A fuel cell stack test bench and back pressure control method

Abstract

The present invention relates to the field of fuel cell production technology, and specifically to a fuel cell stack test bench and a back pressure control method, wherein the fuel cell stack test bench includes a hydrogen system, an air system, and a cooling system connected to the fuel cell stack, and a control system for controlling the hydrogen system, the air system, and the cooling system; the hydrogen system includes a hydrogen intake module and a hydrogen exhaust module, the hydrogen intake module is connected to the air inlet of the fuel cell stack, and the hydrogen exhaust module is connected to the air outlet of the fuel cell stack. The present invention eliminates the influence of the inherent error characteristics of the mechanical back pressure valve through a specific control algorithm and controller structure, and is matched with a parallel switch valve to minimize the back pressure blind area within the full flow range. Compared with the electronically controlled back pressure valve, the back pressure control accuracy of the present invention is higher and the dynamic error is smaller. At the same time, the back pressure range is wider at large flow rates.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cell production and processing, and in particular to a fuel cell stack test bench and a back pressure control method. Background Art

[0002] A fuel cell is a chemical device that converts the chemical energy of a fuel directly into electrical energy, also known as an electrochemical generator. It is the fourth power generation technology after hydropower, thermal power generation, and atomic power generation. Since fuel cells convert part of the Gibbs free energy in the chemical energy of a fuel into electrical energy through electrochemical reactions, they are not limited by the Carnot cycle effect, so they are highly efficient. At the same time, fuel cells use fuel and oxygen as raw materials, and have no mechanical transmission parts, so there is no noise pollution, and very few harmful gases are emitted. Common fuel cells include hydrogen-oxygen fuel cells, solid oxide fuel cells, and methanol fuel cells. As traditional fossil fuels are becoming less and less in the context of large-scale development and utilization by humans, in recent years, the development and utilization of environmentally friendly energy such as hydrogen energy has received increasing attention. Hydrogen-oxygen fuel cells, as an important direction for the application of hydrogen energy, have been increasingly valued by people, and research and development have been continuously carried out, and new products have emerged in an endless stream. Large-scale production of fuel cells to reduce costs has become a consensus and trend. As an important part of accelerating the implementation of the industry, the demand for fuel cell testing equipment is increasing day by day, and the requirements for various performance indicators are becoming higher and more diversified. One of the important indicators is the back pressure control accuracy. However, the back pressure control accuracy is often difficult to guarantee when facing a wide range of flow and pressure conditions.

[0003] Fuel cell stack detection equipment often adopts two back pressure methods: electronically controlled back pressure and mechanical back pressure. Electronically controlled back pressure detects the back pressure point pressure value in real time and adjusts the valve opening in real time through a closed-loop control algorithm. Due to the serious model nonlinearity, traditional control algorithms are difficult to adapt to different flow and pressure conditions, and can often only maintain satisfactory control accuracy near the operating point. In addition, the flow coefficient of the electronically controlled back pressure valve that existing manufacturers can provide is generally small. For high-power stack detection equipment, the pressure loss is too large at large flow rates, and low back pressure values ​​are difficult to achieve. The mechanical back pressure valve is gradually recognized by the market for its good dynamic performance and low pressure loss. In principle, it is easier to adapt to a wide range of changing conditions. Its inlet pressure automatically follows the reference pressure and remains approximately equal. However, when the flow rate increases, the back pressure error will also increase. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a fuel cell stack test bench and a back pressure control method using the above fuel cell stack test bench.

[0005] The present invention is implemented by the following scheme:

[0006] A fuel cell stack test bench is used to test a fuel cell stack, wherein the fuel cell stack has an air inlet and an air outlet, and comprises a hydrogen system connected to the fuel cell stack, an air system connected to the fuel cell stack, a cooling system connected to the fuel cell stack, and a control system for controlling the hydrogen system, the air system, and the cooling system; the hydrogen system comprises a hydrogen intake module and a hydrogen exhaust module, the hydrogen intake module is connected to the air inlet of the fuel cell stack, and the hydrogen exhaust module is connected to the air outlet of the fuel cell stack; the hydrogen exhaust module comprises a terminal processing unit connected to the air outlet of the fuel cell stack, a mechanical back pressure valve arranged between the terminal processing unit and the air outlet of the fuel cell stack, and a first pressure sensor arranged between the mechanical back pressure valve and the air outlet of the fuel cell stack.

