JP2018137220A - Fuel cell control device, control method thereof, and fuel cell vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the charging time of a secondary battery of a fuel cell system in cases where starting and stopping of the fuel cell system are repeated.SOLUTION: A fuel cell system includes a fuel cell and a secondary battery. Under a condition that a command to stop the fuel cell system is received and a state of charge of the secondary battery is equal to or lower than a threshold which is a value obtained by adding a first predetermined value to a lower limit at which electric power required to stop and start the fuel cell system is supplied, a controller to control the fuel cell system controls the fuel cell system to perform forced charging from the fuel cell to the secondary battery until a state of charge reaches the threshold. After the forced charging is performed, in cases where the command to stop the fuel cell system is received within a predetermined period, the controller sets the threshold to a value obtained by adding a second predetermined value lower than the first predetermined value to the lower limit under the condition.SELECTED DRAWING: Figure 2

Description

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

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

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

  Patent Document 1 discloses that charging is performed to ensure the amount of charge of a secondary battery necessary for the next start of the system when the fuel cell system is stopped.

JP 2007-165055 A

  However, the above-described charging when the fuel cell system is stopped may take a long time to secure the amount of charge necessary for the next start. In addition, if the start and stop of the fuel cell system is repeated in a short time due to repeated short trip traveling, the fuel cell system is stopped as a result of shortening the charging time of the secondary battery during traveling relative to the power consumption. The amount of charge of the secondary battery at that time is often less than the value required for the next start. Therefore, if the start and stop of the fuel cell system are repeated, it often takes a long time to charge the secondary battery to ensure 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 acknowledgment comprising a fuel cell system having a fuel cell and a secondary battery, and a control unit for controlling the fuel cell system. The control unit determines whether or not a charge amount of the secondary battery is equal to or less than a threshold value that is a value obtained by adding a first predetermined value to a lower limit value capable of supplying power for stopping and starting the fuel cell system. judge. When the control unit receives an instruction 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 determined to be a forced charge from the fuel cell to the secondary battery. The fuel cell system is controlled to be carried out until the threshold value is reached. Furthermore, the control unit stops the fuel cell system after the forced charging is performed. The control unit, after stopping the fuel cell system, within a predetermined period (i) to start the fuel cell system based on a request to start the fuel cell system, and (ii) to stop the fuel cell system 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 aspect, the control unit may set the threshold based on the temperature of the secondary battery. Further, in this aspect, when the second forced charging is performed within the predetermined period after the first forced charging is performed, the control unit is longer than a time for performing the first forced charging. In this way, the charging time for the second forced charging may be set. Furthermore, in this first aspect, the speed of forced charging may be set based on the temperature of the secondary battery.
A 2nd aspect of this invention is related with a fuel cell vehicle provided with the said fuel cell control apparatus.
A third aspect of the present invention relates to 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 that controls the fuel cell system.
This method
(i) stop of the fuel cell system is instructed; and (ii) a charge amount of the secondary battery is a first predetermined value that is a lower limit value capable of supplying power for stopping and starting the fuel cell system. Carrying out forced charging from the fuel cell to the secondary battery on the condition that the amount is equal to or less than a threshold value obtained by adding
After the forced charging is performed, stopping the fuel cell system;
When the fuel cell system is stopped within a predetermined period of time (i) the fuel cell system is started based on the start request of the fuel cell system, and (ii) a stop command of the fuel cell system is issued Setting the threshold to a value obtained by adding a second predetermined value lower than the first predetermined value to the lower limit value;
Including.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which shortens the charge time of the secondary battery of a fuel cell system in case the start and stop of a fuel cell system are repeated can be provided.

It is a figure showing a schematic structure of a fuel cell system concerning one embodiment. It is a flowchart which shows control of charging / discharging of the 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 control of charging / discharging of the secondary battery in the fuel cell system which concerns on one Embodiment. It is a graph which shows control of charging / discharging of the secondary battery in the fuel cell system concerning one embodiment. It is a flowchart which shows control of charging / discharging of the 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. Configuration of Fuel Cell System An example of a schematic configuration of a fuel cell system according to an 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 components. The control unit 11 controls the fuel cell system 100. The control unit 11 and the fuel cell system 100 constitute a fuel cell control device according to this embodiment.

