JP2018101543A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system capable of suppressing deterioration of a battery, by restraining precipitation of lithium.SOLUTION: A control section 7 of vehicle mounting an inventive fuel cell system has a step of selecting any one of the charge/discharge power for controlling the charge/discharge amount so that the residual capacity of a lithium ion battery 62 approaches a target residual capacity, or the deterioration suppression request power that is found based on the accumulated charge amount and the lithium deposition detection value, and employing the selected one as the charge/discharge power of the lithium ion battery 62, and a step of determining the power generation amount of the fuel cell 2 based on the charge/discharge power after selection, and the vehicle total power required for driving the vehicle, and discharging the lithium ion battery 62.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fuel cell system.

  Vehicles equipped with a fuel cell system equipped with a fuel cell that generates electric power by receiving supply of reaction gas (fuel gas and oxidizing gas) are being put to practical use.

  In this fuel cell system, a secondary battery is usually mounted in addition to the fuel cell. When the fuel cell is started or when the power required by the vehicle cannot be provided by the output of the fuel cell alone, this secondary battery is used. Supply the necessary power from. For this reason, after the fuel cell can generate power, it is necessary to store the next starting energy in the secondary battery. As a secondary battery mounted on such a vehicle, it is required to be smaller and lighter and have a higher capacity. For example, a lithium ion battery is usually used as a battery that satisfies this requirement (for example, the following). Patent Document 1).

JP 2009-144208 A

  By the way, in this lithium ion battery, lithium is deposited by charging. It is known that such lithium deposition is a phenomenon that appears remarkably when, for example, charging is performed in a cryogenic environment. When lithium is deposited, the battery is deteriorated. Therefore, it is desirable to suppress the precipitation of lithium in order to suppress the deterioration of the battery.

  Then, an object of this invention is to provide the fuel cell system which can suppress precipitation of lithium and can suppress deterioration of a battery.

  A fuel cell system according to an aspect of the present invention is equipped with a fuel cell, a lithium ion battery capable of storing electric power output from the fuel cell, and a control unit that controls the operation of the fuel cell and charge / discharge of the lithium ion battery. A fuel cell system for a vehicle, wherein the control unit is configured to control charging / discharging power so that the remaining capacity of the lithium ion battery approaches the target remaining capacity, a charge amount integrated value, and a lithium deposition detection value. One of the required degradation suppression required powers based on the above, and the selected one as the charge / discharge power of the lithium ion battery, the selected charge / discharge power, and the total vehicle power required for driving the vehicle And determining a power generation amount of the fuel cell based on the above and discharging the lithium ion battery.

  According to this aspect, the charging / discharging power for controlling the charging / discharging amount so that the remaining capacity of the lithium ion battery approaches the target remaining capacity, the deterioration suppressing power obtained based on the integrated charging amount and the lithium deposition detection value. And the selected one is used as the charge / discharge power of the lithium ion battery. The lithium ion battery is discharged by controlling the power generation amount of the fuel cell based on the selected charge / discharge power. As described above, since the power generation amount of the fuel cell is controlled using the charge / discharge power after selection based on the charge / discharge power and the deterioration suppression power, the charge / discharge power and the total vehicle power considering only the target remaining capacity are used. Compared with the structure which controls the electric power generation amount of a fuel cell based on this, deterioration of a lithium ion battery can be suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell system which can suppress precipitation of lithium and can suppress deterioration of a battery can be provided.

It is the block diagram which showed typically the fuel cell system as one Embodiment of this invention. It is a control block diagram which shows an example of the function implement | achieved by the control part of FIG. It is a flowchart which shows the process performed by the control block (charge / discharge power) of FIG. It is a control block diagram which shows the 1st modification of the function implement | achieved by the control part of FIG. It is a control block diagram which shows the 2nd modification of the function implement | achieved by the control part of FIG. It is a control block diagram which shows the conventional control processing.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. It should be noted that the following description of the preferred embodiment is merely an example, and is not intended to limit the present invention, its application, or its use.

