Impedance measurement and control device and method for vehicle-mounted fuel cell

Abstract

The present invention provides an impedance measurement and control device and method for a vehicle-mounted fuel cell, which belongs to the technical field of fuel cell impedance measurement and solves the problem that the existing technology cannot effectively measure the AC impedance of a single cell and control the operation of the stack. The device includes a stack, a DC-DC converter, a current sensor, a voltage patrol device, and a controller. The DC-DC converter and the voltage patrol device are connected via a signal synchronization line; the current sensor is arranged inside the DC-DC converter; and each electrode of the voltage patrol device is respectively connected to the output end of a single cell in the stack. The controller is used to start the DC-DC converter when the stack is operating normally, send an AC excitation signal to the stack, and start the voltage patrol device after the current sensor value stabilizes. The AC impedance of each single cell in the stack is obtained based on the feedback voltage of each single cell in the stack at the same time combined with the measured current, and the operation of the stack is controlled. The function of measuring and controlling the impedance of the single cell of the stack is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cell impedance measurement, and in particular to an impedance measurement and control device for a vehicle-mounted fuel cell. Background Art

[0002] Hydrogen fuel cell vehicles are new energy vehicles with broad development prospects, offering numerous advantages such as short refueling times and extended driving range. Onboard fuel cell systems typically consist of a fuel cell stack and peripheral hydrogen, air, and cooling subsystems. The stack includes a proton exchange membrane, catalyst layer, gas diffusion layer, and bipolar plates. Because the theoretical voltage of a single cell is 1.23V, high power output is typically achieved by connecting hundreds of cells in series.

[0003] AC impedance is a method for monitoring the internal state of a fuel cell, generally achieved with the help of a DC / DC device, but it can only collect impedance information at the whole stack level. For example, patent CN105699902A proposes an impedance measurement device and method for fuel cell diagnosis, but only calculates the overall impedance of the stack. The stack is actually composed of multiple single cells. Due to their different positions in the stack, different single cells will have inconsistencies in temperature, gas supply status and even current density, resulting in inconsistent impedance of the single cells. The reliability of the stack depends on the single cell with the worst performance in the stack.

[0004] Patent CN111244505A proposes a method for monitoring monolithic AC impedance, in which current acquisition and monolithic voltage acquisition are implemented by the same device. However, during the product integration process, in order to facilitate the independent development of components, the current acquisition function and the monolithic voltage acquisition are implemented by different hardware. In the process of implementing the AC impedance function, the problem of inaccurate impedance results caused by the asynchronous acquisition of voltage and current signals will be encountered. Summary of the Invention

[0005] The embodiment of the present invention aims to provide an impedance measurement and control device for a vehicle-mounted fuel cell, so as to solve the problem that the existing technology cannot effectively measure the AC impedance of a single cell and control the operation of the fuel cell stack.

[0006] On the one hand, an embodiment of the present invention provides an impedance measurement and control device for a vehicle-mounted fuel cell, characterized in that it includes a fuel cell stack, a DC-DC converter, a current sensor, a voltage inspection device, and a controller; wherein,

[0007] The DC-DC converter and the voltage inspection device are connected via a signal synchronization line; the current sensor is disposed inside the DC-DC converter; each electrode of the voltage inspection device is respectively connected to the output end of a single cell in the battery stack; and the output ends of the current sensor and the voltage inspection device are respectively connected to the input end of the controller, and the control end is respectively connected to the output end of the controller;

[0008] The controller is used to start the DC-DC converter when the fuel cell stack is operating normally, send an AC excitation signal of a preset frequency to the fuel cell stack, and start the voltage inspection device after the value measured by the current sensor stabilizes. The AC impedance of each single cell in the fuel cell stack is obtained based on the feedback of the voltage of each single cell in the fuel cell stack at the same time combined with the current measured by the current sensor to control the operation of the fuel cell stack.

[0009] The beneficial effects of the above technical solution are as follows: a fuel cell impedance measurement and control device is provided, which adopts the synchronization mechanism of the signal synchronization line combined with the above-mentioned AC impedance measurement and control configuration, and realizes the coupling design of impedance measurement and control functions with the help of different hardware combined with the measurement and control program, which is conducive to the modularization, interchangeability and independent development of different hardware, and is flexible and convenient.

