the second solar panel 22, and so on up to the nth power generation system 1n to detect the initial value of the maximum power point of the nth solar panel 2n. During the implementation of MPPT control on a particular power generation system, the operation of all other power generation systems can be stopped (no output from the DC-DC circuit section), or only the operation of the other power generation systems that are not under MPPT control can be stopped.

[0034] When the control unit 70 detects the maximum power points of the first solar panel 21, the second solar panel 22, and so on up to the nth solar panel 2n, the process proceeds to step S202.

[0035] (Step S202)

[0036] Based on the maximum power points of the first solar panel 21, the second solar panel 22, and so on up to the nth solar panel 2n detected in step S201 above, the control unit 70 drives the first DC-DC circuit unit 31, the second DC-DC circuit unit 32, and so on up to the nth DC-DC circuit unit 3n respectively when the output of each solar panel reaches the maximum power operating point. That is, the control unit 70 drives the first DC-DC circuit unit 31 with a duty cycle DUTY1 that can obtain the maximum power point of the first solar panel 21, drives the second DC-DC circuit unit 32 with a duty cycle DUTY2 that can obtain the maximum power point of the second solar panel 22, and so on up to the nth DC-DC circuit unit 3n with a duty cycle DUTYn that can obtain the maximum power point of the nth solar panel 2n.

[0037] If the control unit 70 drives the first DC-DC circuit unit 31, the second DC-DC circuit unit 32, and the nth DC-DC circuit unit 3n respectively with the duty cycle of the maximum power point of the first solar panel 21, the second solar panel 22, and the nth solar panel 2n, then the process proceeds to step S203.

[0038] (Step S203)

[0039] The control unit 70 sets the value of variable x to "1" (x = 1 to n). This variable x is used to specify the power generation system (main power generation system) for which MPPT control is implemented. Through this setting in step S203, the object for implementing MPPT control is designated as the first power generation system 11.

[0040] If the control unit 70 sets the value of variable x to "1", the process proceeds to step S204.

[0041] (Step S204)

[0042] Before implementing MPPT control on the xth power generation system 1x, the control unit 70 obtains the input voltage (second control unit) of the DCDC circuit section for all power generation systems (from power generation systems) that do not implement MPPT control. That is, the control unit 70 obtains the input voltage Vyin of the yth DCDC circuit section 3y for all yth power generation systems 1y (y = 1 to n and y ≠ x) from the first power generation system 11 to the nth power generation system 1n, excluding the xth power generation system 1x. The input voltage Vyin obtained here is the voltage before implementing MPPT control, and is therefore denoted as input voltage Vyin-pre for distinction.

[0043] When the control unit 70 acquires the input voltage Vyin-pre of the yth DCDC circuit unit 3y, the process proceeds to step S205.

[0044] (Step S205)

[0045] Control unit 70 performs MPPT control on the xth power generation system 1x and detects the maximum power point of the xth solar panel 2x (first control unit). This process is the same as the process performed in step S201 above.

[0046] When the control unit 70 detects the maximum power point of the xth solar panel 2x, the process proceeds to step S206.

[0047] (Step S206)

[0048] Based on the maximum power point of the xth solar panel 2x detected in step S205 above, the control unit 70 obtains the duty cycle DUTYx of the maximum power point of the xth solar panel 2x and drives the xth DC-DC circuit unit 3x (the first control unit). This process is the same as the process performed in step S202 above.

[0049] When the control unit 70 drives the xth DC-DC circuit unit 3x with the duty cycle DUTYx of the maximum power point of the xth solar panel 2x, the process proceeds to step S207.

[0050] (Step S207)

[0051] After the control unit 70 performs MPPT control on the xth power generation system 1x, it obtains the input voltage of the DCDC circuit section (from the power generation system) for all power generation systems that do not perform MPPT control (the second control unit). That is, the control unit 70 obtains the input voltage Vyin of the yth DCDC circuit section 3y for all yth power generation systems 1y (y = 1 to n and y ≠ x) from the first power generation system 11 to the nth power generation system 1n, excluding the xth power generation system 1x. The input voltage Vyin obtained here is the voltage after performing MPPT control, so it is denoted as input voltage Vyin-post for distinction.

[0052] If the input voltage Vyin-post of the yth DCDC circuit section 3y is obtained by the control unit 70, the process proceeds to step S208.

