JP6982787B2 - Fuel cell control device and its control method, fuel cell vehicle - Google Patents

Description

The present invention relates to a fuel cell control device, a control method thereof, and a fuel cell vehicle.

In recent years, a fuel cell vehicle equipped with a fuel cell system that uses a fuel cell and a secondary battery as a power source has attracted attention. The power supplied from the fuel cell system is supplied to an electric load including a traveling motor and auxiliary equipment (for example, a radiator fan, a cooling water pump, an electric lamp, etc.).

Further, the secondary battery in the fuel cell system stores the electric power generated by the fuel cell. The electric power charged in the secondary battery is used, for example, as the restart electric power of the system after the fuel cell system is stopped. Therefore, when the fuel cell system is stopped and the state of charge (SOC) of the secondary battery is less than the amount required for the next start of the system, the secondary battery is powered by the power generated by the fuel cell. Needs to be charged.

Patent Document 1 discloses that when the fuel cell system is stopped, charging is performed in order to secure the charge amount of the secondary battery required for the next start of the system.

Japanese Unexamined Patent Publication No. 2007-165055

However, the above charging when the fuel cell system is stopped may take a long time to secure the charging amount required for the next start. In addition, if the fuel cell system is repeatedly started and stopped in a short time due to repeated short trip driving, the charging time of the secondary battery during driving becomes shorter than the power consumption, and as a result, the fuel cell system is stopped. In many cases, the charge amount of the secondary battery is less than the value required for the next start. Therefore, when the fuel cell system is repeatedly started and stopped, it often takes a long time to charge the secondary battery to secure the charge amount.

The present invention provides a technique for shortening the charging time of a secondary battery of a fuel cell system when the fuel cell system is repeatedly started and stopped.

A first aspect of the present invention relates to a fuel cell control awareness including a fuel cell system including a fuel cell, a secondary battery, and a control unit for controlling the fuel cell system. The control unit determines whether or not the charge amount of the secondary battery is equal to or less than a threshold value which is a value obtained by adding a first predetermined value to a lower limit value capable of supplying electric power for stopping and starting the fuel cell system. judge. When the control unit receives a command from the fuel cell system and determines that the charge amount of the secondary battery is equal to or less than the threshold value, the charge amount is forced to charge the secondary battery from the fuel cell. The fuel cell system is controlled so as to carry out until the threshold is reached. Further, the control unit stops the fuel cell system after performing the forced charging. After stopping the fuel cell system, the control unit starts the fuel cell system based on (i) a start request of the fuel cell system within a predetermined period, and (ii) an order to stop the fuel cell system. When received, the threshold value is set to a value obtained by adding a second predetermined value lower than the first predetermined value to the lower limit value. In this embodiment, the control unit may set the threshold value based on the temperature of the secondary battery. Further, in this embodiment, when the second forced charging is performed within the predetermined period after the first forced charging is performed, the control unit becomes longer than the first forced charging time. As described above, the charging time of the second forced charging may be set. Further, in this first aspect, the forced charging execution speed may be set based on the temperature of the secondary battery.
A second aspect of the present invention relates to a fuel cell vehicle including the fuel cell control device.
A third aspect of the present invention relates to a control method of a fuel cell control device including a fuel cell, a fuel cell system including a secondary battery, and a control unit for controlling the fuel cell system.
This method
(i) The fuel cell system is instructed to stop, and (ii) the charge amount of the secondary battery is a first predetermined value as a lower limit value capable of supplying electric power for stopping and starting the fuel cell system. On condition that the value is equal to or less than the threshold value obtained by adding the above, the forced charging from the fuel cell to the secondary battery is carried out until the charge amount reaches the threshold value.
After performing the forced charging, stopping the fuel cell system and
After the fuel cell system is stopped, (i) the fuel cell system is started based on the start request of the fuel cell system, and (ii) the stop command of the fuel cell system is issued within a predetermined period. , The threshold value is set to a value obtained by adding a second predetermined value lower than the first predetermined value to the lower limit value.
And include.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a technique for shortening the charging time of a secondary battery of a fuel cell system when the fuel cell system is repeatedly started and stopped.

