JP7786339B2 - Solar Charging System - Google Patents

Description

This disclosure relates to a solar charging system that controls the supply of power generated by a solar panel mounted on a vehicle.

Patent Document 1 discloses a solar charging system that, when the solar panel is in a state where it can generate power, feeds power from the solar panel to an auxiliary system, derives the power actually generated by the solar panel, and, if this derived actual generated power is equal to or greater than a specified value, further charges the drive battery with the power generated by the solar panel.

Japanese Patent Application Laid-Open No. 2021-083248

When a vehicle is parked, for example, a process (hereinafter referred to as "pumping charging process") may be performed to transfer power from the drive battery to the auxiliary battery to prevent the auxiliary battery, which supplies power to devices that operate services provided while the vehicle is parked, from running down. Because this pumping charging process is performed via the main DCDC converter that controls the vehicle's power, there is an issue that the power consumption required to start the main DCDC converter increases, reducing energy charging efficiency. Therefore, there is room for further study of pumping charging process methods using solar charging systems.

This disclosure was made in consideration of the above-mentioned issues, and aims to provide a solar charging system that can improve the energy charging efficiency of the pumping charging process.

In order to solve the above problem, one aspect of the disclosed technology is a solar charging system mounted on a vehicle, comprising a solar panel, a drive battery, an auxiliary battery, a first DC-DC converter capable of supplying power generated by the solar panel to the auxiliary battery, a second DC-DC converter capable of supplying power generated by the solar panel to the drive battery and supplying power from the drive battery to the auxiliary battery via the first DC-DC converter, and a control unit that controls the first DC-DC converter and the second DC-DC converter, wherein, during a process of supplying a predetermined power to the auxiliary battery, if the power generated by the solar panel is less than the predetermined power, the control unit supplies power from the drive battery to the auxiliary battery via the first DC-DC converter and the second DC-DC converter.

The solar charging system disclosed herein can improve the energy charging efficiency of the pumping charging process from the drive battery to the auxiliary battery.

FIG. 1 is a block diagram showing a schematic configuration of a solar charging system according to an embodiment of the present invention. Flowchart of pumping charge control executed by the solar charging system Flowchart of pumping charge control executed by the solar charging system A diagram explaining the flow of power during pumping charge control when there is surplus solar power generation. Diagram explaining the flow of power during pumping charge control when solar power generation is insufficient

The solar charging system according to the present disclosure uses a bidirectional high-voltage DC-DC converter connecting a solar panel and a drive battery. For example, when pumping power from the solar panel to charge the auxiliary battery is used, if the power generated by the solar panel is less than the power required to charge the auxiliary battery, power from the drive battery is supplied to the auxiliary battery via the high-voltage DC-DC converter and the auxiliary DC-DC converter. This supply process improves energy charging efficiency compared to pumping power via the main DC-DC converter, which consumes a lot of power during startup.
Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings.

<Embodiment>
[composition]
Fig. 1 is a block diagram showing an example of a power supply configuration including a solar charging system 1 according to an embodiment of the present disclosure. The solar charging system 1 shown in Fig. 1 includes a solar panel 10, a solar DDC 20, a high-voltage DDC 30, an auxiliary DDC 40, a drive battery 50, an auxiliary battery 60, and a control unit 100.

This solar charging system 1 can be installed in vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs), for example.

The solar panel 10 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. This solar panel 10 can be installed, for example, on the roof of a vehicle (solar roof). Note that the number of solar panels 10 installed on a vehicle is not limited to one, and may be multiple.

The solar DDC 20 is a DC-DC converter that outputs the power generated by the solar panel 10 to the high-voltage DDC 30 and the auxiliary DDC 40. This solar DDC 20 can convert the output voltage of the solar panel 10, which is the input voltage, to a predetermined voltage and output it to the high-voltage DDC 30 and the auxiliary DDC 40. The power generated by this solar panel 10 is calculated using measurements from sensors and measuring instruments (not shown) equipped in the solar DDC 20, etc.

The high-voltage DDC 30 is a bidirectional DC-DC converter (second DC-DC converter) connected to the solar DDC 20. This high-voltage DDC 30 can input the output power of the solar DDC 20, convert it (boost) to a predetermined voltage, and output it to the drive battery 50. The high-voltage DDC 30 can also input the power of the drive battery 50, convert it (step down) to a predetermined voltage, and output it to the auxiliary DDC 40.

The auxiliary DDC 40 is a unidirectional DC-DC converter (first DC-DC converter) connected to the solar DDC 20. This auxiliary DDC 40 can input the output power of the solar DDC 20, convert it (step down) to a predetermined voltage, and output it to the auxiliary battery 60.

