CN113823817A - Impedance measurement and control device and method for vehicle fuel cell - Google Patents

Abstract

The invention provides an impedance measurement and control device and method for a vehicle fuel cell, which belongs to the technical field of fuel cell impedance measurement, and solves the problem that the prior art 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 inspection device, and a controller. Among them, the DC-DC converter and the voltage inspection device are connected by a signal synchronization line; the current sensor is arranged inside the DC-DC converter; each electrode of the voltage inspection device is respectively connected with the output of a single cell of the stack. end connection. The controller is used to start the DC-DC converter when the stack is in normal operation, and send an AC excitation signal to the stack. After the current sensor value is stable, start the voltage inspection device. The voltage of the single cell is combined with the measured current to obtain the AC impedance of each single cell to control the operation of the stack. The function of measuring and controlling the impedance of the stack monolithic battery is realized.

Description

Impedance measurement and control device and method for vehicle fuel cell

technical field

The invention relates to the technical field of fuel cell impedance measurement, in particular to an impedance measurement and control device of a vehicle fuel cell.

Background technique

Hydrogen fuel cell vehicles are new energy vehicles with broad development prospects, which have many advantages such as short hydrogenation time and long driving range. Vehicle fuel cell systems usually include stacks and peripheral hydrogen, air, and cooling subsystems. High power output is achieved by connecting hundreds of chips in series.

AC impedance is a method to monitor the internal state of the fuel cell, which is generally realized by means of a DC/DC device, but it can only collect impedance information at the level of the entire stack. For example, patent CN105699902A proposes an impedance measuring device and method for fuel cell diagnosis, but only the overall impedance of the stack is calculated. The stack is actually composed of multiple single cells. Due to the different positions of different single cells in the stack, there will be inconsistencies in temperature, gas supply state and even current density, resulting in inconsistent impedance of the single cells. The reliability of a stack depends on the worst-performing single cell in the stack.

Patent CN111244505A proposes a method for monitoring single-chip AC impedance. The current acquisition and monolithic voltage acquisition are realized by the same device. However, in the process of product integration, in order to facilitate the independent development of components, the current acquisition function and monolithic voltage acquisition are implemented by the same device. Different hardware implementations, in the process of realizing the AC impedance function, will encounter the problem of inaccurate impedance results due to asynchronous acquisition of voltage and current signals.

SUMMARY OF THE INVENTION

The embodiments of the present invention aim to provide an impedance measurement and control device for a vehicle fuel cell, so as to solve the problem that the prior art cannot effectively measure the AC impedance of a single cell and control the operation of the stack.

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

The DC-DC converter and the voltage inspection device are connected by a signal synchronization line; the current sensor is arranged inside the DC-DC converter; each electrode of the voltage inspection device is respectively connected to the output end of a single cell of the stack ; And, the output ends of the current sensor and the voltage inspection device are respectively connected with the input ends of the controller, and the control ends are respectively connected with the output ends of the controller;

The controller is used to start the DC-DC converter when the stack is in normal operation, send an AC excitation signal of a preset frequency to the stack, and after the value measured by the current sensor is stable, start the voltage inspection device, and according to the feedback At the same time, the voltage of each single cell in the stack is combined with the current measured by the current sensor to obtain the AC impedance of each single cell to control the operation of the stack.

The beneficial effects of the above technical solutions are as follows: an impedance measurement and control device for a fuel cell is provided, which 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 impedance measurement and control functions by means of different hardware and measurement and control programs. , is conducive to the modularization, interchangeability and independent development of different hardware, flexible and convenient.

Based on a further improvement of the above device, the controller further includes:

The data acquisition unit is used to collect the real-time data information in the output signal 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 stack, each monolithic battery The voltage amplitude or effective value of ;

The data processing and control unit is used to start the DC-DC converter when the stack is in normal operation, and send an AC excitation signal with a preset frequency to the stack. After the value measured by the current sensor is stable, start the voltage inspection device. The current amplitude of the feedback at the same time is combined with the voltage amplitude of each monolithic battery to obtain the AC impedance of each monolithic battery and control the operation of the stack;

The actuator is used to change the operating state of the stack according to the control of the data processing unit.

The beneficial effect of the above-mentioned further improvement scheme is that: the structure of the controller is defined, which is used to realize the collection of state information and the measurement and control of the impedance of the fuel cell.

