Fuel cell system

Abstract

This fuel cell system comprises a fuel cell, a battery for charging with power generated by the fuel cell, and a drive device that runs on power supplied from the fuel cell and / or the battery. The output current of the fuel cell is dependent on the voltage of the battery. The system comprises: a control unit for controlling the driving of the drive device; and a calculation unit for calculating a smoothing value on the basis of a switching time for a switch to be made from a non-power generation state in which the fuel cell has stopped generating power to a power generation state in which a predetermined amount of power is generated. The control unit performs smoothing control to slow down changes in the output of the drive device by controlling the output of the drive device to a control value calculated on the basis of the smoothing value in both cases where there has been an output request for the drive device while the fuel cell was in the power generation state and where there has been an output request for the drive device while the fuel cell was in the non-power generation state.

Description

fuel cell system

[0001] The present disclosure relates to a fuel cell system having a fuel cell that generates electricity when supplied with a fuel gas and an oxidant gas.

[0002] Patent Document 1 discloses a fuel cell system having a fuel cell that receives a supply of fuel gas from a fuel gas system and a supply of oxidant gas from an oxidant gas system to generate electricity.

[0003] Japanese Patent Application Laid-Open No. 2022-185247

[0004] In a DCDC converter-less fuel cell system, the fuel cell generates electricity in a natural manner according to the battery voltage, but intermittently stops power generation when the battery's SOC (i.e., state of charge) becomes high. When the required output of the drive device exceeds the battery's maximum output (i.e., maximum output), the drive device is driven by the output of the fuel cell in addition to the battery. However, if the fuel cell is in an intermittently stopped state, a time delay occurs in the fuel cell output until the fuel cell returns to a natural power generation state. This results in a difference in the drive behavior of the drive device when the fuel cell is in a natural power generation state and when the fuel cell is in an intermittently stopped state. This can cause unstable acceleration in a vehicle equipped with a fuel cell system, which can be uncomfortable for the vehicle user.

[0005] Here, Patent Document 1 does not disclose any measures to address the difference in driving behavior of the drive device when the fuel cell is in a state of natural power generation and when the fuel cell is in an intermittently stopped state.

[0006] Therefore, the present disclosure has been made to solve the above-mentioned problems, and aims to provide a fuel cell system that can suppress the difference in driving behavior of the drive device when the fuel cell is in a power generating state and when it is not generating power.

[0007] One form of the present disclosure made to solve the above problem is a fuel cell system comprising a fuel cell, a battery that charges with power generated by the fuel cell, and a drive device that is driven by power supplied from the fuel cell and / or the battery, wherein the output current of the fuel cell depends on the voltage of the battery, the system comprising: a control unit that controls the operation of the drive device; and a calculation unit that calculates an averaging value based on the switching time from a non-power generation state in which the fuel cell has stopped generating power to a power generation state in which a predetermined amount of power is generated, wherein the control unit performs averaging control to smooth changes in the output of the drive device by controlling the output of the drive device to a control value calculated based on the averaging value in both cases where an output request for the drive device is made when the fuel cell is in the power generation state, and where an output request for the drive device is made when the fuel cell is in the non-power generation state.

[0008] According to this aspect, when an output request for the drive device is received and the drive device is driven, smoothing control is performed to make the change in the drive device's output more gradual than the change in the requested output, whether the fuel cell is generating power or not. This makes it possible to reduce the difference in the drive device's behavior when the fuel cell is generating power and when it is not. Therefore, regardless of whether the fuel cell is generating power or not, the acceleration of a vehicle equipped with a fuel cell system is stable, preventing the vehicle user from feeling uncomfortable.

[0009] In the above aspect, the smoothed value is preferably an average value of values ​​calculated based on the switching time each time the fuel cell switches from the non-power generating state to the power generating state.

[0010] According to this aspect, the smoothing value can be updated each time the fuel cell switches from a non-power generating state to a power generating state, thereby reducing the difference in the driving behavior of the drive unit when the fuel cell is in a power generating state and when it is not, depending on the actual situation at the time of switching the fuel cell.

[0011] In the above aspect, it is preferable that the smoothed value is a value calculated based on the switching time when the key switch of the vehicle in which the fuel cell system is installed is turned on and the fuel cell first switches from the non-power-generating state to the power-generating state.

