Power control device, fuel cell system, vehicle, and recording medium

Abstract

Provided are: a power control device that can more accurately determine the internal state of a fuel cell during traveling of a fuel cell vehicle, while inhibiting over-discharge or overcharge of a secondary battery; a fuel cell system; a vehicle; and a recording medium. A processor of the power control device in the fuel cell system, which includes an impedance measurement unit that measures impedance of a fuel cell on the basis of current and voltage measured when alternating-current power is superimposed on output power of the fuel cell, estimates residual capacity of a power storage device after executing the process to measure the impedance, performs charging / discharging of the power storage device before starting the process to measure impedance such that the estimated residual capacity is within a range from a prescribed lower limit value to an upper limit value, and controls power generation of the fuel cell such that the generated current of the fuel cell is constant during execution of the process to measure impedance.

Description

[Technical field]

[0001] The present disclosure relates to a power control device, a fuel cell system, a vehicle, and a recording medium. [Background technology]

[0002] Electrochemical impedance spectroscopy is known as a method for diagnosing the internal state of fuel cells such as polymer electrolyte fuel cells (PEFCs). In electrochemical impedance analysis, a process is performed to calculate the impedance based on the waveform of the output power when a sinusoidal AC signal is superimposed on the output power of a fuel cell. By using electrochemical impedance analysis, the internal state of a fuel cell can be diagnosed from the membrane resistance, reaction resistance, or material transport resistance calculated based on the impedance for each frequency of the superimposed AC signal.

[0003] For example, Patent Document 1 proposes a sequential impedance measuring device that performs measurements in a wide frequency band with relatively high accuracy in a short time while adding a signal similar to the fluctuation of normal battery output, and simultaneously measures phenomena that appear in different frequency bands. Specifically, Patent Document 1 discloses a technology that includes an M-sequence signal generating unit that generates an M-sequence signal having whiteness, a superimposed signal generating unit that generates a superimposed signal, a signal processing unit that outputs the M-sequence signal and the superimposed signal, a signal adding unit that superimposes the output signal of the signal processing unit on the power indication value of the control calculation unit, a current / voltage measuring unit that takes in the current and voltage of the fuel cell, and an impedance calculation unit that calculates the impedance of the fuel cell based on the current / voltage measurement value, and the control calculation unit changes the control method of the fuel cell based on the calculation result of the impedance calculation unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-03120 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the sequential impedance measurement device described in Patent Document 1 is configured to measure impedance using a measuring instrument capable of high-speed sampling and a computer capable of high-speed processing, which makes the system expensive and hinders the installation of a fuel cell in a vehicle. In addition, in the case of a fuel cell vehicle, it is affected by power load fluctuations due to acceleration and deceleration, so it is not easy to diagnose the internal state of the fuel cell while the fuel cell vehicle is running. In particular, the mass transport resistance of a fuel cell can be calculated based on the impedance in a relatively low frequency band of an AC signal, but since power load fluctuations due to fluctuations in driving torque while the fuel cell vehicle is running have a significant effect as measurement errors, it is not easy to measure impedance in a low frequency band.

[0006] In response to this, it is conceivable to reduce the effect of power load fluctuations on impedance measurement by keeping the power generation current of the fuel cell constant. In a fuel cell vehicle, when the output power of the fuel cell is insufficient or excessive with respect to the required power, the excess or deficiency is supplemented by the secondary battery. In order to suppress deterioration due to overcharging or overdischarging, or to prevent a power shortage or a decrease in power efficiency (power utilization efficiency), the secondary battery is controlled so that the remaining capacity is equal to or greater than a predetermined lower limit and equal to or less than an upper limit. However, if the power generation current of the fuel cell is kept constant, there is a risk that the remaining capacity of the secondary battery will be less than or exceed the upper limit after the impedance measurement process is completed.

[0007] The present disclosure has been made in consideration of the above problems, and an object of the present disclosure is to provide a power control device, a fuel cell system, a vehicle, and a recording medium that are capable of more accurately determining the internal state of a fuel cell while the fuel cell vehicle is running, while suppressing over-discharging or over-charging of a secondary battery. [Means for solving the problem]

[0008] In order to solve the above problems, according to one aspect of the present disclosure, there is provided a power control device for a fuel cell system including a fuel cell, a power storage device, and a drive motor, the power control device including an impedance measurement unit that measures the impedance of the fuel cell based on a current and a voltage measured when AC power is superimposed on the output power of the fuel cell, the power control device for the fuel cell system comprising one or more processors and one or more memories communicatively connected to the one or more processors, the processor comprising: The power consumption by the drive motor and the planned power generation by the fuel cell during the period in which the impedance measurement process is executed are estimated in advance, and based on the estimated power consumption and the planned power generation, A power control device is provided that executes processes including estimating the remaining capacity of a power storage device after executing a process to measure impedance, charging and discharging the power storage device before starting the process to measure impedance so that the estimated remaining capacity is within a range between a predetermined lower limit value and an upper limit value, and controlling the power generation of a fuel cell so that the power generation current of the fuel cell is constant while the process to measure impedance is being executed.

[0009] Furthermore, in order to solve the above-mentioned problems, according to another aspect of the present disclosure, there is provided a power control device for a fuel cell system including a fuel cell, a power storage device, and a drive motor, the power control device including an impedance measurement unit that measures the impedance of the fuel cell based on the current and voltage measured when AC power is superimposed on the output power of the fuel cell, the power control device including: a power supply control unit that controls power generation of the fuel cell based on a target drive torque of the drive motor that is set in accordance with the required acceleration of the fuel cell vehicle, and controls power generation of the fuel cell so that the power generation current of the fuel cell is constant while a process for measuring the impedance is being executed; a remaining capacity estimation unit that estimates the remaining capacity of the power storage device after executing the process for measuring the impedance; and a charge / discharge control unit that charges and discharges the power storage device before starting the process for measuring the impedance so that the estimated remaining capacity is equal to or greater than a predetermined lower limit value and equal to or less than a predetermined upper limit value.

[0010] In order to solve the above problem, according to another aspect of the present disclosure, there is provided a fuel cell system including any one of the above power control devices.

[0011] In order to solve the above problem, according to another aspect of the present disclosure, there is provided a vehicle equipped with the above fuel cell system.

[0012] In order to solve the above problems, according to another aspect of the present disclosure, a recording medium having recorded thereon a computer program applicable to a fuel cell system including a fuel cell, a power storage device, and a drive motor, the computer program including an impedance measurement unit that measures the impedance of the fuel cell based on a current and a voltage measured when AC power is superimposed on the output power of the fuel cell, the computer program comprising: The power consumption by the drive motor and the planned power generation by the fuel cell during the period in which the impedance measurement process is executed are estimated in advance, and based on the estimated power consumption and the planned power generation, A recording medium is provided that stores a computer program for executing a process including estimating the remaining capacity of a power storage device after executing a process for measuring impedance, charging and discharging the power storage device before starting the process for measuring impedance so that the estimated remaining capacity is within a range between a predetermined lower limit value and an upper limit value, and controlling the power generation of a fuel cell so that the power generation current of the fuel cell is constant during the process for measuring impedance. Effect of the Invention

[0013] As described above, according to the present disclosure, it is possible to more accurately determine the internal state of a fuel cell while a fuel cell vehicle is running, while suppressing overcharging or overdischarging of a secondary battery. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic diagram illustrating an example of a vehicle equipped with a fuel cell system to which a power control device according to an embodiment of the present disclosure can be applied. [Diagram 2] 2 is a block diagram showing a configuration example of a fuel cell system to which the power control device according to the embodiment is applied. FIG. [Diagram 3] 6 is a flowchart illustrating an example of a process performed by a power control device according to the embodiment. [Figure 4]5 is an explanatory diagram showing an example of a calculation process of a target power generation electric power of a fuel cell until the start of an impedance measurement process by the power control device according to the embodiment; FIG. [Diagram 5] 10 is a flowchart showing a process of the power control device during an impedance measurement process performed by the power control device according to the embodiment. [Figure 6] 5 is a diagram illustrating the operation of power generation control of a fuel cell by the power control device according to the embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configurations are denoted by the same reference numerals, and redundant description will be omitted.

[0016] <1. Overall configuration of fuel cell vehicle> First, an example of the overall configuration of a fuel cell vehicle 1 equipped with a power control device according to an embodiment of the present disclosure will be described. Fig. 1 is a schematic diagram showing an example of a fuel cell vehicle 1 equipped with a fuel cell system 20 including a power control device 50. Fig. 2 is a block diagram showing an example of the configuration of the fuel cell system 20. Fig. 2 shows the functional configuration related to the process of measuring the impedance of a fuel cell 21, among the configurations of an impedance measuring device (impedance measuring unit) 40 and the power control device 50.

