Electric power system

Abstract

To provide an electric power system capable of suppressing the reduction of the conversion efficiency of a DC-DC converter due to fluctuations in the power generated by solar panels.SOLUTION: The electric power system is an electric power system mounted on a vehicle. The system includes: a solar panel; an auxiliary battery; a drive battery; a DC-DC converter that inputs the electric power of the solar panel and the electric power of the auxiliary battery, and outputs the electric power of predetermined voltage to the drive battery; and a control unit that controls the DC-DC converter. The control unit is configured so as to, when the auxiliary battery has a charge equal to or greater than a first value, set the output electric power of the DC-DC converter to be a second value in which the electric power generated by the solar panel and the electric power from the auxiliary battery are supplied to the drive battery in parallel.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a power system mounted on a vehicle.

Background Art

[0002] Patent Document 1 discloses a charging device for a vehicle that can charge a driving battery (high-voltage battery) via a DCDC converter with the power generated by a solar panel or the power stored in an auxiliary battery (low-voltage battery) by switching a switch.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The vehicle charging device described in Patent Document 1 is configured to charge the driving battery with either the generated power of the solar panel or the power of the auxiliary battery selected by switching a switch. Therefore, in a situation where the state of charging the driving battery with the generated power of the solar panel is selected, if the generated power of the solar panel fluctuates due to the influence of sunlight or the like, the conversion efficiency of the DCDC converter may decrease.

[0005] The present disclosure has been made in view of the above problems, and an object thereof is to provide a power system capable of suppressing a decrease in the conversion efficiency of a DCDC converter due to fluctuations in the generated power of a solar panel.

Means for Solving the Problems

[0006] To solve the above problems, one aspect of the disclosed technology is a power system mounted on a vehicle, comprising a solar panel, an auxiliary battery, a driving battery, a DCDC converter that inputs the power of the solar panel and the power of the auxiliary battery and outputs power of a predetermined voltage to the driving battery, and a control unit that controls the DCDC converter. When the power storage amount of the auxiliary battery is equal to or greater than a first value, the control unit sets the output power of the DCDC converter to a second value at which the power generated by the solar panel and the power of the auxiliary battery are supplied to the driving battery in parallel. This is the power system.

Advantages of the Invention

[0007] According to the power system of the present disclosure, when the power storage amount of the auxiliary battery is equal to or greater than a first value, the driving battery is charged with the combined power of the power generated by the solar panel and the power of the auxiliary battery. Therefore, while absorbing fluctuations in the power generated by the solar panel with the auxiliary battery, it is possible to always drive the DCDC converter with high conversion efficiency and suppress a decrease in the conversion efficiency of the DCDC converter.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0009] The power system according to the present disclosure supplies the driving battery with the combined power of the power generated by the solar panel and the power of the auxiliary battery when the auxiliary battery has sufficient power storage. As a result, while absorbing fluctuations in the power generated by the solar panel with the auxiliary battery, it is possible to charge the driving battery while always driving the DCDC converter with high conversion efficiency. Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings.

[0010] <Embodiment> [Configuration] FIG. 1 is a block diagram showing a schematic configuration of a power system 1 according to an embodiment of the present disclosure. The power system 1 illustrated in FIG. 1 includes a solar power generation module 10, an auxiliary battery 20, a drive battery 30, a DCDC converter 40, a control unit 50, and a battery sensor 60. In FIG. 1, power lines through which power is transmitted and received are shown as solid lines, and signal lines through which detection values, control instructions, etc. flow are shown as dashed lines. This power system 1 is mounted on vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs), for example.

[0011] The solar power generation module 10 is a power generation device that generates power by receiving sunlight, and outputs the generated power to the auxiliary battery 20 and the DCDC converter 40 connected to the solar power generation module 10. This solar power generation module 10 includes a solar panel 11 and an MPPT-DDC 12.

[0012] The solar panel 11 is an assembly of solar cells. The MPPT-DDC 12 is a DCDC converter (DDC) that outputs the power generated by the solar panel 11 at a predetermined voltage based on maximum power point tracking (MPPT) control.

[0013] The auxiliary battery 20 is a secondary battery configured to be chargeable and dischargeable, such as a lithium-ion battery, for example. This auxiliary battery 20 is connected to the solar power generation module 10 so as to be chargeable by the power generated by the solar panel 11. Further, the auxiliary battery 20 is connected to the DCDC converter 40 so as to be able to charge the drive battery 30 with the power stored therein.