[0010] Based on the further improvement of the above device, the controller further includes:

[0011] A data acquisition unit is used to collect real-time data information from the output signals of the current sensor and the voltage inspection device and send it to the data processing and control unit; the data information includes the amplitude or effective value of the output current of the battery stack and the voltage amplitude or effective value of each single cell;

[0012] The data processing and control unit is used to start the DC-DC converter when the fuel cell stack is operating normally, send an AC excitation signal of a preset frequency to the fuel cell stack, and start the voltage inspection device after the value measured by the current sensor stabilizes. Based on the feedback of the current amplitude at the same moment and the voltage amplitude of each single cell, the AC impedance of each single cell is obtained to control the operation of the fuel cell stack;

[0013] The actuator is used to change the operating state of the fuel cell stack according to the control of the data processing unit.

[0014] The beneficial effect of the above-mentioned further improvement scheme is that the structure of the controller is limited to realize the state information collection and impedance measurement and control of the fuel cell.

[0015] Furthermore, the execution mechanism further comprises:

[0016] The inlet gas control device is used to control the flow rate and pressure of hydrogen and air entering the stack; its output end is connected to the gas inlet of the fuel cell stack, and its control end is connected to the output end of the controller;

[0017] A coolant temperature regulating device is used to control the water temperature of the coolant entering the stack; its control end is connected to the output end of the controller; and the coolant inlet of the fuel cell stack is connected to its coolant outlet through the above-mentioned coolant temperature regulating device.

[0018] The beneficial effects of the above-mentioned further improvement scheme are: the composition of the actuator is limited, and it can control the input gas flow, pressure and water temperature of the coolant when the vehicle is started or shut down, remove residual oxygen inside the fuel cell stack, and quickly heat the fuel cell stack when the vehicle is cold started to improve the activity of the fuel cell.

[0019] Furthermore, the actuator further includes controllable switches 1 and 2; wherein,

[0020] The controllable switch 1 is used to control the start-up of the DC-DC converter, and its output end is connected to the control end of the DC-DC converter;

[0021] The controllable switch 2 is used to control the start-up of the voltage inspection device, and its output end is connected to the control end of the voltage inspection device.

[0022] The beneficial effect of the above-mentioned further improvement scheme is that the addition of controllable switch 1 and controllable switch 2 can strictly control the signal acquisition time, making the measurement and control process more accurate.

[0023] Furthermore, the data processing and control unit executes the following program:

[0024] Obtaining real-time stack output current to determine whether the fuel cell is operating normally; if not, adjusting the fuel cell operating parameters until it is operating normally; the operating parameters include at least one of the flow rate and pressure of hydrogen and air entering the stack, and the water temperature of the coolant entering the stack;

[0025] Start the DC-DC converter and send an AC excitation signal of a preset frequency to the fuel cell stack;

[0026] Monitor the value measured by the current sensor, and start the voltage inspection device after the value measured by the current sensor stabilizes;

[0027] Obtaining the current measured by the current sensor at the same moment after the voltage inspection device is started, and the voltage of each single battery measured by the voltage inspection device;

[0028] According to the voltage and current, the amplitude and phase of the AC impedance of each single battery cell at the preset frequency are obtained;

[0029] According to the obtained amplitude and phase of the AC impedance of each single cell, the operating parameters of the fuel cell are adjusted to control the operation of the fuel cell stack.

[0030] The beneficial effects of the above further improved solution are: limiting the execution program of the controller, being able to realize the AC impedance measurement function, and realizing the coordinated control and synchronization functions.

[0031] Furthermore, the controller executes the following procedure to determine whether the fuel cell is operating normally:

[0032] Obtaining the real-time output current of the battery stack within a preset time period;

[0033] Determine the effective value and maximum change of the real-time output current;

[0034] Determine whether the effective value of the real-time output current is within a preset range and satisfies the maximum variation not exceeding a preset threshold; if so, determine that the fuel cell is operating normally; otherwise, adjust the operating parameters of the fuel cell, including the flow rate and pressure of the hydrogen and air entering the stack, and the water temperature of the coolant entering the stack, and determine again until the fuel cell is determined to be operating normally.

