Fuel cell test system, method and device integrated with electrochemical AC impedance test function, processor and readable storage medium thereof

Abstract

The invention relates to a fuel cell test system integrated with an electrochemical alternating current impedance test function, which comprises a fuel cell stack, an air supply unit, a fuel supply unit, a cooling supply unit, a control unit, an acquisition and driving unit and an electrochemical impedance measurement system, the output ends of the air supply unit, the fuel supply unit and the cooling supply unit are connected with the fuel cell stack, the acquisition and driving unit is connected with the fuel supply unit, the control unit is connected with the acquisition and driving unit, and the electrochemical impedance measurement system is connected with the fuel cell stack and the control unit. By adopting the fuel cell test system, method and device integrated with the electrochemical alternating-current impedance test function, the processor and the computer readable storage medium, rapid measurement and impedance calculation of electrochemical impedance in a fuel cell stack test process are realized, the integration level is high, the cost is greatly reduced, the operation is simple, and the test efficiency is high. Errors caused by repeated setting of load parameters are avoided, the measurement efficiency is high, and the measurement precision is high.

Description

Technical Field

[0001] The present invention relates to the field of energy conversion technology, in particular to the field of proton exchange membrane fuel cells, and specifically refers to a fuel cell testing system, method, device, processor and computer-readable storage medium thereof that integrates electrochemical AC impedance testing function. Background Art

[0002] Proton exchange membrane fuel cells, as a clean, efficient, environmentally adaptable and high energy density energy conversion technology, have attracted much attention and are widely considered to be a promising solution for future low-carbon energy. The development and testing of proton exchange membrane fuel cells require fuel cell benches and electrochemical workstations.

[0003] The test bench provides air, fuel, and cooling water supply, and monitors the parameters of the inlet and outlet air, hydrogen, and cooling water temperature of the stack and the voltage of each cell to ensure that the stack is operating in a stable state. The stack is equipped with an electronic load. Generally speaking, if the power of the stack is large (generally > 60kW), a bidirectional feedback power supply is configured. The advantage is that the electricity generated by the stack can be fed back to the power grid to save electricity costs; the disadvantage is that the interference is large and there is a certain current ripple; if the load power is small (generally ≤ 60kW), a consumable electronic load is used (generally ≤ 60kW, the electrical energy is converted into heat energy and dissipated), which has higher control accuracy;

[0004] Electrochemical impedance spectroscopy (EIS) is an electrochemical analysis method that applies a small amplitude AC signal to the stack, and then transforms the measured AC current and its corresponding voltage signal (time domain signal) (such as Fourier transform) to obtain impedance values ​​at different frequencies, namely the Nyquist plot; based on the impedance data, further quantitative analysis (such as using DRT (Distribution of Relaxation Time, duration distribution), ECM (Equivalent Circuit Model, equivalent circuit model) and other methods) can be performed to obtain detailed information on the electrochemical process of the fuel cell, including ohmic impedance, oxygen transfer impedance, oxygen activation impedance and other impedances, which plays a good guiding role in the optimization design of the stack, the development of strategies such as stack shutdown purge, and water management. Now, electrochemical impedance spectroscopy technology is increasingly being used in solving practical engineering problems. Electrochemical impedance measurement requires special equipment, and the most common one is an electrochemical workstation that measures low power and low current.

[0005] Currently, the common fuel cell stack test bench and electrochemical impedance test equipment are separated (see the architecture diagram Figure 1), the fuel cell stack test bench is a complete system with a control unit, electronic load and host computer, which provides air, fuel, cooling and current control. The electrochemical impedance test equipment is an independent system with a control unit, electronic load and host computer, with a wide frequency range, and is used to measure the electrochemical impedance of the stack. The common impedance measurement equipment is the electrochemical workstation, which has a very small load power (≤1kW), a small current (≤40A), and is expensive. Some stack test benches are also equipped with internal resistance testers, but they can only measure the internal resistance of the stack at 1kHz.

[0006] In addition, when the electrochemical impedance test is performed on the battery stack, the electronic load 2 is connected in parallel to the busbar between the electronic load 1 and the battery stack, and the host computer of the EIS test equipment is operated to load. Generally speaking, the electronic load 2 is unidirectional, and the current cannot pass through the zero point, so it is necessary to superimpose an alternating current (Iac) on a DC offset (Idc1); in order for the actual DC current (Idc) of the battery stack to be the same as the original current during the EIS measurement, it is necessary to subtract this DC offset from the electronic load 1, that is, the current of the electronic load 2 is set to (Idc-Idc1). Such an operation is time-consuming and prone to errors, resulting in a deviation in the actual working conditions of the battery stack; at the same time, the equipment integration of this solution is low, resulting in a waste of resources, high hardware costs, and high software development costs; and because the data display and storage are all in their respective hardware, it is inconvenient to further search, compare and analyze the data. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a fuel cell testing system, method, device, processor and computer-readable storage medium thereof with integrated electrochemical AC impedance testing function that meets high accuracy, high measurement precision and a wide range of applications.