[0012] According to this aspect, the smoothing value can be updated each time the vehicle key switch is turned on, thereby reducing the difference in driving behavior of the drive unit when the fuel cell is in a power generating state and when it is not, depending on the actual situation at the time of switching the fuel cell.

[0013] According to the fuel cell system of the present disclosure, it is possible to reduce the difference in the driving behavior of the drive device when the fuel cell is in a power generating state and when it is not generating power.

[0014] 1 is a configuration diagram of a fuel cell system according to an embodiment; FIG. 2 is a flowchart illustrating the content of control performed in this embodiment; FIG. 3 is a diagram illustrating an example of a one-dimensional map defining the relationship between FC response time and an averaged value; FIG. 4 is a diagram for explaining FC response time; FIG. 5 is a diagram illustrating changes in motor output when a motor output request is made when the FC stack is in a state of natural power generation according to an embodiment; FIG. 6 is a diagram illustrating changes in motor output when a motor output request is made when the FC stack is in an intermittent stop state according to an embodiment; FIG. 7 is a diagram illustrating changes in motor output when a motor output request is made when the FC stack is in a state of natural power generation according to an explanation of the problem; FIG. 8 is a diagram illustrating changes in motor output when a motor output request is made when the FC stack is in an intermittent stop state according to an explanation of the problem.

[0015] An embodiment of a fuel cell system according to the present disclosure will now be described.

[0016] 1, the fuel cell system 1 includes an FC stack 11, a hydrogen system 12, an air system 13, a cooling system 14, a control unit 15, and a calculation unit 16. The FC stack 11 is an example of the "fuel cell" of the present disclosure.

[0017] The FC stack 11 generates power by receiving a supply of fuel gas and an oxidant gas. In this embodiment, the fuel gas is hydrogen gas, and the oxidant gas is air. That is, the FC stack 11 generates power by receiving a supply of hydrogen gas from the hydrogen system 12 and a supply of air from the air system 13.

[0018] The power generated by the FC stack 11 is supplied to the battery 101 and the motor 102 (or inverter). The battery 101 is then charged with the power generated by the FC stack 11. The motor 102 is driven by power supplied from the FC stack 11 and / or the battery 101. The motor 102 is an example of a "drive device" in this disclosure.

[0019] The hydrogen system 12 is provided on the anode side of the FC stack 11. The hydrogen system 12 includes a hydrogen gas filling passage 20, a hydrogen gas supply passage 21, and a hydrogen off-gas discharge passage 22.

[0020] The hydrogen gas filling passage 20 is a passage for filling hydrogen gas into the hydrogen tank 31 from the filling port 30. The hydrogen gas supply passage 21 is a passage for supplying hydrogen gas from the hydrogen tank 31 to the FC stack 11. The hydrogen off-gas discharge passage 22 is a passage for discharging hydrogen off-gas, which is hydrogen gas not used for power generation, from the FC stack 11.

[0021] The hydrogen system 12 includes a valve 32, a pressure reducing valve 33, an injector 34, and a pressure sensor 35 in this order from the hydrogen tank 31 side in the hydrogen gas supply passage 21.

[0022] The valve 32 switches between supplying and cutting off hydrogen gas from the hydrogen tank 31 to the hydrogen gas supply passage 21, and between supplying and cutting off hydrogen gas from the filling port 30 to the hydrogen tank 31. The pressure reducing valve 33 is a pressure regulating valve for reducing the pressure of hydrogen gas. The injector 34 is a valve for injecting hydrogen gas toward the FC stack 11. The pressure sensor 35 is a device for detecting the pressure of hydrogen gas at a position downstream of the injector 34.

[0023] The hydrogen system 12 also includes a gas-liquid separator 41 and an exhaust drain valve 42 in the hydrogen off-gas discharge passage 22 .

[0024] The gas-liquid separator 41 is a device that separates moisture from the hydrogen off-gas. The exhaust drain valve 42 is a valve that controls the discharge of the hydrogen off-gas discharged from the FC stack 11 to the outside.

[0025] The air system 13 is provided on the cathode side of the FC stack 11. The air system 13 includes an air supply passage 51 and an air off-gas discharge passage 52.