  First, with reference to FIG. 1, the structure of the fuel cell system in embodiment is demonstrated. FIG. 1 is a configuration diagram schematically illustrating a fuel cell system according to an embodiment.

  As shown in the figure, a fuel cell system 1 includes a fuel cell 2 that generates electric power by an electrochemical reaction upon receiving supply of an oxidizing gas and a fuel gas as reaction gases, and air as an oxidizing gas to the fuel cell 2. An oxidizing gas piping system 3 to be supplied; a hydrogen gas piping system 4 for supplying hydrogen as fuel gas to the fuel cell 2; a cooling system 5 (cooling water circulation mechanism) for circulating and supplying cooling water to the fuel cell 2; It has the electric power system 6 which charges / discharges electric power, and the control part 7 which carries out overall control of the whole system.

  The fuel cell 2 is, for example, a polymer electrolyte fuel cell, and has a stack structure in which a large number of single cells are stacked. The single cell has a cathode electrode (air electrode) on one surface of an electrolyte made of an ion exchange membrane, an anode electrode (fuel electrode) on the other surface, and further sandwiches the cathode electrode and anode electrode from both sides. It has the structure which has a pair of separator. In this case, hydrogen gas is supplied to the hydrogen gas flow path of one separator, oxidizing gas is supplied to the oxidizing gas flow path of the other separator, and electric power is generated by the chemical reaction of these reaction gases. The fuel cell 2 is provided with a voltage sensor V that detects the output voltage of the fuel cell and a current sensor A that detects the output current of the fuel cell.

  The oxidizing gas piping system 3 compresses the air taken in through the filter, sends out the compressed air as the oxidizing gas, an oxidizing gas supply flow path 32 for supplying the oxidizing gas to the fuel cell 2, The oxidizing off-gas discharge flow path 33 for discharging the oxidizing off-gas discharged from the fuel cell 2 and a part of the oxidizing gas discharged from the compressor 31 join the oxidizing off-gas discharge flow path 33 by bypassing the fuel cell 2. And a bypass flow path 34 for the purpose.

  On the outlet side of the compressor 31, a flow rate sensor F that measures the flow rate of the oxidizing gas discharged from the compressor 31 is provided. The fuel cell 2 is disposed downstream of the branch point to the bypass channel 34 in the oxidizing gas supply channel 32 and upstream of the junction point with the bypass channel 34 in the oxidizing off-gas discharge channel 33. There are provided shut-off valves 35 and 36 for shutting off or allowing the supply of the oxidizing gas. A back pressure valve 37 for adjusting the pressure of the oxidizing gas in the fuel cell 2 is provided upstream of the shutoff valve 36 in the oxidizing off gas discharge flow path 33. A pressure sensor P for detecting the pressure of the oxidizing gas in the fuel cell 2 is provided on the outlet side of the fuel cell 2 in the oxidizing off gas discharge channel 33.

  The bypass channel 34 is a channel that branches from the downstream side of the compressor 31 in the oxidizing gas supply channel 32, bypasses the fuel cell 2, and joins the oxidizing off gas discharge channel 33. The bypass channel 34 is provided with an adjustment valve 38 that adjusts the flow rate of the oxidizing gas that is merged from the oxidizing gas supply channel 32 to the oxidizing off-gas discharge channel 33. The adjustment valve 38 is electrically connected to the control unit 7, and the opening degree of the adjustment valve 38 is controlled by the control unit 7.

  The hydrogen gas piping system 4 includes a hydrogen tank 40 as a fuel supply source storing high-pressure hydrogen gas, and a hydrogen gas supply flow as a fuel gas supply channel for supplying the hydrogen gas in the hydrogen tank 40 to the fuel cell 2. A passage 41 and a hydrogen circulation passage 42 as a fuel circulation passage for returning the hydrogen off-gas discharged from the fuel cell 2 to the hydrogen gas supply passage 41 are provided. The hydrogen gas supply channel 41 is provided with a regulator 43 that adjusts the pressure of the hydrogen gas to a preset secondary pressure. The hydrogen circulation channel 42 is provided with a hydrogen pump 44 that pressurizes the hydrogen off-gas in the hydrogen circulation channel 42 and sends it to the hydrogen gas supply channel 41 side.

