Solar charging system

Abstract

To inhibit inrush current from flowing through a converter.SOLUTION: A controller 21 supplies power generated by a solar panel 10 and power stored in a first battery 40 to a capacitor 72 of a third converter 70 and, after an amount of charge of the capacitor 72 becomes equal to or larger than a predetermined value, supplies power converted by the third converter 70 to a second battery 50 to start charging of the second battery 50.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a solar charging system.

Background Art

[0002] The solar charging system described in Patent Document 1 includes a solar panel, a first battery, a second battery, and a solar ECU including a converter. The first battery is charged with electric power generated by the solar panel. The converter converts the electric power generated by the solar panel and the electric power stored in the first battery. The second battery stores electric power when supplied with the electric power converted by the converter.

[0003] When electric power is supplied from the converter to the second battery to start charging the second battery, there is a risk that an inrush current flows from the second battery to the converter due to a potential difference between the converter and the second battery. Accordingly, a precharge circuit that suppresses inrush current to the converter may be connected between the converter and the second battery.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] In order to suppress inrush current from flowing into the converter without providing a precharge circuit, it is conceivable to start charging the second battery after charging a capacitor included in the converter to reduce the potential difference.

[0006] In a solar charging system, it is conceivable that electricity generated by solar panels is supplied to the capacitor to charge it. However, the amount of electricity generated by solar panels is unstable due to fluctuations caused by sunlight and other factors. Therefore, it may not be possible to sufficiently increase the charge level of the capacitor. If the charge level of the capacitor cannot be sufficiently increased, there is a risk of inrush current flowing through the converter. [Means for solving the problem]

[0007] A solar charging system for solving the above problems comprises a solar panel, a first battery for charging the electricity generated by the solar panel, a converter for converting the electricity stored in the first battery and the electricity generated by the solar panel, a second battery for charging the electricity converted by the converter, and a control device. The converter has a capacitor that reduces the potential difference between the second battery and the converter by the stored charge. The control device supplies the electricity generated by the solar panel and the electricity stored in the first battery to the capacitor, and after the charge level of the capacitor reaches or exceeds a predetermined value, it executes a process to start charging the second battery. [Effects of the Invention]

[0008] This can suppress the inrush current flowing through the converter. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram of the solar charging system. [Figure 2] Figure 2 is a flowchart showing the steps of the process performed by the control device. [Modes for carrying out the invention]

[0010] <Outline configuration of a solar charging system> An embodiment of the solar charging system will be described below with reference to Figures 1 and 2. The solar charging system of this embodiment is mounted on a vehicle.

[0011] As shown in Figure 1, the solar charging system 100 includes a solar panel 10, a control unit 20, a battery monitoring unit 30, a first battery 40, a second battery 50, a relay 60, and a third converter 70.

[0012] The solar panel 10 is constructed by arranging multiple solar cells, which generate electricity from sunlight, in a panel-like configuration. The solar panel 10 is installed, for example, on the roof of a vehicle VC.

[0013] The control unit 20 includes a control device 21, a first converter 25, and a second converter 26. The control device 21 includes a CPU and a memory device. The CPU of the control device 21 executes programs stored in the memory device of the control device 21 to perform various controls such as power generation control of the solar panel 10, charging control of the first battery 40, and charging control of the second battery 50. The first converter 25 is a DC-DC converter that converts the power generated by the solar panel 10. The second converter 26 is a DC-DC converter that converts the power converted by the first converter 25 and supplies it to the first battery 40.

[0014] The third converter 70 is a DC-DC converter that converts the power stored in the first battery 40 and the power generated by the solar panel 10 and supplies it to the second battery 50. The third converter 70 has a capacitor 72 that reduces the potential difference between the second battery 50 and the third converter 70 by storing charge.

[0015] The control device 21 controls the driving of the first converter 25, the second converter 26, and the third converter 70. The battery monitoring unit 30 includes a battery control device 31. The battery control device 31 includes a CPU and a memory device. The CPU of the battery control device 31 executes a program stored in the memory device of the battery control device 31 to monitor the state of the second battery 50 and to control the opening and closing of the relay 60 for charging the second battery 50. The battery control device 31 is connected to the control device 21 so as to be able to communicate with each other. The battery control device 31 transmits the state of the second battery 50, such as input current, output current, voltage, and temperature, detected by sensors, to the control device 21. The control device 21 transmits an opening and closing instruction signal for the relay 60 to the battery control device 31.

