Solar charging system

Abstract

This invention provides a solar charging system that can accurately estimate the amount of electricity generated by solar panels. [Solution] A solar charging system comprising a solar panel and an electronic control unit for controlling the power generation of the solar panel, wherein the electronic control unit comprises a first processing unit that derives the fill factor of the solar panel based on the short-circuit current of the solar panel, and a second processing unit that estimates the amount of power generated by the solar panel based on the fill factor derived by the first processing unit, the open-circuit voltage of the solar panel, and the short-circuit current.

Description

Technical Field

[0001] The present disclosure relates to a solar charging system including a solar panel and an electronic control unit that controls the power generation of the solar panel.

Background Art

[0002] Patent Document 1 discloses a solar charging control device that estimates the maximum power point (power generation amount) of a solar panel based on the open-circuit voltage and short-circuit current of the solar panel, and charges the battery with the power generated by the solar panel when the estimated maximum power point is greater than or equal to a predetermined value.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When estimating the power generation amount of a solar panel, it may be necessary to consider the fill factor, which is an index representing the performance of the solar panel. Since the value of this fill factor is affected by the solar irradiance and panel temperature, using a fixed fill factor to estimate the power generation amount of the solar panel may cause a deviation (deterioration of estimation accuracy) in the estimated value.

[0005] The present disclosure has been made in view of the above problems, and an object thereof is to provide a solar charging system capable of accurately estimating the power generation amount of a solar panel.

Means for Solving the Problems

[0006] To solve the above problems, one aspect of the disclosed technology is a solar charging system including a solar panel and an electronic control unit for controlling the power generation of the solar panel, wherein the electronic control unit comprises a first processing unit that derives the fill factor of the solar panel based on the short-circuit current of the solar panel, and a second processing unit that estimates the amount of power generated by the solar panel based on the fill factor derived by the first processing unit, the open-circuit voltage of the solar panel, and the short-circuit current. [Effects of the Invention]

[0007] According to the solar charging system described above, the fill factor used to estimate power generation is changed based on the short-circuit current of the solar panel, which fluctuates according to the amount of solar radiation. This suppresses deviations in the estimated value due to the influence of solar radiation, thereby enabling accurate estimation of the power generation of the solar panel. [Brief explanation of the drawing]

[0008] [Figure 1] Schematic diagram of a solar charging system according to one embodiment of this disclosure. [Figure 2] Solar panel IV characteristic diagram [Figure 3] PV characteristic diagram of solar panels [Figure 4] Processing flowchart for power generation estimation control performed by the solar ECU (Example 1) [Figure 5] An example of a correspondence map used in power generation estimation control (Example 1) [Figure 6] Processing flowchart for power generation estimation control performed by the solar ECU (second example) [Figure 7] An example of a correspondence map used in power generation estimation control (second example) [Figure 8] Processing flowchart for power generation estimation control performed by the solar ECU (third example) [Figure 9] An example of a 2D correspondence map used in power generation estimation control (third example) [Modes for carrying out the invention]

[0009] The solar charging system disclosed herein focuses on the short-circuit current of a solar panel, which is affected by solar radiation as well as the fill factor of the solar panel, and improves the accuracy of estimating the amount of power generated by the solar panel by appropriately changing the fill factor value based on the actually measured short-circuit current. Hereinafter, one embodiment of this disclosure will be described in detail with reference to the drawings.

[0010] <Embodiment> [composition] Figure 1 is a diagram showing a schematic configuration of a solar charging system 100 according to one embodiment of the present disclosure. The solar charging system 100 illustrated in Figure 1 comprises a solar panel 110, a solar ECU 120, and a battery 130. This solar charging system 100 can be mounted on a vehicle or the like.

[0011] The solar panel 110 is a power generation device that generates electricity when exposed to sunlight, and is typically a solar cell module, which is an assembly of solar cells. The amount of electricity generated by the solar panel 110 depends on the amount of solar radiation (solar radiation intensity) and the panel temperature. The electricity generated by the solar panel 110 is output to the solar ECU 120. This solar panel 110 can be installed, for example, on the roof of a vehicle.