[0026] The air supply passage 51 is a passage for supplying air to the FC stack 11 from outside the fuel cell system 1. The air off-gas discharge passage 52 is a passage for discharging air off-gas, which is air not used for power generation, from the FC stack 11.

[0027] The air system 13 includes an air compressor 61 and an inlet air valve 62 in the air supply passage 51. The air compressor 61 is a device that supplies air to the FC stack 11. The inlet air valve 62 is a valve that controls the flow rate of air supplied to the FC stack 11.

[0028] The air system 13 also includes an outlet air valve 71 in the air off-gas discharge passage 52. The outlet air valve 71 is a valve that controls the flow rate of air off-gas discharged from the FC stack 11 to the air off-gas discharge passage 52.

[0029] The cooling system 14 is a system that cools the FC stack 11, and includes a cooling water passage 81 and a cooling fan 82. The cooling water passage 81 is a passage through which cooling water flows. The cooling fan 82 is a device that cools the cooling water flowing through the cooling water passage 81.

[0030] The control unit 15 is a device having, for example, an arithmetic processing unit such as a CPU, a storage unit such as a ROM for storing control programs and control data processed by the CPU and a RAM used as various work areas for control processing, and an input / output interface unit. The control unit 15 performs various controls of the fuel cell system 1 in accordance with the control programs stored in the storage unit.

[0031] Specifically, the control unit 15 controls, for example, the rotation speed of the air compressor 61 and the opening and closing of the inlet air valve 62 and the outlet air valve 71. The control unit 15 also controls the valve 32, the pressure reducing valve 33, the injector 34, the exhaust drain valve 42, the cooling fan 82, the motor 102, etc. Furthermore, the control unit 15 receives information on the smoothing value SV, which will be described later, from the calculation unit 16.

[0032] The calculation unit 16 is a device that calculates the smoothed value SV based on information about the FC response time RT received from the FC stack 11. Details of the FC response time RT and the smoothed value SV will be described later.

[0033] (Operation of the fuel cell system) In the fuel cell system 1 configured as described above, in the hydrogen system 12, hydrogen gas supplied from the hydrogen gas supply passage 21 to the FC stack 11 is used for power generation in the FC stack 11, and then discharged from the FC stack 11 as hydrogen off-gas to the outside via the hydrogen off-gas discharge passage 22. In addition, in the air system 13, air supplied from the air supply passage 51 to the FC stack 11 is used for power generation in the FC stack 11, and then discharged from the FC stack 11 as air off-gas to the outside via the air off-gas discharge passage 52.

[0034] (Regarding a DCDC converter-less system) As shown in Figure 1, in a fuel cell system 1 of this embodiment, an FC stack 11, a battery 101, and a motor 102 (or an inverter) are connected in parallel, forming a simple system configuration that does not have a DCDC converter. In other words, the fuel cell system 1 is a DCDC converter-less system. The DCDC converter is a device that converts the FC voltage, which is the output voltage of the FC stack 11 (i.e., the voltage of the generated power).

[0035] As described above, the fuel cell system 1 of this embodiment is a DCDC converter-less system, and since the FC voltage is equal (or nearly equal) to the voltage of the battery 101, the FC current, which is the output current of the FC stack 11 (i.e., the current of the generated power), depends on the voltage of the battery 101. In other words, the fuel cell system 1 supplies the power generated in the FC stack 11 to the battery 101 and the motor 102 without converting the FC voltage.

[0036] In the fuel cell system 1, the FC voltage becomes equal to the voltage of the battery 101 in this way, and therefore the FC stack 11 generates power as it goes according to the voltage of the battery 101. When the SOC (i.e., the charging rate) of the battery 101 becomes high, the outlet pressure of the injector 34 is reduced and / or the inlet air valve 62 and outlet air valve 71 are closed, thereby intermittently stopping power generation by the FC stack 11.

[0037] (Measures to stabilize vehicle acceleration regardless of whether the FC stack is generating power) In a DCDC converter-less fuel cell system 1, the FC stack 11 generates power as it goes, but stops generating power intermittently when the SOC of the battery 101 becomes high. Here, when the required output of the motor 102 exceeds the MAX output (i.e., maximum output) of the battery 101, the motor 102 is driven by the output of the FC stack 11 in addition to the output of the battery 101.