[0008] In order to achieve the above-mentioned object, the fuel cell testing system, method, device, processor and computer-readable storage medium thereof with integrated electrochemical AC impedance testing function of the present invention are as follows:

[0009] The fuel cell test system with integrated electrochemical AC impedance test function has the following main features: the system includes a fuel cell stack, an air supply unit, a fuel supply unit, a cooling supply unit, a control unit, a collection and drive unit, and an electrochemical impedance measurement system; the output ends of the air supply unit, the fuel supply unit, and the cooling supply unit are connected to the fuel cell stack, the collection and drive unit is connected to the fuel supply unit, the control unit is connected to the collection and drive unit, and the electrochemical impedance measurement system is connected to the fuel cell stack and the control unit;

[0010] The air supply unit is used to provide air with preset humidity, flow, pressure and temperature; the fuel supply unit is used to provide hydrogen with preset humidity, flow, pressure and temperature; the cooling supply unit is used to provide cooling water with preset flow, pressure and temperature; the control unit is used to run control logic, control algorithm and strategy; the acquisition and drive unit is used to acquire sensor feedback signals of the air supply unit, the fuel supply unit and the cooling supply unit, and drive the actuator to achieve the set target parameters; the excitation signal unit of the electrochemical impedance measurement system receives the target instruction sent by the control unit and outputs it to the electronic load; the electronic load draws AC current; the acquisition unit acquires the current and voltage of the fuel cell stack; the control unit processes the data to obtain the impedance of the stack at this time.

[0011] Preferably, the electrochemical impedance measurement system includes a collection unit, an excitation signal unit, an electronic load and a current sensor, wherein the current sensor is installed on a busbar between the fuel cell stack and the electronic load, the input end of the current sensor is connected to the positive electrode of the fuel cell stack, the output end of the current sensor is connected to the collection unit, the input end of the collection unit is connected to the fuel cell stack and the current sensor, the output end of the collection unit is connected to the control unit, the input end of the excitation signal unit is connected to the control unit, the output end of the excitation signal unit is connected to the electronic load, the input end of the electronic load is connected to the current sensor, the excitation signal unit and the control unit, and the output end of the electronic load is connected to the negative electrode of the fuel cell stack;

[0012] The current sensor is used to collect the operating current of the fuel cell stack and upload it to the collection unit. The collection unit is used to collect and measure the voltage and current at the positive and negative terminals of the fuel cell stack and the single cell voltage. The excitation signal unit is used to generate a function generator of an arbitrary AC waveform. The electronic load is used to convert the small-amplitude AC voltage signal of the signal generator into an AC current disturbance and inject it into the fuel cell stack under test.

[0013] Preferably, the system also includes a data monitoring unit and a data storage unit, the data monitoring unit is connected to the control unit, the input end of the data storage unit is connected to the control unit, the data monitoring unit is used to input parameters and display various operating parameters of the battery stack, electronic load parameters and battery stack impedance information, and the data storage unit stores data of the data monitoring unit.

[0014] Preferably, the control unit obtains parameters set according to the test operating conditions of the fuel cell stack, and the control unit controls the air supply unit, the fuel supply unit and the cooling supply unit through the acquisition and driving unit to achieve the corresponding set parameters, and the fuel cell stack outputs power. After the fuel cell stack is in a stable state, the control unit sends an instruction to the excitation signal unit to control the amplitude, frequency point and number of cycles of the AC excitation current superimposed on the DC of the electronic load, and injects the AC excitation current into the fuel cell stack. The current sensor collects the total current, and the voltage and total current of the fuel cell stack are synchronously collected through the acquisition unit and sent to the control unit. The control unit processes the collected voltage and current signals online, and uses the FFT algorithm to calculate the impedance of the fuel cell stack in real time. The data monitoring unit displays the data and stores it in the data storage unit.

[0015] Preferably, the acquisition unit includes a multi-channel voltage acquisition module, a current acquisition module and a chassis, the multi-channel voltage acquisition module and the current acquisition module are both installed in the chassis, and the voltage acquisition module and the current acquisition module are connected to the fuel cell stack.

[0016] The main feature of the fuel cell testing method using the above system to realize the integrated electrochemical AC impedance testing function is that the method comprises the following steps:

[0017] (1) Connect the test equipment to the fuel cell stack; set the target parameters of air, fuel, and cooling water according to the test conditions;

[0018] (2) After the parameters are stable, set the electronic load DC current Idc and start loading;

[0019] (3) After the current output of the fuel cell stack is stable, the electronic load AC measurement parameters are set, and the electronic load generates an AC current iac;

[0020] (4) The acquisition unit synchronously collects the current value, stack voltage and cell voltage, and uploads them to the control unit in real time;

[0021] (5) The control unit calculates the frequency domain value of the fuel cell stack;

[0022] (6) After the measurement is completed, the electronic load stops pulling AC and the fuel cell stack returns to DC output.