Further, the executive mechanism further includes:

The gas control equipment for stacking is used to control the flow and pressure of hydrogen and air entering the stack; the output end is connected to the gas inlet of the stack, and the control end is connected to the output end of the controller;

Cooling liquid temperature adjustment equipment, used to control the water temperature of the cooling liquid into the stack; its control end is connected with the output end of the controller; and the cooling liquid inlet of the stack passes through the cooling liquid temperature adjustment equipment and its cooling liquid outlet connect.

The beneficial effects of the above-mentioned further improvement scheme are: the composition of the actuator is limited, and the control of the input gas flow, the pressure and the water temperature of the cooling liquid can be performed when the vehicle is started or shut down, the residual oxygen in the fuel cell stack can be removed, and During a cold start of the vehicle, the fuel cell stack is rapidly heated to increase the activity of the fuel cell.

Further, the actuator also includes controllable switches 1 and 2; wherein,

The first controllable switch 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 second controllable switch is used to control the starting of the voltage inspection device, and its output end is connected to the control end of the voltage inspection device.

The beneficial effect of the above-mentioned further improvement scheme is that the controllable switch 1 and the controllable switch 2 are added, which can strictly control the signal acquisition time and make the measurement and control process more accurate.

Further, the data processing and control unit executes the following procedures:

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

Start the DC-DC converter and send the AC excitation signal of preset frequency to the stack;

Monitor the value measured by the current sensor, and start the voltage inspection device after the value measured by the current sensor is stable;

Obtain the current measured by the current sensor at the same moment after starting the voltage inspection device, and the voltage of each single cell measured by the voltage inspection device;

According to the above voltage and current, obtain the amplitude and phase of the AC impedance of each monolithic battery at the preset frequency;

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

The beneficial effect of the above-mentioned further improvement scheme is that the execution program of the controller is limited, the AC impedance measurement function can be realized, and the coordinated control and synchronization functions can be realized.

Further, the controller executes the following program to determine whether the fuel cell is operating normally:

Obtain the real-time output current of the stack within a preset period;

Determine the effective value and the maximum variation of the above real-time output current;

Determine whether the effective value of the above-mentioned real-time output current is within the preset range, and at the same time satisfy that the maximum change does not exceed the preset threshold; if so, determine that the fuel cell is operating normally; otherwise, adjust the operating parameters of the fuel cell, including the hydrogen and The air flow, pressure, and water temperature of the cooling liquid into the stack are judged again until it is judged that the fuel cell is operating normally.

The beneficial effect of the above-mentioned further improvement scheme is that: the method for judging whether the fuel cell is in normal operation is limited, and whether the effective value of the output current is within the preset range can be strictly judged through the real-time output current of the stack, and at the same time, the maximum change amount can be satisfied. does not exceed the preset threshold. In fact, the accurate AC impedance of the fuel cell cannot be obtained from the data of the fuel cell during abnormal operation, which will interfere with the user's judgment. Base.

Further, the amplitude Z _fi and phase ( Z _fi ) of the AC impedance of the ith monolithic battery are

Z _fi = ΔVi / _ΔI

phase( Z _fi )= β ₂ - β _{1 i}

In the formula, ΔV is the amplitude of the voltage vector of the i -th monolithic battery, ΔI is the amplitude of the current vector, β2 is the phase angle of the current vector, and _β1i is the voltage vector of the _i - th monolithic battery , i =1,…, n , where n is the number of monolithic cells in the stack.

The beneficial effect of the above-mentioned further improvement scheme is that the amplitude and phase determination methods of the AC impedance of each single cell are limited. It lays the foundation for the subsequent control of the stack operation.

Further, the controller executes the following program to control the operation of the stack:

Obtain the amplitude Z _fi and phase ( Z _fi ) of the AC impedance of each single cell, and the amplitude ΔV of the voltage vector of each single cell;

Each of the amplitudes ΔV is compared with the preset value 1, and if the number of single-chip cells with the amplitude ΔV less than or equal to the preset value 1 exceeds the rated value, it is determined that the input gas of the stack is insufficient, and the stacking is controlled. The flow and pressure of hydrogen and air increase, otherwise, the flow and pressure of hydrogen and air into the stack will remain unchanged;

Compare each of the amplitude Z _fi with the preset value 2, if the number of single-chip cells with the amplitude Z _fi greater than or equal to the preset value 2 exceeds the rated value, it is determined that the proton exchange membrane of the stack is in a dry state, and the control is performed. The cooling liquid temperature adjustment equipment reduces the water temperature of the cooling liquid entering the stack, otherwise, the current water temperature remains unchanged;

According to the phase ( Z _fi ), determine the time t between the time when the voltage inspection device is started next time and the time when the signal is collected

t=∑ phase( Z _fi )/(2 n π f ) + t ₀

In the formula, t ₀ is the time from the moment when the voltage inspection device is started to the time of signal acquisition, and f is the frequency of the AC excitation signal.

