Impedance Measurement System

Abstract

To provide an impedance measuring system with which it is possible to improve the accuracy of measuring the impedance of a measurement object such as a power generation module or a secondary cell.SOLUTION: An impedance measuring system for measuring the impedance of a measurement object which is capable of supplying electric power to an electric load apparatus comprises one or a plurality of processors, and a one or a plurality of memories communicably connected to the one or the plurality of processors. The processor executes a process that includes: acquiring the data of output electric power when an AC signal consisting of at least one frequency is superimposed on the output electric power of the measurement object; calculating the impedance of the at least one frequency, excluding the data of a cycle in which a waveform disturbance of the output electric power is detected; and changing the setting of operating condition of an electronic apparatus connected to the measurement object or one of electric load apparatuses and then measuring the impedance when the number of excluded cycles in a prescribed frequency is greater than or equal to a prescribed threshold.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an impedance measurement system. [Background technology]

[0002] Electrochemical impedance spectroscopy (ELA) is known as a method for diagnosing the internal state of power generation modules such as polymer electrolyte fuel cells (PEFCs) and secondary batteries such as lithium-ion batteries (LiBs). In ELA, an AC signal is superimposed on the output power of a measurement object such as a power generation module or a secondary battery, and an impedance is calculated based on the output power data when power is output from the measurement object. Using ELA, the internal state of the measurement object can be diagnosed based on the impedance at the frequency of the superimposed AC signal.

[0003] For example, Patent Document 1 proposes a fuel cell system that accurately grasps the degree of dryness inside the fuel cell using electrochemical impedance analysis. Specifically, Patent Document 1 discloses a fuel cell system that calculates the impedance of the fuel cell, extracts from this impedance a high-frequency impedance that is the impedance in the high-frequency range and a low-frequency impedance in the low-frequency range, calculates a differential impedance by subtracting the high-frequency impedance from the low-frequency impedance, calculates the water content of the electrolyte membrane using the high-frequency impedance, and calculates the water content of the catalyst layer using the differential impedance.

[0004] Furthermore, Patent Document 2 proposes a fuel cell system that improves the impedance measurement performance of a fuel cell in a fuel cell system equipped with a multiphase voltage converter. Specifically, the system discloses a fuel cell system that generates a control signal for controlling each phase of the multiphase voltage converter by superimposing a control waveform for impedance measurement on a voltage that indicates the output target voltage of the multiphase voltage converter, sequentially outputs the control signals for N phases with a predetermined phase difference to the multiphase voltage converter, measures the current and voltage of the fuel cell at periods corresponding to N predetermined sampling frequencies that have the same phase difference as the predetermined phase difference, and calculates the impedance of the fuel cell using the measured current and voltage. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-165463 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-216429 Summary of the Invention [Problem to be solved by the invention]

[0006] In a power system equipped with a fuel cell or secondary battery capable of supplying power to a power load device, such as a fuel cell system in a fuel cell vehicle, electronic devices that consume power are connected to the measurement object such as the fuel cell or secondary battery and the power load device. If the power consumption of the electronic devices fluctuates significantly when measuring impedance, noise generated by these electronic devices may be carried over to the waveform of the output power of the measurement object, causing distortion in the waveform of the measured impedance.

[0007] The present disclosure has been made in consideration of the above problems, and an object of the present disclosure is to provide an impedance measurement system that can improve the measurement accuracy of the impedance of a measurement object such as a power generation module or a secondary battery. [Means for solving the problem]

[0008] In order to solve the above problem, according to one aspect of the present disclosure, there is provided an impedance measurement system that measures the impedance of a measurement object that is capable of supplying power to an electrical load device, the impedance measurement system comprising one or more processors and one or more memories communicably connected to the one or more processors, wherein the processor acquires data on the output power when an AC signal of at least one frequency is superimposed on the output power of the measurement object, calculates the impedance of at least one frequency by excluding data on periods in which a disturbance in the waveform of the output power is detected, and if the number of excluded periods at a predetermined frequency is equal to or greater than a predetermined threshold, changes the settings of the operating conditions of an electronic device connected to either the measurement object or the electrical load device and measures the impedance.

[0009] In addition, in order to solve the above problem, according to another aspect of the present disclosure, there is provided an impedance measurement system that measures the impedance of a measurement object based on the output power measured when an AC signal of at least one frequency is superimposed on the output power of the measurement object that can supply power to an electrical load device, the impedance measurement system comprising: a superimposed signal generation unit that performs a process to superimpose the AC signal; an impedance calculation unit that calculates the impedance of at least one frequency by excluding data of a period in which a disturbance in the waveform of the output power is detected; and an auxiliary control unit that performs a process to change the settings of the operating conditions of an electronic device connected to either the measurement object or the electrical load device when the number of excluded periods at a predetermined frequency is equal to or greater than a predetermined threshold value. [Effects of the Invention]

[0010] As described above, according to the present disclosure, it is possible to improve the measurement accuracy of the impedance of a measurement object such as a power generation module or a secondary battery. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram illustrating an example of a vehicle equipped with a fuel cell system to which an impedance measurement system according to an embodiment of the present disclosure can be applied. [Figure 2] FIG. 2 is a block diagram showing an example of the configuration of a fuel cell system to which the impedance measurement system according to the embodiment is applied. [Figure 3] FIG. 10 is an explanatory diagram showing a decrease in amplitude as one aspect of waveform disturbance. [Figure 4] FIG. 10 is an explanatory diagram showing a phase shift of the amplitude period as one aspect of waveform disturbance. [Figure 5] FIG. 2 is an explanatory diagram showing an equivalent circuit model of a fuel cell stack. [Figure 6] FIG. 10 is an explanatory diagram showing an approximation line representing impedance characteristics. [Figure 7] FIG. 10 is an explanatory diagram showing deviation of an approximation line due to a decrease in accuracy of impedance. [Figure 8] 10 is a flowchart showing an impedance measurement process performed by the impedance measurement system according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0013] <1. Overall configuration of fuel cell system> First, an example of an impedance measurement system according to an embodiment of the present disclosure will be described. In the following embodiment, an example in which the impedance measurement system is applied to a fuel cell system mounted on a fuel cell vehicle will be described, but the application of the impedance measurement system is not limited to fuel cell systems.