[0023] Preferably, the step (5) specifically comprises the following steps:

[0024] (5.1) Read the current, stack voltage and cell voltage;

[0025] (5.2) Extract the AC components of current and voltage;

[0026] (5.3) The frequency and amplitude of the current and voltage are obtained according to the improved FFT calculation, and the total harmonic distortion rate THD and total harmonic distortion rate THDN of the signal are calculated at the same time;

[0027] (5.4) The magnitude of multiple harmonics is determined by the total harmonic distortion rate THD, and the magnitude of interharmonics is determined by the total harmonic distortion rate THDN. If the value of multiple harmonics or interharmonics exceeds the threshold, a warning is given;

[0028] (5.5) Calculate the amplitude and phase of each collected voltage frequency, and the amplitude and phase of the current;

[0029] (5.6) The amplitude and phase of the fuel cell impedance at each frequency are calculated through complex number operations, and the real and imaginary parts of the fuel cell impedance are calculated.

[0030] Preferably, the step (1) is specifically as follows:

[0031] Connect the electronic load to the positive and negative input terminals of the fuel cell stack, connect the current sensor to the positive or negative electrode of the fuel cell stack, and connect the sampling line of the acquisition unit to the fuel cell as needed.

[0032] The main feature of the device for realizing fuel cell testing with integrated electrochemical AC impedance testing function is that the device comprises:

[0033] a processor configured to execute computer executable instructions;

[0034] The memory stores one or more computer executable instructions. When the computer executable instructions are executed by the processor, the various steps of the above-mentioned fuel cell testing method for realizing the integrated electrochemical AC impedance testing function are implemented.

[0035] The main feature of the processor for implementing fuel cell testing with integrated electrochemical AC impedance testing function is that the processor is configured to execute computer executable instructions, and when the computer executable instructions are executed by the processor, the various steps of the above-mentioned fuel cell testing method for implementing integrated electrochemical AC impedance testing function are implemented.

[0036] The main feature of the computer-readable storage medium is that a computer program is stored thereon, and the computer program can be executed by a processor to implement the various steps of the above-mentioned fuel cell testing method for realizing an integrated electrochemical AC impedance testing function.

[0037] The fuel cell test system, method, device, processor and computer-readable storage medium thereof with integrated electrochemical AC impedance test function of the present invention can realize rapid measurement of electrochemical impedance and impedance calculation in the fuel cell stack test process on the basis of meeting the functions of the existing fuel cell test bench. The present invention has high integration, greatly reduces hardware and software costs, is simple to operate, avoids errors caused by repeated setting of load parameters, has high measurement efficiency, high measurement accuracy, is more accurate, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 FIG. 1 is a schematic diagram of the structure of a fuel cell testing system in the prior art.

[0039] Figure 2 It is a schematic diagram of the architecture of a fuel cell testing system with integrated electrochemical AC impedance testing function according to the present invention.

[0040] Figure 3 The present invention is a flow chart of measuring the electrochemical impedance spectrum when the fuel cell stack is running in the fuel cell testing method that realizes the integrated electrochemical AC impedance testing function.

[0041] Figure 4 The present invention is a flow chart of impedance calculation for a fuel cell testing method that implements an integrated electrochemical AC impedance testing function. DETAILED DESCRIPTION

[0042] In order to more clearly describe the technical content of the present invention, further description is given below in conjunction with specific embodiments.

[0043] The fuel cell testing system with integrated electrochemical AC impedance testing function of the present invention comprises a fuel cell stack, an air supply unit, a fuel supply unit, a cooling supply unit, a control unit, a collection and drive unit and an electrochemical impedance measurement system, wherein the output ends of the air supply unit, the fuel supply unit and the cooling supply unit are connected to the fuel cell stack, the collection and drive unit is connected to the fuel supply unit, the control unit is connected to the collection and drive unit, and the electrochemical impedance measurement system is connected to the fuel cell stack and the control unit;

[0044] The air supply unit is used to provide air with preset humidity, flow, pressure and temperature; the fuel supply unit is used to provide hydrogen with preset humidity, flow, pressure and temperature; the cooling supply unit is used to provide cooling water with preset flow, pressure and temperature; the control unit is used to run control logic, control algorithm and strategy; the acquisition and drive unit is used to acquire sensor feedback signals of the air supply unit, the fuel supply unit and the cooling supply unit, and drive the actuator to achieve the set target parameters; the excitation signal unit of the electrochemical impedance measurement system receives the target instruction sent by the control unit and outputs it to the electronic load; the electronic load draws AC current; the acquisition unit acquires the current and voltage of the fuel cell stack; the control unit processes the data to obtain the impedance of the stack at this time.