[0007] Furthermore, the hydrogen exhaust module also includes a first switch valve, and the first switch valve and the mechanical back pressure valve are in parallel relationship.

[0008] Furthermore, the hydrogen exhaust module also includes a first switch valve, a second switch valve, and a third switch valve. The first switch valve is connected in parallel with the mechanical back pressure valve and then in series with the second switch valve. One end of the third switch valve is connected to the terminal processing unit, and the other end of the third switch valve is connected between the second switch valve and the exhaust port of the fuel cell stack.

[0009] Furthermore, the hydrogen exhaust module also includes a first switch valve and a second switch valve, the second switch valve is connected in series between the mechanical back pressure valve and the first pressure sensor, one end of the first switch valve is connected to the terminal processing unit, and the other end of the first switch valve is connected between the second switch valve and the exhaust port of the fuel cell stack.

[0010] Furthermore, the hydrogen intake module includes a hydrogen flow controller connected to the intake port of the fuel cell stack, and a second hydrogen pressure sensor arranged between the hydrogen flow controllers.

[0011] Furthermore, the hydrogen intake module is also provided with a hydrogen flow controller.

[0012] Furthermore, the mechanical back-pressure valve is a pneumatic pressure balanced back-pressure valve.

[0013] A back pressure control method, using the aforementioned fuel cell stack test bench, is characterized in that the control system collects the pressure value of the fuel cell stack air inlet and the pressure value of the fuel cell stack exhaust in real time, compares the two measured pressure values ​​with the target values, calculates the reference pressure value of the back pressure valve in real time through a closed-loop control algorithm, and controls the pressure regulating valve to output the reference pressure in real time.

[0014] Furthermore, the control system collects the pressure value of the fuel cell stack air inlet and the pressure value of the fuel cell stack exhaust port in real time. When the hydrogen backpressure point is set at the fuel cell stack exhaust port, the exhaust port closed-loop control is performed, the fuel cell stack exhaust port pressure is compared with the target value of the fuel cell stack exhaust port pressure in real time, and the closed-loop control calculation is performed through the first controller, and the calculated control quantity is output to the pressure regulating valve; when the hydrogen backpressure point is set at the fuel cell stack air inlet, the air inlet closed-loop control is performed, the target value is compared with the fuel cell stack air inlet pressure in real time, the output value is calculated by the second controller, and the target value of the fuel cell stack exhaust port is then closed-loop controlled.

[0015] Furthermore, an identification model is established in advance, and during the closed-loop control of the exhaust port, the given value of the hydrogen flow controller in the hydrogen intake module is used as the input of the identification model to obtain a feedforward control quantity, which is applied to the input quantity of the pressure regulating valve; the given value is the detection value of the flow sensor connected in series before the mechanical back pressure valve.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention eliminates the influence of the inherent error characteristics of the mechanical back pressure valve through a specific control algorithm and controller structure, and is matched with a parallel switch valve to minimize the back pressure blind area within the full flow range. Compared with the electronically controlled back pressure valve, the back pressure control accuracy of the present invention is higher, the dynamic error is smaller, and the back pressure range is wider at large flow rates. On the other hand, the present invention can use double closed-loop control to shield the characteristics of the fuel cell stack from the inner loop control, effectively reducing the difficulty of setting the control parameters and improving the control performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of a fuel cell stack test bench of the present invention.

[0019] Figure 2 It is a schematic diagram of a hydrogen system of a fuel cell stack test bench of the present invention.

[0020] Figure 3 This is a schematic diagram of Example 2 of a hydrogen system for a fuel cell stack test bench of the present invention.

[0021] Figure 4 This is a schematic diagram of Example 3 of a hydrogen system for a fuel cell stack test bench of the present invention.

[0022] Figure 5 It is a schematic diagram of a preferred scheme for back pressure control of a hydrogen system of a fuel cell stack test bench of the present invention.