[0014] Fig. 1 is a schematic diagram showing an example of a vehicle 1 equipped with a fuel cell system 20. Fig. 2 is a block diagram showing an example of the configuration of the fuel cell system 20. Fig. 2 shows the functional configuration of the impedance measuring device 40 and the control device 50 that is related to the process of measuring the impedance of the fuel cell stack 21.

[0015] 1 is configured as a four-wheel drive fuel cell 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).

[0016] The vehicle 1 may be an electric vehicle equipped with two drive motors, for example, a front-wheel drive motor and a rear-wheel drive motor, or may be an electric vehicle equipped with drive motors corresponding to each of the wheels 3.

[0017] The fuel cell system 20 includes a fuel cell stack 21, a fuel cell auxiliary device 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 control device 50.

[0018] 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 three-phase AC power supplied from the fuel cell system 20.

[0019] The fuel cell stack 21 is configured as, for example, a solid polymer electrolyte fuel cell, and has a stack structure in which a plurality of fuel cell units are stacked. Each fuel cell unit has a hydrogen electrode and an oxygen electrode on each side 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 unit 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 power is generated by an electrochemical reaction between the supplied hydrogen gas and air. The fuel cell stack 21 outputs the generated DC power to the converter device 25.

[0020] The fuel cell auxiliaries 23 include devices that adjust the pressure and flow rate of hydrogen gas (fuel gas) and air (oxidizing gas) supplied to the fuel cell stack 21. For example, the fuel cell auxiliaries 23 are 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 stack 21. The pressure reducing valve reduces the pressure of hydrogen gas in a high-pressure hydrogen tank and supplies it to the fuel cell stack 21. The back pressure control valve adjusts the flow rate of hydrogen off-gas discharged from the fuel cell stack 21, thereby adjusting the pressure of hydrogen gas in the fuel cell stack 21. The hydrogen circulation pump supplies the hydrogen off-gas back to the fuel cell stack 21.

[0021] The fuel cell auxiliary equipment 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 stack 21. The compressor inverter device controls the output of the compressor and adjusts the flow rate of air supplied to the fuel cell stack 21. The back pressure control valve adjusts the flow rate of oxidizing off gas discharged from the fuel cell stack 21, thereby adjusting the pressure of the air inside the fuel cell stack 21.

[0022] The fuel cell auxiliary 23 is an electronic device that operates by receiving a supply of DC power output from the fuel cell stack 21. The operation of the fuel cell auxiliary 23 is controlled by the control device 50. Note that the fuel cell auxiliary 23 for operating the fuel cell stack 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 to cool the fuel cell stack 21.

[0023] The converter device 25 is configured as a DC-DC converter that converts the DC power output from the fuel cell stack 21 into DC power of a desired level and supplies it to the inverter device 27. The converter device 25 is one form of electrical load equipment that receives power from the fuel cell stack 21 as a power generation module. 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 stack 21 and supplies it to the inverter device 27. The driving of the switching elements of the converter device 25 is controlled by the control device 50.

[0024] 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-, v-, 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 stack 21 and a lower arm electrically connected to the negative electrode side of the fuel cell stack 21. The upper arm and lower arm of each arm circuit are provided with switching elements to which diodes are electrically connected in anti-parallel. Examples of switching elements that can be used include MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and IGBTs (Insulated Gate Bipolar Transistors). The u-, v-, and w-phase coils of the drive motor 29 are electrically connected to the connection between the upper arm and lower arm of each arm circuit.

[0025] Furthermore, when the vehicle 1 is decelerating, 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 control device 50. This controls the driving and regeneration of the drive motor 29.

[0026] Furthermore, a secondary battery 31 is connected to a DC stage 35 that connects the converter device 25 and the inverter device 27 via a secondary battery converter device 33. The secondary battery 31 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 generated by the fuel cell stack 21, excluding the power supplied to the drive motor 29. The secondary battery 31 also stores power generated by regeneration of the drive motor 29. The secondary battery 31 supplies the stored power to vehicle accessories 37. The secondary battery 31 may also be configured to supply the stored power to the drive motor 29.

[0027] The secondary battery converter device 33 charges the secondary battery 31 by adjusting the voltage of the power generated by the fuel cell stack 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 DC-DC converter. The secondary battery converter device 33 may also be configured to adjust the voltage of the power output from the secondary battery 31 and supply it to the inverter device 27. The secondary battery converter device 33 includes a chopper circuit, and by operating, for example, two switching elements, the secondary battery converter device 33 increases or decreases the voltage of the power of the DC stage 35 and supplies it to the secondary battery 31, or increases or decreases the voltage of the output power of the secondary battery 31 and supplies it to the DC stage 35. The driving of the switching elements is controlled by the control device 50.

[0028] The vehicle auxiliary equipment 37 is various electronic devices provided in the vehicle 1. Examples of the vehicle auxiliary equipment 37 include an air conditioner, lighting equipment, and audio equipment, but also includes various other electronic devices. The vehicle auxiliary equipment 37 operates by receiving a supply of DC power output from the secondary battery 31. The vehicle auxiliary equipment 37 may also receive a supply of power whose voltage is stepped down via a step-down converter (not shown). In this case, the vehicle auxiliary equipment 37 may include an auxiliary battery whose rated voltage is lower than that of the secondary battery 31.