[0017] 1 is configured as a four-wheel drive vehicle in which drive torque output from a drive motor 29 that generates drive torque for the vehicle is transmitted to a front left wheel 3LF, a front right wheel 3RF, a rear left wheel 3LR, and a rear right wheel 3RR (hereinafter collectively referred to as "wheels 3" unless a distinction is required). The drive motor 29 outputs drive torque that is transmitted to a front drive shaft 5F and a rear drive shaft 5R via a transmission, a front wheel differential mechanism 7F, and a rear wheel differential mechanism 7R (not shown).

[0018] The fuel cell vehicle 1 may be a vehicle equipped with two drive motors, for example a front wheel drive motor and a rear wheel drive motor, or may be a vehicle equipped with drive motors corresponding to each of the wheels 3.

[0019] The fuel cell system 20 includes a fuel cell 21, a fuel cell auxiliary 23, a converter device 25, an inverter device 27, a drive motor 29, a secondary battery 31, a secondary battery converter device 33, an impedance measuring device 40, and a power control device 50.

[0020] The drive motor 29 is a three-phase AC motor having coils of three phases, u-phase, v-phase, and w-phase, and is driven by receiving a supply of three-phase AC power from the fuel cell system 20.

[0021] The fuel cell 21 is configured as, for example, a solid polymer electrolyte fuel cell, and has a stack structure in which a plurality of fuel cell cells are stacked. Each fuel cell has a hydrogen electrode and an oxygen electrode on both sides of an electrolyte membrane made of an ion exchange membrane, respectively, and is equipped with a membrane electrode assembly (MEA) in which gas diffusion layers are formed on the hydrogen electrode and the oxygen electrode. The fuel cell also has a pair of separators arranged to sandwich the MEA. Hydrogen gas is supplied to a hydrogen gas flow path formed in the hydrogen electrode, and air is supplied to an air flow path formed in the oxygen electrode, and the supplied hydrogen gas and air undergo an electrochemical reaction to generate power. The fuel cell 21 outputs the generated DC power to the converter device 25.

[0022] The fuel cell auxiliary equipment 23 includes devices that adjust the pressure and flow rate of hydrogen gas (fuel gas) and air (oxidizing gas) supplied to the fuel cell 21. For example, the fuel cell auxiliary equipment 23 is equipped with a pressure reducing valve, a back pressure control valve, and a hydrogen circulation pump as devices that adjust the pressure and flow rate of hydrogen gas supplied to the fuel cell 21. The pressure reducing valve reduces the pressure of hydrogen gas in the high-pressure hydrogen tank and supplies it to the fuel cell 21. The back pressure control valve adjusts the flow rate of hydrogen off-gas discharged from the fuel cell 21, thereby adjusting the pressure of hydrogen gas in the fuel cell 21. The hydrogen circulation pump supplies hydrogen off-gas again to the fuel cell 21.

[0023] The fuel cell auxiliary 23 also includes a compressor inverter device and a back pressure control valve as devices for adjusting the pressure and flow rate of air supplied to the fuel cell 21. The compressor inverter device controls the output of the compressor and adjusts the flow rate of air supplied to the fuel cell 21. The back pressure control valve adjusts the flow rate of oxidizing off gas discharged from the fuel cell 21, thereby adjusting the pressure of the air in the fuel cell 21.

[0024] The fuel cell auxiliary 23 is an electronic device that operates by receiving a supply of DC power output from the fuel cell 21. The operation of the fuel cell auxiliary 23 is controlled by a power control device 50. Note that the fuel cell auxiliary 23 for operating the fuel cell 21 is not limited to the above example, and may include other devices. For example, the fuel cell auxiliary 23 may include a cooling water circulation pump that circulates cooling water for cooling the fuel cell 21.

[0025] The converter device 25 is configured as a DC-DC converter that converts the DC power output from the fuel cell 21 into DC power of a desired level and supplies it to the inverter device 27. The converter device 25 is configured to include a chopper circuit, and by operating, for example, two switching elements, the converter device 25 increases or decreases the voltage of the DC power output from the fuel cell 21 and supplies it to the inverter device 27. The driving of the switching elements of the converter device 25 is controlled by the power control device 50.

[0026] The inverter device 27 converts the DC power output from the converter device 25 into three-phase AC power and supplies it to the drive motor 29. The inverter device 27 has arm circuits (not shown) corresponding to the u-phase, v-phase, and w-phase coils of the drive motor 29, respectively. Each arm circuit includes an upper arm electrically connected to the positive electrode side of the fuel cell 21 and a lower arm electrically connected to the negative electrode side of the fuel cell 21. The upper arm and the lower arm of each arm circuit are provided with switching elements to which diodes are electrically connected in inverse parallel. For example, a metal oxide semiconductor field effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT) is used as the switching element. The u-phase, v-phase, and w-phase coils of the drive motor 29 are electrically connected to the connection parts between the upper arm and the lower arm of each arm circuit, respectively.

[0027] Furthermore, when the fuel cell vehicle 1 decelerates, the inverter device 27 regenerates the drive motor 29, converts the generated three-phase AC power into DC power, and outputs it to the DC stage 35. The driving of the switching elements provided in each arm circuit of the inverter device 27 is controlled by the vehicle drive control device 60.

[0028] The vehicle drive control device 60 includes one or more processors such as a CPU (Central Processing Unit) and one or more memories communicably connected to the processor. For example, the vehicle drive control device 60 controls the drive of the drive motor 29 based on a required acceleration set based on the amount of operation of an accelerator pedal operated by the driver or a required acceleration set by an automatic driving control process. Specifically, the vehicle drive control device 60 controls the drive of the inverter device 27 according to a target drive torque set based on the required acceleration. As a result, the drive motor 29 is driven, and a drive torque for the fuel cell vehicle 1 is output.

[0029] Furthermore, the vehicle drive control device 60 controls the regeneration of the drive motor 29 based on a required deceleration that is set based on the amount of operation of the brake pedal operated by the driver, for example, or a required deceleration that is set by an automatic driving control process. Specifically, the vehicle drive control device 60 controls the drive of the inverter device 27 in accordance with a target regenerative torque that is set based on the required deceleration. This causes the drive motor 29 to regenerate, generating a deceleration torque for the fuel cell vehicle 1 and outputting regeneratively generated power to the DC stage 35.

[0030] A secondary battery 31 is connected to a DC stage 35 that connects the converter device 25 and the inverter device 27 via a converter device 33 for a secondary battery. The secondary battery 31 is one type of power storage device, and is configured as a chargeable and dischargeable battery such as a lithium ion battery or a nickel-metal hydride battery. The secondary battery 31 stores surplus power obtained by subtracting the power supplied to the drive motor 29 from the power generated by the fuel cell 21. The secondary battery 31 also stores power generated by the regeneration of the drive motor 29. The secondary battery 31 also supplies the drive motor 29 with a shortage of power obtained by subtracting the power generated by the fuel cell 21 from the power supplied to the drive motor 29. The power stored in the secondary battery 31 may be supplied to vehicle accessories (not shown). The secondary battery 31 includes a battery controller (not shown) and transmits information on the open voltage and remaining capacity of the secondary battery 31 to the power control device 50.

[0031] The secondary battery converter device 33 charges the secondary battery 31 by adjusting the voltage of the power generated by the fuel cell 21, which is output to the DC stage 35 via the converter device 25, and the voltage of the regenerated power of the drive motor 29, which is output to the DC stage 35 via the inverter device 27. In other words, the secondary battery converter device 33 is configured as a DCDC converter. The secondary battery converter device 33 is configured to include a chopper circuit, and by operating, for example, two switching elements, the voltage of the power of the DC stage 35 is stepped down and charged to the secondary battery 31. The driving of the switching elements is controlled by the power control device 50.

[0032] The fuel cell vehicle 1 also includes forward-facing cameras 11LF and 11RF, a LiDAR (Light Detection And Ranging) 11S, a vehicle state sensor 15, and a GPS (Global Positioning System) sensor 17.

[0033] The front photographing cameras 11LF, 11RF and the LiDAR 11S constitute an ambient environment sensor for acquiring information on the ambient environment of the fuel cell vehicle 1. The front photographing cameras 11LF, 11RF photograph the area in front of the fuel cell vehicle 1 and generate image data. The front photographing cameras 11LF, 11RF are equipped with imaging elements such as CCD (Charged-Coupled Devices) or CMOS (Complementary Metal-Oxide-Semiconductor), and transmit the generated image data to the power control device 50.

[0034] 1, the front photographing cameras 11LF, 11RF are configured as stereo cameras including a pair of left and right cameras, but may be monocular cameras. In addition to the front photographing cameras 11LF, 11RF, the fuel cell vehicle 1 may also be equipped with at least one of a rear photographing camera 11R, or a camera provided on a side mirror for photographing the left rear or right rear.

