Fuel Cell Air Supply System Simulation Test System and Method under Variable Altitude Conditions

Abstract

The present invention provides a simulation test system and method for a fuel cell air supply system under variable altitude conditions. In a variable altitude environment simulation chamber, there is an air filtration module, an air compression module, an intercooling module, a humidification module, a virtual fuel cell stack module, a back pressure module I, a back pressure module II, and an exhaust module connected in sequence; sensors are also provided between each module; in the upper computer, there is a variable altitude model for calculating the air flow rate, pressure loss, and output power of the virtual fuel cell stack; a state acquisition module for collecting the information of each sensor; and a control module for implementing the control strategy of the fuel cell air supply system. The present invention provides reliable verification and experimental result reference for the development of the control strategy of the variable altitude fuel cell air supply system; the overall test and verification of the air supply system avoid the disadvantages of low analysis efficiency and poor reliability, and can perform tests under complex working conditions. The application of the virtual fuel cell stack reduces the test development cost and time.

Description

Technical Field

[0001] The present invention provides a simulation test system and method for a fuel cell air supply system under variable altitude conditions, belonging to the technical field of fuel cells. Background Art

[0002] In recent years, with the increasing international attention to environmental protection and energy conservation, hydrogen energy, as an emerging clean energy technology, has the advantages of cleanness and high calorific value. Proton exchange membrane fuel cell (PEMFC) is an important form of hydrogen energy development and application, with the advantages of high efficiency, pollution-free, and low noise. However, since the fuel cell is a complex, non-linear, and large time-delay strong coupling system, its dynamic performance, safety, and economy are affected by many factors, so it is necessary to design safe and efficient control methods and management strategies for the fuel cell.

[0003] The dynamic output performance of the fuel cell system is often determined by the air supply system. Under variable altitude environments, the reduction of atmospheric pressure, atmospheric temperature, and atmospheric density further increases the influence of the air supply system. Oxygen excess ratio (OER) is an important parameter of the air supply system. OER refers to the ratio of the supplied air mass flow rate to the air mass flow rate required by the load. OER is particularly important for the control of the air supply system. Therefore, accurately controlling OER is beneficial to improving the efficiency, safety, and service life of the fuel cell system.

[0004] During the development of OER control, it is necessary to test whether the steady-state and transient operating conditions of the fuel cell system are optimized to verify the adopted control strategy. However, currently, the development of a fuel cell controller based entirely on hardware takes a long time and is costly, and requires a hydrogen-related laboratory with a very high safety level, which greatly increases the development and verification difficulty of the control strategy. The development of a controller based entirely on software takes a short time and has a relatively low cost, but it highly depends on the accuracy of the model, cannot fully reflect the corresponding characteristics of each component in the air path, and cannot verify the advantages and disadvantages of the developed control strategy.

[0005] Under variable altitude environments, due to the reduction of atmospheric pressure, temperature, and density, during the OER control process, the operating curve of the air compressor is very likely to exceed the surge safety range, and the system pressure will show a periodic oscillation phenomenon, resulting in damage to the proton exchange membrane and further leading to fuel cell failure.

[0006] In the prior art, two model building modules are used to build a fuel cell model and an initial control strategy model, two hardware simulation modules are used to run the fuel cell model and the control strategy, and a control module (200) is used to connect the two hardware simulation modules and optimize the initial control strategy model. It can realize the real-time simulation verification of the fuel cell control strategy model, adjust and optimize the control strategy based on the simulation results, and finally realize the rapid development of the fuel cell control strategy without manually writing and modifying codes.

[0007] The accuracy of this test method highly depends on the accuracy of the established empirical model of the fuel cell system. In a variable altitude environment, due to changes in external atmospheric pressure, temperature, humidity and other conditions, the pressure and flow dynamic response of the fuel cell air supply system, the polarization curve of the stack, etc. will all change greatly. Therefore, a single model cannot accurately describe the real operating conditions of the fuel cell under variable altitude, resulting in the inability to guarantee the effect of the tested control strategy. The decrease in atmospheric pressure and temperature caused by altitude change will cause the air compressor to operate in the surge zone under the control strategy, resulting in periodic oscillations of the pressure and flow of the air supply system, and even causing fuel cell failures. However, the system empirical model cannot effectively characterize this situation, making the verification of the control strategy incomplete and insufficient.