The beneficial effect of the above-mentioned further improvement scheme is that: the method for controlling the operation of the stack according to the impedance of the monolithic battery is limited, and the time between the time when the voltage inspection device is started and the time when the signal is collected can be more accurately controlled during a low temperature cold start. time t to ensure the accuracy of the collected data.

Further, the data processing and control unit has a display module; and,

The display screen of the display module displays the overall internal resistance Z _f of the fuel cell stack and the internal resistance Z _fi of each single cell in the stack;

The overall internal resistance Z _f of the fuel cell stack is obtained by the following formula

Z _{f =} ∑ Z _fi

In the formula, t ₀ is the time between the moment of starting the voltage inspection device and the time of signal acquisition, f is the frequency of the AC excitation signal, i = 1,…, n , n is the number of monolithic cells in the stack .

The beneficial effects of the above-mentioned further improvement scheme are: the display module and the displayed content are limited, and the fuel cell stack is composed of a plurality of single cells. There will be inconsistencies in the supply state and even the current density, resulting in inconsistencies in the impedance of the cells. The reliability of a stack depends on the state of the worst performing cells in the stack. The impedance of the above single cell can provide the most accurate data for the fault diagnosis of the fuel cell.

On the other hand, an embodiment of the present invention provides an impedance measurement and control method for a vehicle fuel cell corresponding to the above device, including the following steps:

When the stack is in normal operation, start the DC-DC converter and send the AC excitation signal of preset frequency to the stack;

After the value measured by the current sensor is stable, start the voltage inspection device;

According to the feedback of the voltage of each single cell in the stack at the same time, combined with the current measured by the current sensor, the AC impedance of each single cell is obtained, and the operation of the stack is controlled.

The beneficial effects of adopting the above scheme are as follows: an impedance measurement and control method for a fuel cell 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 the impedance measurement and the control function by means of the measurement and control program, which is flexible and convenient. .

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.

Description of drawings

The above and other objects, features and advantages of the present disclosure will become more apparent from the more detailed description of the exemplary embodiments of the present disclosure, taken in conjunction with the accompanying drawings, wherein the same reference numerals generally refer to the exemplary embodiments of the present disclosure. same parts.

Fig. 1 shows the composition schematic diagram of the impedance measurement and control device of Embodiment 1;

Fig. 2 shows the circuit connection schematic diagram of the impedance measurement and control device of Embodiment 1;

FIG. 3 shows a schematic diagram of the composition of the impedance measurement and control device of the second embodiment.

Reference number:

41- end plate of the stack; 42- insulating plate; 43- collector plate; 44- monolithic battery; 10- DC-DC converter; 11- current sensor inside the DC-DC converter; 20- signal synchronization line ; 30- controller; 50- voltage inspection device.

Detailed ways

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 drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

As used herein, the term "including" and variations thereof mean open-ended inclusion, ie, "including but not limited to". The term "or" means "and/or" unless specifically stated otherwise. The term "based on" means "based at least in part on". The terms "one example embodiment" and "one 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.

Example 1

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

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

The above signal synchronization line is used for the trigger synchronization or clock synchronization function of the voltage inspection device to collect the voltage signal of the monolithic battery and the DC-DC converter to collect the current signal when the AC impedance function is turned on. Optionally, an existing signal synchronization line, such as the signal synchronization line in the patent CN201910237668.0, etc. can be used.

The current sensor is used to collect the output current (signal) of the stack.

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

The controller is used to start the DC-DC converter when the stack is in normal operation, and send an AC excitation signal of a preset frequency to the stack. After the value measured by the current sensor is stable, start the voltage inspection device. At time, the voltage of each single cell in the stack is combined with the current measured by the current sensor to obtain the AC impedance of each single cell to control the operation of the stack.