It is a figure which shows the schematic structure of the fuel cell system which concerns on one Embodiment. It is a flowchart which shows the control of charge / discharge of a secondary battery in the fuel cell system which concerns on one Embodiment. It is a figure which shows the example of the setting method of the threshold value used for the control of charge / discharge of a secondary battery in the fuel cell system which concerns on one Embodiment. It is a graph which shows the control of charge / discharge of a secondary battery in the fuel cell system which concerns on one Embodiment. It is a flowchart which shows the control of charge / discharge of a secondary battery in the fuel cell system which concerns on one Embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to these.

1. 1. Configuration of Fuel Cell System An example of the schematic configuration of the fuel cell system according to the embodiment of the present invention will be described with reference to FIG. The fuel cell system 100 includes a secondary battery 12, a boost converter 13, a fuel cell 14, a boost converter 15, an inverter 16, a motor 17, an auxiliary machine 18, and a speed sensor S as main configurations. The control unit 11 controls the fuel cell system 100. The fuel cell control device according to the present embodiment is configured from the control unit 11 and the fuel cell system 100.

The fuel cell system 100 is mounted on a vehicle (mobile body) such as a fuel cell vehicle (FCV). It should be noted that FIG. 1 only shows the main configuration included in the fuel cell system 100, and the fuel cell system 100 can include other configurations included in any fuel cell system mounted on the mobile body. .. Further, the fuel cell system 100 does not have to be mounted on the mobile body, and may be installed in a facility that requires electric power, such as a general house.

The secondary battery 12 is a power storage unit that can be charged and discharged. The secondary battery 12 is composed of, for example, a lithium ion battery or the like. The secondary battery 12 is inserted in the discharge path of the fuel cell 14 and is connected to the inverter 16 in parallel with the fuel cell 14. The secondary battery 12 outputs the power obtained by subtracting the preset target output of the fuel cell from the required power of the electric load including the motor 17 and the auxiliary machine 18 as the driving power of the electric load. That is, the secondary battery 12 supplies the driving power to the motor 17 and the auxiliary machine 18. Further, the secondary battery 12 supplies electric power necessary for starting and stopping the fuel cell system 100. Further, the secondary battery 12 stores the electric power obtained by the power generation of the fuel cell 14 and the electric power obtained by the regeneration from the motor 17.

Further, the secondary battery 12 includes a temperature sensor T and a current sensor IB. The temperature sensor T is a sensor that measures the temperature of the secondary battery 12 and outputs the measurement result. The current sensor IB is a sensor that measures the discharge current of the secondary battery 12.

The boost converter 13 is a DC (direct current) voltage converter provided between the secondary battery 12 and the inverter 16. The boost converter 13 is configured by using, for example, an IPM (Intelligent Power Module). The boost converter 13 boosts the DC voltage of the electric power supplied from the secondary battery 12 and outputs it to the inverter 16.

The fuel cell 14 includes a cell stack in the form of a solid polymer electrolyte, which is formed by stacking a plurality of cells (a single battery (generator) having an anode, a cathode, and an electrolyte) in series. In the normal operation of the fuel cell 14 during power generation, the oxidation reaction of the formula (1) occurs at the anode and the reduction reaction of the formula (2) occurs at the cathode. The fuel cell 14 as a whole generates electric power by the electromotive reaction of the equation (3).
_{^{H 2 → 2H + + 2e -}} (1)
^{_{(1/2) O 2 + 2H +}} + 2e - → H 2 O (2)
H ₂ + (1/2) O ₂ → H ₂ O (3)

The boost converter 15 is a DC voltage converter provided between the fuel cell 14 and the inverter 16. The boost converter 15 boosts the DC voltage of the electric power supplied from the fuel cell 14 and outputs the DC voltage to the inverter 16. The boost converter 15 is composed of, for example, an IPM or the like.