The drive battery 50 is a rechargeable secondary battery, such as a lithium-ion battery or nickel-metal hydride battery. The drive battery 50 is connected to a main device (not shown) for driving the vehicle and can supply the power necessary to operate the main device. Examples of main devices include a starter motor and a traction electric motor. The drive battery 50 is connected to the solar panel 10 via the solar DDC 20 and high-voltage DDC 30 so that it can be charged using power generated by the solar panel 10. The drive battery 50 is also connected to the main DDC 200 so that it can be charged and discharged between the drive battery 50 and the auxiliary battery 60. The drive battery 50 has a higher rated voltage than the auxiliary battery 60.

The auxiliary battery 60 is a rechargeable secondary battery, such as a lithium-ion battery or a lead-acid battery. This auxiliary battery 60 is connected to auxiliary devices (not shown) other than those used to drive the vehicle, and can supply the power necessary to operate these auxiliary devices. Examples of auxiliary devices include lighting such as headlamps and interior lights, air conditioning devices such as heaters and coolers, and autonomous driving and advanced driving assistance devices. The auxiliary battery 60 is connected to the solar panel 10 via the solar DDC 20 and the auxiliary DDC 40 so that it can be charged using power generated by the solar panel 10. The auxiliary battery 60 is also connected to the main DDC 200 so that it can be charged and discharged between it and the drive battery 50. The auxiliary battery 60 has a lower rated voltage than the drive battery 50.

The solar DDC 20, high-voltage DDC 30, and auxiliary DDC 40 described above typically constitute a solar ECU (Electronic Control Unit) 70. In this solar ECU 70, the functions of the auxiliary DDC 40 may be included in the solar DDC 20. Furthermore, if multiple solar panels 10 are installed on the vehicle, multiple solar DDCs 20 may be provided in parallel to individually control each solar panel 10. Furthermore, the solar ECU 70 may be configured integrally with the solar panel 10, or may be configured in an integrated manner with other powertrain components.

The control unit 100 controls the power states of the solar panel 10, drive battery 50, and auxiliary battery 60 by controlling the solar DDC 20, high-voltage DDC 30, auxiliary DDC 40, and main DDC 200. Specifically, the control unit 100 controls the power supply from the solar panel 10 to the drive battery 50 by controlling the high-voltage DDC 30 to a step-up operation state. The control unit 100 also controls the power supply from the drive battery 50 to the auxiliary battery 60 by controlling the high-voltage DDC 30 to a step-down operation state and the auxiliary DDC 40 to a step-down operation state.

The control unit 100 may be realized as a function of the HV-ECU (not shown) that performs hybrid control of the vehicle, or as a function of the solar ECU 70, or may be realized by an ECU other than the HV-ECU and solar ECU 70. The ECU that realizes the control unit 100 typically includes a processor, memory, input/output interface, etc., and can perform the various controls described above by having the processor read and execute programs stored in the memory.

The main DDC 200 is a DCDC converter that supplies power from the drive battery 50 to the auxiliary battery 60 and auxiliary devices, and supplies power from the auxiliary battery 60 to the drive battery 50, when the solar ECU 70 is not in use, such as when the battery is not being charged with power generated by the solar panel 10. This main DDC 200 consumes more power for startup than the high-voltage DDC 30 and auxiliary DDC 40.

[control]
Next, the control executed by the solar charging system 1 will be described with further reference to Figures 2A, 2B, 3, and 4. Figures 2A and 2B are flowcharts explaining the pumping charge control process executed by the control unit 100 and solar ECU 70 of the solar charging system 1. The process of Figure 2A and the process of Figure 2B are connected by connectors X and Y. Figure 3 is a diagram explaining the power flow of the pumping charge control when the solar panel 10 in the solar charging system 1 generates surplus power. Figure 4 is a diagram explaining the power flow of the pumping charge control when the solar panel 10 in the solar charging system generates insufficient power.

The pumping charge control illustrated in Figures 2A and 2B is initiated, for example, when the solar ECU 70, which has had some or all of its functions suspended (sleep) while the vehicle is parked, is activated (wakes up) by sunlight irradiating the solar panel 10, which is now capable of generating electricity.

(Step S201)
The solar ECU 70 acquires the generated power Wgen, which is the power generated by the solar panel 10. This generated power Wgen can be derived from the voltage and current output by the solar panel 10. The generated power Wgen may be notified to the control unit 100. Once the generated power Wgen of the solar panel 10 is acquired by the solar ECU 70, the process proceeds to step S202.