[0016] The first battery 40 is a secondary battery that charges with electricity generated by the solar panel 10, and is, for example, a lithium-ion battery. The first battery 40 is not limited to a lithium-ion battery and may be of other types. The first battery 40 is an auxiliary battery that supplies power to the auxiliary equipment of the vehicle VC. The auxiliary equipment of the vehicle VC includes, for example, an electric oil pump, a navigation system, lamps, and various sensors. The control device 21 acquires the state of the first battery 40 detected by sensors, i.e., input current, output current, voltage, temperature, etc. Then, the control device 21 calculates the state of charge (SOC) of the first battery 40 based on the acquired data. The state of charge (SOC) is the value obtained by dividing the current full charge capacity CHmax of the first battery 40 by the current charge capacity CH.

[0017] The second battery 50 is a secondary battery that charges the power converted by the third converter 70, that is, the power stored in the first battery 40 or the power generated by the solar panel 10, and is, for example, a lithium-ion battery. The first battery 40 is not limited to a lithium-ion battery and may be of other types. The second battery 50 is a drive battery that supplies power to the motor that drives the vehicle VC.

[0018] The relay 60 is provided in a circuit between the third converter 70 and the second battery 50. When the relay 60 is closed, electric power is transferred between the third converter 70 and the second battery 50. When the relay 60 is opened, the transfer of electric power between the third converter 70 and the second battery 50 is interrupted.

[0019] <Processing executed by control device 21> FIG. 2 shows a procedure of processing executed by the control device 21. The control device 21 starts execution of the present processing when a request for charging the second battery 50 is generated. Note that the request for charging the second battery 50 is generated, for example, when a state of charge (SOC) of the first battery 40 becomes equal to or higher than a predetermined threshold. Further, hereinafter, step numbers of respective processes are represented by numerals prefixed with "S".

[0020] When starting the present processing, the control device 21 determines whether or not the solar panel 10 is generating power (S100). In S100, the control device 21 determines that the solar panel 10 is generating power when generated power of the solar panel 10 is equal to or higher than a predetermined value WSref. The predetermined value WSref is a predetermined appropriate value.

[0021] In the processing of S100, when the control device 21 determines that the solar panel 10 is generating power (S100: YES), the control device 21 determines whether or not the first battery 40 is usable (S110).

[0022] In the processing of S110, the control device 21 acquires a current SOC of the first battery 40. Then, when the acquired SOC is equal to or higher than a predetermined value SOCref, the control device 21 determines that the first battery 40 is usable. The predetermined value SOCref is a predetermined appropriate value. For example, the value of the predetermined value SOCref can be set in consideration of electric power required to charge a capacitor 72, power consumption of auxiliary machinery during charging of the second battery 50, and the like.

[0023] In the process of S110, if the charge level (SOC) of the first battery 40 is less than the default value SOCref, the control device 21 determines that the first battery 40 is not usable (S110: NO). In this case, the control device 21 charges the first battery 40 (S130). In the process of S130, the control device 21 supplies power generated by the solar panel 10 to the first battery 40 to increase the charge level of the first battery 40. The charging of the first battery 40 in S130 is performed until the charge level (SOC) of the first battery 40 is equal to or greater than the default value SOCref. Once the charging of the first battery 40 is complete, the control device 21 resumes the process from S110 onwards.

[0024] In the process of S110 described above, if the control device 21 determines that the first battery 40 is usable (S110: YES), the control device 21 starts charging the capacitor 72 (S120). In the process of S120, the control device 21 charges the capacitor 72 by supplying the power generated by the solar panel 10 and the power stored in the first battery 40 to the capacitor 72.

[0025] Next, the control device 21 determines whether the charge level of the capacitor 72 is equal to or greater than a predetermined value Cref (S140). The predetermined value Cref is a predetermined suitable value. For example, the predetermined value Cref is the charge level at which the potential difference between the third converter 70 and the second battery 50 when charging of the second battery 50 begins is less than or equal to a predetermined value ΔV. The predetermined value ΔV is the maximum potential difference that can suppress the inflow of inrush current from the second battery 50 to the third converter 70.

[0026] In the process of S140, for example, the control device 21 determines that the charge level of capacitor 72 has exceeded a default value Cref when the elapsed time since the start of charging of capacitor 72 exceeds a default value. Alternatively, the control device 21 may determine that the charge level of capacitor 72 has exceeded a default value Cref when the voltage across capacitor 72 exceeds a default value. Furthermore, the control device 21 may determine that the charge level of capacitor 72 has exceeded a default value Cref when the current flowing through capacitor 72 becomes approximately "0".

[0027] The control device 21 repeatedly executes the process in S140 until it is determined to be positive in the process in S140. On the other hand, in the process of S140, if the control device 21 determines that the charge level of the capacitor 72 is equal to or greater than a predetermined value Cref (S140: YES), it starts charging the second battery 50 (S150). In the process of S150, the control device 21 outputs a signal to the battery control device 31 instructing the relay 60 to close. Upon receiving this signal, the battery control device 31 closes the relay 60, thereby starting the supply of power from the third converter 70 to the second battery 50 and starting the charging of the second battery 50.