[0008] In addition, there is also a variable altitude simulation test system for fuel cell superchargers. By sequentially connecting an intake pressure regulation module, a supercharger under test installation platform, a supercharger intercooling module (30), a stack air resistance simulation module, and an exhaust pressure regulation module, it simulates the working environment of the fuel cell supercharger to realize the real response characteristics of the supercharger in the fuel cell system under different altitude conditions. Its advantage lies in using the intake pressure regulation module to adjust the intake temperature and pressure to simulate the atmospheric environment at different altitudes; by using the stack air resistance simulation module to replace the real stack, it can be modified and expanded on a conventional supercharger performance test system, without the need for additional hydrogen-related safety explosion-proof facilities, reducing costs.

[0009] Since the air consumption of the stack changes with parameters such as current and air flow state in this technology, the fixed-structure stack air resistance simulation module cannot accurately characterize the air consumption of the fuel cell stack under different working conditions. In the fuel cell air supply system, from the supercharger, pipeline to the intercooler and then to the humidifier, all have an impact on the intake air pressure and flow. The test of the supercharger alone helps limited in verifying the proposed control strategy, thus unable to conduct a more comprehensive analysis of the fuel cell air supply system function and optimize the control strategy. Summary of the Invention

[0010] To solve the above technical problems, the present invention provides a simulation test system and method for a fuel cell air supply system under variable altitude conditions, so as to solve the defect in the prior art that the test and verification of the fuel cell air supply system ignore the influence of the variable altitude environment, and to meet the overall function analysis requirements of the air supply system, improving the analysis efficiency and reliability.

[0011] The specific technical solution is as follows:

[0012] First, a simulation test system for a fuel cell air supply system under variable altitude conditions is provided, including:

[0013] In the variable altitude environment simulation chamber, there is an air filtration module, an air compression module, an intercooling module, a humidification module, a virtual fuel cell stack module, a back pressure module I, a back pressure module II, and an exhaust module connected in sequence;

[0014] In the upper computer, there is a variable altitude model for calculating the air flow rate, pressure loss, and output power of the virtual fuel cell stack; a state acquisition module for collecting information of each sensor; and a control module for implementing the control strategy of the fuel cell air supply system.

[0015] Specifically, in the variable altitude environment simulation chamber, the air filtration module is used to filter the inlet air;

[0016] The air compression module is used to pressurize the inlet air so that the air inlet flow rate of the fuel cell stack meets the requirements of the control strategy;

[0017] The intercooling module is used to cool the air overheated due to compression so that the air inlet temperature of the fuel cell stack meets the requirements of the control strategy;

[0018] The humidification module is used to humidify the air so that the air inlet humidity of the fuel cell stack meets the requirements of the control strategy;

[0019] The virtual fuel cell stack module adjusts the back pressure module II according to the pressure difference and flow rate difference transmitted by the variable altitude model, so that the air pressure and flow rate passing through the back pressure module I are in line with the actual situation;

[0020] The back pressure module I is used to adjust the cathode pressure of the virtual fuel cell stack so that the air inlet pressure of the fuel cell stack meets the requirements of the control strategy;

[0021] The back pressure module II is used to adjust the air flow rate difference and pressure difference of the air passing through the virtual fuel cell stack so that the change of air parameters is in line with the actual situation;

[0022] The exhaust module is used to discharge the pressurized air to complete the cycle of the fuel cell air supply system;

[0023] A first group of sensors, including a pressure sensor, a temperature sensor, a humidity sensor, and a flow sensor, are installed between the air filtration module and the air compression module, and are used to measure whether the variable altitude environment reaches the preset index;

[0024] Install a second set of sensors between the air compression module and the intercooling module, including pressure sensors, temperature sensors and flow sensors, and combine the data of the first set of sensors to evaluate the working condition of the air compression module;

[0025] Install a third set of sensors between the intercooling module and the humidification module, including pressure sensors and temperature sensors, and combine the data of the second set of sensors to evaluate the working state of the intercooling module;

[0026] Install a fourth set of sensors between the humidification module and the virtual stack, including humidity sensors, flow sensors and pressure sensors. The data of the humidity sensors and flow sensors are used to evaluate the working state of the humidification module, and the pressure sensor is used to evaluate the working state of the back pressure module Ⅰ;

[0027] Install a fifth set of sensors between the virtual stack and the back pressure module Ⅰ, including pressure sensors and flow sensors, to evaluate the working state of the virtual stack.

[0028] Specifically, in the upper computer, the state acquisition module is used to collect the pressure, flow, temperature and humidity information from each sensor, analyze the working state of each module and the implementation of the control strategy, and give early warnings of dangerous situations and timely control the system to stop;

[0029] The variable altitude model is used to calculate the pressure and flow losses that the virtual stack should generate through the set altitude and load information, and transmit them to the virtual stack module;

[0030] The variable altitude model can select a model in the prior art, such as the "Fuel Cell External Characteristic Model for Variable Altitude Environment" in the patent application No. 202211702467.1, or it can be calibrated according to the fuel cell used in the subsequent physical stack experiment. The fitting equation is shown as follows:

[0031]

[0032] Among them, ΔP is the pressure difference before and after passing through the fuel cell stack, ΔW is the flow difference before and after passing through the fuel cell stack, h is the set altitude, Ist is the set load current, and a0-a3, b0-b3, c0-c3, d0-d3 are the parameters to be calibrated.

