JP2020110028A - Power control device - Google Patents

Abstract

To provide a power control device that includes a fuel cell system and is able to avoid starting power generation for charging a low voltage battery during parking, without influence on emission control.SOLUTION: A power control device, which is mounted in a vehicle, comprises: a high voltage battery capable of charging a low voltage battery via a voltage conversion unit during stop and having a higher rating voltage than the low voltage battery; a fuel cell system capable of charging the high voltage battery; and a control unit that controls charging of the high voltage battery by the fuel cell system. If the amount of power that can be discharged to the low voltage battery from the high voltage battery is smaller than the amount of power required to charge the low voltage battery to a predetermined amount of stored power when ignition is turned off during power generation of the fuel cell system, the control unit continues the power generation of the fuel cell system until the amount of power that can be discharged becomes equal to or larger than a required amount of power.SELECTED DRAWING: Figure 1

Description

The present invention relates to a power control device including a fuel cell system mounted on a vehicle.

When the vehicle does not travel for a long time, the auxiliary battery (low voltage battery) may be discharged and the battery may run out. Therefore, it is known that the auxiliary battery is prevented from running out of battery by charging the auxiliary battery with the main battery (high voltage battery) during parking, as in the method of Patent Document 1, for example. However, in the method described in Patent Document 1, since the amount of electricity stored in the main battery depends on the traveling state before parking, it is not possible to sufficiently secure the amount of electricity stored in the main battery after parking depending on the traveling state, and the auxiliary battery is charged. There was a possibility that I could not.

Therefore, in Patent Document 2, when charging the auxiliary battery during parking, if the amount of electricity stored in the high-voltage battery is sufficiently secured, the auxiliary battery is charged by the high-voltage battery, and the amount of electricity stored in the high-voltage battery is There is disclosed a technique of charging an auxiliary battery by a generator by starting the engine when the temperature is low.

JP, 2006-174619, A JP, 2013-224070, A

However, in the method described in Patent Document 2, the engine is started at a timing unintended by the parked user or a third party, and power generation is started, which gives a feeling of strangeness to users and third parties around the vehicle. There is a possibility that it will end up. Further, since the engine is started during parking, the engine is cold started, and more nitrogen oxides (NOx) are emitted than during traveling, and the exhaust gas regulation may not be satisfied.

By the way, recently, a fuel cell vehicle is drawing attention because it does not emit nitrogen oxides. When the technology of Patent Document 2 is applied to a fuel cell vehicle, power generation during parking is performed not by the engine but by the fuel cell system, so that nitrogen oxides are not discharged and exhaust gas regulations are not affected. However, since the power generation is suddenly started while the vehicle is still parked, it is impossible to eliminate the discomfort felt by the users and third parties around the vehicle.

The present invention has been made in view of the above problems, and includes a fuel cell system, and electric power that can avoid starting power generation for charging a low-voltage battery during parking without affecting exhaust gas regulations. An object is to provide a control device.

In order to solve the above-mentioned problem, one aspect of the present invention is a power control device mounted on a vehicle, which can charge a low-voltage battery via a voltage conversion unit while the vehicle is stopped, and is lower than a low-voltage battery. A high-voltage battery having a high rated voltage, a fuel cell system capable of charging the high-voltage battery, and a control unit that controls charging of the high-voltage battery by the fuel cell system are provided. If the amount of electric power that can be discharged from the high-voltage battery to the low-voltage battery when the ignition is turned off is less than the amount of electric power required to charge the low-voltage battery to a predetermined storage amount, the amount of electric power that can be discharged is required. Continue to generate power from the fuel cell system until the amount of electric power exceeds a certain level.

According to the present invention, it is possible to provide a power control device that includes a fuel cell system and that can avoid starting power generation for charging a low-voltage battery during parking without affecting exhaust gas regulations.

1 is a diagram of a system including a power control device according to an embodiment of the present invention. The flowchart explaining the processing procedure which the electric power control apparatus which concerns on one Embodiment of this invention performs.

In the power control device according to the present invention, the fuel cell system is generating power when the ignition is turned off, and the amount of power that can be discharged from the high-voltage battery to the low-voltage battery sufficiently charges the low-voltage battery. If it is less than the amount of electric power necessary for this, the power generation of the fuel cell system is continued. As a result, after the ignition is turned off, the high-voltage battery can secure a sufficient amount of electricity stored in the fuel cell to charge the low-voltage battery sufficiently. Therefore, in order to charge the high-voltage battery or the low-voltage battery, it is not necessary to start the engine or to start the power generation system during parking, and the operation noise for power generation gives a sense of discomfort to the people around the vehicle. There is no. In addition, since the fuel cell system is used for power generation, nitrogen oxides are not emitted and the exhaust gas regulations are not affected.