[0035] The beneficial effect of this further improvement is that it limits the method for determining whether a fuel cell is operating normally. The real-time output current of the fuel cell stack can be used to strictly determine whether the effective value of the output current is within a preset range, while also ensuring that the maximum change does not exceed a preset threshold. In practice, using data from a fuel cell operating abnormally cannot accurately determine the AC impedance of the fuel cell, which can interfere with the user's judgment. This solution lays the foundation for subsequent accurate data collection and fuel cell fault correction (such as temperature control).

[0036] Furthermore, the amplitude of the AC impedance of the i-th single cell is Z fi and phase(Z fi )for

[0037] Z fi =ΔV i / ΔI

[0038] phase(Z fi )=β2-β 1i

[0039] Where ΔV is the amplitude of the voltage vector of the i-th single cell, ΔI is the amplitude of the current vector, β2 is the phase angle of the current vector, and β 1i is the phase angle of the voltage vector of the i-th single-cell battery, i = 1,…,n, and n is the number of single-cell batteries in the battery stack.

[0040] The beneficial effect of the above-mentioned further improvement scheme is that it defines the method for determining the amplitude and phase of the AC impedance of each single cell, laying the foundation for subsequent control of the battery stack operation.

[0041] Furthermore, the controller executes the following program to control the operation of the fuel cell stack:

[0042] Get the magnitude Z of the AC impedance of each single cell fi and phase(Zfi ), and the magnitude ΔV of the voltage vector of each single cell;

[0043] Compare each of the amplitudes ΔV with a preset value of one. If the number of cells with an amplitude ΔV less than or equal to the preset value of one exceeds the rated value, it is determined that the stack has insufficient input gas, and the flow rate and pressure of the hydrogen and air entering the stack are increased. Otherwise, the flow rate and pressure of the hydrogen and air entering the stack are maintained unchanged.

[0044] Each of the amplitudes Z fi Compare with the preset value 2, if the amplitude Z fi If the number of single-cell batteries greater than or equal to the preset value 2 exceeds the rated value, the proton exchange membrane of the stack is determined to be in a dry state, and the coolant temperature regulating device is controlled to lower the water temperature of the coolant entering the stack. Otherwise, the current water temperature is maintained unchanged;

[0045] According to the phase phase (Z fi ), determine the time t between the next start-up of the voltage inspection device and the signal acquisition time

[0046] t=∑phase(Z fi ) / (2nπf)+t0

[0047] Where t0 is the time between the start-up of the voltage inspection device and the signal acquisition time, and f is the frequency of the AC excitation signal.

[0048] The beneficial effect of the above-mentioned further improvement scheme is: it limits the method of controlling the operation of the battery stack according to the impedance of the single-chip battery, and can more accurately control the time t between the moment of starting the voltage inspection device and the moment of signal collection during low-temperature cold start, thereby ensuring the accuracy of the collected data.

[0049] Furthermore, the data processing and control unit has a display module; and

[0050] The display screen of the display module displays the overall internal resistance Z of the fuel cell stack f , and the internal resistance Z of each single cell in the stack fi ;

[0051] The overall internal resistance Z of the fuel cell stack f Obtained by the following formula

[0052] Z f＝ ∑Z fi

[0053] Where t0 is the time between the start-up of the voltage inspection device and the signal acquisition time, f is the frequency of the AC excitation signal, i = 1,…,n, and n is the number of single cells in the stack.

[0054] The beneficial effect of the above-mentioned further improvement scheme is that it limits the display module and displayed content. A fuel cell stack is composed of multiple single cells. Due to their different positions in the stack, the temperature, gas supply status, and even current density of each cell can be inconsistent, resulting in inconsistent impedance of each cell. The reliability of the stack depends on the status of the cell with the worst performance in the stack. The impedance of the above-mentioned single cell provides the most accurate data for fuel cell fault diagnosis.