[0014] The drive battery 30 is a secondary battery configured to be chargeable and dischargeable, such as a lithium-ion battery, for example. This drive battery 30 can be charged by the power generated by the solar panel 11 and the power of the auxiliary battery 20, and is connected to the solar power generation module 10 and the auxiliary battery 20 via a DCDC converter 40. The drive battery 30 is a high-voltage battery with a rated voltage higher than that of the auxiliary battery 20.

[0015] The DCDC converter 40 is a power converter that can convert the input power into power of a predetermined voltage and output it. One end (primary side) of this DCDC converter 40 is connected to the solar power generation module 10 and the auxiliary battery 20, and the other end (secondary side) is connected to the drive battery 30. The DCDC converter 40 can boost the voltage of the solar power generation module 10 and the auxiliary battery 20 input to the primary side and output it as the voltage on the secondary side. The operation of the DCDC converter 40 is controlled by the control unit 50.

[0016] The control unit 50 is an electronic control unit (ECU) that controls the power system 1. This control unit 50 acquires information on the generated power from the solar power generation module 10 and acquires information on the power storage amount of the auxiliary battery 20 from the battery sensor 60. Then, the control unit 50 controls the operation of the DCDC converter 40 based on the acquired information.

[0017] The battery sensor 60 is a sensor for detecting the physical quantity of the auxiliary battery 20. Examples of the physical quantity of the auxiliary battery 20 include voltage, current, temperature, and state of charge (SOC).

[0018] [Control] Next, with further reference to FIG. 2, the control performed in the power system 1 according to the present embodiment will be described. FIG. 2 is a flowchart for explaining the processing procedure of the charge control executed by the power system 1.

[0019] The charging control illustrated in FIG. 2 starts when it is determined in the vehicle that the power storage amount of the drive battery 30 has decreased to a predetermined value and charging of the drive battery 30 by the power system 1 is necessary.

[0020] (Step S201) The control unit 50 of the power system 1 acquires the power (solar power generation power SOL_W) generated by the solar panel 11 of the solar power generation module 10 from the MPPT-DDC12. When the solar power generation power SOL_W is acquired by the control unit 50, the process proceeds to step S202.

[0021] (Step S202) The control unit 50 of the power system 1 acquires the power stored in the auxiliary battery 20 (auxiliary battery stored power amount Lib_SOC) from the battery sensor 60. When the auxiliary battery stored power amount Lib_SOC is acquired by the control unit 50, the process proceeds to step S203.

[0022] (Step S203) The control unit 50 of the power system 1 determines whether the auxiliary battery stored power amount Lib_SOC is equal to or greater than the discharge allowable SOC. This discharge allowable SOC is a predetermined power storage amount (first value) at which power supply (charging) from the auxiliary battery 20 to the drive battery 30 is allowed, and is set to an appropriate value based on the performance, capacity, and guaranteed life of the auxiliary battery 20. If the control unit 50 determines that the auxiliary battery stored power amount Lib_SOC is equal to or greater than the discharge allowable SOC (step S203, yes), the process proceeds to step S204. On the other hand, if the control unit 50 determines that the auxiliary battery stored power amount Lib_SOC is less than the discharge allowable SOC (step S203, no), the process proceeds to step S206.

[0023] (Step S204) The control unit 50 of the power system 1 sets (controls) the output power of the DCDC converter 40 (DDC) to a power (second value) at which the conversion operation of the DCDC converter 40 has a predetermined high efficiency. FIG. 3 shows an example of the conversion efficiency of the output power of the DCDC converter 40. As in the example of FIG. 3, as the output power of the DCDC converter 40, the output power Wa at which the conversion efficiency is maximized may be set, or any value of the output powers Wb to Wc at which the conversion efficiency is relatively high may be set. When the output power of the DCDC converter 40 (DDC) is set to a high conversion efficiency by the control unit 50, the process proceeds to step S205.