Optionally, in the program executed by the controller, the above-mentioned basis for judging the normal operation of the stack may be the output current, voltage or power of the stack. The output current, voltage or power of the stack is compared with the preset range of normal operation that has been calibrated in advance. If it falls within the preset range, it is determined that the stack is in normal operation, otherwise, it is abnormal.

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

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

Optionally, the controller can obtain the AC impedance Z of the monolithic battery by the following formula, or use the method described in Embodiment 2 to obtain the amplitude and phase of the AC impedance of the monolithic battery.

Z = U / I (1)

In the formula, U is the voltage vector of the i -th monolithic battery collected by the voltage inspection device, and I is the current vector collected by the current and current sensor.

Optionally, controlling the operation of the stack includes controlling the flow and pressure of hydrogen and air entering the stack, the water temperature of the cooling liquid entering the stack, and the timing (or time) of signal acquisition, which can be understood by those skilled in the art, and is not detailed here. limited. Exemplarily, the amplitude or phase of the AC impedance can be compared with a plurality of thresholds, thereby obtaining the adjustment information of the flow rate, pressure of the incoming hydrogen and air, the water temperature of the incoming cooling liquid, and the signal acquisition time.

Compared with the prior art, this embodiment provides a new type of impedance measurement and control device for fuel cells, 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 the impedance measurement function by means of different hardware. It is conducive to the modularization, interchangeability and independent development of different hardware, and is flexible and convenient.

Example 2

Improvements are made on the basis of Embodiment 1. The controller further includes a data acquisition unit, a data processing and control unit, and an executive mechanism that are connected in sequence, as shown in FIG. 3 . The input end of the data acquisition unit is respectively connected with the output end of the current sensor and the voltage inspection device; the output end of the actuator is respectively connected with the control end of the DC-DC converter, the voltage inspection device and the operation state of the stack. Specifically, the control end of the operating state of the stack includes the stack air hydrogen, the hydrogen input end, the cooling liquid inlet and the like of the stack.

The data acquisition unit is used to collect the real-time data information in the output signal 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 stack, each monolithic battery The voltage amplitude or rms value.

The data processing and control unit is used to start the DC-DC converter when the stack is in normal operation, and send an AC excitation signal with a preset frequency to the stack. After the value measured by the current sensor is stable, start the voltage inspection device. The current amplitude of the feedback at the same time is combined with the voltage amplitude of each monolithic battery to obtain the AC impedance of each monolithic battery to control the operation of the stack.

The actuator is used to start the DC-DC converter, the voltage inspection device, or change the operating state of the stack according to the control of the data processing unit.

Preferably, the actuator further includes a stack inlet gas control device, a coolant temperature adjustment device, and controllable switches 1 and 2. Among them, the output end of the gas control device for entering the stack is connected to the gas inlet of the stack, and the control end is connected to the output end of the controller; the cooling liquid inlet of the stack is connected to its cooling liquid outlet through the above-mentioned cooling liquid temperature adjusting device; the cooling liquid temperature The control end of the regulating device is connected to the output end of the controller. The output end of the controllable switch 1 is connected with the control end of the DC-DC converter; the output end of the controllable switch 2 is connected with the control end of the voltage inspection device.

The reactor entry gas control equipment is used to control the flow and pressure of hydrogen and air into the reactor.

Coolant temperature adjustment equipment, used to control the water temperature of the cooling liquid into the stack.

The controllable switch 1 is used to control the starting of the DC-DC converter.

The second controllable switch is used to control the startup of the voltage inspection device.

Preferably, the data processing and control unit executes the following procedures:

SS1. Obtain the real-time output current of the stack to determine whether the fuel cell is operating normally; if it is not operating normally, adjust the operating parameters of the fuel cell until it is operating normally; the operating parameters include the flow, pressure, and at least one of the water temperatures of the stack coolant;

SS2. Start the DC-DC converter and send the AC excitation signal of preset frequency to the stack;

SS3. Monitor the value measured by the current sensor, and start the voltage inspection device after the value measured by the current sensor is stable;

SS4. Obtain the current measured by the current sensor at the same moment after starting the voltage inspection device, and the voltage of each single battery measured by the voltage inspection device;

SS5. According to the above-mentioned voltage and current, obtain the amplitude and phase of the AC impedance of each monolithic battery at the preset frequency;

SS6. According to the obtained amplitude and phase of the AC impedance of each single cell, adjust the operating parameters of the fuel cell and control the operation of the stack.