[0035] The LiDAR 11S transmits optical waves and receives reflected waves of the optical waves, and detects an object and the distance to the object based on the time from transmitting the optical waves to receiving the reflected waves. The LiDAR 11S transmits the detection data to the power control device 50. The fuel cell vehicle 1 may be equipped with one or more sensors selected from a radar sensor such as a millimeter wave radar and an ultrasonic sensor as an ambient environment sensor for acquiring information about the ambient environment, instead of or in addition to the LiDAR 11S.

[0036] The vehicle state sensor 15 is composed of one or more sensors that detect the operation state and behavior of the fuel cell vehicle 1. The vehicle state sensor 15 includes at least one of, for example, a steering angle sensor, an accelerator position sensor, a brake stroke sensor, a brake pressure sensor, or an engine revolution speed sensor, and detects the operation state of the fuel cell vehicle 1, such as the steering angle of the steering wheel or steering wheels, the accelerator opening, the amount of brake operation, or the engine revolution speed. The vehicle state sensor 15 also includes at least one of, for example, a vehicle speed sensor, an acceleration sensor, or an angular velocity sensor, and detects the behavior of the fuel cell vehicle 1, such as the vehicle speed, longitudinal acceleration, lateral acceleration, and yaw rate. The vehicle state sensor 15 transmits a sensor signal including the detected information to the power control device 50.

[0037] The GPS sensor 17 receives satellite signals from GPS satellites and acquires position information of the fuel cell vehicle 1. Note that instead of the GPS sensor 17, an antenna that receives satellite signals from other satellite systems that identify the position of the fuel cell vehicle 1 may be used.

[0038] The power control device 50 executes a process for controlling power generation and charging by the fuel cell system 20. For example, the power control device 50 controls power generation by the fuel cell 21 based on the power required by the drive motor 29. When the power generated by the fuel cell 21 exceeds the required power, the power control device 50 charges the secondary battery 31 with the surplus power output from the converter device 25. When the power generated by the fuel cell 21 is less than the required power, the power control device 50 supplements the power shortage with the output power of the secondary battery 31. When the fuel cell vehicle 1 decelerates, the power control device 50 charges the secondary battery 31 with regenerative power generated by the drive motor 29.

[0039] Furthermore, the impedance measuring device 40 and the power control device 50 cooperate to execute a process for measuring the impedance of the fuel cell 21 and a process for diagnosing the state of the fuel cell 21. Below, the parts of the configuration of the impedance measuring device 40 and the power control device 50 that are related to the process for measuring the impedance of the fuel cell 21 and the process for diagnosing the state of the fuel cell 21 will be specifically described.

[0040] <2. Impedance measuring device and control device> Next, a detailed description will be given of the impedance measuring device 40 and the power control device 50. First, an overview of the processes executed by the impedance measuring device 40 and the power control device 50 will be given.

[0041] (2-1. Overview) In the fuel cell system 20 according to this embodiment, the power control device 50 outputs a command signal to the impedance measuring device 40 to acquire the impedance of the fuel cell 21. Upon receiving the command signal, the impedance measuring device 40 executes a process of measuring the impedance of the fuel cell 21. The impedance measuring device 40 generates an AC signal for impedance measurement based on the command signal transmitted from the power control device 50, and outputs the AC signal to the converter device 25, thereby superimposing an AC signal of a predetermined frequency on the output power from the fuel cell 21. The impedance measuring device 40 also detects the power waveform of the fuel cell 21 when the AC signal is superimposed on the output power of the fuel cell 21, and calculates the impedance of the fuel cell 21 based on the data of the detected power waveform. The power control device 50 acquires impedance information from the impedance measuring device 40 and diagnoses the state of the fuel cell 21.

[0042] Furthermore, the power control device 50 according to this embodiment controls the output of the fuel cell 21 so that the generated current of the fuel cell 21 is constant during the period in which the impedance measuring device 40 measures the impedance (impedance measurement period). This improves the accuracy of the impedance calculation based on the data of the power waveform when an AC signal is superimposed. Furthermore, by keeping the generated current of the fuel cell 21 constant during the impedance measurement period, the power control device 50 charges and discharges the secondary battery 31 in advance before starting the process of measuring the impedance (impedance measurement process) so that the remaining capacity of the secondary battery 31 does not fall below a predetermined lower limit or exceed an upper limit during or after the impedance measurement period.

[0043] Below, the functional configurations of the impedance measuring device 40 and the power control device 50 will be briefly described, and then the processing operation by the processing unit 51 of the power control device 50 will be specifically described. Note that in this embodiment, the impedance measuring device 40 is configured as a device separate from the power control device 50, but the impedance measuring device 40 may be configured integrally with the power control device 50 and provided as one function of the power control device 50.

[0044] (2-2. Impedance measuring device) The impedance measuring device 40 functions as a device that measures the impedance of the fuel cell 21 by one or more processors such as CPUs executing a computer program. The computer program is a computer program for causing the processor to execute operations to be performed by the impedance measuring device 40, which will be described later. The computer program executed by the processor may be recorded on a recording medium that functions as a storage unit (memory) 49 provided in the impedance measuring device 40, or may be recorded on a recording medium built into the impedance measuring device 40 or on any recording medium that can be externally attached to the impedance measuring device 40.

[0045] Examples of recording media for recording computer programs include magnetic media such as hard disks, floppy disks, and magnetic tapes; optical recording media such as CD-ROMs (Compact Disk Read Only Memory), DVDs (Digital Versatile Disks), and Blu-ray (registered trademark); magneto-optical media such as floptical disks; memory elements such as RAMs (Random Access Memory) and ROMs (Read Only Memory); and flash memories such as USB (Universal Serial Bus) memories and SSDs (Solid State Drives), as well as other media capable of storing programs.

[0046] The impedance measuring device 40 includes a processing unit 41 and a storage unit 49. The processing unit 41 includes one or more processors such as a CPU and an electric circuit. A part or the whole of the processing unit 41 may be configured with updatable firmware or the like, or may be a program module executed by a command from the CPU or the like.

[0047] The storage unit 49 is communicably connected to the processor and includes a memory for storing computer programs executed by the processor, control parameters, acquired information, etc. The storage unit 49 may include memory elements such as RAM and ROM, or may include a storage device such as a CD-ROM or a storage device.

[0048] The impedance measuring device 40 is communicatively connected to the power control device 50 via a communication means such as a controller area network (CAN) or a dedicated line. The impedance measuring device 40 is also configured to be able to acquire sensor signals from a voltage sensor 81 that detects the output voltage of the fuel cell 21 and a current sensor 83 that detects the output current from the fuel cell 21.

[0049] The processing unit 41 includes a superimposed signal generating unit 42, an output power detecting unit 44, and an impedance calculating unit 46. Some or all of the superimposed signal generating unit 42, the output power detecting unit 44, and the impedance calculating unit 46 are functions realized by the execution of a computer program by a processor. However, some or all of these units may be configured by analog circuits.

[0050] (Superimposed signal generator) The superimposed signal generating unit 42 sets the waveform of an AC signal for impedance measurement to be superimposed on the output power of the fuel cell 21 based on a command signal from the power control device 50, and outputs the set AC signal to the converter device 25. Specifically, the superimposed signal generating unit 42 sets the frequency and amplitude of the sine wave of the superimposed current to be superimposed on the output power based on a command signal transmitted from the power control device 50. The frequency of the superimposed current is set based on frequency information included in the command signal. The amplitude of the superimposed current may be set to an appropriate value according to the specifications of the fuel cell system 20. Alternatively, a square wave signal or an M sequence signal generated by superimposing waveform signals of multiple frequencies may be used as a signal for impedance measurement to be superimposed on the output signal of the fuel cell 21. The superimposed signal generating unit 42 outputs the AC signal of the set frequency and amplitude to the converter device 25. The converter device 25 operates a switching element based on the input AC signal, and superimposes an AC current waveform on the output current from the fuel cell 21.

[0051] (Output power detection section) The output power detection unit 44 executes a process to detect the current (output current) I and voltage (output voltage) V of the output power of the fuel cell 21 output while an AC current waveform is superimposed on the output power from the fuel cell 21, based on the sensor signals output from the voltage sensor 81 and the current sensor 83. The data of the output current I and the output voltage V are detected at a preset sampling period, and recorded as an AC current waveform and an AC voltage waveform superimposed with an AC signal for impedance measurement.