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

  The secondary battery 12 is a chargeable / dischargeable power storage unit. The secondary battery 12 is composed of, for example, a lithium ion battery. The secondary battery 12 is inserted in the discharge path of the fuel cell 14 and connected to the inverter 16 in parallel with the fuel cell 14. The secondary battery 12 outputs electric power obtained by subtracting a preset target output of the fuel cell from the required electric power of the electric load including the motor 17 and the auxiliary machine 18 as driving electric power for the electric load. That is, the secondary battery 12 supplies 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 electric power obtained by power generation of the fuel cell 14 and electric power obtained by regeneration from the motor 17.

  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 a measurement result. The current sensor IB is a sensor that measures the discharge current of the secondary battery 12.

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

The fuel cell 14 includes a solid polymer electrolyte type cell stack formed by stacking a plurality of cells (a single battery (power generation body) including an anode, a cathode, and an electrolyte) in series. In the normal power generation operation by the fuel cell 14, 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 formula (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)

  Boost converter 15 is a DC voltage converter provided between fuel cell 14 and inverter 16. Boost converter 15 boosts the DC voltage of the power supplied from fuel cell 14 and outputs the boosted voltage to inverter 16. The boost converter 15 is configured by, for example, an IPM.

  The inverter 16 is an inverter provided between the boost converter 13 and 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 configured by IPM, for example.

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

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

  The speed sensor S is a sensor that acquires a measurement 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 number of revolutions of the motor 17.

  The control unit 11 includes a computer having a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The control unit 11 controls processing and operation of each component included in the fuel cell system 100 based on a signal input from another configuration, a program stored in a storage unit such as a RAM, and the like. Performs various operations necessary 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 the threshold value is set to an amount exceeding the charge amount necessary for supplying power necessary for the next start operation (the method for setting the threshold will be described in detail later). 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 before the fuel cell system 100 stops, and charges the secondary battery 12 with the generated power. In particular, in an extremely low temperature state (for example, a state of 0 ° C. or less), the fuel cell 14 termination process, parking purge (PPG), and sub-freezing start operation, which are referred to as three-freezing operation, are performed. The secondary battery 12 is charged so as to secure a charge amount capable of supplying power necessary for operation. Details of the control processing 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 moisture in the stack of the fuel cell 14 that is performed immediately after the operation of the fuel cell 14 stops and immediately before the temperature becomes 0 ° C. or lower. The below-freezing start is an operation of starting the fuel cell system 100 when the temperature is below freezing.

2. Control Flow of Stop and Start of Fuel Cell System An example of stop and start control of the fuel cell system 100 will be described with reference to FIGS. First, with reference to FIG. 2, a flow of processing control in an extremely low temperature state (that is, a situation where the above-described three operations below freezing point are performed) will be described. This process is executed by the control of the control unit 11.

  In the processing shown in FIG. 2, first, when an ignition OFF operation that is a vehicle stop command is performed (when a stop command (stop command) for the fuel cell system 100 is received (step S11)), the control unit 11 It is determined whether or not the amount of charge of the secondary battery 12 is equal to or less than a preset threshold (SOC threshold) (step S12). If the charge amount of the secondary battery 12 is equal to or lower than the SOC threshold value (Yes in step S12), the process proceeds to step S13, and if larger than the SOC threshold value (No in step S12), the process proceeds to step S14.

  As the SOC threshold value, a predetermined value (charge amount addition value) is added to the charge amount (SOC lower limit value) necessary for supplying power necessary for the operation of stopping the fuel cell system 100 and the next start operation of the fuel cell system 100. ) Is added. The charge amount addition value is the number of times that the secondary battery 12 is continuously forcedly charged within a predetermined period in step S13 to be described later (or the forced charging whose execution interval is within the predetermined period is continuously performed. Is set to a value according to the number of times. Specifically, the charge amount addition value can be set to a lower value as the number of times of continuous execution increases. 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, the SOC threshold value when the forced charging of the secondary battery 12 is performed is set lower than the first SOC threshold value, and the SOC value when the second continuous operation is performed is set to be lower. It is shown that the threshold is set lower. Further, it is shown that the SOC threshold is set higher as the temperature of the secondary battery 12 is lower.

  Returning to the description of FIG. In step S <b> 13, the control unit 11 controls the fuel cell 14 to operate to generate power and charge the secondary battery 12 (forced charging). The charging of the secondary battery 12 in step S13 is performed until the amount of charge of the secondary battery 12 exceeds the SOC threshold (No in step S12). Therefore, charging is performed for a longer time as the SOC threshold is higher, and charging is performed for a shorter time as the SOC threshold is lower.