[0029] The control device 50 executes a process for controlling power generation by the fuel cell system 20. For example, the control device 50 calculates the required power based on information such as accelerator operation amount during manual driving or required acceleration during autonomous driving. The control device 50 also controls the operation of the fuel cell auxiliary device 23 based on the required power, thereby adjusting the amount of hydrogen gas and air supplied to the fuel cell stack 21. The control device 50 controls the operation of the converter device 25, thereby controlling the output voltage and output current of the fuel cell stack 21. When the amount of power generated by the fuel cell stack 21 exceeds the required power, the control device 50 controls the operation of the secondary battery converter device 33 to step down the voltage of the surplus power supplied from the converter device 25 to the DC stage 35 and charge the secondary battery 31. On the other hand, when the amount of power generated by the fuel cell stack 21 is less than the required power, the control device 50 controls the operation of the secondary battery converter device 33 to boost the voltage of the output power of the secondary battery 31 and supply the insufficient power to the DC stage 35.

[0030] The control device 50 also controls the drive of the inverter device 27 to control the output torque and rotation speed of the drive motor 29 so as to achieve the acceleration required for the vehicle 1. Furthermore, the control device 50 controls the regeneration of the drive motor 29 when the vehicle 1 decelerates. Specifically, when the vehicle 1 decelerates, the control device 50 controls the drive of the inverter device 27 in accordance with a target regenerative torque set based on the required braking torque, causing the drive motor 29 to regenerate. The control device 50 controls the drive of the secondary battery converter device 33 to charge the secondary battery 31 with electric power generated by regeneration of the drive motor 29.

[0031] Furthermore, the impedance measuring device 40 and the control device 50 cooperate to perform a process of measuring the impedance of the fuel cell stack 21 and a process of diagnosing the state of the fuel cell stack 21. Below, the parts of the configuration of the impedance measuring device 40 and the control device 50 that are related to the process of measuring the impedance of the fuel cell stack 21 and the process of diagnosing the state of the fuel cell stack 21 will be specifically described.

[0032] <2. Impedance measuring device and control device> (2-1. Overview) First, an outline of the processing executed by the control device 50 and the impedance measuring device 40 will be described.

[0033] In the fuel cell system 20 according to this embodiment, the control device 50 outputs a command signal to the impedance measuring device 40 to acquire the impedance of the fuel cell stack 21. Specifically, the control device 50 outputs a command signal to the impedance measuring device 40 indicating at which frequency the impedance should be measured.

[0034] The impedance measuring device 40 executes a process for measuring the impedance of the fuel cell stack 21. The impedance measuring device 40 generates an AC signal for impedance measurement based on a command signal sent from the control device 50, and outputs the AC signal to the converter device 25, thereby superimposing the AC signal of a predetermined frequency on the power output from the fuel cell stack 21. The impedance measuring device 40 also detects the output power of the fuel cell stack 21 when the AC signal is superimposed on the output power of the fuel cell stack 21, and calculates the impedance of the fuel cell stack 21 based on the detected output power data.

[0035] In this embodiment, the impedance measuring device 40 calculates the impedance at each frequency by excluding data for a period in which waveform disturbance is detected from the acquired waveform data of the output power. The impedance measuring device 40 outputs information on the calculated impedance, information on the waveform disturbance, and information on the accuracy of the impedance at each frequency calculated based on the waveform disturbance (hereinafter also referred to as "weight information") to the control device 50.

[0036] The control device 50 acquires information on the calculated impedance, information on waveform disturbance, and information on the calculated impedance weight for each frequency from the impedance measuring device 40, and diagnoses the state of the fuel cell stack 21.

[0037] (2-2. Impedance measuring device) The impedance measuring device 40 includes a control unit 41 and a storage unit 49. The control unit 41 includes one or more processors, such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit), and an electric circuit. Part or all of the control unit 41 may be configured with updatable firmware or the like, or may be a program module executed by commands from the CPU or the like.

[0038] 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 a RAM (Random Access Memory) and a ROM (Read Only Memory), or may include a storage device such as a CD-ROM or storage device.

[0039] The impedance measuring device 40 is communicably connected to the control device 50 via a communication means such as a CAN (Controller Area Network) 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 stack 21 and a current sensor 83 that detects the output current of the fuel cell stack 21.

[0040] The control unit 41 includes a superimposed signal generation unit 42, an output power detection unit 44, and an impedance calculation unit 46. Some or all of the superimposed signal generation unit 42, the output power detection unit 44, and the impedance calculation unit 46 are functions realized by a processor executing a computer program. However, some or all of these units may be configured by hardware.

[0041] The superimposed signal generator 42 sets the waveform of an AC signal for impedance measurement to be superimposed on the output power of the fuel cell stack 21 based on a command signal from the control device 50, and outputs the set AC signal to the converter device 25. In this embodiment, the superimposed signal generator 42 sets the frequency and amplitude of the sine wave of the superimposed current to be superimposed on the output power based on the command signal transmitted from the 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 depending on 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 the signal for impedance measurement to be superimposed on the output signal of the fuel cell stack 21. The superimposed signal generator 42 outputs the AC signal with the set frequency and amplitude to the converter device 25. The converter device 25 operates switching elements based on the input AC signal, and superimposes an AC current waveform on the output power of the fuel cell stack 21.

[0042] The AC signal superimposed on the output power of the fuel cell stack 21 may be an AC voltage instead of an AC current.

[0043] 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 stack 21 that is output while an AC current waveform is superimposed on the output power of the fuel cell stack 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 are recorded as an AC current waveform and an AC voltage waveform on which an AC signal for impedance measurement is superimposed.

[0044] The impedance calculation unit 46 executes a process of calculating the impedance of the fuel cell stack 21 based on the recorded AC current waveform and AC voltage waveform. It is known that the output voltage V, output current I, and impedance Z of the fuel cell stack 21 when an AC signal is superimposed on the fuel cell stack 21 satisfy the relationship of the following equations. 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

[0045] Based on the above equations, the impedance calculation unit 46 calculates the impedance at 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, if a square wave signal or an M-sequence signal generated by superimposing waveform signals of multiple frequencies is used as the signal for impedance measurement and superimposed on the output signal of the fuel cell stack 21, the impedance at each frequency may be determined by separating the overlapped signals through FFT (Fast Fourier Transform) analysis of the obtained AC current waveform and AC voltage waveform. The impedance calculation unit 46 determines the impedance at each frequency as 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 more frequencies. The amplitude of each cycle of the AC current waveform and the AC voltage waveform can be determined, for example, as the difference between the maximum values ​​of the current I or the voltage V in each cycle.