[0045] As a preferred embodiment of the present invention, the electrochemical impedance measurement system includes a collection unit, an excitation signal unit, an electronic load and a current sensor, wherein the current sensor is installed on a busbar between the fuel cell stack and the electronic load, the input end of the current sensor is connected to the positive electrode of the fuel cell stack, the output end of the current sensor is connected to the collection unit, the input end of the collection unit is connected to the fuel cell stack and the current sensor, the output end of the collection unit is connected to the control unit, the input end of the excitation signal unit is connected to the control unit, the output end of the excitation signal unit is connected to the electronic load, the input end of the electronic load is connected to the current sensor, the excitation signal unit and the control unit, and the output end of the electronic load is connected to the negative electrode of the fuel cell stack;

[0046] The current sensor is used to collect the operating current of the fuel cell stack and upload it to the collection unit. The collection unit is used to collect and measure the voltage and current at the positive and negative terminals of the fuel cell stack and the single cell voltage. The excitation signal unit is used to generate a function generator of an arbitrary AC waveform. The electronic load is used to convert the small-amplitude AC voltage signal of the signal generator into an AC current disturbance and inject it into the fuel cell stack under test.

[0047] As a preferred embodiment of the present invention, the system also includes a data monitoring unit and a data storage unit, the data monitoring unit is connected to the control unit, the input end of the data storage unit is connected to the control unit, the data monitoring unit is used to input parameters and display various operating parameters of the battery stack, electronic load parameters and battery stack impedance information, and the data storage unit stores data of the data monitoring unit.

[0048] As a preferred embodiment of the present invention, the control unit obtains parameters set according to the test operating conditions of the fuel cell stack, and the control unit controls the air supply unit, the fuel supply unit and the cooling supply unit through the acquisition and driving unit to achieve the corresponding set parameters. The fuel cell stack outputs power. After the fuel cell stack is in a stable state, the control unit sends an instruction to the excitation signal unit to control the amplitude, frequency point and number of cycles of the AC excitation current superimposed on the DC of the electronic load, and injects the AC excitation current into the fuel cell stack. The current sensor collects the total current, and the voltage and total current of the fuel cell stack are synchronously collected through the acquisition unit and sent to the control unit. The control unit processes the collected voltage and current signals online, and uses the FFT algorithm to calculate the impedance of the fuel cell stack in real time. The data monitoring unit displays the data and stores it in the data storage unit.

[0049] As a preferred embodiment of the present invention, the acquisition unit includes a multi-channel voltage acquisition module, a current acquisition module and a chassis. The multi-channel voltage acquisition module and current acquisition module are both installed in the chassis, and the voltage acquisition module and current acquisition module are connected to the fuel cell stack.

[0050] The fuel cell testing method of the present invention using the above system to realize the integrated electrochemical AC impedance testing function, wherein the method comprises the following steps:

[0051] (1) Connect the test equipment to the fuel cell stack; set the target parameters of air, fuel, and cooling water according to the test conditions;

[0052] (2) After the parameters are stable, set the electronic load DC current Idc and start loading;

[0053] (3) After the current output of the fuel cell stack is stable, the electronic load AC measurement parameters are set, and the electronic load generates an AC current iac;

[0054] (4) The acquisition unit synchronously collects the current value, stack voltage and cell voltage, and uploads them to the control unit in real time;

[0055] (5) The control unit calculates the frequency domain value of the fuel cell stack;

[0056] (6) After the measurement is completed, the electronic load stops pulling AC and the fuel cell stack returns to DC output.

[0057] As a preferred embodiment of the present invention, the step (5) specifically comprises the following steps:

[0058] (5.1) Read the current, stack voltage and cell voltage;

[0059] (5.2) Extract the AC components of current and voltage;

[0060] (5.3) The frequency and amplitude of the current and voltage are obtained according to the improved FFT calculation, and the total harmonic distortion rate THD and total harmonic distortion rate THDN of the signal are calculated at the same time;

[0061] (5.4) The magnitude of multiple harmonics is determined by the total harmonic distortion rate THD, and the magnitude of interharmonics is determined by the total harmonic distortion rate THDN. If the value of multiple harmonics or interharmonics exceeds the threshold, a warning is given;

[0062] (5.5) Calculate the amplitude and phase of each collected voltage frequency, and the amplitude and phase of the current;

[0063] (5.6) The amplitude and phase of the fuel cell impedance at each frequency are calculated through complex number operations, and the real and imaginary parts of the fuel cell impedance are calculated.

[0064] As a preferred embodiment of the present invention, the step (1) is specifically:

[0065] Connect the electronic load to the positive and negative input terminals of the fuel cell stack, connect the current sensor to the positive or negative electrode of the fuel cell stack, and connect the sampling line of the acquisition unit to the fuel cell as needed.

[0066] The device for implementing fuel cell testing with integrated electrochemical AC impedance testing function of the present invention comprises:

[0067] a processor configured to execute computer executable instructions;

[0068] The memory stores one or more computer executable instructions. When the computer executable instructions are executed by the processor, the various steps of the above-mentioned fuel cell testing method for realizing the integrated electrochemical AC impedance testing function are implemented.