(Embodiment)
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

<Structure>
The configuration of the power control device according to the embodiment will be described with reference to FIG. 1. FIG. 1 is a diagram of a system including a power control device according to an embodiment of the present invention. The power control device 1 is mounted on a fuel cell vehicle (FCV) that runs on a motor using a fuel cell as a power source, and includes a high voltage battery 10, a fuel cell system 40, and a control unit 50. The high voltage battery 10 is connected to the low voltage battery 20 via the DC/DC converter 30. The control unit 50 is connected to the high-voltage battery 10 and the low-voltage battery 20 via the DC/DC converter 30, the fuel cell system 40, and the battery sensor 60. In FIG. 1, wirings through which power flows are indicated by solid lines, and wirings through which signals flow are indicated by dotted lines. It should be noted that in the present embodiment, the battery sensor 60 is assumed to be a sensor provided in advance in the vehicle, and the example in which the battery sensor 60 is not included in the configuration of the power control device 1 has been described. A configuration including the battery sensor 60 may be used.

The fuel cell system 40 (FC system) includes a fuel cell 41 (FC stack), a hydrogen tank 42, and an air compressor 43. The fuel cell 41 is a power generation device that generates electric power by utilizing a chemical reaction between hydrogen and oxygen. In this embodiment, hydrogen is supplied from the hydrogen tank 42 and oxygen is supplied from the air compressor 43 to the fuel cell 41, so that the fuel cell 41 generates electric power. The electric power generated by the fuel cell 41 is stored in the high voltage battery 10.

The high-voltage battery 10 is a high-voltage battery composed of a rechargeable secondary battery that can drive a traveling motor and the like. The high-voltage battery 10 is connected to the fuel cell 41 via an inverter (not shown) so that it can be charged by the electric power generated by the fuel cell 41. The electric power stored in the high voltage battery 10 can be supplied to the low voltage battery 20 via the DC/DC converter 30.

The low-voltage battery 20 is a low-voltage battery of about 12 V that can operate auxiliary equipment such as a radio, a car navigation system, and an electronic control unit (ECU), which is composed of a secondary battery that can be charged and discharged. The low-voltage battery 20 is connected to the high-voltage battery 10 via the DC/DC converter 30 so that the low-voltage battery 20 can be charged by the electric power stored in the high-voltage battery 10.

The DC/DC converter 30 is a voltage conversion unit that steps down the output power of the high-voltage battery 10 and supplies it to the low-voltage battery 20 under the control of the control unit 50.

The battery sensor 60 has a configuration for acquiring information on the high-voltage battery 10 and the low-voltage battery 20, and includes, for example, a voltage sensor, a current sensor, and a temperature sensor. The acquired information on the high voltage battery 10 and the low voltage battery 20 is sent to the control unit 50.

The control unit 50 calculates the charge states of the high-voltage battery 10 and the low-voltage battery 20 based on the information of the high-voltage battery 10 and the low-voltage battery 20 acquired from the battery sensor 60, and based on the calculated charge states of the batteries. Then, it is determined whether or not the dischargeable electric energy of the high voltage battery is less than the required charging electric energy of the low voltage battery. The dischargeable power amount and the required charging power amount will be described later. Further, the control unit 50 has a timer function and manages the time for executing the charging of the low voltage battery 20. The control unit 50 controls the power generation of the fuel cell 41 by the fuel cell system 40 and the DC/DC converter based on the count of the timer, the calculated power storage state, and the magnitude relationship between the dischargeable power amount and the required charging power amount as appropriate. 30 to control charging of the low voltage battery 20 by the high voltage battery 10.

<Control processing>
With further reference to FIG. 2, the charging control performed by the power control device 1 according to the embodiment will be described. FIG. 2 is a flowchart illustrating a processing procedure executed by the power control device according to the embodiment of the present invention. This flow is started on condition that the fuel cell 41 was generating power when the vehicle ignition was turned off.

Step S101: The control unit 50 determines whether or not the dischargeable power amount of the high voltage battery 10 is less than the required charging power amount of the low voltage battery 20. The determination is performed based on the power storage states of the high voltage battery 10 and the low voltage battery 20, which are calculated by the control unit 50 based on the information of the high voltage battery 10 and the low voltage battery 20 acquired from the battery sensor 60. The dischargeable power amount is a power amount obtained by subtracting a predetermined lower limit charge amount (lower limit SOC) of the high voltage battery 10 from a predetermined charge amount (SOC) immediately after the ignition is turned off. This lower limit SOC is a reference SOC for determining whether or not the high-voltage battery 10 stores the electric power that can be discharged, and can be, for example, a storage amount that does not cause the high-voltage battery 10 to be over-discharged. The required charging power amount is calculated by converting the power consumption amount during parking for a predetermined number of days into a power storage amount and adding the start limit power storage amount (starting limit SOC) to the power storage amount of the auxiliary battery 20 immediately after the ignition is turned off. It is the amount of power less the amount. This starting limit SOC can be set to, for example, a low storage amount that allows the auxiliary device to be driven when the ignition is turned on in the low-voltage battery 20. The predetermined number of days is, for example, when it is assumed that the low-voltage battery 20 is charged to the upper limit SOC and parking is started, the low-voltage battery 20 consumes electric power at the time of parking until the storage amount is reduced to the start limit SOC. It can be set within the range of no more than the number of days, and can be set to 30 days as an example. When the dischargeable power amount is equal to or greater than the required charging power amount (YES in S101), the process proceeds to S103, and otherwise (NO in S101), the process proceeds to step S102.