[0052] (Impedance calculation section) The impedance calculation unit 46 executes a process of calculating the impedance of the fuel cell 21 based on the recorded AC current waveform and AC voltage waveform. The impedance calculation unit 46 outputs information on the calculated impedance to the power control device 50. It is known that the output voltage V, output current I, and impedance Z of the fuel cell 21 when an AC signal is superimposed on the fuel cell 21 satisfy the relationship of the following formula. V = V0expj(ωt+Φ) I=I0expjωt Z=V / I=(V0 / I0)expjΦ=Z'+jZ” V0: Output voltage amplitude I0: Output current amplitude ω: each frequency Φ: Initial phase Z': Resistance component (real component) Z: Reactance component (imaginary component) j: imaginary unit t: time

[0053] Based on the above formula, the impedance calculation unit 46 calculates the impedance of each frequency from the amplitude of the AC current waveform and the AC voltage waveform and the phase difference between the AC current waveform and the AC voltage waveform. Alternatively, when a square wave signal or an M-sequence signal generated by overlapping waveform signals of a plurality of frequencies is used as a signal for impedance measurement to be superimposed on the output signal of the fuel cell 21, the impedance calculation unit 46 may perform FFT (Fast Fourier Transform) analysis on the obtained AC current waveform and AC voltage waveform to separate the overlapped signals and obtain the impedance of each frequency. Furthermore, the impedance calculation unit 46 may determine the average value of the impedance calculated from the amplitude and phase difference of each cycle of the AC current waveform and the AC voltage waveform for one or a plurality of frequencies as the impedance of each frequency. The amplitude of each cycle of the AC current waveform and the AC voltage waveform can be obtained, for example, as the difference between the maximum value and the maximum value of the current I or the voltage V in each cycle.

[0054] (2-3. Power control device) The power control device 50 functions as a device that controls the power supply to the inverter device 27 by one or more processors such as CPUs executing a computer program. The power control device 50 also functions as a device that diagnoses the state of the fuel cell 21 by one or more processors such as CPUs executing a computer program. The computer program is a computer program for causing the processor to execute operations to be performed by the power control device 50, which will be described later. The computer program executed by the processor may be recorded on a recording medium that functions as a storage unit (memory) 59 provided in the power control device 50, or may be recorded on a recording medium built into the power control device 50 or on any recording medium that can be externally attached to the power control device 50.

[0055] Examples of recording media for recording computer programs include magnetic media such as hard disks, floppy disks, and magnetic tapes; optical recording media such as CD-ROMs, DVDs, and Blu-ray (registered trademark); magneto-optical media such as floptical disks; memory elements such as RAMs and ROMs; flash memories such as USB memories and SSDs; and other media capable of storing programs.

[0056] The power control device 50 includes a processing unit 51 and a storage unit 59. The processing unit 51 includes one or more processors such as a CPU. A part or all of the processing unit 51 may be configured with updatable firmware or the like, or may be a program module or the like executed by a command from the CPU or the like.

[0057] Moreover, the storage unit 59 is communicably connected to the processor and includes a memory for storing computer programs executed by the processor, control parameters, acquired information, etc. The storage unit 59 may include memory elements such as RAM and ROM, and may include a storage device such as a CD-ROM or a storage device.

[0058] The power control device 50 is communicably connected to the impedance measuring device 40, the vehicle drive control device 60, the surrounding environment sensor 11, the vehicle state sensor 15, and the GPS sensor 17 via a communication means such as CAN or a dedicated line.

[0059] The processing unit 51 includes a power supply control unit 52, a diagnosis unit 53, a power consumption estimation unit 54, a remaining capacity estimation unit 55, and a battery charge / discharge control unit 56. Some or all of the power supply control unit 52, the diagnosis unit 53, the power consumption estimation unit 54, the remaining capacity estimation unit 55, and the battery charge / discharge control unit 56 may be functions realized by the execution of a computer program by a processor. Alternatively, some or all of these units may be configured by analog circuits.

[0060] (Power supply control unit) The power supply control unit 52 executes a process for controlling the power supply to the inverter device 27 that controls the driving of the drive motor 29. The power supply control unit 52 executes different processes during an impedance measurement period and during periods other than the impedance measurement period.

[0061] During periods other than the impedance measurement period, the power supply control unit 52 controls the output of the fuel cell 21 in coordination with torque control that causes the drive motor 29 to output a drive torque corresponding to the required acceleration of the fuel cell vehicle 1. In processing during periods other than the impedance measurement period, the power generation current of the fuel cell 21 changes according to fluctuations in the drive torque of the drive motor 29 and changes in the open circuit voltage of the secondary battery 31. Meanwhile, during the impedance measurement period, the power supply control unit 52 controls the output of the fuel cell 21 by so-called constant current control so that the power generation current of the fuel cell 21 becomes a preset constant value. At this time, if the output power of the fuel cell 21 is insufficient or excessive with respect to the required power of the drive motor 29 due to fluctuations in the required power of the drive motor 29, the excess or deficiency of power is compensated for by the output power of the secondary battery 31.

[0062] Specifically, the power supply control unit 52 fixes the power generation current of the fuel cell 21 to an arbitrary constant value during the impedance measurement period. When the output power of the fuel cell 21 is insufficient for the power required by the drive motor 29, the power supply control unit 52 drives the converter device 25 to make the output voltage of the converter device 25 equal to the open voltage of the secondary battery 31. In this way, the output power of the fuel cell 21 and the output power of the secondary battery 31 are supplied to the drive motor 29. On the other hand, when the output power of the fuel cell 21 is excessive for the power required by the drive motor 29, the power supply control unit 52 drives the converter device 25 to make the output voltage of the converter device 25 higher than the open voltage of the secondary battery 31, and charges the surplus power to the secondary battery 31 via the secondary battery converter device 33.

[0063] (Diagnostics Department) The diagnostic unit 53 executes a process of setting a frequency for measuring the impedance and outputting a command signal to the impedance measuring device 40. The frequency to be set is the frequency of an AC signal to be superimposed on the output power from the fuel cell 21, and is set according to the purpose of diagnosing the fuel cell 21. For example, by setting the frequency in a high frequency range, it is possible to diagnose the wet state of the MEA of the fuel cell 21. Also, by setting the frequency in a low frequency range, it is possible to diagnose the gas supply state, such as whether or not a fuel gas such as hydrogen gas or air is sufficiently supplied to the power generation part of the fuel cell 21. The diagnostic unit 53 may set a frequency for measuring the impedance while sequentially or randomly changing the frequency over the entire low frequency range and high frequency range. Alternatively, the diagnostic unit 53 may set a specific frequency as the frequency for measuring the impedance according to the purpose of the diagnosis.

[0064] Furthermore, the diagnosis unit 53 acquires impedance information for each frequency transmitted from the impedance measuring device 40, and diagnoses the state of the fuel cell 21 based on the acquired information. For example, the diagnosis unit 53 compares the impedance characteristics (reference) in the initial state when the use of the fuel cell 21 begins with the impedance characteristics (measurement results) measured by the impedance measuring device 40. The diagnosis unit 53 can then determine the state of the fuel cell 21 according to the state transition of the impedance characteristics in a known Cole-Cole plot diagram. Since the process of determining the internal state of the fuel cell 21 based on the impedance measurement results can be performed using conventionally known technology, detailed description will be omitted.

[0065] (Power consumption estimation section) The power consumption estimation unit 54 executes a process of estimating the power consumption during the impedance measurement period in advance. Specifically, the power consumption estimation unit 54 estimates the load of the drive motor 29 during the impedance measurement period based on at least information on the current position of the fuel cell vehicle 1, information on road traffic conditions on the planned route of the fuel cell vehicle 1, information on the surrounding environment of the fuel cell vehicle 1, and information on the running state of the fuel cell vehicle 1, and calculates the power consumption. For example, the power consumption during the period in which it is estimated that the drive motor 29 will output a drive torque is a positive value corresponding to the required drive torque. On the other hand, the power consumption during the period in which it is estimated that the drive motor 29 will regenerate is a negative value corresponding to the required braking torque. The power consumption estimation unit 54 integrates the power consumption estimated during the impedance measurement period and calculates the power consumption by the drive motor 29 during the impedance measurement period.

[0066] The power consumption estimation unit 54 may include, in the power consumption during the impedance measurement period, the power consumption of the vehicle accessories supplied from the secondary battery 31. For example, the power consumption estimation unit 54 calculates the power consumption of the vehicle accessories based on the operating state of equipment that consumes relatively large amounts of power, such as an air conditioner, and adds the calculated power consumption to the power consumption of the drive motor 29.