[0046] At this time, the impedance calculation unit 46 determines whether or not there is a disturbance in at least one of the AC current waveform and the AC voltage waveform. Examples of waveform disturbance include a disturbance E1 due to a decrease in amplitude shown in Fig. 3 and a disturbance E2 due to a phase shift in the amplitude period shown in Fig. 4. The disturbance E1 due to a decrease in amplitude shown in Fig. 3 occurs when the amplitude of the superimposed AC current waveform FA itself becomes smaller over a predetermined period fx, resulting in a decrease in the amplitude of the AC voltage waveform FV over a predetermined period fx. It is believed that this waveform disturbance E1 occurs due to the influence of noise, etc., during the process of outputting the AC current signal to be superimposed.

[0047] Furthermore, the disturbance E2 due to a phase shift in the amplitude cycle shown in Figure 4 is a shift in phase between the AC current waveform FA and the AC voltage waveform FV superimposed at a predetermined cycle fy. This waveform disturbance E2 is thought to be caused by the influence of noise or the like having the same cycle as the frequency at which the impedance is measured. The phase shift in the amplitude cycle can be detected, for example, by comparing the positions of the inflection points of the AC current waveform FA and the AC voltage waveform FV. Waveform disturbances are not limited to the above examples, and other types of disturbances may be detected.

[0048] When there is a disturbance in the waveform, the impedance calculation unit 46 calculates the impedance by excluding one cycle of data that includes the disturbance in the waveform. When there is a disturbance in both the AC current waveform and the AC voltage waveform, the data for that cycle may be excluded. However, to increase the accuracy of the calculated impedance, it is preferable to exclude the data for that cycle when there is a disturbance in at least one of the AC current waveform and the AC voltage waveform.

[0049] The impedance calculation unit 46 also performs FFT analysis on the waveform data for the period in which the waveform disturbance was detected, and performs processing to identify the frequencies contained in the waveform. This identifies the frequency of the electromagnetic noise that caused the waveform disturbance. The impedance calculation unit 46 records the identified frequencies.

[0050] The impedance calculation unit 46 also records the number of excluded periods and records this as information on the accuracy of the calculated impedance (weight information). For example, if data for 5 periods out of 100 periods is excluded, the weight is recorded as 95 (=100-5). The impedance calculation unit 46 outputs information on the calculated impedance, information on waveform disturbance, and information on the weight to the control device 50. The information on waveform disturbance includes information on the frequency of noise contained in the data for the period in which waveform disturbance was detected.

[0051] In addition, if the number of excluded periods is equal to or greater than a predetermined threshold, that is, if the weight is equal to or less than a predetermined threshold, the impedance calculation unit 46 may determine that the accuracy of the calculated impedance is low, and output information on the waveform disturbance and information on the weight to the control device 50 without calculating the impedance.

[0052] (2-3. Control device) The control device 50 includes a control unit 51 and a storage unit 59. The control unit 51 includes one or more processors, such as a CPU or an MPU. Part or all of the control unit 51 may be configured with updatable firmware or the like, or may be a program module or the like that is executed by commands from the CPU or the like.

[0053] Furthermore, 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, or may include a storage device such as a CD-ROM or storage device.

[0054] The control device 50 is communicably connected to the impedance measuring device 40 via a communication means such as a CAN or a dedicated line. The control device 50 is configured to transmit a command signal to the impedance measuring device 40 and to acquire information output from the impedance measuring device 40.

[0055] The control unit 51 includes a command signal generation unit 52, a diagnosis unit 54, and an auxiliary control unit 56. Some or all of the command signal generation unit 52, the diagnosis unit 54, and the auxiliary control unit 56 may be functions realized by a processor executing a computer program. Alternatively, some or all of these units may be configured by hardware.

[0056] The command signal generator 52 executes a process of setting a frequency for measuring impedance and outputting a command signal to the impedance measuring device 40. The set frequency is the frequency of an AC signal to be superimposed on the output power from the fuel cell stack 21, and is set according to the purpose of diagnosing the fuel cell stack 21. For example, by setting the frequency in the high frequency range, it is possible to diagnose the moisture state of the MEA of the fuel cell stack 21. Furthermore, by setting the frequency in the low frequency range, it is possible to diagnose the gas supply state, such as whether a sufficient amount of fuel gas, such as hydrogen gas or air, is being supplied to the power generation portion of the fuel cell stack 21.

[0057] The command signal generator 52 may set the frequency at which the impedance is measured while sequentially or randomly changing the frequency across the entire low-frequency and high-frequency ranges, or may set a specific frequency as the frequency at which the impedance is measured depending on the purpose of the diagnosis.

[0058] The diagnostic unit 54 acquires information on the calculated impedance at each frequency, information on waveform disturbance, and information on the weight of the calculated impedance, which are transmitted from the impedance measuring device 40, and diagnoses the state of the fuel cell stack 21 based on the acquired information.

[0059] For example, when impedances at multiple frequencies are used, the diagnosing unit 54 generates a Nyquist diagram using the impedance values ​​at each frequency (average values ​​of impedances over multiple periods) and performs equivalent circuit fitting.

[0060] The impedance measurement process of the fuel cell stack 21 is performed by, for example, the method disclosed in Japanese Patent Application Laid-Open No. 2010-165463. Briefly explaining the impedance measurement process, the impedance Z of the fuel cell stack 21 can be found using the equivalent circuit model shown in FIG. 5. This equivalent circuit model is an equivalent circuit model that combines the parameters of resistance components R1, R2 and capacitance component C that form the internal impedance in series and parallel. The resistance components R1, R2 represent the resistance (MEA resistance) R1 of a pair of MEAs that constitute each cell of the fuel cell stack 21, and the charge transfer resistance R2. Furthermore, the capacitance component C represents the electrode capacitance.