The inverter 16 is an inverter provided between the boost converter 13, the boost converter 15, and the motor 17. The inverter 16 converts the DC power supplied from the fuel cell 14 or the secondary battery 12 into three-phase AC power and supplies it to the motor 17. The inverter 16 is composed of, for example, an IPM.

The motor 17 is a drive motor that generates a driving force for driving a wheel or the like of a moving body on which the fuel cell system 100 is mounted. The motor 17 uses the electric power supplied from the fuel cell 14 or the secondary battery 12 via the inverter 16 as the driving electric power. Further, the motor 17 regenerates the kinetic energy of the moving body on which the fuel cell system 100 is mounted into electric energy (for example, according to the rotation of the motor 17). The electric power generated by the regeneration is charged in the secondary battery 12.

Auxiliary equipment 18 is a group of auxiliary equipment including auxiliary equipment used for power generation by the fuel cell 14. The auxiliary machine 18 includes, for example, a hydrogen pump for a fuel cell, a cooling water pump, and the like. The auxiliary machine 18 uses the electric power supplied from the secondary battery 12 as the driving electric power.

The speed sensor S is a sensor that acquires a measured value of the moving speed of the moving body on which the fuel cell system 100 is mounted. The moving speed is calculated based on, for example, the rotation speed of the motor 17.

The control unit 11 is composed of a computer including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The control unit 11 controls the processing and operation of each configuration included in the fuel cell system 100 based on signals input from other configurations and a program stored in a storage unit such as a RAM, and controls the control. Performs various operations required for.

For example, when the control unit 11 receives a stop command for the fuel cell system 100, the charge amount (SOC: State Of Charge) of the secondary battery 12 is the operation of stopping the fuel cell system 100, and the fuel cell system 100. It is determined whether or not it is equal to or less than the threshold value (details of the setting method of the threshold value will be described later) set in an amount exceeding the charge amount required to supply the power required for the next start operation. When the charge amount of the secondary battery 12 is equal to or less than the threshold value, the control unit 11 continues the power generation of the fuel cell 14 and charges the secondary battery 12 with the generated power before the fuel cell system 100 is stopped. In particular, in an extremely low temperature state (for example, a state of 0 ° C. or lower), the fuel cell 14 termination process, parking purge (PPG), and sub-freezing start operation, which are said to be three sub-zero operations, are performed. The secondary battery 12 is charged so as to secure a charge amount capable of supplying the electric power required for operation. The details of the control process by the control unit 11 when the fuel cell system 100 is stopped will be described later.

Here, the termination process of the fuel cell 14 is a process of discharging water from the stack of the fuel cell 14 by an air compressor. The parking purge is a process of purging the water content in the stack of the fuel cell 14 which is performed immediately after the operation of the fuel cell 14 is stopped and immediately before the temperature becomes 0 ° C. or lower. Sub-zero starting is the operation of starting the fuel cell system 100 when the temperature is below freezing.

2. 2. Control Flow for Stopping and Starting the Fuel Cell System An example of controlling the stopping and starting of the fuel cell system 100 will be described with reference to FIGS. 2 to 4. First, with reference to FIG. 2, a flow of processing control in an extremely low temperature state (that is, a situation in which the above three sub-freezing operations are performed) will be described. This process is controlled by the control unit 11.

In the process shown in FIG. 2, first, when the control unit 11 is operated to turn off the ignition, which is a vehicle stop command (when it receives the stop command (stop instruction) of the fuel cell system 100 (step S11)), the second. It is determined whether or not the charge amount of the next battery 12 is equal to or less than a preset threshold value (SOC threshold value) (step S12). When the charge amount of the secondary battery 12 is equal to or less than the SOC threshold value (Yes in step S12), the process proceeds to step S13, and when the charge amount is larger than the SOC threshold value (No in step S12), the process proceeds to step S14.