[0038] However, if the FC stack 11 is in an intermittent stop state where power generation has been stopped, there will be a time delay in the output of the FC stack 11 until it returns to a natural power generation state where it generates a predetermined amount of power. As a result, the change in the output of the motor 102 (i.e., response speed, amount of change (amount of increase) per unit time) will differ between when the FC stack 11 is in a natural power generation state (see FIG. 7) and when the FC stack 11 is in an intermittent stop state (see FIG. 8), resulting in a difference in the driving behavior of the motor 102. This may cause unstable acceleration in a vehicle equipped with the fuel cell system 1, which may cause discomfort to vehicle users (passengers such as the driver).

[0039] Therefore, in this embodiment, measures are taken to stabilize the acceleration of the vehicle on which the fuel cell system 1 is mounted, regardless of whether the FC stack 11 is generating power or not.

[0040] Specifically, in both cases where an output request for the motor 102 is made when the FC stack 11 is in a continuous power generation state and where an output request for the motor 102 is made when the FC stack 11 is in an intermittent stop state, the control unit 15 performs control to make the change in output of the motor 102 equivalent and suppress differences in behavior of the motor 102. The continuous power generation state is an example of a "power generation state" in the present disclosure. The intermittent stop state is an example of a "non-power generation state" in the present disclosure.

[0041] More specifically, as shown in FIG. 2, the control unit 15 controls the output of the motor 102 to a control value calculated based on the smoothing value SV, thereby performing smoothing control to make the change in the output of the motor 102 gentler.

[0042] The control process shown in Fig. 2 will now be described. The control unit 15 performs the routine process of the control shown in Fig. 2, for example, every 10 ms.

[0043] 2, the control unit 15 calculates the required output RO1 of the motor 102 using, for example, a two-dimensional map based on the accelerator opening AO and the rotation speed of the motor 102 of the vehicle equipped with the fuel cell system 1 (step S1). That is, the control unit 15 calculates the required output RO1 of the motor 102 based on the accelerator opening AO using a two-dimensional map (not shown) that defines the relationship between the accelerator opening AO, the rotation speed of the motor 102, and the required output RO1 of the motor 102. It should be noted that the accelerator opening AO is obtained, for example, from an accelerator position sensor APS provided in the vehicle.

[0044] Next, the control unit 15 calculates the required output RO2 by taking into account the smoothing of the required output RO1 (step S2).

[0045] Specifically, the value of the required output RO2 (i.e., the control value) is calculated based on the smoothed value SV using the following formula: [Formula 1] Control value = previous value + (required value - previous value) / smoothed value SV

[0046] In the formula, the control value is the value of the required output RO2 calculated in the current routine processing (of the control shown in FIG. 2), the previous value is the value of the required output RO2 calculated in the previous routine processing, and the required value is the value of the required output RO1.

[0047] The smoothed value SV is calculated based on the FC response time RT using, for example, the one-dimensional map shown in Fig. 3. Here, the FC response time RT is the switching time from when a request for uninterrupted power generation is made in the intermittent stopped state until the state switches from the intermittent stopped state to the uninterrupted power generation state (i.e., the rise time of the FC output, which is the output of the FC stack 11), as shown in Fig. 4. Note that in Fig. 3, the smoothed value SV is specified to increase as the FC response time RT becomes longer.

[0048] Next, as shown in FIG. 2, the control unit 15 determines whether the required output RO1 exceeds the MAX output (i.e., maximum output, for example, 7 kW) of the battery 101 (step S3).

[0049] If the control unit 15 determines that the required output RO1 exceeds the maximum output of the battery 101 (step S3: YES), it determines whether the FC stack 11 is in an intermittent stop state (step S4).

[0050] If the control unit 15 determines that the FC stack 11 is in an intermittently stopped state (step S4: YES), it causes the FC stack 11 to return from the intermittently stopped state to a power generation state as the situation progresses (step S5).

[0051] Next, the control unit 15 requests the required output RO2 as the output of the motor 102 (step S6). In this way, the control unit 15 controls the output of the motor 102 to the required output RO2 calculated based on the smoothing value SV.

[0052] In addition, the control unit 15 requests the required output RO2 as the motor output (step S6) even if the required output RO1 in step S3 is less than the maximum output of the battery 101 (step S3: NO) or if the FC stack 11 is not in an intermittent stop state (i.e., in a natural power generation state) in step S4 (step S4: NO).