[0033] The virtual stack module and the backpressure module Ⅱ are used together to simulate the air flow rate, pressure loss, and time lag after passing through the stack. Among them, the air resistance material in the virtual stack is used to simulate the time lag of air flow caused by the fuel cell stack. The air compressor in the backpressure module Ⅱ is used to set the air flow rate passing through this path, that is, the flow rate difference ΔW before and after passing through the fuel cell stack calculated in the variable altitude model. The backpressure proportional valve is used to set the air pressure passing through this path, that is, the pressure difference ΔP before and after passing through the fuel cell stack calculated in the variable altitude model. By controlling the air compressor and the backpressure proportional valve in the backpressure module Ⅱ, the gas pressure and flow rate passing through the backpressure module Ⅰ can be made to conform to the actual working conditions of the fuel cell.

[0034] In addition to calculating the pressure, flow rate loss, and time lag that the virtual stack should generate, the variable altitude model calculates the virtual stack voltage and net output power according to the information transmitted by the state acquisition module, in order to evaluate the advantages and disadvantages of the control strategy in terms of fuel cell performance improvement. The calculation formulas for the output voltage and net output power are shown as follows:

[0035]

[0036] Where V fc is the output voltage of a single fuel cell stack cell, E is the ideal single cell output voltage, V act is the activation polarization loss, V ohm is the ohmic loss, V conc is the concentration polarization loss, i is the load current density, i max is the current density when the concentration polarization loss rises sharply, T fc is the internal temperature of the fuel cell, I fc is the load current, P H2 is the hydrogen pressure, P O2 is the oxygen pressure, R ohm is the resistance value of the proton exchange membrane, which is related to the load current, membrane humidity, membrane area, and membrane thickness. R C is related to the actual wiring of the fuel cell and other situations. ξ1~ξ4, β are internal parameters of the fuel cell, P net is the net output power of the fuel cell, n is the number of single fuel cell stack cells, P BOP is the parasitic power of the auxiliary subsystem.

[0037] The control module is used to control each component of the air supply system, execute the designed fuel cell control strategy, including the control of the air compression module, the intercooling module, the humidification module, and the backpressure module Ⅰ, in order to adjust the air pressure, flow rate, temperature, and humidity entering the stack. The control module performs feedback control according to the information transmitted by the state acquisition module, evaluates the advantages and disadvantages of the control strategy based on the collected information and the calculation results of the variable altitude model, and is used for subsequent control strategy optimization.

[0038] A test method for a fuel cell air supply system under variable altitude conditions, using the simulated test system for the fuel cell air supply system under variable altitude conditions, includes the following steps:

[0039] S1. Conduct a fuel cell safety test to ensure safety and accuracy in subsequent tests;

[0040] The step S1 includes the following sub-steps:

[0041] S101. Air tightness test

[0042] Conduct an air tightness test on the air supply system and the simulated stack. The air tightness test method is to close the outlet of the tail exhaust module (70), introduce nitrogen into the air supply system and the simulated stack, and after the nitrogen reaches 200 kPa, close the inlet of the air filtration module (10). According to the information fed back by each pressure sensor, if the pressure change is less than a certain value, the air tightness test is considered to have passed.

[0043] S102. Insulation test

[0044] Conduct an insulation test on each module of the test system; the insulation test method is to measure the ground resistance of each module, and if the resistance values are all greater than a certain value, the insulation test is considered to have passed.

[0045] S2. Activate the stack through activation operation. After activation is completed, conduct an initial fuel cell performance test and record the initial state in subsequent tests.

[0046] The step S2 includes the following sub-steps:

[0047] S201. Stack activation

[0048] When the difference in the output voltage of the fuel cell in each activation cycle is less than a certain value, the fuel cell activation is considered to be completed.

[0049] S202. Initial fuel cell performance test

[0050] To record the initial state of subsequent tests, the initial performance test is to pull the load current to the rated load current and record the fuel cell output voltage, power, and system net output power.

[0051] S3. Rated test. To test the quality of the control strategy under steady-state conditions.