[0069] The processor of the present invention is used to implement fuel cell testing with integrated electrochemical AC impedance testing function, wherein the processor is configured to execute computer executable instructions, and when the computer executable instructions are executed by the processor, the various steps of the above-mentioned fuel cell testing method for implementing integrated electrochemical AC impedance testing function are implemented.

[0070] The computer-readable storage medium of the present invention stores a computer program thereon, and the computer program can be executed by a processor to implement the various steps of the above-mentioned fuel cell testing method for realizing an integrated electrochemical AC impedance testing function.

[0071] In a specific embodiment of the present invention, a fuel cell test device, equipment and bench with integrated electrochemical AC impedance test function are provided, including a fuel cell stack, an air supply unit, a fuel (hydrogen) supply unit, a cooling supply unit, a control unit, a collection and drive unit, a data monitoring unit, a data storage unit, and an electrochemical impedance measurement system; wherein the electrochemical impedance measurement system includes a collection unit, an excitation signal unit, an electronic load, and a current sensor. The device is suitable for stacks with a relatively large current and a certain power range.

[0072] Air supply unit: provides air with certain humidity, flow, pressure and temperature.

[0073] Fuel (hydrogen) supply unit: provides hydrogen with a certain humidity, flow, pressure and temperature.

[0074] Cooling supply unit: provides cooling water with a certain flow rate, pressure and temperature.

[0075] Acquisition and drive unit: collects sensor feedback signals from the air supply unit, fuel supply unit and cooling supply unit, and drives the actuators to achieve the set target parameters, such as PLC and its measurement board. Among them, the actuators refer to various solenoid valves, water pumps, pipeline heaters, gas flow controllers and other actuators of the air supply unit, fuel supply unit and cooling supply unit.

[0076] Data monitoring unit: upper computer interface, parameter input, display of various operating parameters of the fuel cell stack, electronic load parameters, fuel cell stack impedance information, etc.

[0077] Data storage unit: stores the data of the upper computer interface, which can be a solid state drive or NAS (Network Attached Storage) to achieve data sharing.

[0078] Control unit: An industrial computer that runs the control logic, control algorithms and strategies of the device.

[0079] Excitation signal unit: A function generator that generates arbitrary AC waveforms.

[0080] Electronic load: used to convert the small-amplitude AC voltage signal of the signal generator into AC current disturbance, and inject it into the fuel cell stack under test (the excitation signal unit function can also be integrated in the electronic load). The load is a consumable load (to avoid the influence of the power grid on the current control accuracy). The characteristics are that the load has a wide AC frequency range (0.01Hz-50kHz), large current (such as ≥1000A), and supports multiple modes (constant voltage, constant current, constant power), etc.

[0081] Current sensor: used to collect the operating current of the fuel cell stack and upload it to the acquisition unit. It is characterized by high precision, large range and high bandwidth.

[0082] Acquisition unit: includes multi-channel voltage acquisition module, current acquisition module and chassis, which are used to collect and measure the voltage and current at the positive and negative ends of the fuel cell stack and the single cell voltage. It is characterized by high (anti-common mode) voltage, high accuracy, high bandwidth and expandable multi-channel.

[0083] The control unit sends instructions to the excitation signal unit according to the target in the upper computer. The excitation signal unit outputs to the electronic load. The electronic load draws the AC current. The acquisition unit collects the current and voltage of the fuel cell stack and then sends them to the control unit for data processing to obtain the impedance of the stack at this time.

[0084] Figure 2 The present invention is a schematic diagram of the structure of a fuel cell test device, equipment and test bench with integrated electrochemical AC impedance test function. First, according to the test operation conditions of the fuel cell stack, the required reaction gas, cooling temperature, load current and other parameters are set, and the control unit controls the air supply unit, fuel supply unit and cooling supply unit through the acquisition and drive unit to achieve the corresponding set parameters; then, the load current (DC Idc) of the electronic load is set, and the fuel cell stack starts to output power to the outside; after the fuel cell stack is in a stable state (stable cell voltage), the control unit sends instructions to the excitation signal unit to control the amplitude, frequency point and number of cycles of the AC excitation current superimposed on the DC of the electronic load. The AC amplitude is generally 3%-15% of the load current of the fuel cell stack, so as to realize the injection of the AC excitation current of the fuel cell stack. The total current is collected by the current sensor installed on the busbar between the fuel cell stack and the electronic load, and the voltage and total current of the fuel cell stack are synchronously collected by the collection unit of the electrochemical impedance measurement system and sent to the control unit. The control unit processes the collected voltage and current signals online, and uses the FFT algorithm to calculate the impedance of the fuel cell stack in real time, which is displayed in the data monitoring unit and stored in the data storage unit for subsequent analysis.