[0024] (Step S205) The power system 1 charges the drive battery 30 with the solar power generation SOL_W and the power of the auxiliary battery 20. In this charging, if the solar power generation SOL_W is equal to or greater than the output power of the DCDC converter 40 set in step S204 above, no power is taken out from the auxiliary battery 20, and if the solar power generation SOL_W is less than the output power of the DCDC converter 40, power is taken out from the auxiliary battery 20 for the power shortage with respect to the output power. That is, the fluctuation of the solar power generation SOL_W that fluctuates due to environmental factors such as the solar radiation amount on the solar panel 11 is absorbed by the power of the auxiliary battery 20. When the drive battery 30 is charged using the solar power generation SOL_W and the power of the auxiliary battery 20, the process proceeds to step S208.

[0025] (Step S206) The control unit 50 of the power system 1 sets the output power of the DCDC converter 40 (DDC) to the solar power generation SOL_W. With this setting, only the power generated by the solar power generation module 10 is output to the drive battery 30 via the DCDC converter 40. When the output power of the DCDC converter 40 (DDC) is set to the solar power generation SOL_W by the control unit 50, the process proceeds to step S207.

[0026] (Step S207) The power system 1 charges the driving battery 30 with the solar power SOL_W. In this charging process, since the output power of the DCDC converter 40 is equal to the solar power SOL_W, no power is taken out from the auxiliary battery 20. Therefore, the increase of the auxiliary battery 20 can be prevented. When the driving battery 30 is charged using the solar power SOL_W, the process proceeds to step S208.

[0027] (Step S208) The power system 1 determines whether the driving battery 30 needs to be charged. If the power system 1 determines that the driving battery 30 still needs to be charged continuously (step S208, yes), the process proceeds to step S201. On the other hand, if the power system 1 determines that the driving battery 30 no longer needs to be charged (step S208, no), this charging control ends.

[0028] <Function and Effect> As described above, according to the power system 1 according to an embodiment of the present disclosure, when there is enough surplus power in the power storage amount of the auxiliary battery 20 to charge the driving battery 30, the DCDC converter 40 is made to have a higher conversion efficiency so that the generated power of the solar panel 11 can be preferentially supplied, and then the generated power of the solar panel 11 and the power of the auxiliary battery 20 are supplied to the driving battery 30 in parallel.

[0029] By this supply control, the DCDC converter 40 can always be driven in a region with high conversion efficiency. In addition, since the increase and decrease fluctuations of the generated power of the solar panel 11 can be absorbed by adjusting the power taken out from the auxiliary battery 20, there is no need to provide a dedicated battery for absorbing the generated power.

[0030] Also, according to the power system 1 according to an embodiment of the present disclosure, when there is not enough surplus power in the power storage amount of the auxiliary battery 20 to charge the driving battery 30, only the generated power of the solar panel 11 is supplied to the driving battery 30.

[0031] By this supply control, it is possible to prevent the extraction of power from the auxiliary battery 20 and avoid the situation where the auxiliary battery 20 runs out of power.

[0032] As described above, an embodiment of the disclosed technology has been described. However, the present disclosure can be understood not only as a power system, but also as a method executed by the power system, a program of the method, a computer-readable non-transitory storage medium storing the program, a vehicle equipped with the power system, and so on.

Industrial Applicability

[0033] The power system of the present disclosure can be used in vehicles equipped with solar panels and the like.

Explanation of Reference Numerals

[0034] 1 Power system 10 Solar power generation module 11 Solar panel 12 MPPT-DDC 20 Auxiliary battery 30 Driving battery 40 DCDC converter 50 Control unit 60 Battery sensor

Claims

1. A power system mounted on a vehicle, comprising: a solar panel; an auxiliary battery; a drive battery; a DC-DC converter that inputs the power of the solar panel and the power of the auxiliary battery and outputs power of a predetermined voltage to the drive battery; a control unit that controls the DC-DC converter, wherein when the power storage amount of the auxiliary battery is equal to or greater than a first value, the control unit sets the output power of the DC-DC converter to a second value at which the power generated by the solar panel and the power of the auxiliary battery are supplied to the drive battery in parallel. A power system.

2. The power system according to claim 1, wherein the second value is the output power at which the conversion efficiency of the DC-DC converter is maximized.

3. The power system according to claim 1 or 2, wherein when the power storage amount of the auxiliary battery is less than the first value, the control unit sets the output power of the DC-DC converter to the power generated by the solar panel.

4. The power system according to any one of claims 1 to 3, wherein the first value is the power storage amount at which the auxiliary battery does not overcharge.

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