[0055] On the other hand, an embodiment of the present invention provides a method for measuring and controlling the impedance of a vehicle-mounted fuel cell corresponding to the above-mentioned device, comprising the following steps:

[0056] When the fuel cell stack is operating normally, the DC-DC converter is started to send an AC excitation signal of a preset frequency to the fuel cell stack;

[0057] After the value measured by the current sensor stabilizes, start the voltage inspection device;

[0058] The AC impedance of each cell is obtained based on the voltage of each cell in the stack at the same moment of feedback combined with the current measured by the current sensor to control the operation of the stack.

[0059] The beneficial effect of adopting the above scheme is: providing an impedance measurement and control method for a fuel cell, using the synchronization mechanism of the signal synchronization line combined with the above AC impedance measurement and control configuration, and realizing the coupling design of impedance measurement and control functions with the help of the measurement and control program, which is flexible and convenient.

[0060] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the disclosure, nor is it intended to limit the scope of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The above and other objects, features and advantages of the present disclosure will become more apparent through a more detailed description of exemplary embodiments of the present disclosure with reference to the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present disclosure.

[0062] Figure 1 A schematic diagram showing the composition of the impedance measurement and control device of Example 1 is shown;

[0063] Figure 2 A circuit connection diagram of the impedance measurement and control device of Example 1 is shown;

[0064] Figure 3 A schematic diagram of the composition of the impedance measurement and control device of Example 2 is shown.

[0065] Reference numerals:

[0066] 41-end plate of the battery stack; 42-insulating plate; 43-current collecting plate; 44-single cell;

[0067] 10-DC-DC converter; 11-current sensor inside the DC-DC converter; 20-signal synchronization line; 30-controller; 50-voltage inspection device. DETAILED DESCRIPTION

[0068] Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0069] As used herein, the term "including" and its variations represent open inclusion, i.e., "including but not limited to." Unless otherwise stated, the term "or" means "and / or." The term "based on" means "based at least in part on." The terms "an example embodiment" and "an embodiment" mean "at least one example embodiment." The term "another embodiment" means "at least one additional embodiment." The terms "first," "second," etc. may refer to different or the same objects. Other explicit and implicit definitions may also be included below.

[0070] Example 1

[0071] One embodiment of the present invention discloses an impedance measurement and control device for a vehicle-mounted fuel cell, including a fuel cell stack, a DC-DC converter, a current sensor, a voltage inspection device, and a controller. Figures 1-2 shown.

[0072] The DC-DC converter and the voltage patrol device are connected via a signal synchronization line; the current sensor is arranged inside the DC-DC converter; each electrode of the voltage patrol device is respectively connected to the output end of a single battery cell of the battery stack; and the output ends of the current sensor and the voltage patrol device are respectively connected to the input end of the controller, and the control end is respectively connected to the output end of the controller.

[0073] The signal synchronization line is used to trigger or clock synchronization when the voltage inspection device collects the voltage signal of the single battery and the DC-DC converter collects the current signal when the AC impedance function is enabled. Alternatively, an existing signal synchronization line can be used, such as the signal synchronization line described in patent CN201910237668.0.

[0074] The current sensor is used to collect the output current (signal) of the battery stack.

[0075] The voltage inspection device is used to collect the voltage (signal) of each single battery in the battery stack after startup.

[0076] The controller is used to start the DC-DC converter when the fuel cell stack is operating normally, send an AC excitation signal of a preset frequency to the fuel cell stack, and start the voltage inspection device after the value measured by the current sensor stabilizes. The AC impedance of each single cell in the fuel cell stack is obtained based on the feedback of the voltage of each single cell in the fuel cell stack at the same time combined with the current measured by the current sensor to control the operation of the fuel cell stack.

[0077] Optionally, in the program executed by the controller, the basis for determining whether the stack is operating normally may be the stack output current, voltage, or power. The stack output current, voltage, or power is compared with a pre-calibrated preset range for normal operation. If the current, voltage, or power falls within the preset range, the stack is determined to be operating normally; otherwise, the stack is not operating normally.

[0078] Optionally, in the program executed by the controller, the preset frequency range is 0.1-10kHz, preferably, 1kHz can be selected as the high frequency, and 50Hz can be selected as the low frequency. Exemplarily, the AC excitation signal of the preset frequency can be a 5A sinusoidal AC excitation.