[0023] The figure includes:

[0024] 100-Fuel cell stack test bench; 200-Hydrogen system; 300-Air system; 400-Cooling system; 500-Control system; 600-Fuel cell stack; 210-Hydrogen intake module; 202-Hydrogen flow controller; 203-Second pressure sensor, 204-First pressure sensor; 205-Mechanical back pressure valve; 206-First switch valve; 207-Terminal processing unit; 208-Second switch valve; 209-Third switch valve; 220-Hydrogen exhaust module ;701-target value of fuel cell stack air inlet pressure;702-second controller;703-first controller;704-input quantity of pressure regulating valve;705-pressure regulating valve;706-pressure model of mechanical back pressure valve;707-fuel cell stack exhaust pressure;708-pressure model of fuel cell stack;709-fuel cell stack air inlet pressure;710-given value of hydrogen flow controller;711-feedforward controller;712-target value of fuel cell stack exhaust pressure. DETAILED DESCRIPTION

[0025] To facilitate those skilled in the art to understand the present invention, the present invention will be further described in detail below in conjunction with specific embodiments and drawings.

[0026] Example 1

[0027] Reference Figure 1 , Figure 2 The present invention provides a fuel cell stack test bench for testing a fuel cell stack 600, wherein the fuel cell stack 600 has an air inlet and an air outlet, and includes a hydrogen system 200 connected to the fuel cell stack 600, an air system 300 connected to the fuel cell stack 600, a cooling system 400 connected to the fuel cell stack, and a control system 500 for controlling the hydrogen system 200, the air system 300, and the cooling system 400; the hydrogen system 200 includes a hydrogen intake module 210 and a hydrogen exhaust module 220, wherein the hydrogen intake module is connected to the air inlet of the fuel cell stack, and the hydrogen exhaust module is connected to the air outlet of the fuel cell stack; the hydrogen exhaust module includes a terminal treatment unit 207 connected to the air outlet of the fuel cell stack, a mechanical back pressure valve 205 disposed between the terminal treatment unit 207 and the air outlet of the fuel cell stack, and a first pressure sensor disposed between the mechanical back pressure valve and the air outlet of the fuel cell stack. The connection of the various components in the present invention can be connected through pipelines. The terminal treatment unit 207 may be used to treat the gas exhausted from the fuel cell stack.

[0028] The hydrogen exhaust module further includes a first switch valve 206, which is connected in parallel with the mechanical back pressure valve. That is, the first switch valve and the mechanical back pressure valve are connected in parallel with the terminal processing unit 207 and the fuel cell stack at both ends. The first pressure sensor is arranged at Figure 2 The connection on the right side of the first switch valve and the mechanical back pressure valve shown in FIG.

[0029] The hydrogen intake module includes a hydrogen flow controller connected to the air inlet of the fuel cell stack, and a second hydrogen pressure sensor arranged between the hydrogen flow controllers. The hydrogen intake module is also provided with a hydrogen flow controller. The mechanical back pressure valve is a gas pressure balanced back pressure valve, which has a higher back pressure accuracy than the traditional spring back pressure valve.

[0030] The hydrogen flow controller 202 is close to the gas supply end of the fuel cell stack test bench 100 (the reference numeral 201 refers to the gas supply end or a component connected to the gas supply end), and detects and controls the gas flow. The second pressure sensor 203 is close to the output end of the hydrogen intake module 210. The output end of the hydrogen intake module 210 is connected to the hydrogen intake port of the fuel cell stack 600 through a pipeline. The hydrogen exhaust port of the fuel cell stack 600 is connected to the inlet of the hydrogen exhaust module 220 through a pipeline. The outlet end of the hydrogen intake module 210 and / or the inlet end of the hydrogen exhaust module 220 are provided with a second pressure sensor / 203 a first pressure sensor 204, which is used to detect the pressure value of the hydrogen intake port and / or the hydrogen exhaust port of the fuel cell stack. The hydrogen exhaust port of the fuel cell stack 600 is connected to the inlet end of the hydrogen exhaust module 220 through a pipeline, and a mechanical back pressure valve 205 is connected to the inlet end of the hydrogen exhaust module 220 through a pipeline, and the mechanical back pressure valve 205 is connected in parallel with a first switch valve 206, and then connected to the terminal processing part 207 of the hydrogen exhaust module 220 through a pipeline. The parallel first switch valve 206 is opened when it needs to be connected to the atmosphere, otherwise it is closed. The air system 300 has the same or similar structure as the hydrogen system 200. Unless otherwise specified, the structural topology and hydrogen back pressure control method of the hydrogen system 200 of the present invention are fully applicable to the air system 300. The outlet and inlet of the cooling system 400 are respectively connected to the cooling water inlet and cooling water outlet of the fuel cell stack 600 through pipelines, and the inlet temperature and outlet temperature of the fuel cell stack 600 are ensured to be within the target range by water circulation.