[0012] Figure 2 illustrates the IV characteristics representing the power generation capacity of the solar panel 110. This IV characteristic shows the correspondence between the voltage V (horizontal axis) and current I (vertical axis) generated by the solar panel 110 when it receives sunlight. The open-circuit voltage is the voltage value that appears at the output terminal of the solar panel 110 when it is open-circuited without a load connected to the output terminal, that is, when the operating current is "0". The short-circuit current is the current value that flows at the output terminal of the solar panel 110 when it is short-circuited, that is, when the operating voltage is "0". Figure 3 also illustrates the PV characteristics of the solar panel 110. In the example in Figure 3, it is shown that the solar panel 110 can output maximum power Pmp when the operating voltage is voltage Vmp.

[0013] The battery 130 is a rechargeable secondary battery such as a lithium-ion battery or a lead-acid battery. This battery 130 is connected to the solar ECU 120 so as to be rechargeable by the electric power generated by the solar panel 110. As the battery 130 mounted on the vehicle, an auxiliary battery can be exemplified.

[0014] The solar ECU 120 is a connection part that connects the solar panel 110 and the battery 130, and is an electronic control unit (ECU) that can control the power generation of the solar panel 110 and supply the generated electric power to the battery 130. This electronic control unit typically includes a processor, a memory, and an input / output interface, etc., and various processes are performed by the processor reading and executing the program stored in the memory.

[0015] This solar ECU 120 is configured to be able to acquire the short-circuit current, open-circuit voltage, and panel temperature of the solar panel 110. Also, the solar ECU 120 is configured to be able to estimate the power generation amount of the solar panel 110.

[0016] [Control] Next, referring further to FIGS. 4 to 9, the control performed in the solar charging system 100 according to the present embodiment will be described.

[0017] (1) First example FIG. 4 is a flowchart for explaining the processing procedure of the power generation amount estimation control of the first example executed by the solar ECU 120 of the solar charging system 100. The power generation amount estimation control of this first example is started when it is necessary to estimate the power generation amount of the solar panel 110.

[0018] (Step S401) The solar ECU 120 acquires the open-circuit voltage and short-circuit current of the solar panel 110. This open-circuit voltage and short-circuit current can be acquired using voltage sensors and current sensors (not shown) provided in the solar ECU 120 and the solar panel 110.

[0019] Once the open-circuit voltage and short-circuit current of the solar panel 110 are obtained by the solar ECU 120, the process proceeds to step S402.

[0020] (Step S402) The solar ECU 120 derives the fill factor of the solar panel 110 based on the short-circuit current of the solar panel 110 (first processing unit). This fill factor can be derived using a correspondence map or formula prepared in advance in a memory unit or the like. Figure 5 is an example of a correspondence map showing the correlation between the short-circuit current of the solar panel 110 and the fill factor. In the correspondence map shown in Figure 5, the fill factor corresponding to the short-circuit current can be mapped.

[0021] Once the solar ECU 120 derives the fill factor based on the short-circuit current of the solar panel 110, the process proceeds to step S403.

[0022] (Step S403) The solar ECU 120 estimates the amount of power generated by the solar panel 110 (power generation) based on the open-circuit voltage, short-circuit current, and fill factor derived in step S402 (second processing unit). This amount of power W can be calculated using the open-circuit voltage V, short-circuit current I, and fill factor Ff by the following equation. W = V × I × Ff

[0023] Once the solar ECU 120 estimates the amount of power generated by the solar panel 110 based on its open-circuit voltage, short-circuit current, and fill factor, this power generation estimation control (first example) ends.

[0024] As demonstrated in this first example of power generation estimation control, the error between the actual power generation and the estimated power generation can be reduced by estimating the power generation of the solar panel 110 using a fill factor that is varied according to the open-circuit voltage of the solar panel 110. An example of this is shown below.

[0025] We will compare the difference between the conventional case, where the fill factor of the solar panel 110 is fixed at "0.8", and the present disclosure, where it is varied from "0.8 (high short-circuit current) to 0.6 (low short-circuit current)", assuming scenarios with high solar radiation (short-circuit current: 5.5A) and low solar radiation (short-circuit current: 4A). When the actual power generation of the solar panel 110 in the high-radiance scenario is 100W, the estimated power generation is 96.8W (=22V × 5.5A × 0.8) in both the conventional and present disclosure cases, and the error is small at 3.2W. On the other hand, when the actual power generation of the solar panel 110 in a situation with low solar radiation is 50W, the estimated power generation using conventional fixed values ​​is 70.4W (=22V × 4A × 0.8), resulting in a large error of 20.4W, whereas the estimated power generation using the variable values ​​in this disclosure is 52.8W (=22V × 4A × 0.6), resulting in a small error of 2.8W.