[0079] Optionally, in the program executed by the controller, the basis for judging the stability of the value measured by the current sensor may be that the maximum current and the minimum current do not exceed a preset range, or the effective value is within a preset range.

[0080] Optionally, the controller can obtain the AC impedance Z of the single-chip battery by the following formula, or use the method described in Example 2 to obtain the amplitude and phase of the AC impedance of the single-chip battery:

[0081] Z=U / I (1)

[0082] Where U is the voltage vector of the i-th single-cell battery collected by the voltage inspection device, and I is the current vector collected by the current sensor.

[0083] Optionally, controlling the operation of the fuel cell stack includes controlling the flow rate and pressure of hydrogen and air entering the stack, the temperature of the coolant entering the stack, and the timing (or time) of signal acquisition. Persons skilled in the art will appreciate that these are not specifically limited herein. For example, the amplitude or phase of the AC impedance can be compared with multiple thresholds to obtain adjustment information for the flow rate and pressure of hydrogen and air entering the stack, the temperature of the coolant entering the stack, and the timing of signal acquisition.

[0084] Compared with the prior art, this embodiment provides a new type of impedance measurement and control device for a fuel cell. It adopts the synchronization mechanism of the signal synchronization line in combination with the above-mentioned AC impedance measurement and control configuration, and realizes the coupling design of the impedance measurement function with the help of different hardware. It is conducive to the modularization, interchangeability and independent development of different hardware, and is flexible and convenient.

[0085] Example 2

[0086] Based on the improvement of Example 1, the controller further includes a data acquisition unit, a data processing and control unit and an actuator connected in sequence, such as Figure 3 As shown. The input of the data acquisition unit is connected to the output of the current sensor and the voltage inspection device respectively; the output of the actuator is connected to the DC-DC converter, the voltage inspection device, and the control terminal of the fuel cell stack operation status. Specifically, the control terminal of the fuel cell stack operation status includes the fuel cell stack air and hydrogen input terminal, the hydrogen input terminal, the coolant inlet, etc.

[0087] The data acquisition unit is used to collect real-time data information from the output signals of the current sensor and the voltage inspection device and send it to the data processing and control unit; the data information includes the output current amplitude or effective value of the battery stack and the voltage amplitude or effective value of each single battery.

[0088] The data processing and control unit is used to start the DC-DC converter when the fuel cell stack is operating normally, send an AC excitation signal of a preset frequency to the fuel cell stack, and start the voltage inspection device after the value measured by the current sensor stabilizes. Based on the feedback of the current amplitude at the same moment combined with the voltage amplitude of each single cell, the AC impedance of each single cell is obtained to control the operation of the fuel cell stack.

[0089] The actuator is used to start the DC-DC converter, voltage inspection device, or change the operating status of the fuel cell stack according to the control of the data processing unit.

[0090] Preferably, the actuator further includes an inlet gas control device, a coolant temperature control device, and controllable switches 1 and 2. The inlet gas control device's output is connected to the stack's gas inlet, and its control terminal is connected to the controller's output. The stack's coolant inlet is connected to its coolant outlet via the coolant temperature control device. The control terminal of the coolant temperature control device is connected to the controller's output. The output of controllable switch 1 is connected to the control terminal of the DC-DC converter; the output of controllable switch 2 is connected to the control terminal of the voltage inspection device.

[0091] The gas control equipment entering the reactor is used to control the flow and pressure of hydrogen and air entering the reactor.

[0092] Coolant temperature regulating equipment is used to control the water temperature of the coolant entering the reactor.

[0093] Controllable switch 1, used to control the start-up of the DC-DC converter.

[0094] Controllable switch 2 is used to control the start-up of the voltage inspection device.

[0095] Preferably, the data processing and control unit executes the following program:

[0096] SS1. Obtain real-time stack output current to determine whether the fuel cell is operating normally; if not, adjust the fuel cell operating parameters until it is operating normally; the operating parameters include at least one of the flow rate, pressure, and water temperature of the hydrogen and air entering the stack;

[0097] SS2. Start the DC-DC converter and send an AC excitation signal of a preset frequency to the fuel cell stack;

[0098] SS3. Monitor the value measured by the current sensor. Once the value measured by the current sensor stabilizes, activate the voltage inspection device.