[0028] If the process in S150 is completed, or if a negative determination is made in the process in S100, the control device 21 terminates this process. <Operation and Effects of This Embodiment> (1) In the process of S120 shown in Figure 2, the control device 21 supplies the power generated by the solar panel 10 and the power stored in the first battery 40 to the capacitor 72. Then, in the process of S140, the control device 21 determines that the charge level of the capacitor 72 is equal to or greater than a predetermined value Cref, and then in the process of S150, it starts charging the second battery 50.

[0029] In this embodiment, not only the power generated by the solar panel 10 but also the power stored in the first battery 40 is supplied to the capacitor 72. Therefore, even if the power generation amount of the solar panel 10 is unstable, the charge amount of the capacitor 72 of the third converter 70 will increase. Consequently, it is possible to suppress the inrush current flowing through the third converter 70 when charging of the second battery 50 begins.

[0030] (2) In the process of S110 shown in Figure 2, if the control device 21 determines that the charge level (SOC) of the first battery 40 before charging of the second battery 50 is less than a predetermined value (SOCref) (S110: NO), it executes the process of S130. In the process of S130, the control device 21 supplies the power generated by the solar panel 10 to the first battery 40 to increase the charge level of the first battery 40. Then, after increasing the charge level of the first battery 40, the control device 21 executes the process of S120 to supply power from the first battery 40 to the capacitor 72.

[0031] In this way, if the charge level of the first battery 40 is low, power is supplied from the first battery 40 to the capacitor 72 after the first battery 40 has been charged. Therefore, compared to the case where power is supplied from the first battery 40 to the capacitor 72 even though the charge level of the first battery 40 is low, the charge level of the capacitor 72 can be reliably increased.

[0032] <Example of changes> This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically.

[0033] • If the process in S110 shown in Figure 2 determines that the first battery 40 is unavailable (S110: NO), the process shown in Figure 2 may be terminated. In this case as well, effects and benefits other than those described in (2) above can be obtained.

[0034] The first battery 40 was an auxiliary battery that supplied power to the auxiliary equipment of the vehicle VC, but it may also be a battery used for other purposes. The second battery 50 was a drive battery that supplied power to the motor driving the vehicle VC, but it may be a battery used for other purposes.

[0035] Although the battery control device 31 controlled the opening and closing of the relay 60, the control device 21 may directly control the opening and closing of the relay 60. The third converter 70 may be provided within the control unit 20.

[0036] The battery control device 31 may be located within the control unit 20. • The solar charging system 100 was applied to vehicle VCs, but it may also be applied to things other than vehicle VCs.

[0037] The control device 21 is not limited to one that includes a CPU and a memory device and executes software processing. For example, it may include a dedicated hardware circuit, such as an ASIC, that performs hardware processing on at least a portion of what is processed by software in the above embodiment. In other words, the control device may have any of the following configurations (a) to (c): (a) It includes a processing device that executes all of the above processing according to a program and a program storage device such as a ROM that stores the program. (b) It includes a processing device and a program storage device that execute a portion of the above processing according to a program and a dedicated hardware circuit that executes the remaining processing. (c) It includes a dedicated hardware circuit that executes all of the above processing. Here, the software execution device equipped with the processing device and the program storage device, and the dedicated hardware circuit may be one or any number of them. In other words, the above processing can be executed by a processing circuit that includes at least one of one or more software execution devices and one or more dedicated hardware circuits. The program storage device, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer. [Explanation of symbols]

[0038] 10…Solar panels 20…Control Unit 21...Control device 25…First converter 26…Second converter 30…Battery monitoring unit 30…Battery control unit 31...Battery control unit 40…First Battery 50... Second battery 60… Relay 70...Third converter 72... Capacitor 100...Solar charging system VC…Vehicle

Claims

1. A solar panel, a first battery for charging the electricity generated by the solar panel, A solar charging system comprising: a converter that converts the power stored in the first battery and the power generated by the solar panel; a second battery that charges the power converted by the converter; and a control device, The converter has a capacitor that reduces the potential difference between the second battery and the converter by storing charge. When a charge request for the second battery is generated and the charge level of the first battery is below a predetermined value, the control device performs the following processes: supplying power generated by the solar panel to the first battery to increase the charge level of the first battery to the predetermined value or higher, and then supplying power generated by the solar panel and power stored in the first battery to the capacitor; and starting to charge the second battery after the charge level of the capacitor has reached the predetermined value or higher. Solar charging system.

2. The first battery is an auxiliary battery that supplies power to the vehicle's auxiliary equipment. The solar charging system according to claim 1.

3. The second battery is a drive battery that supplies power to the motor that drives the vehicle. The solar charging system according to claim 1.

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