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

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

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

SS13. Determine whether the effective value of the above-mentioned real-time output current is within the preset range, and at the same time, the maximum change does not exceed the preset threshold; if so, determine that the fuel cell is operating normally; otherwise, adjust the operating parameters of the fuel cell, including stacking The flow and pressure of hydrogen and air, as well as the water temperature of the cooling liquid entering the stack, are judged again until it is judged that the fuel cell is operating normally.

Preferably, the controller obtains the amplitude Z _fi and phase ( Z _fi ) of the AC impedance of the i -th monolithic battery through the following formulas:

Z _fi = ΔVi / _ΔI

phase( Z _fi )= β ₂ - β _{1 i}

In the formula, ΔV is the amplitude of the voltage vector of the i -th monolithic battery, ΔI is the amplitude of the current vector, β2 is the phase angle of the current vector, and _β1i is the voltage vector of the _i - th monolithic battery , i =1,…, n , where n is the number of monolithic cells in the stack.

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

SS61. Obtain the amplitude Z _fi and phase phase ( Z _fi ) of the AC impedance of each monolithic battery, and the amplitude ΔV of the voltage vector of each monolithic battery;

SS62. Compare each of the amplitudes ΔV with the preset value 1. If the number of single-chip cells with the amplitude ΔV less than or equal to the preset value 1 exceeds the rated value, it is determined that the input gas of the stack is insufficient, and the control is performed. The flow and pressure of the hydrogen and air entering the stack will increase, otherwise, the flow and pressure of the hydrogen and air entering the stack will remain unchanged;

SS63. Compare each of the amplitude Z _fi with the preset value 2. If the number of single-chip cells with the amplitude Z _fi greater than or equal to the preset value 2 exceeds the rated value, it is determined that the proton exchange membrane of the stack is in a dry state. , control the cooling liquid temperature adjustment equipment to reduce the water temperature of the cooling liquid entering the stack, otherwise, keep the current water temperature unchanged;

SS64. According to the phase ( Z _fi ), determine the time t between the time when the voltage inspection device is started next time to the time when the signal is collected

t=∑ phase( Z _fi )/(2 n π f ) + t ₀

In the formula, t ₀ is the time from the moment when the voltage inspection device is started to the time of signal acquisition, and f is the frequency of the AC excitation signal.

Preferably, the impedance measurement and control device further includes a variable resistor. Wherein, the variable resistor is connected with the power supply end of the fuel cell stack, and the control end thereof is connected with the output end of the controller.

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

Preferably, the data processing unit has a display module. In addition, 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.

The overall internal resistance Z _f of the fuel cell stack is obtained by the following formula

Z _{f =} ∑ Z _fi

In the formula, t ₀ is the time between the moment of starting the voltage inspection device and the time of signal acquisition, f is the frequency of the AC excitation signal, i = 1,…, n , n is the number of monolithic cells in the stack .

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

The multi-phase parallel branch includes multiple boost branches connected in parallel with each other, and each boost branch includes a power inductor, a switch tube and a diode. In each boost branch, the collector of the switch tube is respectively connected to one end of the power inductor and the anode of the diode, and the emitter is respectively connected to the negative electrode of the fuel cell stack and one end of the variable resistor. The pole is connected to the output end of the controller; the other end of the power inductor is connected to the anode of the fuel cell stack; the cathode of the diode is connected to the other end of the variable resistor.

Preferably, the in-stack gas control equipment further includes a control valve and an air compressor. The input end of the control valve is connected with the hydrogen gas inlet pipe, the output end is connected with the hydrogen inlet of the fuel cell stack, and the control end is connected with the control end of the controller. The output end of the air compressor is connected to the air inlet of the stack, and its control end is connected to the control end of the controller.

Preferably, the coolant control device further includes a thermostat, a radiator and a water pump. The coolant output end of the fuel cell stack is respectively connected to the input end of the radiator and the second port of the thermostat through the water pump; the output end of the radiator is connected to the first port of the thermostat; the third port of the thermostat is connected to the second port of the thermostat. The cooling liquid input terminal of the stack is connected.

Compared with Embodiment 1, this embodiment adds variable resistors, heating resistors and batteries, as well as stack gas control equipment and coolant temperature adjustment equipment, and further defines the mechanisms of DC-DC converters and controllers. The above device can measure the impedance of the fuel cell, and provide the most accurate data for the regulation and fault diagnosis of the battery. The reliability of the stack depends on the single cell with the worst performance in the stack.