[0052] The step S3 includes the following sub-steps:

[0053] S301. Loading test

[0054] For testing the polarization steady-state operation of a fuel cell, the load current is gradually pulled to the rated current; first, the load current is pulled to 20% of the rated current and maintained for ten minutes; secondly, the load current is stepwise pulled to 40%, 60%, 80% and 100% of the rated current in sequence and maintained for ten minutes at each current stage to test the polarization steady-state performance of the fuel cell.

[0055] S302. Load reduction test

[0056] For testing the lower polarization steady-state operation of a fuel cell, the load current is gradually reduced from the rated current to shutdown; first, the current is pulled to the rated current and maintained for ten minutes; secondly, the load current is successively reduced to 80%, 60%, 40% and 20% of the rated current, and maintained for ten minutes at each load current stage to test the lower polarization steady-state performance.

[0057] S4. Load cycle test. To test the advantages and disadvantages of the control strategy under dynamic conditions. After all tests are completed, the performance of the fuel cell is retested, and the final state after the test is completed is recorded.

[0058] The step S4 includes the following sub-steps:

[0059] S401. Operating condition test

[0060] The test operating conditions are selected according to the actual operating conditions of the fuel cell after production to be tested, and can include but are not limited to WLTC conditions, CATC conditions, etc., or a composite condition composed of multiple conditions.

[0061] S402. Performance retest. To record the final state after the test is completed, the performance retest is to pull the load current to the rated load current, and record the output voltage, power and system net output power of the fuel cell.

[0062] The technical effects of the present invention are:

[0063] 1. A fuel cell air supply system test system considering the influence of variable altitude environment provides reliable verification and experimental result reference for the development of a control strategy for a variable altitude fuel cell air supply system.

[0064] 2. The overall test and verification of the air supply system avoid the disadvantages of low analysis efficiency and poor reliability in the verification of individual components, and can perform tests under complex conditions.

[0065] 3. The application of a virtual stack avoids the construction of a hydrogen-related laboratory with extremely high safety requirements, and greatly reduces the test development cost and time. Description of the drawings

[0066] Figure 1 It is a simulation test system for a variable altitude fuel cell air supply system of the present invention;

[0067] Figure 2 Specific structure of the virtual stack and backpressure module II of the present invention

[0068] Figure 3 Flowchart of the test method for the fuel cell air supply system under variable altitude conditions of the present invention

[0069] Figure 4 Is the step change of the rated test load current in the embodiment Detailed implementation manners

[0070] Describe the specific technical solutions of the present invention in conjunction with the accompanying drawings

[0071] As Figure 1 shown, the specific implementation structure of the fuel cell air supply system simulation test system under variable altitude conditions is as follows. It includes an air filtration module 10, an air compression module 20, an intercooling module 30, a humidification module 40, a virtual stack module 50, a backpressure module I 60, a backpressure module II 80, and a tail exhaust module 70 that are sequentially connected in a variable altitude environment simulation chamber. In the upper computer, there are a variable altitude model 300 for calculating the air flow rate, pressure loss, and output power of the virtual stack, a status acquisition module 100 for collecting information of each sensor, and a control module 200 for implementing the control strategy of the fuel cell air supply system

[0072] The air filtration module 10 is used to filter the inlet air to prevent dust and polluting gases from entering the stack. The air compression module 20 is used to pressurize the inlet air so that the air inlet flow rate of the stack meets the requirements of the control strategy. The intercooling module 30 is used to cool the air that has been overheated due to compression so that the air inlet temperature of the stack meets the requirements of the control strategy. The humidification module 40 is used to humidify the air so that the air inlet humidity of the stack meets the requirements of the control strategy. The virtual stack module 50 adjusts the backpressure module II 80 according to the pressure difference and flow rate difference transmitted by the variable altitude model 300, so that the air pressure and flow rate passing through the backpressure module I 60 conform to the actual situation. The backpressure module I 60 is used to adjust the cathode pressure of the virtual stack so that the air inlet pressure of the stack meets the requirements of the control strategy. The backpressure module II 80 is used to adjust the air flow rate difference and pressure difference passing through the virtual stack so that the change of air parameters conforms to the actual situation. The tail exhaust module 70 is used to discharge the pressurized air to complete the cycle of the fuel cell air supply system. Except for the virtual stack module 50, the above modules are all physical objects, which can provide a reference for the selection of the later physical stack experiment