[0053] (Step S208)

[0054] The control unit 70 derives the variation ratio Ky of the input voltage Vyin for each of the y-th power generation systems 1y (second control unit). This variation ratio Ky is the proportion of the change in the input voltage Vyin after MPPT control is implemented for the x-th power generation system 1x relative to the change before MPPT control is implemented, and can be obtained by the following [Equation 1].

[0055] Ky=Vyin-post / Vyin-pre…[Formula 1]

[0056] For example, when the MPPT control is implemented on the first power generation system 11 (x = 1), the variation ratio K2 of the second power generation system 12, which is not the target of MPPT control, is derived, the variation ratio K3 of the third power generation system 13 is derived, and so on, the variation ratio Kn of the nth power generation system 1n is derived (y = 2 ~ n).

[0057] When the control unit 70 derives the variation ratio Ky in the y-th power generation system 1y, the process proceeds to step S209.

[0058] (Step S209)

[0059] Control unit 70 corrects the duty cycle DUTYy of the signal driving the DCDC circuit unit 3y for all y-th power generation systems 1y based on the variation ratio Ky. This correction is performed by multiplying the current duty cycle DUTYy by the variation ratio Ky, as described in [Equation 2] below.

[0060] The corrected DUTYy = the current DUTYy × Ky…[Equation 2]

[0061] For example, when the target of MPPT control is the first power generation system 11 (x = 1), the duty cycle DUTY2 of the second power generation system 12, which is not the target, is corrected by the change ratio K2, the duty cycle DUTY3 of the third power generation system 13 is corrected by the change ratio K3, and so on, the duty cycle DUTYn of the nth power generation system 1n is corrected by the change ratio Kn (y = 2 ~ n).

[0062] If the control unit 70 corrects the duty cycle DUTYy of the yth DCDC circuit unit 3y in the yth power generation system 1y by the change ratio Ky, the process proceeds to step S210.

[0063] (Step S210)

[0064] The control unit 70 determines whether the value of variable x, which specifies the power generation system for which MPPT control is implemented, is "n". This determination is made to determine whether MPPT control has been performed sequentially and completely from the first power generation system 11 to the nth power generation system 1n.

[0065] If the control unit 70 determines that the value of variable x is "n" (step S210, yes), the process proceeds to step S203, and the controlled object returns to the first power generation system 11 to re-implement MPPT control. On the other hand, if the control unit 70 determines that the value of variable x is not "n" (step S210, no), the process proceeds to step S211.

[0066] (Step S211)

[0067] The control unit 70 increments the value of variable x of the power generation system that is designated to implement MPPT control by 1 (incrementing).

[0068] If the control unit 70 increases the value of variable x by 1, the process proceeds to step S204, and the controlled object is moved to the next (x+1)th power generation system 1 (x+1) to implement MPPT control.

[0069] <Functions and Effects>

[0070] As described above, in a solar power generation system according to one embodiment of this disclosure, when MPPT control of multiple solar panels connected in parallel is implemented sequentially, even if the current and voltage on the common output side of multiple DC-DC circuits change due to MPPT control implemented on one solar panel, the operation of other DC-DC circuits can be corrected in a direction that eliminates the influence on the input side of other DC-DC circuits that are not under MPPT control. As a specific example of correction control, the case where the duty cycle of the signal driving the other DC-DC circuits is corrected separately can be exemplified.

[0071] This corrective control can suppress the deviation of the operating point of each solar panel from the maximum power point (keeping the operating point at the maximum power point). Therefore, even if MPPT control is performed in any power generation system, it can suppress the reduction in the overall power generation efficiency of the solar power generation system.

[0072] <Variation Example 1>

[0073] In the above embodiment, an example was described where the corrected duty cycle DUTYy for the y-th DCDC circuit section 3y was calculated based on the variation ratio Ky of the input voltage Vyin. However, in addition, the corrected duty cycle DUTYy can also be calculated based on the variation ratio Ky of the output voltage Vyout. In this case, in the above... Figure 2B In the flowchart, "Vyin-pre" is replaced with "Vyout-pre", "Vyin-post" is replaced with "Vyout-post", and [Equation 2] calculated in step S209 is replaced with [Equation 3] below, thereby enabling corrective control.