[0099] SS4. Get the current measured by the current sensor at the same time after starting the voltage inspection device, and the voltage of each single battery measured by the voltage inspection device;

[0100] SS5. Based on the voltage and current, the amplitude and phase of the AC impedance of each single cell at the preset frequency are obtained;

[0101] SS6. Adjust the operating parameters of the fuel cell and control the operation of the fuel cell stack based on the amplitude and phase of the AC impedance of each single cell obtained above.

[0102] Preferably, the controller executes the following procedure to complete step SS1:

[0103] SS11. Obtain the real-time output current of the battery stack within a preset time period;

[0104] SS12. Determine the effective value and maximum change of the real-time output current;

[0105] SS13. Determine whether the effective value of the real-time output current is within a preset range and that the maximum variation does not exceed a preset threshold. If so, determine that the fuel cell is operating normally. Otherwise, adjust the operating parameters of the fuel cell, including the flow and pressure of the hydrogen and air entering the stack, and the water temperature of the coolant entering the stack, and repeat the determination until the fuel cell is determined to be operating normally.

[0106] Preferably, the controller obtains the amplitude Z of the AC impedance of the i-th single-chip battery through the following formula: fi and phase(Z fi )for

[0107] Z fi =ΔV i / ΔI

[0108] phase(Z fi )=β2-β 1i

[0109] Where ΔV is the amplitude of the voltage vector of the i-th single cell, ΔI is the amplitude of the current vector, β2 is the phase angle of the current vector, and β 1i is the phase angle of the voltage vector of the i-th single-cell battery, i = 1,…,n, and n is the number of single-cell batteries in the battery stack.

[0110] Preferably, the controller executes the following procedure to complete step SS6:

[0111] SS61. Obtain the magnitude Z of the AC impedance of each single cell fi and phase(Z fi ), and the magnitude ΔV of the voltage vector of each single cell;

[0112] SS62. Compare each of the amplitudes ΔV with a preset value of one. If the number of cells with an amplitude ΔV less than or equal to the preset value of one exceeds the rated value, determine that the stack is insufficiently supplied with gas, and increase the flow and pressure of hydrogen and air entering the stack. Otherwise, maintain the flow and pressure of hydrogen and air entering the stack unchanged.

[0113] SS63. Each of the amplitudes Z fi Compare with the preset value 2, if the amplitude Z fi If the number of single-cell batteries greater than or equal to the preset value 2 exceeds the rated value, the proton exchange membrane of the stack is determined to be in a dry state, and the coolant temperature regulating device is controlled to lower the water temperature of the coolant entering the stack. Otherwise, the current water temperature is maintained unchanged;

[0114] SS64. According to the phase phase (Z fi ), determine the time t between the next start-up of the voltage inspection device and the signal acquisition time

[0115] t=∑phase(Z fi ) / (2nπf)+t0

[0116] Where t0 is the time between the start-up of the voltage inspection device and the signal acquisition time, and f is the frequency of the AC excitation signal.

[0117] Preferably, the impedance measurement and control device further comprises a variable resistor, wherein the variable resistor is connected to the power supply terminal of the fuel cell stack, and its control terminal is connected to the output terminal of the controller.

[0118] Preferably, the impedance measurement and control device further comprises a heating resistor and a battery. The heating resistor is arranged between any two adjacent battery cells of the fuel cell stack, and its power supply end is connected to the output end of the battery.

[0119] Preferably, the data processing unit has a display module, and the display screen of the display module displays the overall internal resistance of the fuel cell stack (for example, the sum of the internal resistances of all single cells) and the internal resistance of each single cell in the stack.

[0120] The overall internal resistance Z of the fuel cell stack f Obtained by the following formula

[0121] Z f＝ ∑Z fi

[0122] Where t0 is the time between the start-up of the voltage inspection device and the signal acquisition time, f is the frequency of the AC excitation signal, i = 1,…,n, and n is the number of single cells in the stack.

[0123] Preferably, the DC-DC converter further includes an input capacitor, an output capacitor and a multi-phase parallel branch.