[0073] A first set of sensors 1, including a pressure sensor, a temperature sensor, a humidity sensor, and a flow sensor, is installed between the air filtration module 10 and the air compression module 20, mainly used to measure whether the variable altitude environment reaches the preset indicators. A second set of sensors 2, including a pressure sensor, a temperature sensor, and a flow sensor, is installed between the air compression module 20 and the intercooling module 30, and combined with the data of the first set of sensors 1, is used to evaluate the working condition of the air compression module 20. A third set of sensors 3, including a pressure sensor and a temperature sensor, is installed between the intercooling module 30 and the humidification module 40, and combined with the data of the second set of sensors 2, is used to evaluate the working state of the intercooling module 30. A fourth set of sensors 4, including a humidity sensor, a flow sensor, and a pressure sensor, is installed between the humidification module 40 and the virtual stack. The data of the humidity sensor and the flow sensor are used to evaluate the working state of the humidification module 40, and the pressure sensor is used to evaluate the working state of the back pressure module I 60. A fifth set of sensors 5, including a pressure sensor and a flow sensor, is installed between the virtual stack and the back pressure module I 60, and is used to evaluate the working state of the virtual stack. To avoid information redundancy and reduce the number of sensors, the gas parameters between two similar sensors are regarded as unchanged.

[0074] In the host computer, the status acquisition module 100 collects the pressure, flow, temperature, and humidity information from each sensor, analyzes the working state of each module and the implementation of the control strategy, and warns of dangerous situations and timely shuts down the control system. The variable altitude model 300 calculates the pressure and flow losses that the virtual stack should generate through the set altitude and load information, and transmits them to the virtual stack module 50. The variable altitude model 300 of the fuel cell air supply system can select an existing model, such as the "Fuel Cell External Characteristic Model for Variable Altitude Environment" in the patent application No. 202211702467.1, or can be calibrated according to the fuel cell used in the subsequent physical stack experiment. The fitting equation is shown as follows:

[0075]

[0076] Among them, ΔP is the pressure difference before and after passing through the fuel cell stack, ΔW is the flow difference before and after passing through the fuel cell stack, h is the set altitude, I st is the set load current, and a0~a3, b0~b3, c0~c3, d0~d3 are the parameters to be calibrated.

[0077] The virtual stack module 50 and the back pressure module II 80 are used together to simulate the air flow rate, pressure loss, and time lag after passing through the stack. The air resistance material in the virtual stack is used to simulate the time lag of air flow caused by the fuel cell stack. The air compressor in the back pressure module II 80 is used to set the air flow rate passing through this path, i.e., ΔW, and the back pressure proportional valve is used to set the air pressure passing through this path, i.e., ΔP. By controlling the air compressor and the back pressure proportional valve in the back pressure module II 80, the gas pressure and flow rate passing through the back pressure module I 60 can be made to conform to the actual working conditions of the fuel cell.

[0078] The specific structures of the virtual stack module 50 and the back pressure module II 80 are as Figure 2 shown:

[0079] In addition to calculating the pressure, flow rate loss, and time lag that the virtual stack should generate, the variable altitude model 300 calculates the virtual stack voltage and net output power conditions based on the information transmitted by the state acquisition module 100 to evaluate the advantages and disadvantages of the control strategy in terms of improving fuel cell performance. The calculation formulas for the output voltage and net output power are as shown in the following equations:

[0080]

[0081] where V fc is the output voltage of a single fuel cell stack cell, E is the ideal single cell output voltage, V act is the activation polarization loss,

[0082] V ohm is the ohmic loss, V conc is the concentration polarization loss, i is the load current density, i max is the current density when the concentration polarization loss rises sharply, T fc is the internal temperature of the fuel cell, I fc is the load current, P H2 is the hydrogen pressure, P O2 is the oxygen pressure, R ohm is the resistance value of the proton exchange membrane, which is related to the load current, membrane humidity, membrane area, and membrane thickness. R C is related to the actual wiring of the fuel cell, etc. ξ1 to ξ4, β are internal parameters of the fuel cell, P net is the net output power of the fuel cell, n is the number of single cells in the fuel cell stack, P BOP is the parasitic power of the auxiliary subsystem.

[0083] The control module 200 is used to control the components of the air supply system, execute the designed fuel cell control strategy, including the control of the air compression module 20, the intercooling module 30, the humidification module 40, and the back pressure module I 60, so as to adjust the inlet air pressure, flow rate, temperature, and humidity. The control module 200 performs feedback control according to the information transmitted by the state acquisition module 100, evaluates the advantages and disadvantages of the control strategy based on the acquired information and the calculation results of the variable altitude model 300, and is used for subsequent optimization of the control strategy.

[0084] The test method for a fuel cell air supply system under variable altitude conditions of the present invention:

[0085] Based on the simulated test system of the fuel cell air supply system under variable altitude conditions, a test method for verifying the advantages and disadvantages of the control strategy is designed, including safety tests, activation preparations, rated tests, load cycle tests, etc. The specific process is as Figure 3 shown.