[0053] In this way, in this embodiment, the control unit 15 performs smoothing control to smooth the change in the output of the motor 102 in both cases where an output request for the motor 102 is made when the FC stack 11 is in a natural power generation state, and where an output request for the motor 102 is made when the FC stack 11 is in an intermittent stop state.

[0054] Specifically, as a smoothing control, the control unit 15 controls the output of the motor 102 to the required output RO2 calculated based on the smoothing value SV, thereby controlling the change in the output of the motor 102 (referred to as "actual output" in the figure) to be more gradual than the change in the required output RO1 in both cases where an output request for the motor 102 is made when the FC stack 11 is in a natural power generation state (see Figure 5) and where an output request for the motor 102 is made when the FC stack 11 is in an intermittent stop state (see Figure 6).

[0055] This makes it possible to suppress the difference in behavior of the motor 102 when the FC stack 11 is in a continuous power generation state and when it is in an intermittently stopped state. As a result, regardless of whether the FC stack 11 is generating power or not, the acceleration of the vehicle equipped with the fuel cell system 1 is stable, preventing the vehicle user from feeling uncomfortable.

[0056] The smoothed value SV may be set to the average value of values ​​calculated based on the FC response time RT each time the FC stack 11 switches from an intermittent stop state to a natural power generation state.

[0057] This allows the smoothing value SV to be updated every time the FC stack 11 switches from an intermittent stop state to a natural power generation state, thereby reducing the difference in the driving behavior of the motor 102 when the FC stack 11 is in a natural power generation state and when it is in an intermittent stop state, depending on the actual state of the FC response time RT.

[0058] In addition, the smoothed value SV may be a value calculated based on the FC response time RT when the key switch KS of the vehicle in which the fuel cell system 1 is installed is turned on and the FC stack 11 first switches from an intermittent stop state to a natural power generation state.

[0059] This allows the smoothing value SV to be updated every time the vehicle key switch KS is turned on, thereby reducing the difference in driving behavior of the motor 102 between when the FC stack 11 is in a natural power generation state and when it is in an intermittent stop state, depending on the actual state of the FC response time RT.

[0060] Furthermore, if the smoothed value SV is not updated frequently after the vehicle key switch KS is turned on and the smoothed value SV is calculated, the driving behavior of the motor 102 can be stabilized, and the acceleration of the vehicle can be stabilized more effectively.

[0061] It should be noted that the above-described embodiments are merely examples and do not limit the present disclosure in any way. It goes without saying that various improvements and modifications are possible within the scope of the gist of the present disclosure.

[0062] REFERENCE SIGNS LIST 1 fuel cell system 11 FC stack 12 hydrogen system 13 air system 14 cooling system 15 control unit 16 calculation unit 21 hydrogen gas supply passage 22 hydrogen off-gas discharge passage 34 injector 51 air supply passage 52 air off-gas discharge passage 62 inlet air valve 71 outlet air valve 101 battery 102 motor SV smoothing value RT FC response time RO1 required output RO2 required output KS key switch

Claims

1. A fuel cell system comprising a fuel cell, a battery for charging with power generated by the fuel cell, and a drive device that is driven by power supplied from the fuel cell and / or the battery, wherein the output current of the fuel cell depends on the voltage of the battery, the system comprising: a control unit that controls the operation of the drive device; and a calculation unit that calculates an averaging value based on the switching time from a non-power generation state in which the fuel cell has stopped generating power to a power generation state in which a predetermined amount of power is generated, wherein the control unit performs averaging control to smooth changes in the output of the drive device by controlling the output of the drive device to a control value calculated based on the averaging value in both cases where an output request for the drive device is made when the fuel cell is in the power generation state, and where an output request for the drive device is made when the fuel cell is in the non-power generation state.

2. A fuel cell system according to claim 1, wherein the smoothed value is an average value of values ​​calculated based on the switching time each time the fuel cell switches from the non-power generating state to the power generating state.

3. A fuel cell system according to claim 1, wherein the smoothed value is a value calculated based on the switching time when the key switch of the vehicle in which the fuel cell system is mounted is turned on and the fuel cell first switches from the non-power generating state to the power generating state.

Images