[0067] (Remaining capacity estimator) The remaining capacity estimation unit 55 executes a process of estimating the remaining capacity of the secondary battery 31 after the impedance measurement process is executed, based on the planned power generation of the fuel cell 21 during the impedance measurement period and the power consumption estimated by the power consumption estimation unit 54. Specifically, in this embodiment, the power generation current is set to a constant value during the impedance measurement period, so that the remaining capacity estimation unit 55 calculates the planned power generation of the fuel cell 21 by multiplying the power generation per unit time by the expected impedance measurement time. For example, a unit measurement time for measuring the impedance of one frequency is set, and the impedance measurement time can be obtained by multiplying the unit measurement time by the number of frequencies at which the impedance is measured. However, the method of calculating the impedance measurement time is not limited to this example.

[0068] Furthermore, the remaining capacity estimation unit 55 estimates the remaining capacity of the secondary battery 31 at the end of the impedance measurement period, assuming that the value obtained by subtracting the power consumption estimated by the power consumption estimation unit 54 from the calculated planned power generation of the fuel cell 21 is charged to the secondary battery 31. If the value obtained by subtracting the power consumption from the planned power generation is a negative value, this indicates that the secondary battery 31 is being discharged.

[0069] (Battery charge / discharge control unit) The battery charge / discharge control unit 56 executes a process of charging / discharging the secondary battery 31 before starting the impedance measurement process so that the remaining capacity of the secondary battery 31 estimated by the remaining capacity estimation unit 55 is equal to or greater than a predetermined lower limit and equal to or less than a predetermined upper limit. When the estimated remaining capacity is less than the predetermined lower limit, the battery charge / discharge control unit 56 executes a process of charging at least the shortage of power below the lower limit to the secondary battery 31. On the other hand, when the estimated remaining capacity exceeds the predetermined upper limit, the battery charge / discharge control unit 56 executes a process of discharging at least the surplus power exceeding the upper limit from the secondary battery 31.

[0070] In this embodiment, the battery charge / discharge control unit 56 increases or decreases the output power of the fuel cell 21, thereby charging the secondary battery 31 with the output power of the fuel cell 21, or supplying the output power of the secondary battery 31 to the drive motor 29, thereby charging or discharging the secondary battery 31. Specifically, the battery charge / discharge control unit 56 increases or decreases a predetermined amount of power with respect to the power generation target power set by the power supply control unit 52, thereby increasing or decreasing the output power of the fuel cell 21 and charging or discharging the secondary battery 31.

[0071] <3.Operation> So far, we have described examples of the configuration of the impedance measuring device 40 and the power control device 50. Next, a series of operations for power generation control during impedance measurement processing by the impedance measuring device 40 and the power control device 50 will be described in detail.

[0072] Fig. 3 is a flowchart showing an example of a process executed by the power control device 50. The process shown in the flowchart of Fig. 3 is constantly executed while the fuel cell system 20 is in operation.

[0073] First, the diagnosis unit 53 judges whether or not to execute impedance measurement processing of the fuel cell 21 (step S11). The method of judging whether or not to execute impedance measurement processing is not particularly limited, and the judgment may be made based on whether a preset execution timing has arrived. If it is not judged that the impedance measurement processing is to be executed (S11 / No), the power supply control unit 52 controls the power generation of the fuel cell 21 in coordination with the drive torque control of the drive motor 29 executed by the vehicle drive control device 60 (step S13).

[0074] An example of power generation control of the fuel cell 21 in cooperation with drive torque control of the drive motor 29 will be described. For example, the power supply control unit 52 acquires information on the target drive torque of the drive motor 29 from the vehicle drive control device 60 and calculates the required power W_ve_dem of the drive motor 29. The power supply control unit 52 may acquire information on the required power W_ve_dem calculated in the vehicle drive control device 60. The power supply control unit 52 also acquires information on the open circuit voltage or remaining capacity W_soc of the secondary battery 31 and determines whether or not the secondary battery 31 needs to be charged. For example, when the remaining capacity W_soc of the secondary battery 31 falls below a preset lower limit, the power supply control unit 52 determines that the secondary battery 31 needs to be charged. The lower limit may be, for example, a value equivalent to 20% when the remaining capacity at the beginning of use of the secondary battery 31 is taken as 100%. This makes it possible to suppress deterioration of the secondary battery 31 due to overdischarge and a power shortage state.

[0075] When the power required by the drive motor 29, W_ve_dem, is equal to or less than the maximum power generation of the fuel cell 21 and charging of the secondary battery 31 is unnecessary, the power supply control unit 52 sets the power required by the drive motor 29, W_ve_dem, to the target power generation power W_fc_dem of the fuel cell 21. As a result, the power control device 50 drives the drive motor 29 with the output power of the fuel cell 21. At this time, the power supply control unit 52 sets the output of the fuel cell 21 so that the power generation efficiency is at a high level, and if there is surplus power, the surplus power may be charged to the secondary battery 31 via the secondary battery converter device 33.

[0076] Furthermore, when the required power W_ve_dem of the drive motor 29 is equal to or less than the maximum power generation of the fuel cell 21 and charging of the secondary battery 31 is required, the power supply control unit 52 sets the maximum power generation target power W_fc_dem and drives the converter device 25 to make the output voltage of the converter device 25 higher than the open circuit voltage of the secondary battery 31. As a result, the power control device 50 drives the drive motor 29 with the output power of the fuel cell 21 and charges the secondary battery 31 with surplus power via the secondary battery converter device 33.

[0077] Furthermore, when the power requirement W_ve_dem of the drive motor 29 exceeds the maximum power generation of the fuel cell 21, the power supply control unit 52 sets the maximum power generation as the power generation target power, and drives the converter device 25 to make the output voltage of the converter device 25 equivalent to the open circuit voltage of the secondary battery 31, thereby distributing the power requirement W_ve_dem of the drive motor 29 to the fuel cell 21 and the secondary battery 31. In this way, the drive motor 29 is driven by the output power of the fuel cell 21 and the output power of the secondary battery 31.

[0078] The power supply control unit 52 may set not only the maximum power generation of the fuel cell 21 but also the target power generation power W_fc_dem of the fuel cell 21 so that the rate of increase in the output power of the fuel cell 21 is equal to or lower than a preset threshold value. When the remaining capacity W_soc of the secondary battery 31 exceeds a preset upper limit value W_soc_max, the power supply control unit 52 may stop power generation of the fuel cell 21 and drive the drive motor 29 only by the output power of the secondary battery 31 to discharge the secondary battery 31. The upper limit value may be, for example, a value equivalent to 80% of the remaining capacity at the beginning of use of the secondary battery 31, which is taken as 100%. This makes it possible to suppress deterioration of the secondary battery 31 due to overcharging and a decrease in power efficiency due to power discharge.

[0079] The power control device 50 executes power generation control in coordination with the drive torque control of step S13, unless it is determined in step S11 that the impedance measurement process is to be executed. On the other hand, if it is determined in step S11 that the impedance measurement process is to be executed (S11 / Yes), the diagnosis unit 53 sets the power generation current of the fuel cell 21 during the impedance measurement period (step S15). The value of the power generation current may be any value, or may be a preset fixed value. Furthermore, if the power generation current of the fuel cell 21 during the impedance measurement process is set to a fixed value, the process of step S15 may be omitted.

[0080] Next, the remaining capacity estimation unit 55 estimates the planned power generation W_fc_est of the fuel cell 21 during the impedance measurement period (step S17). Specifically, the remaining capacity estimation unit 55 calculates the planned power generation W_fc_est of the fuel cell 21 by multiplying the power generation current set in step S15 or the power generation power per unit time equivalent to a preset fixed value of the power generation current by an expected impedance measurement time. For example, a unit measurement time for measuring the impedance of each frequency is set, and the impedance measurement time can be obtained by multiplying the unit measurement time by the number of frequencies at which the impedance is measured. However, the method of calculating the impedance measurement time is not limited to this example.

[0081] Next, the power consumption estimation unit 54 acquires information on the driving conditions of the fuel cell vehicle 1 (step S19). Specifically, the power consumption estimation unit 54 acquires information on the current position of the fuel cell vehicle 1, information on traffic conditions on the planned driving route of the fuel cell vehicle 1, information on the surrounding environment of the fuel cell vehicle 1, and information on the driving state of the fuel cell vehicle 1. The information on the current position of the fuel cell vehicle 1 can be acquired based on the position information transmitted from the GPS sensor 17. The information on the traffic conditions on the planned driving route of the fuel cell vehicle 1 includes information on the legal speed limit on the planned driving route during the impedance measurement period, congestion information, information on road shapes such as the radius of curvature and the degree of inclination, and information on road types such as general roads and expressways. The congestion information can be acquired from a road information service provider via communication means such as mobile communication, road-to-vehicle communication, and beacons. Information on the traffic conditions on the planned driving route other than the congestion information is acquired from a database that records map data and road information. The database may be a cloud server (not shown) connected to the power control device 50 via mobile communication, or may be an in-vehicle database.