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

  Thereafter, when the control unit 11 receives a start command for the fuel cell system 100, the control unit 11 performs an operation for starting the fuel cell system 100 when the temperature is below freezing (step S17). Thereafter, the vehicle including the fuel cell system 100 travels with the supply of power 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 within a predetermined period by the control unit 11 according to the control shown in FIG. 2 when the short trip traveling is repeated in a cryogenic state. 12 shows time-series changes in the charge amount. The SOC lower limit value is a lower limit value of the charge amount of the secondary battery 12 that can supply 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 of different magnitudes to the SOC lower limit value.

  According to FIG. 4, when the control unit 11 performs an ignition OFF operation that is a vehicle stop command at timing t1 (when the stop command for the fuel cell system 100 is received), the charge amount of the secondary battery 12 is increased at timing t1. Since it is higher than the SOC threshold value 1 (SOC lower limit value + δSOC1), the stop operation of the fuel cell system 100 and the like (S14 to S16) are performed. Electric power is consumed by the stop operation of the fuel cell system 100 and the charge amount of the secondary battery 12 is reduced. Thereafter, when the start command of the fuel cell system 100 is received, the start operation (S17) of the fuel cell system 100 when the temperature is below freezing is performed, and the vehicle starts running (S18). At the timing t2 when the short trip traveling is finished and the stop command for 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 timing t2 is equal to or lower than the SOC threshold value 1, forced charging of the secondary battery 12 by the fuel cell system 100 is performed (S13). Thereafter, when the charge amount increases to the SOC threshold value 1 (timing t3), since the stop command for the fuel cell system 100 is being issued, the control unit 11 stops the fuel cell system 100 (S14 to S16). The amount of charge of the secondary battery 14 is reduced by the stop operation of the fuel cell 14.

  Thereafter, when a short trip traveling with a short traveling time is performed between the timing t3 and the timing t4, the power of the secondary battery 12 is used due to the three-freezing operation, and the charge amount is further reduced. When the short trip traveling is finished and an ignition OFF operation that is a vehicle stop command is performed again at timing t4 (when the stop command (S11) of the fuel cell system 100 is received), the secondary battery 12 at that time Charge amount is SOC threshold value 2 (a threshold value that is set when forced charging is continuously performed for a short time, and a value that is lower than SOC threshold value 1 used in the previous determination is set: SOC lower limit) Therefore, forced charging by the fuel cell system 100 is performed (S13). Thereafter, when the amount of charge increases to the SOC threshold 2 (timing t5), the forced charging ends (timing t5), the operation of stopping the fuel cell 14 (S14 to S16) is performed, and the amount of charging is decreased.

  Thereafter, after the short trip running, when an ignition OFF operation that is a vehicle stop command is performed again at timing t6 (when the fuel cell 14 stop command is received), the charge amount of the secondary battery 12 at that time is SOC threshold value 3 (SOC threshold value: a threshold value that is set when forced charging is carried out continuously for a short time and is lower than the SOC threshold value 2 used in the previous determination: SOC lower limit value + SOCδ3) The forced charging is performed because of the following. Thereafter, when the charge amount increases to the SOC threshold 3 (timing t7), the operation of stopping the fuel cell 14 is performed, and the charge amount is decreased.

  As described above, according to the present embodiment, the controller 11 is instructed to stop the fuel cell system 100 and the charge amount of the secondary battery 12 is less than or equal to the SOC threshold value 1. The forced charging from the fuel cell 14 to the secondary battery 12 is performed until the SOC threshold value 1 is reached. Thereafter, when a short trip traveling is performed within a predetermined period and then the stop of the fuel cell system 100 is instructed, the control unit 11 performs the condition that the charge amount of the secondary battery 12 is equal to or less than the SOC threshold 2. The fuel cell system 100 forcibly charges the secondary battery 12 until the amount of charge reaches the SOC threshold value 2. Further, as shown in FIG. 4, the charge amount addition value added to the SOC lower limit value at the SOC threshold 2 is lower than the charge amount addition value added to the SOC lower limit value at the SOC threshold 1. Therefore, the SOC threshold 2 is set to a value lower than the SOC threshold 1.

  That is, the control unit 11 performs the first forced charging until the amount of charge of the secondary battery 12 reaches the SOC threshold 1, and then performs the second forced charging within a predetermined period. Control is performed so that the second forcible charging is performed until the charge amount reaches an 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 compared to the case where the charging is continued until the charging amount reaches the SOC threshold value 1. The charging time of the secondary battery 12 of the fuel cell 14 when the start and stop of the fuel cell 14 are repeated can be shortened.