(Step S202)
The solar ECU 70 determines whether the power generation Wgen of the solar panel 10 exceeds a predetermined threshold Wsol. This determination is made to determine whether the solar panel 10 is generating enough power to perform efficient pumping charge control. For example, if the power generation Wgen of the solar panel 10 is less than the power required for the pumping charge operation of the solar charging system 1, the auxiliary battery 60 will discharge, resulting in more battery power being consumed than the power obtained through solar power generation, making the pumping charge control meaningless. Therefore, the threshold Wsol can be set to a value equal to or greater than the power at which pumping charge control is possible without causing discharge from the auxiliary battery 60.

If the solar ECU 70 determines that the generated power Wgen exceeds the threshold value Wsol (Wgen > Wsol) (step S202, Yes), processing proceeds to step S204. On the other hand, if the solar ECU 70 determines that the generated power Wgen does not exceed the threshold value Wsol (Wgen <= Wsol) (step S202, No), processing proceeds to step S203.

(Step S203)
The solar ECU 70 is unable to perform efficient pumping charge control using the power generated by the solar panel 10, so it stops the operation of some or all of its predetermined functions and goes into sleep mode, thereby ending the pumping charge control.

(Step S204)
The solar ECU 70 starts power generation by the solar panel 10. That is, the solar ECU 70 starts outputting the power generated by the solar panel 10, Wgen, to the auxiliary battery 60 or the like. This power generation uses well-known maximum power point tracking (MPPT) control or the like. When the solar ECU 70 starts power generation by the solar panel 10, the process proceeds to step S205.

(Step S205)
The control unit 100 acquires the processing power Waux consumed in the process of charging the auxiliary battery 60 (hereinafter referred to as the "solar charging process"). More specifically, the processing power Waux is the power required for the control operations of the ECUs and other devices involved in the execution of the solar charging process. This processing power Waux can be derived from the current flowing out of the auxiliary battery 60, the output voltage, and other data detected by the control unit 100 and other devices. The processing power Waux is also notified to the solar ECU 70. Once the processing power Waux has been acquired by the control unit 100, the process proceeds to step S206.

(Step S206)
The control unit 100 acquires the required power Wpump consumed in the pumping charging process that supplies a predetermined amount of power to the auxiliary battery 60. More specifically, the required power Wpump is the sum of the power charged to the auxiliary battery 60 and the power consumed by auxiliary devices (not shown) (power consumption of the auxiliary system). This required power Wpump can be derived from the state of charge (SOC), outflow current, output voltage, and the like of the auxiliary battery 60 detected by the control unit 100 or the like. Once the required power Wpump has been acquired by the control unit 100, the process proceeds to step S207.

(Step S207)
The control unit 100 notifies the solar ECU 70 of the processing power Waux and the required power Wpump. When the control unit 100 notifies the solar ECU 70 of the processing power Waux and the required power Wpump, the process proceeds to step S208.

(Step S208)
The solar ECU 70 determines whether the power generated by the solar panel 10, Wgen, is equal to or greater than the total power of the processing power Waux consumed in the solar charging process and the required power Wpump consumed in the pumping charge process. This determination is made to determine whether pumping charge of the auxiliary battery 60 is possible using only the power generated by the solar panel 10, Wgen.

If the solar ECU 70 determines that the generated power Wgen is greater than or equal to the total power of the processing power Waux and the required power Wpump (Wgen ≥ Waux + Wpump) (step S208, Yes), processing proceeds to step S209. On the other hand, if the solar ECU 70 determines that the generated power Wgen is less than the total power of the processing power Waux and the required power Wpump (Wgen < Waux + Wpump) (step S208, No), processing proceeds to step S210.

(Step S209)
The control unit 100 and the solar ECU 70 supply the total power of the processing power Waux and the required power Wpump, which is part of the generated power Wgen of the solar panel 10, to the auxiliary battery 60. The flow of power in this case is shown by the solid line in Figure 3. When the control unit 100 and the solar ECU 70 have supplied the total power of the processing power Waux and the required power Wpump to the auxiliary battery 60, the process proceeds to step S211.

(Step S210)
The control unit 100 and the solar ECU 70 supply all of the generated power Wgen of the solar panel 10 to the auxiliary battery 60. The flow of power in this case is indicated by the solid lines in Figure 4. When all of the generated power Wgen has been supplied to the auxiliary battery 60 by the control unit 100 and the solar ECU 70, the process proceeds to step S212.