[0061] FIG. 6 shows a Nyquist diagram representing the measurement results of the impedance of the fuel cell stack 21 on a complex plane. The Nyquist diagram shown in FIG. 6 is obtained by calculating the impedance of the fuel cell stack 21 when AC signals of various frequencies are superimposed on the output power of the fuel cell stack 21, plotting the impedance locus with changes in frequency on a complex plane, and obtaining an approximate line (approximate equation). In this case, if the accuracy of the impedance measured at a certain frequency is low, an error will occur in the impedance at that frequency, indicated by a square mark (◆), as shown in FIG. 7, and the obtained Nyquist diagram will deviate from the actual Nyquist diagram. Deviation of the obtained Nyquist diagram from the actual Nyquist diagram makes it impossible to correctly identify the constants (equivalent circuit constants) of the equivalent circuit shown in FIG. 5, and therefore makes it impossible to correctly diagnose the state of the fuel cell stack 21.

[0062] However, in this embodiment, if the impedance measuring device 40 detects waveform disturbance, it calculates the impedance by excluding data from that period. Even if waveform disturbance is not detected, the accuracy of the impedance measurement is likely to be reduced if the frequency of the measurement target and the frequency and phase of external noise are identical. Therefore, in the impedance measuring device 40, a large number of periods excluded due to waveform disturbance is considered to indicate a large amount of noise, and a low weight is set for the average impedance value of that frequency. Therefore, the diagnostic unit 54 performs equivalent circuit fitting taking the set weights into account, thereby improving the accuracy of identifying each equivalent circuit constant. As a result, the humidity level and gas supply state within the fuel cell stack 21 can be accurately diagnosed.

[0063] Furthermore, when diagnosing the state of the fuel cell stack 21 using the impedance of a single frequency, if a large number of cycles are excluded from the impedance calculation, it is likely that noise is included and the accuracy of the calculated impedance measurement is low. Therefore, based on the weight information, the diagnoser 54 can determine whether or not to execute control using the impedance value of that frequency as a threshold, or whether or not to measure the impedance again.

[0064] The auxiliary control unit 56 executes a process for changing the settings of the operating conditions of electronic devices connected to either the fuel cell stack 21 or the converter device 25 based on the weight information transmitted from the impedance measurement device 40. The electronic devices include the fuel cell auxiliary device 23 and the vehicle auxiliary device 37. Based on the weight information, when the measurement accuracy of the impedance at a predetermined frequency is low, the auxiliary control unit 56 changes the settings of the operating conditions of the electronic devices connected to either the fuel cell stack 21 or the converter device 25 in order to suppress the generation of noise that may affect the output power of the fuel cell stack 21. Changing the settings of the operating conditions also includes stopping the operation of the electronic devices.

[0065] The electronic devices whose operating condition settings are changed may include not only the fuel cell auxiliary devices 23 and the vehicle auxiliary devices 37, but also external devices that may generate electromagnetic noise. For example, the electronic devices may be configured to change the operating condition settings of a contactless charging system for charging the secondary battery 31. In this case, the auxiliary device control unit 56 is configured to communicate with a control device of the contactless charging system and output a command signal to change the operating condition settings. Furthermore, in the vehicle 1, the grounds of various electronic devices are connected to a common body earth, and fluctuations in the power consumption of the electronic devices make it easy for noise to be introduced into the output power of the fuel cell stack 21. Therefore, the electronic devices whose operating condition settings are changed may include not only the fuel cell auxiliary devices 23 and the vehicle auxiliary devices 37, but also electronic devices connected to the common body earth.

[0066] For example, if the weight is equal to or smaller than a predetermined threshold, i.e., if the number of periods excluded when measuring the impedance of a predetermined frequency is equal to or larger than a predetermined threshold, the auxiliary equipment control unit 56 changes the setting of the operating conditions of at least one of the electronic devices. The threshold for the weight or the threshold for the number of periods is set to an appropriate value in advance depending on the accuracy of the impedance measurement results. The threshold may be common to all frequencies, or may be set for each frequency.

[0067] Furthermore, when the weight is equal to or less than a predetermined threshold, the auxiliary control unit 56 may stop the operation of all electronic devices that may affect the waveform of the output power of the fuel cell stack 21. This makes it possible to reliably reduce the influence of electromagnetic waves and the like generated by the operation of the electronic devices on the waveform of the output power of the fuel cell stack 21.

[0068] On the other hand, the auxiliary control unit 56 may select an electronic device for which to change the operating condition settings based on the waveform disturbance information transmitted from the impedance measuring device 40. Stopping the operation of an electronic device that does not affect the waveform of the output power of the fuel cell stack 21 will result in inadvertently restricting the functions of the vehicle 1. Therefore, by selecting an electronic device that causes a disturbance in the waveform of the output power of the fuel cell stack 21 and stopping the operation of that electronic device, it is possible to avoid restricting the functions of the vehicle 1 more than necessary.

[0069] Specifically, the memory unit 59 stores data on the frequency of electromagnetic noise that may be generated, which data is obtained in advance for each electronic device electrically connected to the fuel cell stack 21 or the converter device 25. Therefore, the auxiliary device control unit 56 refers to the data on the frequency of electromagnetic noise stored in the memory unit 59, and selects an electronic device for which the setting of the operating conditions is to be changed in accordance with the noise frequency identified from the waveform in which waveform disturbance has been detected.

[0070] When the auxiliary control unit 56 executes the process of changing the settings of the deactivation conditions of any or all of the electronic devices, the command signal generating unit 52 sets the frequency at which waveform disturbance was detected during impedance measurement to the frequency at which impedance is measured again, and outputs a command signal to the impedance measuring device 40. This improves the accuracy of the impedance measurement.

[0071] <3.Operation> So far, we have described exemplary configurations of the impedance measuring device 40 and the control device 50. Next, we will explain in detail the series of operations performed by the impedance measuring device 40 and the control device 50 to measure impedance and determine the state of the fuel cell stack 21.