Step S102: The control unit 50 continues the power generation of the fuel cell 41 without stopping the fuel cell system 40. At this time, the high voltage battery 10 is charged with the electric power generated by the fuel cell 41. After that, the process proceeds to step S101.

Step S103: The control unit 50 stops the fuel cell system 40 and stops the power generation of the fuel cell 41. The upper limit SOC is, for example, an upper limit amount of stored electricity that does not cause the high-voltage battery 10 to be overcharged. Then, a process progresses to step S104.

Step S104: The control unit 50 sets a starting time for starting the DC/DC converter 30. The start-up time can be set, for example, by providing a count-up timer function in the control unit 50, and can be set to, for example, the time until the stored amount of the low-voltage battery 20 at the ignition-off time falls to the start-up limit SOC. it can. In this case, the start-up time is calculated based on the power consumption and the amount of electricity stored in the low-voltage battery 20 per unit time when the ignition is turned off. Then, a process progresses to step S105.

Step S105: The control unit 50 determines whether or not the activation time set in step S104 has elapsed. If the startup time has elapsed (YES in S105), the process proceeds to step S106, and otherwise (NO in S105), the process proceeds to S105.

Step S106: The control unit 50 activates the DC/DC converter and starts charging the low-voltage battery 20 using the electric power of the high-voltage battery 10. After that, the process proceeds to step S107.

Step S107: The control unit 50 determines whether or not the amount of electricity stored in the low-voltage battery 20 has exceeded a predetermined value. The predetermined value at this time is set each time as a value at which it can be determined that the low-voltage battery 20 can secure the required charging power amount used in step S101. However, when the amount of electricity stored in the high-voltage battery 10 is lower than expected from the time point of step S103 (time point of power generation of the fuel cell 41), the high-voltage battery 10 is transferred to the low-voltage battery 20 before the SOC reaches the starting limit SOC. The discharge may be stopped. After that, the flow ends.

In the control of steps S101 and S103, the case where the fuel cell system 40 is stopped after the dischargeable power amount becomes equal to or more than the required charging power amount has been described. However, if the charged amount of the high voltage battery 10 reaches a predetermined upper limit SOC (overcharge SOC or the like) for some reason, the dischargeable power amount becomes the required charged power amount from the viewpoint of protection of the high voltage battery 10. The fuel cell system 40 may be stopped even if it has not reached the limit.

<Actions, effects, etc.>
As described above, according to the power control device 1 according to the embodiment of the present invention, the fuel cell 41 is generating power when the ignition is off, and the power that can be discharged from the high-voltage battery 10 to the low-voltage battery 20. If the amount is less than the amount of electric power required to sufficiently charge the low-voltage battery 20, the fuel cell 41 continues to generate power and the high-voltage battery 10 is sufficiently charged.

As a result, it is possible to charge the low-voltage battery without starting power generation during parking and without affecting exhaust gas regulations.

The present invention can be understood not only as a power control device but also as a computer and a program having a power control function, or as a vehicle.

INDUSTRIAL APPLICABILITY The power control device of the present invention is useful, for example, it can be applied to a vehicle equipped with a fuel cell system.

1 Power Control Device 10 High Voltage Battery 20 Low Voltage Battery 30 DC/DC Converter 40 Fuel Cell System 41 Fuel Cell 50 Control Unit

Claims (1)

A power control device mounted on a vehicle,
A low-voltage battery can be charged through the voltage conversion unit while the vehicle is stopped, and a high-voltage battery having a higher rated voltage than the low-voltage battery,
A fuel cell system capable of charging the high-voltage battery,
A control unit that controls charging of the high-voltage battery by the fuel cell system,
The control unit is
When the ignition is turned off during power generation of the fuel cell system,
If the amount of electric power that can be discharged from the high-voltage battery to the low-voltage battery is less than the amount of electric power required to charge the low-voltage battery to a predetermined storage amount,
A power control device for continuing the power generation of the fuel cell system until the amount of power that can be discharged becomes equal to or greater than the required amount of power.

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