Example 3

The present invention also provides a method for measuring and controlling the impedance of a vehicle fuel cell corresponding to the devices of the above-mentioned Embodiments 1 and 2, comprising the following steps:

S1. When the stack is in normal operation, start the DC-DC converter and send an AC excitation signal with a preset frequency to the stack;

S2. After the value measured by the current sensor is stable, start the voltage inspection device;

S3. Obtain the AC impedance of each single cell according to the voltage of each single cell in the stack at the same time fed back and the current measured by the current sensor, and control the operation of the stack.

Various embodiments of the present disclosure have been described above, and the foregoing descriptions are exemplary, not exhaustive, and not limiting of the disclosed embodiments. Numerous modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the various embodiments, the practical application or improvement over the prior art, or to enable others of ordinary skill in the art to understand the various embodiments disclosed herein.

Claims (10)

1. An impedance measurement and control device of a vehicle-mounted fuel cell is characterized by comprising an electric pile, a DC-DC converter, a current sensor, a voltage inspection device and a controller; wherein,

the DC-DC converter and the voltage inspection device are connected through a signal synchronization line; the current sensor is arranged inside the DC-DC converter; each electrode of the voltage inspection device is respectively connected with the output end of a single battery of the electric pile; the output ends of the current sensor and the voltage inspection device are respectively connected with the input end of the controller, and the control ends are respectively connected with the output end of the controller;

the controller is used for starting the DC-DC converter when the galvanic pile normally operates, sending an alternating current excitation signal with preset frequency to the galvanic pile, starting the voltage inspection device after the value measured by the current sensor is stable, and controlling the operation of the galvanic pile by obtaining the alternating current impedance of each single battery according to the voltage of each single battery in the galvanic pile at the same feedback moment and the current measured by the current sensor.

2. The impedance measurement and control device of the vehicle-mounted fuel cell according to claim 1, wherein the controller further comprises:

the data acquisition unit is used for acquiring real-time data information in output signals of the current sensor and the voltage inspection device and sending the real-time data information to the data processing and control unit; the data information comprises the amplitude or effective value of the output current of the electric pile, and the amplitude or effective value of the voltage of each single battery;

the data processing and control unit is used for starting the DC-DC converter when the galvanic pile normally operates, sending an alternating current excitation signal with preset frequency to the galvanic pile, starting the voltage inspection device after the value measured by the current sensor is stable, combining the current amplitude with the voltage amplitude of each single battery at the same moment according to feedback to obtain the alternating current impedance of each single battery, and controlling the operation of the galvanic pile;

and the execution mechanism is used for changing the running state of the electric pile according to the control of the data processing unit.

3. The impedance measurement and control device for the vehicle-mounted fuel cell according to claim 2, wherein the actuator further comprises:

the reactor gas control equipment is used for controlling the flow and pressure of reactor hydrogen and air; the output end of the controller is connected with the gas inlet of the galvanic pile, and the control end of the controller is connected with the output end of the controller;

a coolant temperature adjusting device for controlling a temperature of the cooling liquid fed into the stack; the control end of the controller is connected with the output end of the controller; and a coolant inlet of the cell stack is connected to a coolant outlet thereof through the coolant temperature adjusting apparatus.

4. The impedance measurement and control device of the vehicle-mounted fuel cell according to claim 2 or 3, wherein the actuator further comprises a first controllable switch and a second controllable switch; wherein,

the controllable switch I is used for controlling the starting of the DC-DC converter, and the output end of the controllable switch I is connected with the control end of the DC-DC converter;

and the controllable switch II is used for controlling the starting of the voltage inspection device, and the output end of the controllable switch II is connected with the control end of the voltage inspection device.

5. The impedance measurement and control device of a vehicle-mounted fuel cell according to any one of claims 1 to 3, wherein the data processing and control unit executes the following program:

acquiring real-time electric pile output current and judging whether the fuel cell normally operates or not; if the fuel cell is abnormally operated, adjusting the operation parameters of the fuel cell until the fuel cell is normally operated; the operation parameters comprise at least one of flow rate, pressure and water temperature of reactor entering cooling liquid of reactor entering hydrogen and air;

starting the DC-DC converter and sending an alternating current excitation signal with preset frequency to the galvanic pile;

monitoring the value measured by the current sensor, and starting the voltage inspection device after the value measured by the current sensor is stable;

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;

obtaining the amplitude and the phase of the alternating current impedance of each single battery under the preset frequency according to the voltage and the current;

and adjusting the operation parameters of the fuel cell according to the obtained amplitude and phase of the alternating current impedance of each single cell, and controlling the operation of the electric pile.