[0082] Information on the surrounding environment of the fuel cell vehicle 1 can be acquired based on detection signals transmitted from the surrounding environment sensor 11. The information on the surrounding environment includes at least information on other vehicles traveling in front of the fuel cell vehicle 1 and the shape of the road ahead. This information on the surrounding environment includes information on things that may be an obstacle to the traveling of the fuel cell vehicle 1. Information on the traveling state of the fuel cell vehicle 1 can be acquired based on detection signals transmitted from the vehicle state sensor 15. The information on the traveling state includes at least information on the vehicle speed and acceleration of the fuel cell vehicle 1. If the fuel cell vehicle 1 is a vehicle capable of executing automatic driving control such as ACC (Adaptive Cruise Control), the information on the traveling state includes information on the control state of the automatic driving control.

[0083] In addition, information on the operating status of the fuel cell vehicle 1 may include information other than information on the current location of the fuel cell vehicle 1, information on traffic conditions on the planned route of the fuel cell vehicle 1, information on the surrounding environment of the fuel cell vehicle 1, and information on the operating status of the fuel cell vehicle 1.

[0084] Next, the power consumption estimation unit 54 estimates the power consumption W_con during the impedance measurement period (step S21). Specifically, the power consumption estimation unit 54 predicts the transition of the drive torque of the drive motor 29 based on the acquired information on the operating state of the fuel cell vehicle 1. For example, during a period in which the required acceleration of the fuel cell vehicle 1 is predicted to be a positive value, the drive motor 29 outputs drive torque, so the drive torque is a positive value. Also, during a period in which the required acceleration of the fuel cell vehicle 1 is predicted to be a negative value (required deceleration is a positive value), the drive motor 29 outputs braking torque, so the drive torque is a negative value. The power consumption estimation unit 54 calculates the drive torque for each predetermined unit time during the impedance measurement period, and calculates the power consumption W_con by the drive motor 29 during the impedance measurement period by integrating the calculated drive torque.

[0085] The power consumption estimation unit 54 may calculate the power consumption W_con during the impedance measurement period including the power consumption of the vehicle accessories supplied from the secondary battery 31. For example, the power consumption estimation unit 54 calculates the power consumption of the vehicle accessories based on the operating state of equipment with relatively large power consumption, such as an air conditioner, and adds it to the power consumption by the drive motor 29. This can improve the accuracy of estimating the power consumption until the end of the impedance measurement period.

[0086] Next, the remaining capacity estimating unit 55 calculates the remaining capacity estimated value W_soc_est of the secondary battery 31 after the impedance measurement process is completed (step S23). Specifically, the remaining capacity estimating unit 55 adds the planned power generation W_fc_est estimated in step S17 to the remaining capacity W_soc of the secondary battery 31 at the start of the impedance measurement process, and subtracts the power consumption W_con estimated in step S21 to calculate the remaining capacity estimated value W_soc_est of the secondary battery 31 after the impedance measurement process is completed. If the time from the estimation time of the remaining capacity of the secondary battery 31 after the impedance measurement process is completed to the start time of the impedance measurement process is short, the current remaining capacity value of the secondary battery 31 may be used as the remaining capacity W_soc of the secondary battery 31 at the start of the impedance measurement process. Alternatively, the remaining capacity W_soc of the secondary battery 31 at the start of the impedance measurement process may be estimated in the same procedure as the method of estimating the remaining capacity of the secondary battery 31 after the impedance measurement process is completed.

[0087] Furthermore, the planned power generation W_fc_est and power consumption W_con for the period from when it is determined in step S11 that the impedance measurement process is to be executed to the end of execution of the impedance measurement process, including the impedance measurement process period, may be estimated, and the planned power generation W_fc_est may be added to the remaining capacity W_soc of the secondary battery 31 at the time when it is determined that the impedance measurement process is to be executed and the power consumption W_con may be subtracted to calculate an estimated remaining capacity W_soc_est of the secondary battery 31 after execution of the impedance measurement process is completed.

[0088] Next, the remaining capacity estimating unit 55 determines whether the estimated remaining capacity W_soc_est of the secondary battery 31 after the impedance measurement process is completed is equal to or greater than a preset lower limit W_soc_min (step S25). The lower limit W_soc_min may be a lower limit (e.g., 20%) set to suppress deterioration or power shortage due to overdischarge of the secondary battery 31, but may be a different value.

[0089] If the remaining capacity estimate W_soc_est of the secondary battery 31 after the estimated impedance measurement process is less than the lower limit W_soc_min (S25 / No), the battery charge / discharge control unit 56 charges the secondary battery 31 before starting the impedance measurement process so that the remaining capacity estimate W_soc_est of the secondary battery 31 after the estimated impedance measurement process is equal to or greater than the lower limit W_soc_min and equal to or less than the upper limit W_soc_max (step S27). In this embodiment, the battery charge / discharge control unit 56 adds a predetermined amount of correction power value W_fc_rev to the power generation target power W_fc_dem in the power generation control of the fuel cell 21 (processing of step S13) executed during a period other than the impedance measurement process period, and executes a process of charging the secondary battery 31.

[0090] The battery charge / discharge control unit 56 increases the power generation target power W_fc_dem so that the sum of the correction power values ​​W_fc_rev to be added is equal to the difference obtained by subtracting the remaining capacity estimate value W_soc_est estimated in step S23 from the target value of the remaining capacity of the secondary battery 31 after the impedance measurement process is completed. For example, the battery charge / discharge control unit 56 adds the amount of power obtained by dividing the difference by the time until the impedance measurement process is started as the correction power value W_fc_rev to the power generation target power W_fc_dem during the period until the impedance measurement process is started. The battery charge / discharge control unit 56 may add a constant correction power value W_fc_rev set in advance, or may vary the correction power value W_fc_rev to be added depending on the difference between the power generation target power before the addition and the maximum power generation power or depending on the power generation efficiency.

[0091] The target value of the remaining capacity of the secondary battery 31 after the impedance measurement process is completed may be set arbitrarily as long as it is equal to or greater than the lower limit W_soc_min and equal to or less than the upper limit W_soc_max of the remaining capacity of the secondary battery 31, but in order to prevent a significant delay in the start of the impedance measurement process, it is preferable to set it within the range of the lower limit W_soc_min plus 0 to 10%. In addition, if the target drive torque of the drive motor 29 after the impedance measurement process is expected to be large, it is preferable to set the target value of the remaining capacity higher than the above example, for example, within the range of the lower limit W_soc_min plus 20 to 30%, in order to prevent a decrease in the remaining capacity W_soc of the secondary battery 31 after the impedance measurement process.

[0092] After completing the process in step S27, the diagnosis unit 53 executes the impedance measurement process (step S33). On the other hand, if the estimated remaining capacity W_soc_est of the secondary battery 31 after the estimated impedance measurement process is equal to or greater than the lower limit W_soc_min in step S25 (S25 / Yes), the remaining capacity estimation unit 55 determines whether the estimated remaining capacity W_soc_est of the secondary battery 31 after the estimated impedance measurement process is equal to or less than the upper limit W_soc_max set in advance (step S29). The upper limit W_soc_max may be, for example, an upper limit (e.g., 80%) set to suppress deterioration of the secondary battery 31 due to overcharging or a decrease in power efficiency, but a different value may also be set.

[0093] If the remaining capacity estimate W_soc_est of the secondary battery 31 after the estimated impedance measurement process is equal to or smaller than the upper limit W_soc_max (S29 / Yes), the diagnosis unit 53 executes the impedance measurement process (step S33). On the other hand, if the remaining capacity estimate W_soc_est of the secondary battery 31 after the estimated impedance measurement process is greater than the upper limit W_soc_max (S29 / No), the battery charge / discharge control unit 56 charges the secondary battery 31 before starting the impedance measurement process so that the remaining capacity estimate W_soc_est of the secondary battery 31 after the estimated impedance measurement process is equal to or larger than the lower limit W_soc_min and equal to or smaller than the upper limit W_soc_max (step S31). In this embodiment, the battery charge / discharge control unit 56 subtracts a predetermined amount of correction power value W_fc_rev from the power generation target power in the power generation control of the fuel cell 21 (processing of step S13) that is executed during periods other than the impedance measurement processing period, and executes processing to supply power from the secondary battery 31 to the drive motor 29.