(Step S211)
The control unit 100 and the solar ECU 70 control the high-voltage DDC 30 to a boost operation state, thereby enabling the power Wgen generated by the solar panel 10 to be supplied to the drive battery 50. When the control unit 100 and the solar ECU 70 control the high-voltage DDC 30 to a boost operation state, the process proceeds to step S213.

(Step S212)
The control unit 100 and the solar ECU 70 control the high-voltage DDC 30 to a step-down operation state. This allows power from the drive battery 50 to be supplied to the auxiliary battery 60 via the auxiliary DDC 40, which is in step-down operation. When the control unit 100 and the solar ECU 70 control the high-voltage DDC 30 to a step-down operation state, the process proceeds to step S214.

(Step S213)
The control unit 100 and solar ECU 70 supply surplus power Wrem, which is not supplied to the auxiliary battery 60, out of the power generated by the solar panel 10, to the drive battery 50. This surplus power Wrem is the power obtained by subtracting the processing power Waux and the required power Wpump from the generated power Wgen (Wrem = Wgen - (Waux + Wpump)). The flow of power in this case is shown by the dashed line in Figure 3. Once the control unit 100 and solar ECU 70 have supplied surplus power Wrem of the generated power Wgen to the drive battery 50, the process proceeds to step S201.

(Step S214)
The control unit 100 and solar ECU 70 supply a power shortage Wlack, which is the power required for the auxiliary battery 60 that is not met by the power generated by the solar panel 10 alone, from the drive battery 50 to the auxiliary battery 60 (dashed line in FIG. 4). This power shortage Wlack is the power obtained by adding the processing power Waux to the required power Wpump and subtracting the generated power Wgen from the sum (Wlack = (Waux + Wpump) - Wgen). The flow of power in this case is shown by the dashed line in FIG. 4. Once the control unit 100 and solar ECU 70 have supplied the power shortage Wlack of the auxiliary battery 60 from the drive battery 50 to the auxiliary battery 60, the process proceeds to step S201.

<Actions and Effects>
As described above, in the solar charging system 1 according to one embodiment of the present disclosure, the high-voltage DDC 30 provided in the solar ECU 70 is configured as a bidirectional DC-DC converter. When it is necessary to perform pumping charging from the drive battery 50 to the auxiliary battery 60, such as when the power generated by the solar panel 10 alone, Wgen, is insufficient, the control unit 100 controls the power transfer to be via the high-voltage DDC 30 and the auxiliary DDC 40 of the solar ECU 70, rather than via the main DDC 200.

This control enables pumping charging of the auxiliary battery 60 by operating the high-voltage DDC 30 and the auxiliary DDC 40, which consume less power for startup than the main DDC 200, without operating the main DDC 200, which consumes a lot of power for startup. This reduces the power consumed by the pumping charging process, reduces energy loss throughout the vehicle, and improves energy charging efficiency.

The above describes one embodiment of the disclosed technology, but the present disclosure can be understood not only as a solar charging system, but also as a method performed by a solar charging system, a program for that method, a computer-readable non-transitory storage medium storing that program, a vehicle equipped with a solar charging system, etc.

The solar charging system disclosed herein can be used in vehicles that charge their batteries using power generated by solar panels.

1 Solar charging system 10 Solar panel 20 Solar DDC
30 High-voltage DDC
40 Auxiliary DDC
50 Drive battery 60 Auxiliary battery 70 Solar ECU
100 Control unit 200 Main DDC

Claims (3)

A solar charging system mounted on a vehicle,
Solar panels and
A drive battery;
An auxiliary battery;
a first DC-DC converter capable of supplying power generated by the solar panel to the auxiliary battery;
a second DC-DC converter that can supply power generated by the solar panel to the drive battery and can supply power from the drive battery to the auxiliary battery via the first DC-DC converter;
a control unit that controls the first DC-DC converter and the second DC-DC converter,
the control unit, in the process of supplying a predetermined power to the auxiliary battery, supplies power from the drive battery to the auxiliary battery via the first DC-DC converter and the second DC-DC converter when the power generated by the solar panel is less than the predetermined power.
Solar charging system. When the power generated by the solar panel is less than the predetermined power, the control unit supplies the power that is insufficient to be generated by the solar panel from the drive battery to the auxiliary battery.
The solar charging system according to claim 1 . In the process of supplying the predetermined power to the auxiliary battery, if the power generated by the solar panel is equal to or greater than the predetermined power, the control unit supplies the power generated by the solar panel to the auxiliary battery and supplies surplus power, which is obtained by excluding the predetermined power from the power generated by the solar panel, to the drive battery.
The solar charging system according to claim 1 or 2.