[0026] (2) Second example Figure 6 is a flowchart illustrating the processing procedure for a second example of power generation estimation control performed by the solar ECU 120 of the solar charging system 100. This second example of power generation estimation control is initiated when it becomes necessary to estimate the power generation of the solar panel 110.

[0027] (Step S601) The solar ECU 120 acquires the short-circuit current of the solar panel 110. This short-circuit current can be acquired using a current sensor (not shown) provided in the solar ECU 120 or the solar panel 110.

[0028] Once the solar ECU 120 obtains the short-circuit current of the solar panel 110, the process proceeds to step S602.

[0029] (Step S602) The solar ECU 120 derives the estimated power generation amount (generated power) of the solar panel 110 based on the short-circuit current of the solar panel 110 (third processing unit). This power generation amount can be derived using a correspondence map (first correspondence map) or mathematical formula prepared in advance in a memory unit (first memory unit). Figure 7 is an example of a correspondence map showing the correlation between the short-circuit current of the solar panel 110 and the power generation amount. The power generation amount shown in this correspondence map reflects a correction related to the shift in the fill factor due to fluctuations in the short-circuit current of the solar panel 110. The value corrected here can be obtained in advance from measured values ​​using the solar panel 110 or from simulations. In the correspondence map shown in Figure 7, the power generation amount corresponding to the short-circuit current can be mapped.

[0030] When the solar ECU 120 derives the estimated power generation amount of the solar panel 110 based on the short-circuit current of the solar panel 110, this power generation estimation control (second example) ends.

[0031] According to this second example of power generation estimation control, the amount of power generated can be directly determined from the short-circuit current of the solar panel 110, thus eliminating the need to obtain the open-circuit voltage of the solar panel 110 (simplification of the measurement system).

[0032] (3) Third example Figure 8 is a flowchart illustrating the processing procedure for a third example of power generation estimation control performed by the solar ECU 120 of the solar charging system 100. This third example of power generation estimation control is initiated when it becomes necessary to estimate the power generation of the solar panel 110.

[0033] (Step S801) The solar ECU 120 acquires the open-circuit voltage, short-circuit current, and panel temperature of the solar panel 110. This open-circuit voltage, short-circuit current, and panel temperature can be acquired using voltage sensors, current sensors, and temperature sensors (such as thermistors) provided on the solar ECU 120 and the solar panel 110 (not shown).

[0034] Furthermore, instead of directly measuring the actual temperature of the solar panel 110 using a temperature sensor or the like, the panel temperature of the solar panel 110 may be predicted indirectly using the value of the open-circuit voltage of the solar panel 110, which fluctuates depending on the panel temperature.

[0035] Once the solar ECU 120 obtains the open-circuit voltage, short-circuit current, and panel temperature of the solar panel 110, the process proceeds to step S802.

[0036] (Step S802) The solar ECU 120 derives the fill factor of the solar panel 110 based on the short-circuit current and panel temperature of the solar panel 110 (fourth processing unit). This fill factor can be derived using a two-dimensional correspondence map (second correspondence map) that is prepared in advance in a storage unit (second storage unit) or the like. Figure 9 is an example of a two-dimensional correspondence map showing the correlation between the short-circuit current and panel temperature of the solar panel 110 and the fill factor. In the two-dimensional correspondence map shown in Figure 9, the fill factor according to the short-circuit current and panel temperature can be mapped.

[0037] Once the solar ECU 120 derives the fill factor based on the short-circuit current and panel temperature of the solar panel 110, the process proceeds to step S803.

[0038] (Step S803) The solar ECU 120 estimates the amount of power generated by the solar panel 110 (power generation) based on the open-circuit voltage, short-circuit current, and the fill factor derived in step S802 (5th processing unit). The method for determining this amount of power generation is as described above.

[0039] Once the solar ECU 120 estimates the amount of power generated by the solar panel 110 based on its open-circuit voltage, short-circuit current, and fill factor, this power generation estimation control (third example) ends.

[0040] As demonstrated in this third example of power generation estimation control, the fill factor is derived not only based on the open-circuit voltage of the solar panel 110 but also on the panel temperature of the solar panel 110. This further reduces the error between the actual power generation of the solar panel 110 and the estimated power generation. An example is shown below.