[0094] The battery charge / discharge control unit 56 reduces the power generation target power W_fc_dem so that the sum of the correction power values ​​W_fc_rev to be subtracted becomes the difference obtained by subtracting the target value of the remaining capacity of the secondary battery 31 after the execution of the impedance measurement process from the remaining capacity estimated value W_soc_est estimated in step S23. For example, the battery charge / discharge control unit 56 subtracts the correction power value W_fc_rev obtained by dividing the difference by the time until the impedance measurement process is started from the power generation target power during the period until the impedance measurement process is started. The battery charge / discharge control unit 56 may subtract a constant correction power value W_fc_rev set in advance, or may set the correction power value W_fc_rev to be subtracted according to the power generation efficiency. The target value for the remaining capacity of the secondary battery 31 after the impedance measurement process is completed may be set arbitrarily as long as it is greater than or equal to the lower limit W_soc_min of the remaining capacity estimate W_soc_est of the secondary battery 31 and less than or equal to the upper limit W_soc_max. However, in order to prevent a significant delay in the start of the impedance measurement process, it is preferable to set it within a range of, for example, the upper limit W_soc_max minus 0 to 10%.

[0095] After completing the process in step S31, the diagnosis unit 53 executes an impedance measurement process (step S33).

[0096] FIG. 4 is an explanatory diagram showing an example of the calculation process of the target power generation power of the fuel cell 21 until the impedance measurement process is started, which is executed in steps S17 to S31. The remaining capacity estimation unit 55 calculates the power balance W_a during the impedance measurement period by adding the estimated power consumption W_con during the impedance measurement period and the planned power generation W_fc_est. The remaining capacity estimation unit 55 also adds the power balance W_a to the remaining capacity W_soc of the secondary battery 31 to calculate the remaining capacity estimate W_soc_est of the secondary battery 31 after the impedance measurement process.

[0097] The battery charge / discharge control unit 56 compares the remaining capacity estimate W_soc_est with the upper limit W_soc_max and lower limit W_soc_min to calculate the charge / discharge required power W_bat_dem of the secondary battery 31. Specifically, when the remaining capacity estimate W_soc_est exceeds the upper limit W_soc_max, the battery charge / discharge control unit 56 sets the difference (<0) obtained by subtracting the remaining capacity estimate W_soc_est from the upper limit W_soc_max as the charge / discharge required power W_bat_dem. In this case, the charge / discharge required power W_bat_dem (<0) means a discharge required power value.

[0098] On the other hand, when the remaining capacity estimate W_soc_est is below the lower limit W_soc_min, the battery charge / discharge control unit 56 sets the difference (>0) obtained by subtracting the remaining capacity estimate W_soc_est from the lower limit W_soc_min as the charge / discharge required power W_bat_dem. In this case, the charge / discharge required power W_bat_dem (>0) means the charging required power value. When the remaining capacity estimate W_soc_est is equal to or greater than the lower limit W_soc_min and less than the upper limit W_soc_max, the battery charge / discharge control unit 56 sets the charge / discharge required power W_bat_dem to zero.

[0099] The battery charge / discharge control unit 56 calculates a corrected power value W_fc_rev of the power generation target power of the fuel cell 21 by dividing the calculated charge / discharge required power W_bat_dem by the time T_est until the impedance measurement process is started. During the period until the impedance measurement process is started, the power supply control unit 52 calculates the power generation target power W_fc_dem of the fuel cell 21 by adding the corrected power value W_fc_rev to the required power W_ve_dem calculated based on the target drive torque acquired from the vehicle drive control device 60. The power generation target power W_fc_dem may further be calculated by adding the required power of vehicle accessories such as an air conditioner. The power supply control unit 52 controls the drive of the fuel cell accessories 23 based on the calculated power generation target power W_fc_dem, and executes power generation control of the fuel cell 21.

[0100] 3 is started when a command signal is transmitted from the power control device 50 to the impedance measuring device 40. The impedance measuring process by the impedance measuring device 40 will be briefly described below.

[0101] The superimposed signal generating unit 42 of the impedance measuring device 40 sets an AC current waveform for impedance measurement based on a command signal transmitted from the power control device 50, and outputs the set AC current signal to the converter device 25. As a result, the converter device 25 operates the switching element based on the input AC current signal, and superimposes the AC current waveform on the output power of the fuel cell 21. Next, the output power detecting unit 44 acquires sensor signals from the voltage sensor 81 and the current sensor 83 at a preset sampling period, and records data on the output current I and output voltage V. The detected data on the output current I and output voltage V are recorded as data on the AC current waveform and AC voltage waveform on which the AC signal for impedance measurement is superimposed.

[0102] Next, the impedance calculation unit 46 executes a process of calculating the impedance of the fuel cell 21 based on the recorded AC current waveform and AC voltage waveform. For example, the impedance calculation unit 46 calculates the impedance for each cycle from the amplitude of the AC current waveform and AC voltage waveform and the phase difference between the AC current waveform and AC voltage waveform, and sets the average value of the impedances as the impedance for the current frequency. The impedance calculation unit 46 calculates the impedance for all frequencies specified by the power control device 50, and outputs information on the calculated impedance to the power control device 50.

[0103] Next, a description will be given of the processing of the power control device 50 during the impedance measurement processing. Fig. 5 is a flowchart showing the processing of the power control device 50 during the impedance measurement processing.

[0104] First, the diagnosis unit 53 outputs an impedance measurement command signal to the impedance measuring device 40 (step S41). The impedance measurement command signal may include, for example, information on the frequency at which the impedance is measured. Next, the power supply control unit 52 fixes the power generation current of the fuel cell 21 to the measurement current set in step S15, and starts output control of the fuel cell 21 by constant current control (step S43).

[0105] Next, the power supply control unit 52 calculates the required power W_ve_dem of the drive motor 29 based on information on the target drive torque of the drive motor 29 from the vehicle drive control device 60 (step S45). Next, the power supply control unit 52 determines whether the generated power W_fc of the fuel cell 21 exceeds the required power W_ve_dem (step S47). If the generated power W_fc of the fuel cell 21 exceeds the required power W_ve_dem (S47 / Yes), the power supply control unit 52 executes a charging process for the secondary battery 31 (step S49). Specifically, the power supply control unit 52 drives the converter device 25 to make the output voltage of the converter device 25 higher than the open voltage of the secondary battery 31, and charges the secondary battery 31 with surplus power via the secondary battery converter device 33.

[0106] On the other hand, if the generated power W_fc of the fuel cell 21 does not exceed the required power W_ve_dem (S47 / No), the power supply control unit 52 judges whether the generated power W_fc of the fuel cell 21 is below the required power W_ve_dem (step S51). If the generated power W_fc of the fuel cell 21 is below the required power W_ve_dem (S51 / Yes), the power supply control unit 52 executes a process of outputting power from the secondary battery 31 (step S53). Specifically, the power supply control unit 52 drives the converter device 25 to make the output voltage of the converter device 25 equal to the open voltage of the secondary battery 31. As a result, the output power of the fuel cell 21 and the output power of the secondary battery 31 are supplied to the drive motor 29.

[0107] On the other hand, if the generated power W_fc of the fuel cell 21 is not below the required power W_ve_dem (S51 / No), ie, if the generated power W_fc of the fuel cell 21 is equal to the required power W_ve_dem, the power supply control unit 52 proceeds directly to step S55.

[0108] Next, the power supply control unit 52 determines whether the impedance measurement process has been completed (step S55). For example, the power supply control unit 52 may determine that the impedance measurement process has been completed when the diagnosis unit 53 has acquired information on the impedance measurement results for all frequencies from the impedance measuring device 40. If it is not determined that the impedance measurement process has been completed (S55 / No), the power supply control unit 52 returns to step S45 and repeatedly executes the processes of the above-mentioned steps.

[0109] On the other hand, if it is determined that the impedance measurement process has ended (S55 / No), the power supply control unit 52 switches to power generation control of the fuel cell 21 in coordination with drive torque control of the drive motor 29 by the vehicle drive control device 60 (step S57). After that, the process returns to step S41 and repeatedly executes the processes of the above-mentioned steps.

[0110] <4. Effect> Next, the operation of power generation control of the fuel cell 21 by the power control device 50 according to this embodiment will be described. Figure 6 is an explanatory diagram showing an example of power generation control when it is determined that the remaining capacity W_soc of the secondary battery 31 after the impedance measurement process is completed falls below the lower limit value W_soc_min, and shows the trends in the remaining capacity W_soc of the secondary battery 31, the generated power W_fc of the fuel cell 21, and the corrected power value W_fc_rev.

[0111] The remaining capacity W_soc' indicated by the dashed line indicates the transition of the remaining capacity in the case where the secondary battery 31 is not charged or discharged so that the estimated remaining capacity W_soc of the secondary battery 31 falls within the range from the lower limit W_soc_min to the upper limit W_soc_max before the start of the impedance measurement process. In the example shown in Fig. 6, the remaining capacity W_soc' falls below the lower limit W_soc_min during the impedance measurement process. Therefore, for example, at time T1, the battery charge / discharge control unit 56 determines that the remaining capacity W_soc' after the impedance measurement process falls below the lower limit W_soc_min.