As the SOC threshold, a predetermined value (charge amount addition value) is set to the charge amount (SOC lower limit value) required to supply the power required for the operation of stopping the fuel cell system 100 and the operation of the next start of the fuel cell system 100. ) Is added and the value is set. The charge amount addition value is the number of times that the secondary battery 12 is continuously forcibly charged within a predetermined period in step S13 described later (or the forcible charging for which the execution interval is within a predetermined period is continuously performed. It is set to a value according to the number of times. Specifically, the larger the number of consecutive executions, the lower the charge amount addition value can be set. Further, the charge amount addition value can be set to a value corresponding to the temperature of the secondary battery 12 acquired from the temperature sensor T. For example, the charge amount addition value can be set higher as the temperature of the secondary battery 12 is lower.

The graph of FIG. 3 conceptually shows the SOC threshold value determined according to the charge amount addition value. In FIG. 3, when the forced charging of the secondary battery 12 is performed, the SOC threshold value at the time of the second continuous execution is set lower than that at the first SOC threshold value, and the SOC at the time of the third continuous execution is set. It has been shown that the threshold is set even lower. It is also shown that the lower the temperature of the secondary battery 12, the higher the SOC threshold is set.

Returning to the description of FIG. In step S13, the control unit 11 operates the fuel cell 14 to generate electricity, and controls the secondary battery 12 to be charged (forced charging). Charging of the secondary battery 12 in step S13 is carried out until the charge amount of the secondary battery 12 exceeds the SOC threshold value (No in step S12). Therefore, the higher the SOC threshold, the longer the charging, and the lower the SOC threshold, the shorter the charging.

After the charge amount of the secondary battery 12 exceeds the SOC threshold value (No in step S12), the control unit 11 discharges water from the stack of the fuel cell 14 by an air compressor as a process of terminating the fuel cell 14 (No). Step S14), the operation of the fuel cell 14 is stopped (step S15), and the parking purge (step S16) is performed.

After that, when the control unit 11 receives the start command of the fuel cell system 100, the control unit 11 executes the operation of starting the fuel cell system 100 at the time of below freezing point (step S17). After that, the vehicle equipped with the fuel cell system 100 travels by receiving the electric power supplied from the fuel cell system 100 (step S18), and the process proceeds to step S11 again.

FIG. 4 shows a secondary battery when the fuel cell system 100 is repeatedly stopped and started by the control unit 11 according to the control shown in FIG. 2 when the short trip running is repeated in an extremely low temperature state. It shows the time-series change of the charge amount of 12. The SOC lower limit is the lower limit of the charge amount of the secondary battery 12 capable of supplying electric power for stopping and starting the fuel cell system 100. The SOC threshold values 1 to 3 are values obtained by adding charge amount addition values having different sizes to the SOC lower limit value.

According to FIG. 4, when the control unit 11 operates the ignition OFF, which is a vehicle stop command, at the timing t1 (when the fuel cell system 100 is stopped), the charge amount of the secondary battery 12 is charged at the timing t1. Since it is higher than the SOC threshold value 1 (SOC lower limit value + δ SOC1), the fuel cell system 100 is stopped (S14 to S16). Electric power is consumed by the stop operation of the fuel cell system 100 and the like, and the charge amount of the secondary battery 12 is reduced. After that, when the start command of the fuel cell system 100 is received, the operation of starting the fuel cell system 100 at the time of below freezing point (S17) is executed, and the vehicle starts running (S18). At the timing t2 when the short trip run is completed and the stop command of the fuel cell system 100 is instructed (S11), the control unit 11 determines whether the charge amount of the secondary battery 12 is equal to or less than the SOC threshold value 1 (S12). As shown in FIG. 4, since the SOC at the timing t2 is equal to or less than the SOC threshold value 1, the fuel cell system 100 performs forced charging of the secondary battery 12 (S13). After that, when the charge amount increases to the SOC threshold value 1 (timing t3), the fuel cell system 100 is being instructed to stop, so the control unit 11 stops the fuel cell system 100 (S14 to S16). The charge amount of the secondary battery 14 is reduced by the stop operation of the fuel cell 14.