  The cooling system 5 includes a radiator 51 that cools the cooling water, a cooling water circulation passage 52 that circulates and supplies the cooling water to the fuel cell 2 and the radiator 51, and a cooling water circulation pump 53 that circulates the cooling water to the cooling water circulation passage 52. Have The radiator 51 is provided with a radiator fan 54. A temperature sensor T that detects the temperature of the cooling water is provided on the outlet side of the fuel cell 2 in the cooling water circulation passage 52. The position where the temperature sensor T is provided may be on the inlet side of the fuel cell 2.

  The power system 6 includes a DC / DC converter 61, a battery 62 as a secondary battery, a traction inverter 63, a traction motor 64 as a power consuming device, and various auxiliary inverters not shown. The DC / DC converter 61 is a direct-current voltage converter that adjusts the direct-current voltage input from the battery 62 and outputs it to the traction inverter 63 side, and the direct-current voltage input from the fuel cell 2 or the traction motor 64. And adjusting the output to the battery 62. By such a function of the DC / DC converter 61, charging / discharging of the battery 62 is realized.

  The battery 62 is configured as, for example, a lithium ion secondary battery (lithium ion battery), and the remaining capacity (State of Charge) is estimated based on a detection result of a current sensor or a voltage sensor (not shown). The traction inverter 63 converts a direct current into a three-phase alternating current and supplies it to the traction motor 64. The traction motor 64 is, for example, a three-phase AC motor, and constitutes a main power source of a fuel cell vehicle on which the fuel cell system 1 is mounted. The auxiliary inverter is an electric motor control unit that controls driving of each motor, converts a direct current into a three-phase alternating current, and supplies the three-phase alternating current to each motor.

  The control unit 7 measures an operation amount of an acceleration operation member (for example, an accelerator) provided in the fuel cell vehicle, and controls an acceleration request value (for example, a required power generation amount from a power consuming device such as the traction motor 64). Receives information and controls the operation of various devices in the system. In addition to the traction motor 64, the power consuming device includes, for example, auxiliary equipment required for operating the fuel cell 2 (for example, the motor of the compressor 31, the hydrogen pump 44, the cooling water circulation pump 53, etc.), the vehicle This includes actuators used in various devices (transmissions, wheel control devices, steering devices, suspension devices, etc.) involved in traveling, air conditioning devices (air conditioners) for passenger spaces, lighting, audio, and the like.

  The control unit 7 physically includes, for example, a CPU, a memory, and an input / output interface. The memory includes, for example, a ROM that stores control programs and control data processed by the CPU, and a RAM that is mainly used as various work areas for control processing. These elements are connected to each other via a bus. Various sensors such as a temperature sensor T and a flow rate sensor F are connected to the input / output interface, and various drivers for driving the compressor 31, the shutoff valves 35 and 36, the adjustment valve 38, and the like are connected.

  The CPU receives various measurement results from various sensors via the input / output interface according to a control program stored in the ROM, and executes various control processes by processing using various data in the RAM. Further, the CPU controls the entire fuel cell system 1 by outputting control signals to various drivers via the input / output interface. Below, the control process performed by the control part 7 of this embodiment is demonstrated.

  FIG. 2 is a control block diagram for explaining a control process performed by the control unit 7. Each control block shown in the figure indicates a function realized by the control unit 7. The control part 7 implement | achieves each function by running the predetermined program stored in ROM by CPU.