[0124] The multi-phase parallel branch includes multiple boost branches connected in parallel, each of which includes a power inductor, a switch, and a diode. In each boost branch, the collector of the switch is connected to one end of the power inductor and the anode of the diode, the emitter is connected to the cathode of the fuel cell stack and one end of a variable resistor, and the base is connected to the output of the controller. The other end of the power inductor is connected to the anode of the fuel cell stack, and the cathode of the diode is connected to the other end of the variable resistor.

[0125] Preferably, the inlet gas control device further includes a control valve and an air compressor. The control valve has its input connected to the hydrogen inlet pipe, its output connected to the hydrogen inlet of the fuel cell stack, and its control terminal connected to the control terminal of the controller. The air compressor has its output connected to the air inlet of the fuel cell stack and its control terminal connected to the control terminal of the controller.

[0126] Preferably, the coolant control device further includes a thermostat, a radiator, and a water pump. The coolant output of the fuel cell stack is connected to the radiator input and thermostat port 2 via the water pump; the radiator output is connected to thermostat port 1; and thermostat port 3 is connected to the coolant input of the fuel cell stack.

[0127] Compared to Example 1, this embodiment adds a variable resistor, a heating resistor, and a battery, as well as inlet gas control equipment and coolant temperature control equipment. It also further defines the DC-DC converter and controller. These devices can measure the impedance of fuel cell cells, providing the most accurate data for battery regulation and fault diagnosis. The reliability of a fuel cell stack depends on the performance of its lowest-performing cell.

[0128] Example 3

[0129] The present invention also provides a method for measuring and controlling the impedance of a vehicle-mounted fuel cell corresponding to the apparatus of embodiments 1 and 2 above, comprising the following steps:

[0130] S1. When the stack is operating normally, start the DC-DC converter and send an AC excitation signal of a preset frequency to the stack;

[0131] S2. After the current sensor value is stable, start the voltage inspection device;

[0132] S3. Based on the feedback of the voltage of each single cell in the stack at the same moment and the current measured by the current sensor, the AC impedance of each single cell is obtained to control the operation of the stack.