[0086] A test method for a fuel cell air supply system under variable altitude conditions includes the following steps:

[0087] S1. Conduct a fuel cell safety test to ensure safety and accuracy in subsequent tests. The step S1 includes the following sub-steps:

[0088] S101. Air tightness test. To ensure that the pressure of the air supply system does not change abnormally during the test, it is necessary to conduct an air tightness test on the air supply system and the simulated fuel cell stack. The air tightness test method is to close the outlet of the tail exhaust module 70, introduce nitrogen into the air supply system and the simulated fuel cell stack, and after the nitrogen reaches 200 kPa, close the inlet of the air filter module 10. According to the information fed back by each pressure sensor, if the pressure change is less than a certain value, the air tightness test can be regarded as passed.

[0089] S102. Insulation test. To ensure the safety of personnel during the test, it is necessary to conduct an insulation test on each module of the test system. The insulation test method is to measure the grounding resistance of each module. If the resistance values are all greater than a certain value, the insulation test can be regarded as passed.

[0090] S2. Since problems such as membrane drying and blockage of the gas-water transmission channel may occur after the fuel cell has been static for a long time, it is necessary to activate the fuel cell stack through activation operations. After activation is completed, a preliminary performance test of the fuel cell is conducted to record the initial state in subsequent tests. The step S2 includes the following sub-steps:

[0091] S201. Activation of the fuel cell stack. The activation method can adopt the methods in existing patents, such as the "activation method of a proton exchange membrane fuel cell" in the patent application No. 200910252441.X. When the difference in the output voltage of the fuel cell in each activation cycle is less than a certain value, the activation of the fuel cell is regarded as completed.

[0092] S202. Initial measurement of fuel cell performance. To record the initial state for subsequent tests, in the initial measurement of performance, the load current is pulled to the rated load current, and the output voltage, power, and net output power of the fuel cell are recorded.

[0093] S3. Rated test. To test the advantages and disadvantages of the control strategy under steady-state conditions. The following sub-steps are included in step S3:

[0094] S301. Loading test. Mainly used to test the polarization steady-state working condition of the fuel cell. The load current is gradually pulled to the rated current. The specific current change can be referred to Figure 4 . First, the load current is pulled to 20% of the rated current and maintained for ten minutes. Secondly, the load current is stepwise pulled to 40%, 60%, 80%, and 100% of the rated current in sequence and maintained for ten minutes at each current stage to test the polarization steady-state performance of the fuel cell.

[0095] S302. Unloading test. Mainly used to test the depolarization steady-state working condition of the fuel cell. The load current is gradually unloaded from the rated current to shutdown. The specific current change can be referred to Figure 4 . First, the current is pulled to the rated current and maintained for ten minutes. Secondly, the load current is unloaded to 80%, 60%, 40%, and 20% of the rated current in sequence, and maintained for ten minutes at each load current stage to test the depolarization steady-state performance.

[0096] S4. Load cycle test. To test the advantages and disadvantages of the control strategy under dynamic conditions. After all tests are completed, a retest of the fuel cell performance is carried out to record the final state after the test. The following sub-steps are included in step S4:

[0097] S401. Working condition test. The test working conditions are selected according to the actual working conditions of the fuel cell after production. It can be selected including but not limited to WLTC working conditions, CATC working conditions, etc., or a composite working condition composed of multiple working conditions.

[0098] S402. Retest of performance. To record the final state after the test, in the retest of performance, the load current is pulled to the rated load current, and the output voltage, power, and net output power of the fuel cell are recorded.

[0099] During the experiment, the control module 200 should perform corresponding feedback control according to the real-time data collected by the state acquisition module 100, and determine whether the adopted control strategy and the air supply system module meet the requirements. Taking the air compression module 20 as an example, if the pressure and flow information fed back by the second group of sensors 2 do not meet the requirements of the control strategy, feedback control needs to be performed on the air compression module 20 to increase or decrease the rotational speed of the air compressor. If the air compressor still cannot meet the requirements of the control strategy when it reaches the maximum rotational speed or exceeds the surge line, it should be immediately shut down to detect and determine whether it is due to the selection problem of the air compression module 20 or the control strategy does not conform to the actual situation. Similarly, similar test and verification methods are adopted for the intercooling module 30, the humidification module 40, and the backpressure module I 60. After all the tests are completed, the applicability of the adopted control strategy can be verified, and it can guide the selection of each module of the air supply system.