[0031] Example 2

[0032] Reference Figure 1 , Figure 3The hydrogen exhaust module also includes a first switch valve 206, a second switch valve 208, and a third switch valve 209. The first switch valve is connected in parallel with the mechanical back pressure valve and then connected in series with the second switch valve. One end of the third switch valve is connected to the terminal processing unit 207, and the other end of the third switch valve is connected between the second switch valve and the exhaust port of the fuel cell stack. That is, after the mechanical back pressure valve and the first switch valve are connected in parallel, the parallel body of the two is connected in series with the second switch valve, and the third switch valve is connected to the pipeline between the second switch valve and the exhaust port of the fuel cell stack. The first pressure sensor is arranged in Figure 4 The third switch valve and the aforementioned pipeline connection shown in. The other parts of the structure of this embodiment are the same as those of embodiment 1, and will not be described here in detail.

[0033] Before the mechanical back pressure valve 205 is connected in parallel with the first switch valve 206, a second switch valve 208 is first connected in series, and then connected in parallel with the third switch valve 209. When the pipeline needs to be connected to the atmosphere, the first switch valve 206 and the second switch valve 208 are opened, and the third switch valve 209 is closed, otherwise the second switch valve 208 is closed. When in the pulse row mode, the first switch valve 206 and the second switch valve 208 are closed, and the third switch valve 209 is periodically opened or closed. This solution is applicable to fuel cell stack test benches of all power ranges.

[0034] Example 3

[0035] Reference Figure 1 , Figure 4 The hydrogen exhaust module further includes a first switch valve 206 and a second switch valve 208, wherein the second switch valve is connected in series between the mechanical back pressure valve 205 and the first pressure sensor 204, one end of the first switch valve is connected to the terminal processing unit, and the other end of the first switch valve is connected between the second switch valve and the exhaust port of the fuel cell stack (where the first pressure sensor is arranged). The other parts of the structure of this embodiment are the same as those of embodiment 1, and will not be described here in detail.

[0036] A second switch valve 208 can be connected in series before the mechanical back pressure valve 205 in the hydrogen exhaust module 220, and then connected in parallel with the first switch valve 206. The second switch valve 208 is closed when back pressure is not needed. The first switch valve 206 is opened when the pipeline needs to be connected to the atmosphere, or is periodically opened and closed in pulse row mode. The first switch valve 206 requires a faster switching speed in pulse row mode, and it is difficult to adapt to the needs of large flow at the same time. Therefore, this solution is suitable for low-power battery stack test benches or battery stack test benches that do not require pulse row mode.

[0037] Reference Figure 5The present invention also provides a back pressure control method, which uses the aforementioned fuel cell stack test bench, and the control system 500 collects the pressure value of the fuel cell stack air inlet and the pressure value of the fuel cell stack exhaust in real time, compares the two measured pressure values ​​with the target values, and calculates the reference pressure value of the mechanical back pressure valve in real time through a closed-loop control algorithm, and controls the pressure regulating valve to output the reference pressure in real time.

[0038] like Figure 5 The features shown are: 701-target value of fuel cell stack air inlet pressure; 702-second controller (controller for controlling fuel cell stack air inlet pressure); 703-first controller (controller for controlling fuel cell stack exhaust pressure); 704-input amount of pressure regulating valve; 705-pressure regulating valve; 706-pressure model of mechanical back pressure valve (the model refers to mechanical back pressure valve 205); 707-fuel cell stack exhaust pressure; 708-pressure model of fuel cell stack (the model refers to fuel cell stack 600); 709-fuel cell stack air inlet pressure; 710-given value of hydrogen flow controller; 711-feedforward controller; 712-target value of fuel cell stack exhaust pressure.

[0039] Specifically, the control system 500 collects the pressure value of the first pressure sensor 204 or the second pressure sensor 203 in real time, compares it with the target value, and calculates the mechanical back pressure valve 205 ( Figure 5 The pressure model 706 of the mechanical back pressure valve (i.e., the reference pressure value of the mechanical back pressure valve) is obtained, and a command is issued to the downstream controller, such as a PLC, and then the reference pressure is output in real time through actuators such as pressure regulating valves. Through the closed-loop control, on the one hand, the influence of the inherent error characteristics of the mechanical back pressure valve 205 can be eliminated, that is, as the flow rate and pressure change, the difference between the actual back pressure value and the target value also changes; on the other hand, the mechanical back pressure valve 205 is matched with the parallel switch valve 206 to minimize the back pressure blind area within the full flow range.