[0133] While various embodiments of the present disclosure have been described above, the foregoing description is intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or improvements over the prior art, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. An impedance measurement and control device for a vehicle-mounted fuel cell, characterized in that: It includes a battery stack, a DC-DC converter, a current sensor, a voltage inspection device and a controller; among which, The DC-DC converter and the voltage inspection device are connected via a signal synchronization line; the current sensor is disposed inside the DC-DC converter; each electrode of the voltage inspection device is respectively connected to the output end of a single cell in the battery stack; and the output ends of the current sensor and the voltage inspection device are respectively connected to the input end of the controller, and the control end is respectively connected to the output end of the controller; The controller is used to start the DC-DC converter when the stack is operating normally, send an AC excitation signal of a preset frequency to the stack, and start the voltage inspection device after the value measured by the current sensor stabilizes. The AC impedance of each single cell in the stack is obtained based on the feedback of the voltage of each single cell in the stack at the same time and the current measured by the current sensor, and control the operation of the stack; The controller further comprises: A data acquisition unit is used to collect real-time data information from the output signals of the current sensor and the voltage inspection device and send it to the data processing and control unit; the data information includes the amplitude or effective value of the output current of the battery stack and the voltage amplitude or effective value of each single cell; The data processing and control unit is used to start the DC-DC converter when the fuel cell stack is operating normally, send an AC excitation signal of a preset frequency to the fuel cell stack, and start the voltage inspection device after the value measured by the current sensor stabilizes. Based on the feedback of the current amplitude at the same moment and the voltage amplitude of each single cell, the AC impedance of each single cell is obtained to control the operation of the fuel cell stack; An actuator, used to change the operating state of the fuel cell stack according to the control of the data processing unit; The execution mechanism further comprises: The inlet gas control device is used to control the flow rate and pressure of hydrogen and air entering the stack; its output end is connected to the gas inlet of the fuel cell stack, and its control end is connected to the output end of the controller; A coolant temperature regulating device is used to control the water temperature of the coolant entering the stack; its control end is connected to the output end of the controller; and the coolant inlet of the fuel cell stack is connected to its coolant outlet via the coolant temperature regulating device; The actuator also includes controllable switches 1 and 2; wherein, The controllable switch 1 is used to control the start-up of the DC-DC converter, and its output end is connected to the control end of the DC-DC converter; The controllable switch 2 is used to control the start-up of the voltage inspection device, and its output end is connected to the control end of the voltage inspection device; The data processing and control unit executes the following procedures: Obtaining real-time stack output current to determine whether the fuel cell is operating normally; if not, adjusting the fuel cell operating parameters until it is operating normally; the operating parameters include at least one of the flow rate and pressure of hydrogen and air entering the stack, and the water temperature of the coolant entering the stack; Start the DC-DC converter and send an AC excitation signal of a preset frequency to the fuel cell stack; Monitor the value measured by the current sensor, and start the voltage inspection device after the value measured by the current sensor stabilizes; Obtaining the current measured by the current sensor at the same moment after the voltage inspection device is started, and the voltage of each single battery measured by the voltage inspection device; According to the voltage and current, the amplitude and phase of the AC impedance of each single battery cell at the preset frequency are obtained; Adjusting the operating parameters of the fuel cell and controlling the operation of the fuel cell stack according to the obtained amplitude and phase of the AC impedance of each single cell; The controller executes the following procedure to determine whether the fuel cell is operating normally: Obtaining the real-time output current of the battery stack within a preset time period; Determine the effective value and maximum change of the real-time output current; determining whether the effective value of the real-time output current is within a preset range and whether the maximum variation does not exceed a preset threshold; if so, determining that the fuel cell is operating normally; otherwise, adjusting the operating parameters of the fuel cell, including the flow and pressure of hydrogen and air entering the stack, and the temperature of the coolant entering the stack, and re-determining the fuel cell until the fuel cell is determined to be operating normally; The amplitude Z of the AC impedance of the i-th single cell fi and phase(Z fi )for Z fi =ΔV i / ΔI phase(Z fi )=β2-β 1i Where ΔV is the amplitude of the voltage vector of the i-th single cell, ΔI is the amplitude of the current vector, β2 is the phase angle of the current vector, and β 1i is the phase angle of the voltage vector of the i-th single cell, i = 1,…,n, n is the number of single cells in the stack; The controller executes the following program to control the operation of the fuel cell stack: Get the magnitude Z of the AC impedance of each single cell fi and phase(Z fi ), and the magnitude ΔV of the voltage vector of each single cell; Compare each of the amplitudes ΔV with a preset value of one. If the number of cells with an amplitude ΔV less than or equal to the preset value of one exceeds the rated value, it is determined that the stack has insufficient input gas, and the flow rate and pressure of the hydrogen and air entering the stack are increased. Otherwise, the flow rate and pressure of the hydrogen and air entering the stack are maintained unchanged. Each of the amplitudes Z fi Compare with the preset value 2, if the amplitude Z fi If the number of single-cell batteries greater than or equal to the preset value 2 exceeds the rated value, the proton exchange membrane of the stack is determined to be in a dry state, and the coolant temperature regulating device is controlled to lower the water temperature of the coolant entering the stack. Otherwise, the current water temperature is maintained unchanged; According to the phase phase (Z fi ), determine the time t between the next start-up of the voltage inspection device and the signal acquisition time t=∑phase(Z fi ) / (2nπf)+t0 Where t0 is the time between the start-up of the voltage inspection device and the signal acquisition time, and f is the frequency of the AC excitation signal; The data processing and control unit has a display module; and, The display screen of the display module displays the overall internal resistance Z of the fuel cell stack f , and the internal resistance Z of each single cell in the stack fi ; The overall internal resistance Z of the fuel cell stack f Obtained by the following formula WITH f＝ ∑Z fi Where t0 is the time between the start-up of the voltage inspection device and the signal acquisition time, f is the frequency of the AC excitation signal, i = 1,…,n, and n is the number of single cells in the stack; The steps include: When the fuel cell stack is operating normally, the DC-DC converter is started to send an AC excitation signal of a preset frequency to the fuel cell stack; After the value measured by the current sensor stabilizes, start the voltage inspection device; The AC impedance of each cell is obtained based on the voltage of each cell in the stack at the same moment of feedback combined with the current measured by the current sensor to control the operation of the stack.

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