[0072] FIG. 8 is a flowchart showing an example of processing executed by the impedance measuring device 40 and the control device 50. First, the command signal generating unit 52 of the control device 50 outputs a command signal for measuring impedance to the impedance measuring device 40 (step S11). Specifically, the command signal generating unit 52 sets one or more frequencies to be superimposed on the output power of the fuel cell stack 21 according to the purpose of diagnosing the fuel cell stack 21, and transmits the frequencies to the impedance measuring device 40. The command signal generating unit 52 may set the frequency for measuring impedance by sequentially or randomly changing the frequency across the entire low-frequency region and high-frequency region. Alternatively, the command signal generating unit 52 may set a specific frequency as the frequency for measuring impedance according to the purpose of diagnosing.

[0073] Next, the superimposed signal generation unit 42 of the impedance measurement device 40 starts a process of superimposing an AC current of each frequency on the output power of the fuel cell stack 21 based on the command signal transmitted from the control device 50 (step S13). Specifically, the superimposed signal generation unit 42 sets an AC current waveform for impedance measurement based on the command signal transmitted from the control device 50, and outputs the set AC current signal to the converter device 25. The amplitude of the AC current to be superimposed is set in advance to an appropriate value depending on the specifications of the fuel cell system 20, etc. 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 stack 21. Note that a square wave signal or an M-sequence signal generated by superimposing waveform signals of multiple frequencies may also be used as the signal for impedance measurement to be superimposed on the output signal of the fuel cell stack 21.

[0074] Next, the output power detection unit 44 of the impedance measuring device 40 detects the output current I and output voltage V of the fuel cell stack 21 based on the sensor signals output from the voltage sensor 81 and the current sensor 83 (step S15). Specifically, the output power detection unit 44 acquires the sensor signals from the voltage sensor 81 and the current sensor 83 at a preset sampling period, and records the data on the output current I and the output voltage V. The output power detection unit 44 may perform known signal processing such as filtering on the acquired sensor signals. The data on the detected output current I and output voltage V is recorded as data on an AC current waveform and an AC voltage waveform on which an AC signal for impedance measurement is superimposed.

[0075] Next, the impedance calculation unit 46 of the impedance measuring device 40 executes a process of determining waveform disturbance for each of the recorded AC current waveform and AC voltage waveform data (step S17). In this embodiment, the impedance calculation unit 46 determines whether or not there is a decrease in the amplitude of the output current I and output voltage V in each cycle, or a phase shift in the amplitude cycle, for each of the detected AC current waveform and AC voltage waveform.

[0076] For example, the impedance calculation unit 46 determines whether the detected AC current waveform and AC voltage waveform are different from the AC signals transmitted to the converter device 25 by the superimposed signal generation unit 42. If the detected AC signals are different from the AC signals transmitted to the converter device 25, the impedance calculation unit 46 determines that the diagnostic waveform for measuring the impedance is not being applied normally. Furthermore, if the amplitude of the output current I and output voltage V in each cycle is less than a predetermined ratio (e.g., 0.95) of the amplitude of the AC signal, the impedance calculation unit 46 determines that the amplitude in that cycle is not high enough to calculate the impedance and that there is a disturbance in the waveform. The amplitude of each cycle of the AC current waveform and AC voltage waveform can be calculated, for example, as the difference between the maximum values ​​of the current I or voltage V in each cycle.

[0077] Furthermore, the impedance calculation unit 46 performs FFT analysis on the AC current waveform or AC voltage waveform of each cycle to determine whether or not a frequency component other than the frequency contained in the AC signal transmitted to the superimposed signal generation unit 42 is detected in a frequency surrounding the frequency of the impedance to be calculated (for example, a frequency range of ±5 to 10% of the frequency to be measured).If a frequency component other than the frequency contained in the AC signal transmitted to the converter device 25 is detected, the impedance calculation unit 46 determines that noise from other than the converter device 25 is included, that the AC current waveform and AC voltage waveform of the cycle are not data from which the impedance can be calculated, and that there is waveform disturbance.

[0078] When a waveform disturbance is detected, the impedance calculation unit 46 performs FFT analysis on the data of the output current I or output voltage V in the cycle in which the waveform disturbance occurs, and identifies the frequency contained in the waveform in that cycle. This identifies the frequency of the electromagnetic noise that caused the waveform disturbance. When a decrease in amplitude or a phase shift in the amplitude cycle is detected, the impedance calculation unit 46 records the detection result and information on the identified noise frequency as information on the waveform disturbance.

[0079] Next, the impedance calculation unit 46 determines whether or not each of the recorded AC current waveform and AC voltage waveform data is a normal waveform without any waveform disturbances (step S19). For example, the impedance measurement device 40 determines whether or not each of the AC current waveform and AC voltage waveform data for 100 cycles is a normal waveform without any waveform disturbances. However, the number of cycles may be set arbitrarily.

[0080] If the recorded AC current waveform and AC voltage waveform data are not determined to be normal waveforms without waveform disturbances (S19 / No), the impedance calculation unit 46 excludes data for periods in which waveform disturbances were detected from the data for impedance calculation, and calculates a weight according to the number of excluded periods (step S21). For example, if five periods in which waveform disturbances were detected are excluded from 100 periods of data, the weight is set to 95 (=100-5). In other words, the more periods excluded, the smaller the weight.

[0081] Next, the impedance calculation unit 46 determines whether the number of excluded cycles is equal to or greater than a preset threshold (step S23). The threshold is set to an appropriate value depending on the tolerance for error in the calculated impedance. When calculating the impedance based on data for 100 cycles, the threshold may be set to, for example, 20, but is not particularly limited thereto.

[0082] If it is determined that the number of excluded periods is equal to or greater than the threshold value (S23 / Yes), the impedance calculation unit 46 outputs the recorded waveform disturbance information and weight information to the control device 50 (step S25).

[0083] Next, the auxiliary control unit 56 of the control device 50 changes the settings of the operating conditions of the electronic devices connected to the fuel cell stack 21 or the converter device 25 based on the waveform disturbance information and weight information transmitted from the impedance measuring device 40 (step S27).