  The vehicle total power control block a shown in FIG. 2 is a control block for calculating electric power provided by power generation of the fuel cell (hereinafter also referred to as FC power generation) and charging / discharging of the battery (hereinafter also referred to as BAT charging / discharging). The vehicle total power includes, for example, drive motor power, FC pump power, auxiliary power, AC power, heater power, etc., but is not limited to the example shown in the figure, and is necessary power for driving equipment mounted on the vehicle. If so, it is included in the “total vehicle power” in this specification.

  The charge / discharge power control block b (deterioration suppression control block) is a control block that determines a target value for BAT charge / discharge. Specifically, as will be described later with reference to FIG. 3, one of the SOC control (charge / discharge power) and the lithium ion battery deterioration suppression control (deterioration suppression required power) is selected and selected. Is a control block that determines the charge / discharge power of the battery (determines the charge / discharge power of the battery).

  The FC power generation power control block c is a control block for operating an actuator that extracts power from the fuel cell. Examples of the actuator include an FC boost converter (not shown) that is electrically connected between a fuel cell and an inverter (a traction inverter 63 shown in FIG. 1). The output voltage from the fuel cell is boosted to an arbitrary voltage within the range that can be controlled by the FC boost converter and supplied to the inverter. The boost converter has a plurality of switching elements, a plurality of diodes, and a reactor. Is provided. The boost converter receives a current command and performs a switching operation by a switching element in order to extract desired power from the fuel cell.

  The FC pump drive control value determination block d is a control block for determining and operating a fuel supply amount for generating power in the fuel cell.

  The charge / discharge power control block b (deterioration suppression control block) shown in FIG. 2 will be further described with reference to FIG. In the present embodiment, in the charge / discharge power control block b, the processing of the control flow b1 in FIG. 3A, the control flow b2 in FIG. 3B, and the control flow b3 in FIG. FIG. 3A is a flowchart showing processing for determining battery charge / discharge power (BAT charge / discharge amount) for controlling the remaining battery capacity (BATSOC) to the target SOC. FIG. 3B is a flowchart showing a process for calculating the battery deterioration suppression required power. FIG. 3C is a flowchart showing a process for selecting one of the charge / discharge power of FIG. 3A or the battery deterioration suppression required power of FIG. 3B and determining the charge / discharge power. In the following, the control flow b1 in FIG. 3A is also referred to as BAT energy management control, the control flow b2 in FIG. 3B is also referred to as BAT deterioration suppression control, and the control flow b3 in FIG. Is also referred to as BAT power determination control.

  In the BAT energy management control of FIG. 3A, first, in step b11, it is determined whether or not the current remaining battery capacity (BATSOC) is less than the target remaining capacity (target SOC). When the condition of step b11 is satisfied (step b11 (Yes)), the process proceeds to step b12 to determine the battery charge amount. When the condition of step b11 is not satisfied (step b11 (No)), the process proceeds to step b13 to determine the battery discharge amount. In this way, in the control flow b1 of FIG. 3A, the battery charge / discharge power for controlling the charge / discharge amount is determined so that the remaining battery capacity (BATSOC) approaches the target SOC. Note that the value of the target SOC is arbitrary and is preset by the control unit 7 (FIG. 1).

  In the BAT deterioration suppression control of FIG. 3B, first, in step b21, it is determined whether or not the battery charge amount integrated value is larger than a predetermined amount E1 (Ah). When the condition of step b21 is satisfied (step b21 (Yes)), the process proceeds to step b22, where the deterioration suppression discharge power is output and the output value is set as the deterioration suppression required power. The deterioration suppressing discharge power is set to an arbitrary value as the power for discharging the lithium ion battery so that the deposition of lithium is suppressed. For example, the deterioration suppressing discharge power is obtained based on the battery charge amount integrated value and the lithium deposition detection value when the battery charge amount integrated value is equal to or greater than a predetermined amount E1 (Ah). On the other hand, when the condition of step b21 is not satisfied (step b21 (No)), the process proceeds to step b23, and it is determined whether or not the discharge amount integrated value is larger than the predetermined amount E2 (Ah). When the condition of step b23 is satisfied (step b23 (Yes)), the process proceeds to step b24 to perform a process for setting the degradation suppression discharge power to 0 W, and the value after the process (that is, 0 W) is set as the degradation suppression required power. . On the other hand, when the condition of step b23 is not satisfied (step b23 (No)), the process proceeds to step b25 to perform the process of setting the deterioration suppression discharge power to the previous value (the value of the previous deterioration suppression discharge power). The later value (that is, the previous value) is set as the degradation suppression required power.