[0040] The control system 500 collects the pressure value of the fuel cell stack air inlet and the pressure value of the fuel cell stack air exhaust in real time. When the hydrogen back pressure point is set at the fuel cell stack air exhaust, the exhaust closed-loop control is performed, and the fuel cell stack air exhaust pressure 707 is compared with the target value 712 of the fuel cell stack air exhaust pressure in real time, and the closed-loop control calculation is performed through the first controller 703, and the calculated control quantity is output to the pressure regulating valve 705; when the hydrogen back pressure point is set at the fuel cell stack air inlet, the air inlet closed-loop control is performed, and the air inlet target value 701 (the target value of the fuel cell stack air inlet pressure) and the fuel cell stack air inlet pressure 709 are compared in real time, and the output value is calculated by the second controller 702, the target value 712 of the fuel cell stack air exhaust pressure (the target value of the fuel cell stack air exhaust pressure), and then the exhaust closed-loop control is performed.

[0041] Specifically, the control system 500 collects the hydrogen exhaust port pressure (i.e., the fuel cell stack exhaust port pressure 707) and the hydrogen inlet pressure (the fuel cell stack inlet pressure 709) of the fuel cell stack 600 in real time. When the hydrogen back pressure point is set at the detection point of the first pressure sensor 204, the hydrogen exhaust port pressure is compared with the target value 712 of the fuel cell stack exhaust port pressure of its back pressure (i.e., the target value of the fuel cell stack exhaust port pressure) in real time, and the closed-loop control calculation is performed through the controller 703, and the calculated control amount is output to the pressure regulating valve 705. When the hydrogen back pressure point is set at the detection point of the pressure sensor 203, the inlet closed-loop control is performed, that is, the inlet target value 701 is compared with the hydrogen inlet pressure 709 in real time, and the output value is calculated by the controller 702, the hydrogen exhaust port pressure 707 and the target value 712 of the fuel cell stack exhaust port pressure, and then the aforementioned exhaust port closed-loop control (i.e., double closed-loop control) is performed. The use of dual closed-loop control shields the characteristics of the fuel cell stack from the inner-loop control, effectively reducing the difficulty of setting control parameters and improving control performance.

[0042] An identification model is established in advance. In the process of closed-loop control of the exhaust port, the given value of the hydrogen flow controller in the hydrogen intake module is used as the input of the identification model to obtain a feedforward control amount, which is applied to the input amount of the pressure regulating valve; the given value is the detection value of the flow sensor connected in series before the back pressure valve. Specifically, in the closed-loop control of the exhaust port pressure 707 of the fuel cell stack, feedforward control of the hydrogen flow can be considered. When the reference pressure is given, the actual back pressure value of the mechanical back pressure valve will increase with the increase of the hydrogen flow rate. This process is often nonlinear. Tests can be carried out for this process to obtain experimental data, and then identification is performed to establish an identification model. In the control process, the given value of the hydrogen flow controller 202 in the hydrogen intake module 200 is used as the input of the identification model to obtain a feedforward control amount, which is applied to the input amount 704 of the pressure regulating valve.

[0043] The input value of the feedforward controller 711 can also be the detection value of the hydrogen flow controller 202. In this case, the feedforward control becomes feedback control. Of course, the detection value of the hydrogen flow controller 202 cannot accurately reflect the instantaneous flow through the mechanical back pressure valve 205. For this reason, a flow sensor can be connected in series before the mechanical back pressure valve 205 to transmit and assign the detection value to the given value 710 of the hydrogen flow controller.

[0044] The present invention eliminates the influence of the inherent error characteristics of the mechanical back pressure valve through a specific control algorithm and controller structure, and is matched with a parallel switch valve to minimize the back pressure blind area within the full flow range. Compared with the electronically controlled back pressure valve, the back pressure control accuracy of the present invention is higher, the dynamic error is smaller, and the back pressure range is wider at large flow rates. On the other hand, the present invention can use double closed-loop control to shield the characteristics of the fuel cell stack from the inner loop control, effectively reducing the difficulty of setting the control parameters and improving the control performance.