[0084] Specifically, the auxiliary control unit 56 executes a process of changing the settings of the operating conditions of the electronic devices connected to either the fuel cell stack 21 or the converter device 25 based on the weight information. For example, when the weight is equal to or less than a predetermined threshold, i.e., when the number of excluded periods is equal to or greater than a predetermined threshold, the auxiliary control unit 56 selects an electronic device whose settings of the operating conditions are to be changed based on the waveform disturbance information. In this embodiment, the auxiliary control unit 56 refers to data on the frequency of electromagnetic noise that may be generated by each electronic device stored in the memory unit 59 and identifies the electronic device that caused the waveform disturbance. Then, the auxiliary control unit 56 executes a process of changing the operating point of the identified electronic device to an operating point that does not generate electromagnetic noise, changing the operating state of the electronic device to an operating state that does not cause disturbance in the waveform of the output power of the fuel cell stack 21, electrically shutting off the electronic device, or the like.

[0085] For example, the auxiliary control unit 56 may change the settings of the operating conditions to suppress fluctuations in the power consumption of the identified electronic device. This reduces electromagnetic noise generated by the operation of the electronic device. More specifically, if the disturbance in the AC voltage waveform is caused by excessive fluctuations in the rotation speed of the compressor of the fuel cell auxiliary device 23, the auxiliary control unit 56 maintains the compressor rotation speed at a constant level. Furthermore, when electrically shutting off the electronic device identified as the cause of the waveform disturbance, the auxiliary control unit 56 may shut off a relay provided in the path supplying power to the electronic device.

[0086] The auxiliary control unit 56 may change the settings of the operating conditions of all electronic devices that may affect the waveform disturbance or may stop the operation of the electronic devices, or may change the settings of the operating conditions of some of the electronic devices or may stop the operation of some of the electronic devices. When changing the settings of the operating conditions of some of the electronic devices, the auxiliary control unit 56 may change the settings of the operating conditions of some of the electronic devices and measure the impedance, and if the accuracy of the calculated impedance is still low, the auxiliary control unit 56 may change the settings of the operating conditions of the electronic devices or increase the number of the electronic devices.

[0087] In addition, the auxiliary equipment control unit 56 may omit the process of selecting the electronic equipment whose operating condition settings are to be changed based on the waveform disturbance information, and instead change the operating condition settings of all pre-set electronic equipment.

[0088] After the auxiliary control unit 56 changes the settings of the operating conditions of any or all of the electronic devices, the process returns to step S11, and the command signal generation unit 52 sets the frequency at which waveform disturbance was detected during impedance measurement to the frequency at which impedance is measured again, and outputs a command signal to the impedance measuring device 40. This allows the impedance measurement process to be performed in a state where waveform disturbance has been reduced.

[0089] On the other hand, if it is determined in step S19 that the recorded AC current waveform and AC voltage waveform data are normal waveforms without any waveform disturbances (S19 / Yes), or if it is determined in step S23 that the number of excluded cycles is not equal to or greater than the threshold (S23 / No), the impedance calculation unit 46 of the impedance measuring device 40 executes a process of calculating the impedance of the fuel cell stack 21 based on the recorded AC current waveform and AC voltage waveform (step S29). Specifically, the impedance calculation unit 46 calculates the impedance for each cycle 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, and sets the average value of the impedances as the impedance for the current frequency. At this time, the impedance calculation unit 46 calculates the impedance based on data other than the data for the cycles excluded in step S21.

[0090] Next, the impedance calculation unit 46 outputs information about the calculated impedance to the control device 50 together with information about the detected waveform disturbance and information about the weight (step S31).

[0091] Next, the command signal generating unit 52 of the control device 50 determines whether or not the impedance has been acquired for all frequencies at which the impedance is measured (step S33). If the impedance of any frequency has not been acquired (S33 / No), the command signal generating unit 52 returns to step S11, sets the frequency at which the impedance has not been acquired as the frequency at which the impedance is to be acquired, and outputs a command signal (step S11).

[0092] On the other hand, if the impedances of all frequencies have been acquired (S33 / Yes), the diagnosis unit 54 identifies an approximation formula of the impedance characteristics based on the acquired impedance information and weight information (step S35). Specifically, as shown in Fig. 6, the trajectory of the impedance accompanying the change in frequency is plotted on a complex plane to calculate an approximation formula (approximation line). At this time, the diagnosis unit 54 calculates the approximation formula taking into account the weight of the impedance of each frequency.

[0093] For example, the diagnosis unit 54 calculates an approximation equation by giving a higher priority to approximating the impedance of frequencies with a larger weight. Furthermore, frequencies with a weight equal to or less than a threshold value and with a low accuracy of the impedance may be calculated by interpolation without being included in the calculation of the approximation equation. Therefore, the impedance characteristics are determined based on the calculation result of the impedance with a higher accuracy, and the accuracy of the diagnosis result of the state of the fuel cell stack 21 can be improved.

[0094] A conventionally known method can be used to diagnose the state of the fuel cell stack 21 based on the impedance characteristics. Briefly explaining one example, the diagnosis unit 54 creates a Nyquist diagram based on the impedance measured at multiple frequencies, and identifies equivalent circuit constants so that the Nyquist diagram matches a pre-prepared equivalent circuit of the fuel cell stack 21. The diagnosis unit 54 then determines the state of the fuel cell stack 21 based on information indicating the relationship between the pre-prepared equivalent circuit constants and the state of the fuel cell stack 21.

[0095] As described above, in the fuel cell system 20 of this embodiment, when measuring the impedance of the fuel cell stack 21 based on the output current I and output voltage V when an AC current is superimposed on the output power of the fuel cell stack 21, the impedance is calculated by excluding data for periods in which disturbances are detected in the output AC current waveform or AC voltage waveform. This improves the accuracy of the impedance measurement. Furthermore, in the fuel cell system 20 of this embodiment, if the number of excluded periods is equal to or greater than a predetermined threshold, the operating conditions of the electronic devices connected to either the fuel cell stack 21 or the converter device 25 are changed and the impedance is measured. This reduces the number of periods excluded due to waveform disturbances, thereby improving the accuracy of the impedance measurement.