After that, when a short trip running with a short running time is performed between the timing t3 and the timing t4, the power of the secondary battery 12 is used by the operation below the freezing point 3, and the charge amount is further reduced. When the short trip run is completed and the ignition OFF operation, which is a vehicle stop command, is performed again at the timing t4 (when the fuel cell system 100 stop command (S11) is received), the secondary battery 12 at that time The amount of charge is SOC threshold 2 (a threshold set when forced charging is continuously performed in a short period of time, and a value lower than the SOC threshold 1 used in the previous judgment is set. SOC threshold: SOC lower limit Since the value is + δSOC2) or less, forced charging by the fuel cell system 100 is carried out (S13). After that, when the charge amount increases to the SOC threshold value 2 (timing t5), the forced charging ends (timing t5), the fuel cell 14 is stopped (S14 to S16), and the charge amount decreases.

After that, when the ignition OFF operation, which is a vehicle stop command, is performed again at the timing t6 after the short trip run is completed (when the fuel cell 14 stop command is received), the charge amount of the secondary battery 12 at that time is reduced. SOC threshold 3 (SOC threshold set when forced charging is continuously performed for a short period of time and lower than SOC threshold 2 used in the previous judgment: SOC lower limit value + SOCδ3) Since it is as follows, forced charging is carried out. After that, when the charge amount increases to the SOC threshold value 3 (timing t7), the fuel cell 14 is stopped and the charge amount decreases.

As described above, according to the present embodiment, the control unit 11 is instructed to stop the fuel cell system 100, and the charge amount of the secondary battery 12 is equal to or less than the SOC threshold value 1. The fuel cell 14 is forcibly charged to the secondary battery 12 until the SOC threshold value is 1. After that, when a short trip run is performed within a predetermined period and then the fuel cell system 100 is instructed to stop, the control unit 11 sets the condition that the charge amount of the secondary battery 12 is equal to or less than the SOC threshold value 2. The secondary battery 12 is forcibly charged by the fuel cell system 100 until the charge amount reaches the SOC threshold value 2. Further, as shown in FIG. 4, the above-mentioned charge amount addition value added to the SOC lower limit value in the SOC threshold value 2 is lower than the charge amount addition value added to the SOC lower limit value in the SOC threshold value 1. Therefore, the SOC threshold value 2 is set to a value lower than the SOC threshold value 1.

That is, when the control unit 11 performs the first forced charging until the charge amount of the secondary battery 12 reaches the SOC threshold value 1, and then performs the second forced charging within a predetermined period, the control unit 11 of the secondary battery 12 The second forced charge is controlled until the charge amount reaches the SOC threshold value 2 lower than the SOC threshold value 1. As a result, the second forced charging can be completed in a shorter time as compared with the case where the charging amount continues to be charged up to the SOC threshold value 1. It is possible to shorten the charging time of the secondary battery 12 of the fuel cell 14 when the fuel cell 14 is repeatedly started and stopped.

In the present embodiment, the SOC threshold value is set so that the execution time of forced charging gradually increases when the fuel cell system 100 is repeatedly started and stopped within a predetermined period. That is, as shown in FIG. 4, as the difference between the SOC threshold value 2 and the SOC threshold value 3 is set smaller than the difference between the SOC threshold value 1 and the SOC threshold value 2, the number of forced charges within a predetermined period increases. The decrease value of the SOC threshold was set small. As a result, assuming that the amount of decrease in the charge amount in the three sub-zero operations is substantially constant, as the number of forced charges increases, the time for forced charging until the SOC threshold value at that time is reached can be lengthened. Therefore, when the control unit 11 performs the second forced charging within a predetermined period after the execution of the first forced charging, the control unit 11 performs the second forced charging so as to be longer than the execution time of the first forced charging. The implementation time of is controlled. For example, the execution time of the first forced charging can be set to 5 minutes, and the execution time of the second forced charging can be set to 10 minutes.

In the control shown in FIG. 4, SOC threshold values 1 to 3 are set so that the forced charging execution time (t2 to t3, t4 to t5, and t6 to t7) gradually increases as the number of forced chargings increases. ing.

By controlling so that the execution time of the forced charging gradually becomes longer as the forced charging is repeated in this way, the user (for example, the driver of the fuel cell vehicle equipped with the fuel cell system 100) gradually increases the charge amount. It can be grasped that the lower limit value (SOC lower limit value) is approaching.