[0085] It sets the required reaction gas, cooling temperature, load current and other parameters, and has manual and automatic mode settings:

[0086] 1. Manual mode: manually set all operating parameters;

[0087] 2. Automatic mode: Pre-edit the operating conditions, store them as scripts, and select them from the drop-down box in automatic mode.

[0088] Figure 3-4 It is a schematic diagram of the measurement of electrochemical impedance spectrum and impedance calculation when the battery stack of the present invention is in operation.

[0089] The measurement flow chart of the electrochemical impedance spectroscopy of the fuel cell stack is as follows: Figure 3As shown, first, connect the test equipment to the fuel cell stack; connect the electronic load to the positive and negative input terminals of the fuel cell stack, connect the current sensor to the positive (or negative) terminal of the fuel cell stack, and connect the sampling line of the acquisition unit to the positive and negative terminals of the fuel cell or to both ends of a single chip or several chips as needed.

[0090] According to the test conditions, set the target parameters of air, fuel and cooling water.

[0091] After the parameters are stable, set the electronic load DC current Idc and start loading.

[0092] After the current output of the fuel cell stack is stable, the electronic load AC iac measurement parameters (waveform, frequency point, period, amplitude, etc.) are set, such as the frequency sweep of the sine wave. The frequency range of the AC signal is generally 0.1-10kHz, and the amplitude range is generally 3%-10% of the DC current. The electronic load generates an AC current iac. At this time, an AC current, i.e., Idc+iac, is superimposed on the output current bus of the fuel cell stack.

[0093] The acquisition unit synchronously collects the current value, stack voltage and single cell voltage, and uploads them to the control unit in real time. The control unit calculates the frequency domain values ​​of the AC impedance amplitude, phase, imaginary part and real part of the fuel cell stack according to the algorithm (such as Fourier transform (FFT)). After the EIS measurement is completed, the electronic load stops pulling AC, and the stack returns to DC output.

[0094] In order to calculate the impedance, the collected voltage and current time domain signals need to be converted into frequency signals. The impedance calculation process is as follows: Figure 4 shown.

[0095] First, the AC components of current and voltage are extracted. Then the frequency and amplitude are calculated based on the improved FFT, and the THD (total harmonic distortion) and THDN (total harmony distortion) of the signal are calculated at the same time.

[0096] The size of multiple harmonics can be determined by THD, and the size of interharmonics can be determined by THDN. When these two values ​​exceed a certain threshold, a warning is given: "The waveform distortion at these frequency points is high, and re-measurement is recommended."

[0097] At the same time, the amplitude and phase of the voltage and the amplitude and phase of the current at each collected frequency are calculated, and then the amplitude Zamp = ampv / ampi and the phase Zpha = (phav-phai) / pi×180 at each frequency are obtained through complex operation.

[0098] Obtain the Bode diagram of amplitude and frequency, and the Bode diagram of phase and frequency.

[0099] Finally, the real part of the impedance at each frequency Zre(j) = Zamp × cos(phav-phai); the imaginary part Zim(j) = Zamp × sin(phav-phai) is calculated to form a Nyquist diagram. The amplitude and phase, imaginary and real parts of the voltage at each frequency, and the amplitude and phase, imaginary and real parts of the current are all stored in the data storage unit for further analysis.

[0100] The present invention provides a detailed measurement architecture and principle of electrochemical impedance spectroscopy (EIS) of a high-power battery stack, and explains the role of each unit and the relationship between them. The use of an external current sensor and its reason are particularly critical, which ensures the accuracy (amplitude and phase) of the battery stack bus current during EIS measurement, thereby ensuring the accuracy of impedance calculation and analysis, and also simplifies the EIS measurement system.

[0101] The present invention provides a detailed measurement process of electrochemical impedance spectroscopy (EIS) during the operation of a fuel cell stack, especially the setting of the electronic load current to ensure that the current operating point remains unchanged during EIS measurement. At the same time, a method for evaluating the quality of current and voltage data obtained during EIS measurement is provided, namely, using THD and THDN.

[0102] The present invention provides a calculation process for obtaining impedance information in the frequency domain by using the collected time domain waveform signals of the current and the voltage of each channel (multiple monomers and the entire stack).

[0103] The present invention has the following characteristics:

[0104] High integration, greatly reduced hardware and software costs: The present invention highly integrates the electrochemical test system, test software integration (a data monitoring unit), hardware and control integration (a control unit and a data storage unit), which not only saves hardware costs, but also eliminates the program writing and maintenance links of the information interaction interface definitions of multiple control units, saving software development costs; more importantly, the present invention uses the same electronic load for high-current battery stacks to achieve the superposition of DC and AC currents, avoiding the substantial cost increase caused by the additional parallel AC excitation electronic load.