[0096] In particular, the fuel cell system 20 of this embodiment is a system mounted on a fuel cell vehicle, and by changing the settings of the operating conditions of electronic devices connected to the body earth common to the fuel cell stack 21, it is possible to reduce the risk of noise being introduced into the output power of the fuel cell stack 21. This makes it possible to improve the accuracy of impedance measurement.

[0097] Furthermore, in the fuel cell system 20 of this embodiment, the electronic device that caused the detected waveform disturbance is identified and a process for changing the settings of its operating conditions is executed. This makes it possible to efficiently reduce the waveform disturbance of the output power of the fuel cell stack 21, and also prevents the operation of the electronic device from being inadvertently restricted because the operating conditions of the electronic device that has little effect on the impedance measurement accuracy are not changed.

[0098] Although the preferred embodiments of the present disclosure have 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 skilled in the art to which the present disclosure pertains can conceive of various modifications or alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

[0099] For example, in the above embodiment, the fuel cell stack 21 is used as an example of an object whose impedance is to be measured, but the object is not limited to the fuel cell stack 21. For example, the technology of the present disclosure can be applied to measuring the impedance of a secondary battery 31 provided in a fuel cell system 20. Furthermore, the technology of the present disclosure can be applied to devices capable of supplying power, such as power generation modules and secondary batteries of power systems other than the fuel cell system 20.

[0100] Furthermore, in the above embodiment, a current sweep device (converter device) has been taken as an example of an electrical load device that receives a supply of power, but the electrical load device is not limited to a current sweep device.

[0101] The following aspects also fall within the technical scope of the present disclosure. (1) An impedance measurement system in which a processor of the impedance measurement system sets a weight for each frequency that is set smaller the greater the number of excluded periods, and calculates an approximation equation by giving higher priority to approximating the impedance of frequencies with larger weights. (2) A computer program applied to an impedance measurement system that measures the impedance of a measurement object capable of supplying power to an electrical load device, one or more processors, Acquiring data on output power when an AC signal of at least one frequency is superimposed on the output power of the measurement object; calculating the impedance of at least one frequency while excluding data of a period in which a disturbance in the waveform of the output power is detected; If the number of excluded periods at a predetermined frequency is equal to or greater than a predetermined threshold, changing the settings of the operating conditions of an electronic device connected to either the measurement object or the electrical load device to measure the impedance; A computer program for executing a process including the above, and a recording medium on which the computer program is recorded. [Explanation of symbols]

[0102] 1: vehicle, 20: fuel cell system, 21: fuel cell stack, 23: fuel cell auxiliary equipment, 25: converter device, 27: inverter device, 29: drive motor, 31: secondary battery, 33: secondary battery converter device, 40: impedance measuring device, 41: control unit, 42: superimposed signal generating unit, 44: output power detecting unit, 46: impedance calculating unit, 49: memory unit, 50: control device, 51: control unit, 52: command signal generating unit, 54: diagnosis unit, 56: auxiliary equipment control unit, 59: memory unit, 81: voltage sensor, 83: current sensor

Claims

1. An impedance measurement system for measuring the impedance of a measurement object capable of supplying power to an electrical load device, one or more processors; and one or more memories communicatively coupled to the one or more processors; the one or more processors: Acquire data on an output current waveform or an output voltage waveform when an AC signal of at least one frequency is superimposed on the output power of the measurement object, calculating the impedance of the at least one frequency by excluding data of a period in which a waveform disturbance is detected from data of a plurality of periods included in the acquired data of the output current waveform or the output voltage waveform; An impedance measurement system that performs processing including: when the number of periods excluded from the data of the output current waveform or the output voltage waveform when an AC signal of a predetermined frequency is superimposed is equal to or greater than a predetermined threshold, changing the settings of the operating conditions of an electronic device connected to either the object to be measured or the electrical load device, and measuring the impedance of the predetermined frequency.

2. the one or more processors:

2. The impedance measurement system of claim 1, wherein, when the number of periods excluded from the data of the output current waveform or the output voltage waveform when an AC signal of a predetermined frequency is superimposed is equal to or greater than a predetermined threshold, the operating conditions are changed to suppress fluctuations in power consumption of electronic devices connected to either the object to be measured or the electrical load device, and the impedance of the predetermined frequency is measured.

3. the one or more processors:

2. The impedance measurement system according to claim 1, wherein the system identifies a frequency of noise contained in data of a period in which waveform disturbance is detected among data of multiple periods contained in the output current waveform or the output voltage waveform acquired when the AC signal is superimposed, and selects the electronic device for which the setting of the operating condition is changed in accordance with the frequency of the noise.

4. the one or more processors: Acquire data of the output current waveform or the output voltage waveform when AC signals of a plurality of frequencies are superimposed, calculating an approximate expression showing the relationship between the frequency and the impedance by setting a weight to the impedance of each of the frequencies based on the number of periods excluded from the data of the output current waveform or the output voltage waveform when the AC signals of each of the frequencies are superimposed; 2. The impedance measurement system according to claim 1, wherein the state of the measurement object is diagnosed based on the approximate expression.

5. An impedance measurement system for measuring the impedance of a measurement object capable of supplying power to an electrical load device based on an output current waveform or an output voltage waveform measured when an AC signal of at least one frequency is superimposed on the output power of the measurement object, the impedance measurement system comprising: a superimposed signal generating unit that performs processing to superimpose the AC signals; an impedance calculation unit that calculates the impedance of the at least one frequency by excluding data of a period in which waveform disturbance is detected from data of a plurality of periods included in the data of the output current waveform or the output voltage waveform; an auxiliary control unit that executes a process of changing the settings of operating conditions of an electronic device connected to either the object to be measured or the electrical load device when the number of periods excluded from the data of the output current waveform or the output voltage waveform when an AC signal of a predetermined frequency is superimposed is equal to or greater than a predetermined threshold; An impedance measurement system comprising:

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