As will be described below, it is also possible to set the execution time of forced charging by a method that does not depend on the SOC threshold value.

The above-mentioned modification will be described with reference to FIG. Steps S11 and S12 perform the same processing as that shown in FIG. If Yes is determined in step S12 of FIG. 5, the control unit 11 starts forced charging in step S13-1 and continues forced charging until the charging time reaches a preset time threshold value (step S13-). 1 and S13-2). After the forced charging is completed (No in S13-2), the process proceeds to step S14. The processing of steps S14 to S18 is the same as the processing shown in FIG.

The time threshold can be changed according to the temperature of the secondary battery 12 (for example, the lower the temperature, the longer the charging time is set).

Further, the time threshold value corresponds to the number of times that the forced charging of the secondary battery 12 is continuously carried out within a predetermined period (or the number of times that the forced charging is continuously carried out within the predetermined period). It can be set to a value. Specifically, the larger the number of consecutive executions within a predetermined period, the longer the time threshold can be set.

Although the embodiments of the present invention have been described above with reference to the drawings, the scope of the present invention is not limited to such embodiments. It is clear that one of ordinary skill in the art can come up with various modifications or modifications, which naturally belong to the technical scope of the present invention.

For example, in the above embodiment, an example in which δSOC changes depending on a condition has been described, but it does not exclude fixing δSOC.

100 Fuel cell system 11 Control unit 12 Secondary battery 13 Boost converter 14 Fuel cell 15 Boost converter 16 Inverter 17 Motor 18 Auxiliary S Speed sensor IB Current sensor T Temperature sensor

Claims (6)

A fuel cell control device including a fuel cell system having a fuel cell, a secondary battery, and a control unit for controlling the fuel cell system.
The control unit determines whether or not the charge amount of the secondary battery is equal to or less than a threshold value which is a value obtained by adding a first predetermined value to a lower limit value capable of supplying electric power for stopping and starting the fuel cell system. Judgment,
When the stop command of the fuel cell system is received and it is determined that the charge amount of the secondary battery is equal to or less than the threshold value, the charge amount becomes the threshold value for forced charging from the fuel cell to the secondary battery. Control the fuel cell system to carry out
After performing the forced charging, the fuel cell system is stopped and the fuel cell system is stopped.
After the fuel cell system is stopped, (i) the fuel cell system is started based on the start request of the fuel cell system, and (ii) the stop command of the fuel cell system is received within a predetermined period. , A fuel cell control device configured to set the threshold value to a value obtained by adding a second predetermined value lower than the first predetermined value to the lower limit value. The fuel cell control device according to claim 1, wherein the threshold value is set based on the temperature of the secondary battery. When the second forced charging is carried out within the predetermined period after the first forced charging is carried out, the control unit may use the second forced charging longer than the first forced charging time. The fuel cell control device according to claim 1, wherein the execution time of forced charging is set. The fuel cell control device according to any one of claims 1 to 3, wherein the forced charging execution time is set based on the temperature of the secondary battery. A fuel cell vehicle comprising the fuel cell control device according to any one of claims 1 to 4. It is a control method of a fuel cell control device including a fuel cell system including a fuel cell and a secondary battery, and a control unit for controlling the fuel cell system.
(i) The stop of the fuel cell system is instructed, and (ii) the charge amount of the secondary battery is a first predetermined value as a lower limit value capable of supplying electric power for stopping and starting the fuel cell system. On condition that the value is equal to or less than the threshold value obtained by adding the above, the forced charging from the fuel cell to the secondary battery is carried out until the charge amount reaches the threshold value.
After performing the forced charging, stopping the fuel cell system and
After the fuel cell system is stopped, (i) the fuel cell system is started based on the start request of the fuel cell system, and (ii) the stop command of the fuel cell system is issued within a predetermined period. , The threshold value is set to a value obtained by adding a second predetermined value lower than the first predetermined value to the lower limit value.
Control methods including.

Images