[0074] The corrected DUTYy = the current DUTYy × (1 / Ky)...[Equation 3]

[0075] <Variation Example 2>

[0076] In the above embodiments, an example was described where each DC-DC circuit section includes a buck DC-DC converter that satisfies the input-output relationship of "input voltage × duty cycle = output voltage". However, it is also possible for each DC-DC circuit section to include a boost DC-DC converter. For example, if the DC-DC circuit section of a power generation system operates with a boost ratio (output / input) of α, enabling the solar panel to operate at the maximum power point, and if the output voltage changes from mV to (m×β)V due to the MPPT control of other power generation systems, the duty cycle is corrected so that the boost ratio of the DC-DC circuit section becomes α×β. Therefore, the input voltage of the DC-DC circuit section does not change, allowing the solar panel to operate continuously at the maximum power point.

[0077] In this example, the corrected duty cycle can be obtained either through calculation using a prescribed formula or by extracting values ​​from a pre-made mapping. In the latter case, for example, if a two-dimensional mapping of the duty cycle variation correction based on the values ​​of α and β is pre-made through experiments, the corrected duty cycle can be easily determined from the two-dimensional mapping.

[0078] Of course, if the duty cycle of the signal driving the DC-DC circuit can be modified (changed) by any method so that the input voltage can be maintained when the output voltage of the DC-DC circuit changes (so that the operation of the maximum power point of the solar panel continues), then it is not limited to the above-mentioned variation, and various DC-DC circuits with other characteristics can be used to achieve the same effect.

[0079] <Application Examples>

[0080] This solar power generation control is described based on a system that uses a structure in which three or more power generation systems are connected in parallel, which significantly reduces power generation efficiency. However, for example, a system in which two power generation systems (first power generation system 11 and second power generation system 12) are connected in parallel can also be effective.

[0081] For example, consider the case where the ECU implementing solar power generation control (e.g., solar control ECU 100) combines its functions with those of other ECUs, and a single processor on the ECU handles both solar power generation control and other functions. In this case, if only the implementation of MPPT control for the first power generation system 11, the implementation of MPPT control for the second power generation system 12, and the implementation of other functions besides solar power generation control can be executed sequentially, the operating point of the solar panel cannot be corrected during the implementation of other functions. Therefore, in such a case, by performing the duty cycle correction disclosed herein, it is expected to mitigate the reduction in power generation efficiency.

[0082] The above describes one embodiment of the present disclosure. However, in addition to a solar power generation system, the present disclosure can also be understood as a method for controlling solar power generation performed by a solar power generation system, a program of the method, a computer-readable non-transitory recording medium storing the program, and a vehicle equipped with a solar power generation system.

[0083] Industrial availability

[0084] This disclosure can be used in solar power generation systems, etc., by connecting multiple power generation systems, including solar panels and DC-DC circuit sections, in parallel.

Claims

1. A solar power generation system, configured by connecting multiple power generation systems in parallel, the power generation system comprising a solar panel and a DC-DC converter circuit, wherein the DC-DC converter circuit controls the operating point of the solar panel's power generation based on the duty cycle of the DC-DC converter's drive signal, wherein... The solar power generation system has the following features: The first control unit implements maximum power point following control for the main power generation system, which is one of the multiple power generation systems, to drive the DC-DC circuit unit by the duty cycle that becomes the maximum power point of the solar panel. as well as The second control unit, for each of the plurality of power generation systems that becomes a slave power generation system other than the master power generation system, derives the change ratio of the input voltage or output voltage of the DC-DC circuit before and after the implementation of the maximum power point following control implemented by the first control unit, and corrects the duty cycle of the DC-DC circuit based on the change ratio.

2. The solar power generation system according to claim 1, wherein, The first control unit sequentially switches the multiple power generation systems to the main power generation system to implement the maximum power point following control.

3. The solar power generation system according to claim 1 or 2, wherein, When the variation ratio is the ratio of the input voltage after the implementation of the maximum power point follower control to the input voltage before the implementation of the maximum power point follower control, the second control unit corrects the error by multiplying the duty cycle by the variation ratio.

4. The solar power generation system according to claim 1 or 2, wherein, When the variation ratio is the ratio of the output voltage after the implementation of the maximum power point follower control to the output voltage before the implementation of the maximum power point follower control, the second control unit corrects the duty cycle by dividing the variation ratio.

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