[0100] After the overall test process, a comprehensive evaluation of the control strategy is carried out according to the data collected by the state acquisition module 100 and the results output by the variable altitude model 300. First is the rated test stage, where the pros and cons of the control strategy in terms of output power are evaluated according to the net output power of the fuel cell system under different load currents. According to the comparison of the voltages of the upper and lower polarizations, the pros and cons of the control strategy in terms of upper and lower polarization voltage control can be evaluated. Secondly is the load test stage, where it is judged whether the control strategy and the actuator can accurately follow the dynamic and complex working conditions according to the information fed back by each sensor. Finally, based on the comparison of the results of the performance retest and the initial performance test, the ability of the control strategy to suppress the performance degradation of the fuel cell is evaluated, and the strategy developers can optimize the control strategy according to the test results. This simulation test system and test method provide a reliable reference for performance development.

Claims

1. A fuel cell air supply system simulation test system under variable altitude conditions, characterized in that, Comprising: In a variable altitude environment simulation chamber, there is an air filtration module (10), an air compression module (20), an intercooling module (30), a humidification module (40), a virtual stack module (50), a back pressure module I (60), a back pressure module II (80) and an exhaust module (70) connected in sequence; sensors are also provided between each module; In the host computer, there is a variable altitude model (300) for calculating the air flow rate, pressure loss and output power of the virtual stack; a status acquisition module (100) for collecting information of each sensor; a control module (200) for implementing the control strategy of the fuel cell air supply system; Among them, in the variable altitude environment simulation chamber, the air filtration module (10) is used to filter the inlet air; The air compression module (20) is used to pressurize the inlet air so that the air inlet flow rate into the stack meets the requirements of the control strategy; The intercooling module (30) is used to cool the air overheated due to compression so that the air inlet temperature into the stack meets the requirements of the control strategy; The humidification module (40) is used to humidify the air so that the air inlet humidity into the stack meets the requirements of the control strategy; The virtual stack module (50) adjusts the back pressure module II (80) according to the pressure difference and flow difference transmitted by the variable altitude model (300), so that the air pressure and flow rate through the back pressure module I (60) conform to the actual situation; The back pressure module I (60) is used to adjust the cathode pressure of the virtual stack so that the air inlet pressure into the stack meets the requirements of the control strategy; The back pressure module II (80) is used to adjust the air flow difference and pressure difference through the virtual stack so that the change of air parameters conforms to the actual situation; The exhaust module (70) is used to discharge the pressurized air to complete the cycle of the fuel cell air supply system; The specific setting of the said sensors is as follows: A first group of sensors (1) including a pressure sensor, a temperature sensor, a humidity sensor and a flow sensor is installed between the air filtration module (10) and the air compression module (20) for measuring whether the variable altitude environment reaches the preset index; A second group of sensors (2) including a pressure sensor, a temperature sensor and a flow sensor is installed between the air compression module (20) and the intercooling module (30), and combined with the data of the first group of sensors (1) for evaluating the working condition of the air compression module (20); A third group of sensors (3) including a pressure sensor and a temperature sensor is installed between the intercooling module (30) and the humidification module (40), and combined with the data of the second group of sensors (2) for evaluating the working state of the intercooling module (30); A fourth group of sensors (4) including a humidity sensor, a flow sensor and a pressure sensor is installed between the humidification module (40) and the virtual stack. Among them, the data of the humidity sensor and the flow sensor are used for evaluating the working state of the humidification module (40), and the pressure sensor is used for evaluating the working state of the back pressure module I (60); A fifth group of sensors (5) including a pressure sensor and a flow sensor is installed between the virtual stack and the back pressure module I (60) for evaluating the working state of the virtual stack; In the host computer, a status acquisition module (100) is used to collect pressure, flow, temperature, and humidity information from various sensors, analyze the working status of each module and the implementation of control strategies, and give early warnings of dangerous situations and timely control the system to stop. A variable altitude model (300) is used to calculate the pressure and flow losses that the virtual stack should generate based on the set altitude and load information, and transmit them to the virtual stack module (50). A control module (200) is used to control each component of the air supply system and execute the designed fuel cell control strategy, including the control of the air compression module (20), the intercooling module (30), the humidification module (40), and the back pressure module I (60) to adjust the pressure, flow, temperature, and humidity of the air entering the stack. The control module (200) performs feedback control according to the information transmitted by the status acquisition module (100), evaluates the advantages and disadvantages of the control strategy based on the collected information and the calculation results of the variable altitude model (300), and is used for subsequent optimization of the control strategy.

2. The fuel cell air supply system simulation test system under variable altitude conditions according to claim 1, characterized in that The described variable altitude model (300) is calibrated according to the fuel cell used in the physical stack experiment, and the fitting equation is shown as follows: Where, ΔP is the pressure difference before and after passing through the fuel cell stack, ΔW is the flow rate difference before and after passing through the fuel cell stack, h is the set altitude, and I st is the set load current, and a0 to a3, b0 to b3, c0 to c3, and d0 to d3 are parameters to be calibrated.