  In the BAT power determination control in FIG. 3C, first, in step b31, it is determined whether or not the deterioration suppression request power calculated in FIG. When the condition of step b31 is satisfied (step b31 (Yes)), the process proceeds to step b32, the degradation suppression request power calculated in FIG. 3B is selected, and when the condition of step b31 is not satisfied (step b31 (No)), the process proceeds to step b33, and the charge / discharge power calculated in FIG. 3A is selected.

  As shown in FIGS. 2 and 3 described above, the battery charge / discharge power in the present embodiment is the charge / discharge power obtained by the BAT energy management control of FIG. 3 (A) and the BAT deterioration of FIG. 3 (B). Either one of the degradation suppression request power obtained by the suppression control is selected, and the selected one is set as the battery charge / discharge power (FIG. 3C). Based on the selected battery charge / discharge power (control block b in FIG. 2) and total vehicle power (control block a in FIG. 2), the power generation amount of the fuel cell is determined (control block c in FIG. 2). Based on the determined power generation amount of the fuel cell, the fuel supply amount to the fuel cell and the coolant circulation amount are determined (control block d in FIG. 2).

  Thus, in the present embodiment, the battery charge / discharge power (BAT energy management) for controlling the charge / discharge amount so that the battery remaining capacity (BATSOC) approaches the target SOC, the battery charge amount integrated value, and the lithium deposition detection value Either one of the required degradation suppression required powers is selected, and the selected one is set as the battery charge / discharge power (degradation suppression). Temporary discharge from the battery can be realized by changing the power generation amount of the fuel cell so that the selected battery charge / discharge power (deterioration suppression) is obtained. Compared to the conventional example shown in FIG. 6, it is difficult to suppress lithium deposition by the control (charge / discharge power (energy management) shown in FIG. 6) in consideration only of the battery charge / discharge power (BAT energy management) of FIG. 6. In the present embodiment, the SOC controllability can be improved while suppressing lithium deposition by taking into consideration the battery charge / discharge power and the power required to suppress deterioration (charge / discharge power (deterioration suppression shown in FIG. 2)). .

  Next, a modified example of the control process described with reference to FIGS. 2 and 3 will be described. FIG. 4 is a diagram illustrating a first modification of the control process performed by the control unit. 4 is different from the control process of FIG. 2 described above in that the input of the FC pump drive control value determination block d is changed to the battery charge / discharge power (FIG. 3A). The other functions are the same as those in FIG. Therefore, the description of the same parts as those already described is omitted.

  As shown in the control block d of FIG. 4, the power generation amount of the fuel cell determined based on the battery charge / discharge power determined by the BAT energy management control (see the control flow b1 shown in FIG. 3A) and the total vehicle power. The fuel supply amount to the fuel cell and the cooling water circulation amount are determined. That is, in the modification shown in FIG. 4, the fuel supply amount to the fuel cell and the cooling water circulation amount from the power generation amount of the fuel cell not reflecting the degradation suppression required power (see the control flow b2 shown in FIG. 3B) are set. decide. Normally, the amount of fuel (oxygen or hydrogen) supplied varies depending on the amount of power generated by the fuel cell. However, if the amount of power generated by the fuel cell is changed, the actuator drive of the FC pump that drives for fuel supply However, there is a risk of vibration and noise problems. According to the modification shown in FIG. 4, the drive of the FC pump (hydrogen pump, cooling water circulation pump) is not changed by the battery charge / discharge power that is changed by the temporary deterioration suppression control. It is possible to suppress the generation of vibration noise. As described above, when the control process shown in the first modified example of FIG. 4 is compared with the control process described above (see FIG. 2), the control process described with reference to FIG. 3 (B)), the amount of power generated by the fuel cell is changed and the fuel supply of the fuel cell is also changed. However, in the modification shown in FIG. By executing B)), the amount of power generated by the fuel cell is changed, while the fuel supply of the fuel cell is controlled not to change.