[0105] The operation is simple and can avoid errors caused by repeated setting of load parameters: in the present invention, after the electronic load outputs DC and the stack runs stably, the AC current can be directly loaded, and the operation is simple, and a fully automated process test can be realized; while in the traditional test bench external electrochemical impedance measurement system, the DC current of the electronic load 1 is set first, and then the DC offset and AC value of the electronic load 2 in the electrochemical impedance measurement system are set, and the current of the original electronic load 1 is restored after the EIS test is completed, so it is necessary to manually adjust the current of the electronic load 1 twice; the present invention avoids the problems of current operating point offset and cumbersome operation that may be caused by manual adjustment of the current of the electronic load 1 during stack measurement.

[0106] High measurement efficiency: The parameter settings of the battery stack operating conditions and the electrochemical impedance measurement are both performed in the upper computer in the same data monitoring unit, which greatly facilitates the operation of the experimenter; at the same time, the control of the battery stack operating conditions and the control of the electrochemical impedance measurement system are integrated in the control unit, which truly realizes the synchronization of command sending and data storage, and reduces the complexity of multi-object control.

[0107] High measurement precision and more accurate: The present invention is equipped with a separate high-precision current sensor to ensure the current measurement accuracy and authenticity during the operation of the battery stack, avoiding errors caused by directly using the set current of the load or inaccurate internal collection feedback current; at the same time, the current sensor can also be integrated in the packaging shell of the electronic load to achieve higher integration; it is also equipped with a high-precision, high-bandwidth voltage acquisition board.

[0108] The specific implementation scheme of this embodiment can refer to the relevant description in the above embodiment, which will not be repeated here.

[0109] It can be understood that the same or similar parts of the above embodiments can be referenced to each other, and the contents not described in detail in some embodiments can refer to the same or similar contents in other embodiments.

[0110] It should be noted that, in the description of the present invention, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, the meaning of "plurality" refers to at least two.

[0111] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0112] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution device. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0113] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the corresponding program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0114] In addition, each functional unit in each embodiment of the present invention may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0115] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0116] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0117] The fuel cell test system, method, device, processor and computer-readable storage medium thereof with integrated electrochemical AC impedance test function of the present invention can realize rapid measurement of electrochemical impedance and impedance calculation in the fuel cell stack test process on the basis of meeting the functions of the existing fuel cell test bench. The present invention has high integration, greatly reduces hardware and software costs, is simple to operate, avoids errors caused by repeated setting of load parameters, has high measurement efficiency, high measurement accuracy, is more accurate, and has a wide range of applications.

[0118] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it is apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Therefore, the specification and drawings should be regarded as illustrative rather than restrictive.

Claims

1. A fuel cell testing system with integrated electrochemical AC impedance testing function, characterized in that: The system comprises a fuel cell stack, an air supply unit, a fuel supply unit, a cooling supply unit, a control unit, a collection and drive unit and an electrochemical impedance measurement system, wherein the output ends of the air supply unit, the fuel supply unit and the cooling supply unit are connected to the fuel cell stack, the collection and drive unit is connected to the fuel supply unit, the control unit is connected to the collection and drive unit, and the electrochemical impedance measurement system is connected to the fuel cell stack and the control unit; The air supply unit is used to provide air with preset humidity, flow, pressure and temperature; the fuel supply unit is used to provide hydrogen with preset humidity, flow, pressure and temperature; the cooling supply unit is used to provide cooling water with preset flow, pressure and temperature; the control unit is used to run control logic, control algorithm and strategy; the acquisition and drive unit is used to acquire sensor feedback signals of the air supply unit, the fuel supply unit and the cooling supply unit, and drive the actuator to achieve the set target parameters; the excitation signal unit of the electrochemical impedance measurement system receives the target instruction sent by the control unit and outputs it to the electronic load; the electronic load draws AC current; the acquisition unit acquires the current and voltage of the fuel cell stack; the control unit processes the data to obtain the impedance of the stack at this time.

2. The fuel cell testing system with integrated electrochemical AC impedance testing function according to claim 1, characterized in that: The electrochemical impedance measurement system includes a collection unit, an excitation signal unit, an electronic load and a current sensor. The current sensor is installed on the busbar between the fuel cell stack and the electronic load. The input end of the current sensor is connected to the positive electrode of the fuel cell stack, and the output end of the current sensor is connected to the collection unit. The input end of the collection unit is connected to the fuel cell stack and the current sensor, and the output end of the collection unit is connected to the control unit. The current sensor is ring-shaped and is sleeved on the busbar between the fuel cell stack and the electronic load. The current sensor outputs a signal to the collection unit, the input end of the excitation signal unit is connected to the control unit, and the output end of the excitation signal unit is connected to the electronic load. The input end of the electronic load is connected to the current sensor, the excitation signal unit and the control unit, and the output end of the electronic load is connected to the negative electrode of the fuel cell stack. The current sensor is used to collect the operating current of the fuel cell stack and upload it to the collection unit. The collection unit is used to collect and measure the voltage and current at the positive and negative terminals of the fuel cell stack and the single cell voltage. The excitation signal unit is used to generate a function generator of an arbitrary AC waveform. The electronic load is used to convert the small-amplitude AC voltage signal of the signal generator into an AC current disturbance and inject it into the fuel cell stack under test.