3. The fuel cell air supply system simulation test system under variable altitude conditions according to claim 1, characterized in that, The described variable altitude model (300) calculates the virtual stack voltage and net output power conditions according to the information transmitted by the status acquisition module (100) to evaluate the advantages and disadvantages of the control strategy in terms of improving fuel cell performance. The calculation formulas for the output voltage and net output power are shown as follows: Among them, V fc is the output voltage of a single fuel cell stack unit, E is the ideal single unit output voltage, V act is the activation polarization loss, V ohm is the ohmic loss, V conc is the concentration polarization loss, i is the load current density, i max is the current density when the concentration polarization loss rises sharply, T fc is the internal temperature of the fuel cell, I fc is the load current, P H2 is the hydrogen pressure, P O2 is the oxygen pressure, R ohm is the resistance value of the proton exchange membrane, which is related to the load current, membrane humidity, membrane area and membrane thickness, R C is related to the actual wiring of the fuel cell, etc. ξ1~ξ4, β are the internal parameters of the fuel cell, P net is the net output power of the fuel cell, n is the number of single fuel cell stack units, P BOP is the parasitic power of the attached subsystem.

4. A test method for a fuel cell air supply system under variable altitude conditions, characterized in that, Using the fuel cell air supply system simulation test system under variable altitude conditions described in any one of claims 1 to 3, includes the following steps: S1. Conduct fuel cell safety tests to ensure safety and accuracy in subsequent tests. S2. Activate the stack through activation operations; after activation is completed, conduct an initial fuel cell performance test and record the initial state in subsequent tests. S3. Rated test to test the advantages and disadvantages of the control strategy under steady-state conditions. S4. Load cycle test to test the advantages and disadvantages of the control strategy under dynamic conditions; after all tests are completed, conduct a retest of fuel cell performance and record the final state after the test is completed.

5. A method for testing a fuel cell air supply system under variable altitude conditions according to claim 4, characterized in that, The steps in S1 include the following sub-steps: S101. Air tightness test Conduct an air tightness test on the air supply system and the simulated stack; the air tightness test method is to close the outlet of the tail exhaust module (70), introduce nitrogen into the air supply system and the simulated stack, and after the nitrogen reaches 200 kPa, close the inlet of the air filter module (10). According to the information fed back by each pressure sensor, if the pressure change is less than a certain value, it is regarded as passing the air tightness test. S102. Insulation test Conduct an insulation test on each module of the test system; the insulation test method is to measure the grounding resistance of each module. If the resistance values are all greater than a certain value, it is regarded as passing the insulation test. S2. Activate the stack through activation operations; after activation is completed, conduct an initial fuel cell performance test and record the initial state in subsequent tests.

6. The test method for a fuel cell air supply system under variable altitude conditions according to claim 4, characterized in that The steps in S2 include the following sub-steps: S201. Stack activation When the difference in fuel cell output voltage in each activation cycle is less than a certain value, it is regarded as the completion of fuel cell activation. S202. Initial fuel cell performance test To record the initial state for subsequent tests, the initial performance test is to pull the load current to the rated load current and record the output voltage, power, and net output power of the fuel cell.

7. A test method for a fuel cell air supply system under variable altitude conditions according to claim 4, characterized in that The steps in step S3 include the following sub-steps: S301. Loading test Used to test the polarization steady-state working condition of the fuel cell, gradually pull the load current to the rated current; first, pull the load current to 20% of the rated current and maintain for ten minutes. Secondly, stepwise pull the load current to 40%, 60%, 80%, and 100% of the rated current in sequence and maintain for ten minutes at each current stage to test the polarization steady-state performance of the fuel cell. S302. Unloading test Used to test the under-polarization steady-state working condition of the fuel cell, gradually unload the load current from the rated current to shutdown; first, pull the current to the rated current and maintain for ten minutes. Secondly, unload the load current to 80%, 60%, 40%, and 20% of the rated current in sequence and maintain for ten minutes at each load current stage to test the under-polarization steady-state performance.

8. A method for testing a fuel cell air supply system under variable altitude conditions according to claim 4, characterized in that The steps in step S4 include the following sub-steps: S401. Operating condition test The test operating conditions are selected according to the actual working conditions after the fuel cell to be tested is put into production. S402. Performance re-test. To record the final state after the test is completed, the performance re-test is to pull the load current to the rated load current and record the output voltage, power, and net output power of the fuel cell.

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