6. The impedance measurement and control device of the vehicle-mounted fuel cell according to claim 5, wherein the controller executes the following program to determine whether the fuel cell is operating normally:

acquiring real-time output current of the galvanic pile in a preset time period;

determining the effective value and the maximum variation of the real-time output current;

judging whether the effective value of the real-time output current is within a preset range or not, and simultaneously, meeting the condition that the maximum variation does not exceed a preset threshold; if yes, judging that the fuel cell normally operates; otherwise, adjusting the operation parameters of the fuel cell, including the flow and pressure of the hydrogen and air in the stack and the water temperature of the cooling liquid in the stack, and judging again until the fuel cell is judged to normally operate.

7. The on-vehicle fuel cell impedance measurement and control device of claim 6, wherein the second step isiAmplitude of AC impedance of single-chip batteryZ _fi And phase (Z _fi ) Is composed of

Z _fi =ΔV _i /ΔI

phase(Z _fi )=β ₂ -β _i1

In the formula,. DELTA.VIs as followsiMagnitude of voltage vector, Delta, of individual monolithic cellsIIs the magnitude of the current vector and,β ₂ is the phase angle of the current vector,β _i1is as followsiThe phase angle of the voltage vector of the individual monolithic cells,i=1,…,n，nis the number of single cells in the stack.

8. The on-vehicle fuel cell impedance measurement and control device according to any one of claims 1 to 3 and 6 to 7, wherein the controller executes the following program to control stack operation:

obtaining the amplitude of the AC impedance of each single batteryZ _fi And phase (Z _fi ) And the magnitude of the voltage vector of each monolithic cellV；

Each of the amplitudes ΔVRespectively, are compared with a preset value one if the amplitude value deltaVIf the number of the single-chip batteries smaller than or equal to the preset value I exceeds a rated value, judging that the input gas of the galvanic pile is insufficient, and controlling the flow and pressure of the hydrogen and air entering the galvanic pile to increase, otherwise, maintaining the flow and pressure of the hydrogen and air entering the galvanic pile unchanged;

each of the amplitude valuesZ _fi Comparing with the second preset value, if the amplitude value is larger than the second preset valueZ _fi If the number of the single-chip batteries greater than or equal to the second preset value exceeds a rated value, the proton exchange membrane of the galvanic pile is judged to be in a dry state, the cooling liquid temperature regulating equipment is controlled to reduce the water temperature of the cooling liquid entering the galvanic pile, and if not, the current water temperature is maintained unchanged;

according to said phase (Z _fi ) Determining the time from the next starting time of the voltage inspection device to the signal acquisition timet

t=∑phase(Z _fi )/（2nπf）+t ₀

In the formula,t ₀the time from the moment of starting the voltage inspection device to the moment of signal acquisition,fthe frequency of the ac excitation signal.

9. The impedance measurement and control device of the vehicle-mounted fuel cell according to claim 8, wherein the data processing and control unit has a display module; and,

the display screen of the display module displays the integral internal resistance of the fuel cell stackZ _f And the internal resistance of each single cell in the stackZ _fi ；

The overall internal resistance of the fuel cell stackZ _f Obtained by the following formula

Z _f= ∑Z _fi

In the formula,t ₀the time from the moment of starting the voltage inspection device to the moment of signal acquisition,fis the frequency of the ac excitation signal,i=1,…,n，nis the number of single cells in the stack.

10. An impedance measurement and control method of a vehicle-mounted fuel cell corresponding to the device according to claims 1-9, characterized by comprising the following steps:

when the galvanic pile normally operates, starting the DC-DC converter, and sending an alternating current excitation signal with preset frequency to the galvanic pile;

starting the voltage inspection device after the value measured by the current sensor is stable;

and according to the voltage of each single battery in the galvanic pile at the same time and the current measured by the current sensor, the alternating current impedance of each single battery is obtained, and the galvanic pile is controlled to operate.

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