  Subsequently, a second modification of the control process will be described. FIG. 5 is a diagram illustrating a second modification of the control process performed by the control unit. The control process of FIG. 5 is different from the control process of FIG. 2 described above in that the degradation suppression required power is consumed by the heater power of the vehicle total power control block, and other functions are the same as those in FIG. It is. Therefore, the description of the same parts as those already described is omitted.

  In the second modification shown in FIG. 5, the operating power (heater power) of the water heater for heating the fuel cell cooling water is controlled according to the degradation suppression required power (see FIG. 3B), in other words. For example, the power required for deterioration suppression is consumed by the water heater at a preset timing. As a result, it is possible to suppress the change in the FC power generation power (the amount of power generated by the fuel cell) with the battery charge / discharge power that is changed by the temporary deterioration suppression control. Vibration noise can be suppressed. As described above, when the control process shown in the second modified example of FIG. 5 is compared with the above-described control process (see FIG. 2), the control process described with reference to FIG. 3 (B)), the power generation amount of the fuel cell is changed and the fuel supply of the fuel cell is also changed. In the second modification of FIG. 5, the BAT deterioration suppression control (FIG. 3) is performed. Although (B)) is executed, control is performed so that the power generation amount of the fuel cell is not changed and the fuel supply of the fuel cell is not changed. By controlling in this way, in addition to improving the SOC controllability while suppressing lithium deposition, generation of vibration noise due to the actuator driving described above can be suppressed.

  The embodiments described above are for facilitating the understanding of the present invention, and are not intended to limit the present invention. Each element included in the embodiment and its arrangement, material, condition, shape, size, and the like are not limited to those illustrated, and can be changed as appropriate. In addition, it is possible to partially replace or combine the configurations shown in the modified examples in which some of the embodiments are different.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell system 2 ... Fuel cell 3 ... Oxidation gas piping system 4 ... Hydrogen gas piping system 5 ... Cooling system 6 ... Electric power system 7 ... Control part 31 ... Compressor 32 ... Oxidation gas supply flow path 33 ... Oxidation off gas discharge flow path 34 ... Bypass passage 35, 36 ... Shut-off valve 37 ... Back pressure valve 38 ... Adjustment valve 40 ... Hydrogen tank 41 ... Hydrogen gas supply passage 42 ... Hydrogen circulation passage 43 ... Regulator 44 ... Hydrogen pump 51 ... Radiator 52 ... Cooling water circulation Flow path 53 ... Cooling water circulation pump 54 ... Radiator fan 61 ... Converter 62 ... Battery (lithium ion battery)
63 ... Traction inverter 64 ... Traction motor a ... Total vehicle power control block b ... Charge / discharge power control block c ... Power generation power control block d ... Pump drive control value determination block

Claims (1)

A fuel cell system for a vehicle equipped with a fuel cell, a lithium ion battery capable of storing electric power output from the fuel cell, and a control unit for controlling operation of the fuel cell and charge / discharge of the lithium ion battery. ,
The controller is
One of the charge / discharge power for controlling the charge / discharge amount so that the remaining capacity of the lithium ion battery approaches the target remaining capacity, and the degradation suppression required power obtained based on the integrated charge amount value and the lithium deposition detection value And selecting the selected one as the charge / discharge power of the lithium ion battery,
Determining the power generation amount of the fuel cell based on the charge / discharge power after the selection and the total vehicle power required for driving the vehicle, and discharging the lithium ion battery;
A fuel cell system.