[0041] Assuming the same amount of solar radiation (short-circuit current: 5.5A), but different panel temperatures, such as 25°C (open-circuit voltage: 22V) and 0°C (open-circuit voltage: 23V), we compare the cases where the fill factor of solar panel 110 is "0.80 (panel temperature: 25°C)" and "0.85 (panel temperature: 0°C)". When the actual power generation of solar panel 110 at a panel temperature of 25°C is 100W, the estimated power generation is 96.8W (=22V × 5.5A × 0.80), with an error of 3.2W. In contrast, when the actual power generation of solar panel 110 at a panel temperature of 0°C is 108W, the estimated power generation is 107.5W (=23V × 5.5A × 0.85), with an error of 0.5W. In this way, even without considering the panel temperature of the solar panel 110, the error (6.8W = 108W - 101.2W) can be reduced compared to the estimated power generation (101.2W = 23V × 5.5A × 0.80) when using a fill factor of "0.80" even when the panel temperature is 0°C.

[0042] <Effects and Actions> As described above, according to the solar charging system 100 according to one embodiment of the present disclosure, the fill factor of the solar panel 110 is derived based on the short-circuit current of the solar panel 110, and the amount of power generated by the solar panel 110 is estimated based on the derived fill factor of the solar panel 110, the open-circuit voltage and the short-circuit current. Alternatively, the estimated amount of power generated by the solar panel 110 is derived based on the short-circuit current and the correspondence map, using a correspondence map that shows the correlation between the short-circuit current and the amount of power generated by the solar panel 110, corrected for any deviation in the fill factor of the solar panel 110. Alternatively, the fill factor is derived based on the short-circuit current, the panel temperature and the correspondence map, using a correspondence map that shows the correlation between the short-circuit current and the panel temperature and the fill factor of the solar panel 110, and the amount of power generated by the solar panel 110 is estimated based on the derived fill factor, the open-circuit voltage and the short-circuit current.

[0043] These estimation methods suppress deviations in estimated values ​​due to the influence of solar radiation, allowing for accurate estimation of the power generation of the solar panel 110. Therefore, the number of times the solar charging system 100 needs to be started in situations where power generation is low can be reduced, thereby improving the power generation efficiency of the system.

[0044] Although one embodiment of the present disclosure has been described above, the present disclosure can be understood not only as a solar charging system, but also as a method performed by the solar charging system, a program for that method, a computer-readable non-temporary storage medium storing that program, and a vehicle equipped with the solar charging system. [Industrial applicability]

[0045] This disclosure can be used in vehicles that charge batteries using electricity generated by solar panels. [Explanation of Symbols]

[0046] 100 Solar Charging Systems 110 Solar Panels 120 Solar ECU 130 batteries

Claims

1. A solar charging system comprising a solar panel and an electronic control unit for controlling the power generation of the solar panel, The aforementioned electronic control unit is A first processing unit that derives the fill factor of the solar panel based on the short-circuit current of the solar panel, The system includes a second processing unit that estimates the amount of power generated by the solar panel based on the fill factor derived by the first processing unit, the open-circuit voltage of the solar panel, and the short-circuit current. Solar charging system.

2. A solar charging system comprising a solar panel and an electronic control unit for controlling the power generation of the solar panel, The aforementioned electronic control unit is A first storage unit stores a first correspondence map showing the correlation between the short-circuit current of the solar panel and the amount of power generated by the solar panel, with the deviation of the fill factor of the solar panel corrected. The system includes a third processing unit that derives the amount of power generated based on the short-circuit current and the first corresponding map, Solar charging system.

3. A solar charging system comprising a solar panel and an electronic control unit for controlling the power generation of the solar panel, The aforementioned electronic control unit is A second storage unit stores a second correspondence map showing the correlation between the short-circuit current and panel temperature of the solar panel and the fill factor of the solar panel, A fourth processing unit that derives the fill factor based on the short-circuit current, the panel temperature, and the second corresponding map, The system includes a fifth processing unit that estimates the amount of power generated by the solar panel based on the fill factor derived by the fourth processing unit, the open-circuit voltage of the solar panel, and the short-circuit current. Solar charging system.

4. The panel temperature is derived from the open-circuit voltage. The solar charging system according to claim 3.

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