  In the present embodiment, the SOC threshold is set so that the forced charging time is gradually increased 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 1 and the SOC threshold 2 is set to be smaller than the difference between the SOC threshold 1 and the SOC threshold 2, the number of times of forced charging 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 operations below freezing point is almost constant, the time for forced charge until the SOC threshold value at that time is reached can be increased as the number of times of forced charge increases. Therefore, when the second forced charging is performed within a predetermined period after the first forced charging is performed, the control unit 11 performs the second forced charging so as to be longer than the time for performing the first forced charging. The execution time 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, the SOC threshold values 1 to 3 are set such that the forced charging time (t2 to t3, t4 to t5, and t6 to t7) gradually increases as the number of times of forced charging increases. ing.

  In this way, by performing control so that the forced charging time is gradually increased as the forced charging is repeated, the user (for example, a driver of a fuel cell vehicle equipped with the fuel cell system 100) is gradually charged. It can be understood that the lower limit value (SOC lower limit value) is approaching.

  In addition, 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 modification will be described with reference to FIG. Steps S11 and S12 perform the same processing as the processing shown in FIG. In Step S12 of FIG. 5, when it is determined Yes, in Step S13-1, the control unit 11 starts forced charging and continues forced charging until the charging time reaches a preset time threshold (Step S13-). 1 and S13-2). After the end of forced charging (No in S13-2), the process proceeds to step S14. The processing from step S14 to S18 is the same as the processing shown in FIG.

  The time threshold value 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).

  In addition, the time threshold corresponds to the number of times that the forced charging of the secondary battery 12 is continuously performed within the predetermined period (or the number of times that the forced charging is continuously performed within the predetermined period). Can be set to a value. Specifically, the time threshold can be set to a longer time as the number of times of continuous execution within a predetermined period increases.

  As mentioned above, although embodiment of this invention was described referring drawings, the scope of the present invention is not limited to this embodiment. It will be apparent to those skilled in the art that various changes and modifications can be made and these are naturally within the technical scope of the present invention.

  For example, in the above-described embodiment, an example in which δSOC changes according to conditions has been described, but it is not excluded to fix δSOC.

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

Claims (6)

A fuel cell control device comprising a fuel cell system having a fuel cell and a secondary battery, and a control unit for controlling the fuel cell system,
The control unit determines whether or not a charge amount of the secondary battery is equal to or less than a threshold value that is a value obtained by adding a first predetermined value to a lower limit value capable of supplying power for stopping and starting the fuel cell system. Judgment,
When the fuel cell system is instructed to stop and when it is determined that the charge amount of the secondary battery is equal to or less than the threshold value, the charge amount is the threshold value for forced charging from the fuel cell to the secondary battery. Controlling the fuel cell system to carry out until
After the forced charging, the fuel cell system is stopped,
After the fuel cell system is stopped, within a predetermined period, (i) when the fuel cell system is started based on the start request of the fuel cell system, and (ii) when the stop command of the fuel cell system is received The fuel cell control device is 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 is set based on a temperature of the secondary battery.   When the second forced charging is performed within the predetermined period after the first forced charging is performed, the control unit is configured to make the second forced charging time longer than the first forced charging time. The fuel cell control device according to claim 1, wherein the fuel cell control device is configured to set an execution time of forced charging.   4. The fuel cell control device according to claim 1, wherein the forced charging time is set based on a temperature of the secondary battery. 5.   A fuel cell vehicle comprising the fuel cell control device according to any one of claims 1 to 4. A control method of a fuel cell control device comprising a fuel cell system having a fuel cell and a secondary battery, and a control unit for controlling the fuel cell system,
(i) stop of the fuel cell system is instructed; and (ii) a charge amount of the secondary battery is a first predetermined value that is a lower limit value capable of supplying power for stopping and starting the fuel cell system. Carrying out forced charging from the fuel cell to the secondary battery on the condition that the amount is equal to or less than a threshold value obtained by adding
After the forced charging is performed, stopping the fuel cell system;
When the fuel cell system is stopped within a predetermined period of time (i) the fuel cell system is started based on the start request of the fuel cell system, and (ii) a stop command of the fuel cell system is issued Setting the threshold to a value obtained by adding a second predetermined value lower than the first predetermined value to the lower limit value;
Control method.