[0045] In the description of the present invention, it is necessary to understand that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0046] In addition, the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0047] In the present invention, unless otherwise clearly specified and limited, the terms "connection", "fixation" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0048] Although the present invention is described in conjunction with the above specific embodiments, it is obvious that those skilled in the art can make many substitutions, modifications and changes according to the above content. Therefore, all such substitutions, improvements and changes are included in the scope of the appended claims.

Claims

1. A fuel cell stack test bench for testing a fuel cell stack, wherein the fuel cell stack has an air inlet and an air outlet, and is characterized in that: It includes a hydrogen system connected to the fuel cell stack, an air system connected to the fuel cell stack, a cooling system connected to the fuel cell stack, and a control system for controlling the hydrogen system, the air system, and the cooling system; the hydrogen system includes a hydrogen intake module and a hydrogen exhaust module, the hydrogen intake module is connected to the air inlet of the fuel cell stack, and the hydrogen exhaust module is connected to the air outlet of the fuel cell stack; the hydrogen exhaust module includes a terminal processing unit connected to the air outlet of the fuel cell stack, a mechanical back pressure valve arranged between the terminal processing unit and the air outlet of the fuel cell stack, and a first pressure sensor arranged between the mechanical back pressure valve and the air outlet of the fuel cell stack; The control system collects the pressure value of the fuel cell stack air inlet and the pressure value of the fuel cell stack exhaust in real time, compares the measured two pressure values ​​with the target value, calculates the reference pressure value of the mechanical back pressure valve in real time through the closed-loop control algorithm, and controls the pressure regulating valve to output the reference pressure in real time; The control system collects the pressure value of the fuel cell stack air inlet and the pressure value of the fuel cell stack exhaust in real time. When the hydrogen back pressure point is set at the fuel cell stack exhaust, the exhaust closed-loop control is performed, the fuel cell stack exhaust pressure is compared with the target value of the fuel cell stack exhaust pressure in real time, and the closed-loop control calculation is performed through the first controller, and the calculated control amount is output to the pressure regulating valve; When the hydrogen back pressure point is set at the fuel cell stack inlet, the inlet closed-loop control is performed, the inlet target value and the fuel cell stack inlet pressure are compared in real time, the output value is calculated by the second controller, and the target value of the fuel cell stack exhaust pressure at the fuel cell stack exhaust port is then used for exhaust port closed-loop control.

2. The fuel cell stack test bench according to claim 1, characterized in that: The hydrogen exhaust module further includes a first switch valve, and the first switch valve is connected in parallel with the mechanical back pressure valve.

3. The fuel cell stack test bench according to claim 2, characterized in that: The hydrogen exhaust module also includes a first switch valve, a second switch valve, and a third switch valve. The first switch valve is connected in parallel with the mechanical back pressure valve and then in series with the second switch valve. One end of the third switch valve is connected to the terminal processing unit, and the other end of the third switch valve is connected between the second switch valve and the exhaust port of the fuel cell stack.

4. The fuel cell stack test bench according to claim 1, characterized in that: The hydrogen exhaust module also includes a first switch valve and a second switch valve, the second switch valve is connected in series between the mechanical back pressure valve and the first pressure sensor, one end of the first switch valve is connected to the terminal processing unit, and the other end of the first switch valve is connected between the second switch valve and the exhaust port of the fuel cell stack.

5. The fuel cell stack test bench according to claim 1, characterized in that: The hydrogen intake module includes a hydrogen flow controller connected to the intake port of the fuel cell stack, and a second hydrogen pressure sensor arranged between the hydrogen flow controllers.

6. The fuel cell stack test bench according to claim 1, characterized in that: The hydrogen intake module is also provided with a hydrogen flow controller.

7. The fuel cell stack test bench according to claim 1, characterized in that: The mechanical back pressure valve is a gas pressure balanced back pressure valve.

8. The fuel cell stack test bench according to claim 1, characterized in that: An identification model is established in advance. During the closed-loop control of the exhaust port, the given value of the hydrogen flow controller in the hydrogen intake module is used as the input of the identification model to obtain a feedforward control quantity, which is applied to the input quantity of the pressure regulating valve; the given value is the detection value of the flow sensor connected in series before the mechanical back pressure valve.

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