[0112] For this reason, the power supply control unit 52 corrects the power generation W_fc of the fuel cell 21 to increase it during the period from time T2 to T3 before the impedance measurement period X. In the example shown in FIG. 6, the difference obtained by subtracting the remaining capacity W_soc at time T2 from the upper limit value W_soc_max of the remaining capacity is set as the charge / discharge required power W_bat_dem (>0), and the value obtained by dividing the charge / discharge required power W_bat_dem by the time T_est from time T2 to T3 is set as the correction power value W_fc_rev. Then, during the period from time T2 to T3, the power supply control unit 52 adds the correction power value W_fc_rev to the required power W_ve_dem of the drive motor 29 to execute power generation control of the fuel cell 21. As a result, the remaining capacity W_soc of the secondary battery 31 at time T3 rises to the upper limit value W_soc_max.

[0113] During the impedance measurement period X, the power supply control unit 52 sets the power generation current of the fuel cell 21 to a constant value and executes constant current control. During the impedance measurement period X, an AC signal for impedance measurement is superimposed on the output power of the fuel cell 21. During the period from time T4 to T5 corresponding to the impedance measurement period X, the difference power W_bat obtained by subtracting the power generation power W_fc of the fuel cell 21 from the power required for the drive motor 29 W_ve_dem is supplemented by the output power of the secondary battery 31. Therefore, although the remaining capacity W_soc of the secondary battery 31 decreases during the impedance measurement period X, the remaining capacity W_soc is kept within a range not less than the lower limit value W_soc_min and not more than the upper limit value W_soc_max even after the end of the impedance measurement period X because the remaining capacity W_soc has been increased in advance to the upper limit value W_soc_max.

[0114] As described above, the power control device 50 of the fuel cell system 20 of this embodiment performs constant current control to control the power generation of the fuel cell 21 during the impedance measurement period, and supplements any excess or deficiency of power relative to the power demand W_ve_dem of the drive motor 29 with power from the secondary battery 31. This makes it possible to ensure the power demand W_ve_dem of the drive motor 29, while measuring the impedance by superimposing an AC signal in a state where the output of the fuel cell 21 is stable. This makes it possible to improve the measurement accuracy of the impedance in all frequency bands, and to accurately diagnose the state of the fuel cell 21.

[0115] Furthermore, the power control device 50 of this embodiment estimates in advance the remaining capacity estimate W_soc_est of the secondary battery 31 after the impedance measurement process is completed, and charges and discharges the secondary battery 31 before the start of the impedance measurement process so that the estimated remaining capacity estimate W_soc_est is within a range from a predetermined lower limit W_soc_min to an upper limit W_soc_max. This makes it possible to keep the remaining capacity W_soc of the secondary battery 31 equal to or greater than the lower limit W_soc_min and equal to or less than W_soc_max even after the impedance measurement process is completed, even if the power generation control of the fuel cell 21 is performed by constant current control during the impedance measurement period. This makes it possible to suppress deterioration of the secondary battery 31 due to overcharging or overdischarging, and to prevent power shortages when the target drive torque of the drive motor 29 is large, such as during rapid acceleration.

[0116] Furthermore, the power control device 50 of this embodiment estimates the power consumption W_con of the drive motor and the planned power generation W_fc_est of the fuel cell 21 during the impedance measurement processing period, and calculates a remaining capacity estimate W_soc_est based on the power consumption W_con and the planned power generation W_fc_est. As a result, the remaining capacity estimate W_soc_est of the secondary battery 31 after completion of the impedance measurement processing is estimated based on the predicted load of the drive motor 29, and it is possible to increase the certainty that the remaining capacity W_soc of the secondary battery 31 after completion of the impedance measurement processing will be equal to or greater than the lower limit W_soc_min and equal to or less than W_soc_max.

[0117] Furthermore, when charging / discharging the secondary battery 31 before starting the impedance measurement process, the power control device 50 of this embodiment adds or subtracts a correction power value W_fc_rev to the power generated by the fuel cell 21 according to the power W_ve_dem required by the drive motor 29. This prevents power from being wasted and makes it possible to suppress a decrease in power efficiency.

[0118] Furthermore, in the power control device 50 of this embodiment, when charging / discharging the secondary battery 31 before starting the impedance measurement process, it is preferable to add or subtract a fixed correction power value W_fc_rev during the period in which the secondary battery 31 is pre-charged / discharged. This allows power generation control of the fuel cell 21 to be performed with the same fluctuation range as the fluctuation range of the power generation target power when control for pre-charging / discharging the secondary battery 31 is not executed, making it possible to prevent an increase in the power generation load of the fuel cell 21.

[0119] Although the preferred embodiment of the present disclosure has been described in detail above with reference to the accompanying drawings, the present disclosure is not limited to such examples. It is clear that a person having ordinary knowledge in the technical field to which the present disclosure belongs can conceive of various modified or amended examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally belong to the technical scope of the present disclosure. .

[0120] For example, a computer program that causes the processing unit 51 of the power control device 50 to execute a series of processes also falls within the technical scope of the present disclosure. [Explanation of symbols]

[0121] 1: fuel cell vehicle, 11: ambient environment sensor, 15: vehicle state sensor, 17: GPS sensor, 20: fuel cell system, 21: fuel cell, 25: converter device, 27: inverter device, 29: drive motor, 31: secondary battery, 33: secondary battery converter device, 40: impedance measurement device, 41: processing unit, 42: superimposed signal generation unit, 44: output power detection unit, 46: impedance calculation unit, 49: memory unit, 50: power control device, 51: processing unit, 52: power supply control unit, 53: diagnosis unit, 54: power consumption estimation unit, 55: remaining capacity estimation unit, 56: battery charge / discharge control unit, 59: memory unit, 60: vehicle drive control device, 81: voltage sensor, 83: current sensor

Claims

1. A power control device for a fuel cell system including a fuel cell, a power storage device, and a drive motor, the power control device including an impedance measurement unit that measures an impedance of the fuel cell based on a current and a voltage measured when AC power is superimposed on an output power of the fuel cell, one or more processors; and one or more memories communicatively coupled to the one or more processors; The processor, estimating in advance the power consumption by the drive motor and the planned power generation by the fuel cell during a period in which the process of measuring the impedance is executed; estimating in advance a remaining capacity of the power storage device after a process of measuring the impedance is executed based on the estimated power consumption and the planned power generation; charging and discharging the power storage device before starting a process of measuring the impedance so that the estimated remaining capacity falls within a range from a predetermined lower limit value to an upper limit value; During the process of measuring the impedance, the power generation of the fuel cell is controlled so that a power generation current of the fuel cell is kept constant. The power control device performs a process including:

2. The processor, 2 . The power control device according to claim 1 , wherein the power storage device is charged or discharged by increasing or decreasing the power generated by the fuel cell before starting the process of measuring the impedance.

3. A power control device for a fuel cell system including a fuel cell, a power storage device, and a drive motor, the power control device including an impedance measurement unit that measures an impedance of the fuel cell based on a current and a voltage measured when AC power is superimposed on an output power of the fuel cell, a power supply control unit that controls power generation of the fuel cell based on a target drive torque of the drive motor that is set in accordance with a required acceleration of the fuel cell vehicle, and controls power generation of the fuel cell so that a generated current of the fuel cell is constant during execution of a process for measuring the impedance; a remaining capacity estimation unit that estimates in advance a remaining capacity of the power storage device after the process of measuring the impedance is executed; a battery charge / discharge control unit that charges and discharges the power storage device before starting a process of measuring the impedance so that the estimated remaining capacity is equal to or greater than a predetermined lower limit value and equal to or less than a predetermined upper limit value; A power control device comprising:

4. A fuel cell system comprising the power control device according to any one of claims 1 to 3.

5. A vehicle comprising the fuel cell system according to claim 4.

6. A recording medium having recorded thereon a computer program applicable to a fuel cell system including a fuel cell, a power storage device, and a drive motor, the fuel cell system including an impedance measurement unit that measures an impedance of the fuel cell based on a current and a voltage measured when AC power is superimposed on an output power of the fuel cell, One or more processors, estimating in advance the power consumption by the drive motor and the planned power generation by the fuel cell during a period in which the impedance measurement process is executed; estimating in advance a remaining capacity of the power storage device after a process of measuring the impedance is executed based on the estimated power consumption and the planned power generation; charging and discharging the power storage device before starting a process of measuring the impedance so that the estimated remaining capacity falls within a range from a predetermined lower limit value to an upper limit value; During the process of measuring the impedance, controlling the power generation of the fuel cell so that a power generation current of the fuel cell is constant; A recording medium on which a computer program for executing a process including the steps of:

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