3. The fuel cell testing system with integrated electrochemical AC impedance testing function according to claim 1, characterized in that: The system also includes a data monitoring unit and a data storage unit. The data monitoring unit is connected to the control unit, and the input end of the data storage unit is connected to the control unit. The data monitoring unit is used to input parameters and display various operating parameters of the battery stack, electronic load parameters and battery stack impedance information. The data storage unit stores data of the data monitoring unit.

4. The fuel cell testing system with integrated electrochemical AC impedance testing function according to claim 1, characterized in that: The control unit obtains parameters set according to the test operating conditions of the fuel cell stack. The control unit controls the air supply unit, the fuel supply unit and the cooling supply unit through the acquisition and driving unit to achieve the corresponding set parameters. The fuel cell stack outputs power. After the fuel cell stack is in a stable state, the control unit sends instructions to the excitation signal unit to control the amplitude, frequency point and number of cycles of the AC excitation current superimposed on the DC of the electronic load, and injects the AC excitation current into the fuel cell stack. The current sensor collects the total current, and the voltage and total current of the fuel cell stack are synchronously collected through the acquisition unit and sent to the control unit. The control unit processes the collected voltage and current signals online, and uses the FFT algorithm to calculate the impedance of the fuel cell stack in real time. The data monitoring unit displays the data and stores it in the data storage unit.

5. The fuel cell testing system with integrated electrochemical AC impedance testing function according to claim 2, characterized in that: The acquisition unit includes a multi-channel voltage acquisition module, a current acquisition module and a chassis. The multi-channel voltage acquisition module and the current acquisition module are both installed in the chassis. The voltage acquisition module and the current acquisition module are connected to the fuel cell stack.

6. A fuel cell testing method based on the system of claim 1 to realize an integrated electrochemical AC impedance testing function, characterized in that: The method comprises the following steps: (1) Connect the test equipment to the fuel cell stack; set the target parameters of air, fuel, and cooling water according to the test conditions; (2) After the parameters are stable, set the electronic load DC current Idc and start loading; (3) After the current output of the fuel cell stack is stable, the electronic load AC measurement parameters are set, and the electronic load generates an AC current iac; (4) The acquisition unit synchronously collects the current value, stack voltage and cell voltage, and uploads them to the control unit in real time; (5) The control unit calculates the frequency domain value of the fuel cell stack; (6) After the measurement is completed, the electronic load stops pulling AC and the fuel cell stack returns to DC output.

7. The fuel cell testing method for realizing integrated electrochemical AC impedance testing function according to claim 1, characterized in that: The step (5) specifically comprises the following steps: (5.1) Read the current, stack voltage and cell voltage; (5.2) Extract the AC components of current and voltage; (5.3) The frequency and amplitude of the current and voltage are obtained according to the improved FFT calculation, and the total harmonic distortion rate THD and total harmonic distortion rate THDN of the signal are calculated at the same time; (5.4) The magnitude of multiple harmonics is determined by the total harmonic distortion rate THD, and the magnitude of interharmonics is determined by the total harmonic distortion rate THDN. If the value of multiple harmonics or interharmonics exceeds the threshold, a warning is given; (5.5) Calculate the amplitude and phase of each collected voltage frequency, and the amplitude and phase of the current; (5.6) The amplitude and phase of the fuel cell impedance at each frequency are calculated through complex number operations, and the real and imaginary parts of the fuel cell impedance are calculated.

8. The fuel cell testing method for realizing integrated electrochemical AC impedance testing function according to claim 1, characterized in that: The step (1) is specifically as follows: Connect the electronic load to the positive and negative input terminals of the fuel cell stack, connect the current sensor to the positive or negative electrode of the fuel cell stack, and connect the sampling line of the acquisition unit to the fuel cell as needed.

9. A fuel cell testing device for realizing an integrated electrochemical AC impedance testing function, characterized in that: The device comprises: a processor configured to execute computer executable instructions; A memory storing one or more computer executable instructions, wherein when the computer executable instructions are executed by the processor, the steps of the fuel cell testing method for realizing an integrated electrochemical AC impedance testing function as described in any one of claims 6 to 8 are implemented.

10. A processor for implementing a fuel cell test with an integrated electrochemical AC impedance test function, characterized in that: The processor is configured to execute computer executable instructions. When the computer executable instructions are executed by the processor, the various steps of the fuel cell testing method for realizing an integrated electrochemical AC impedance testing function as described in any one of claims 6 to 8 are implemented.

11. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and the computer program can be executed by a processor to implement the various steps of the fuel cell testing method for realizing an integrated electrochemical AC impedance testing function as described in any one of claims 6 to 8.

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