Method of diagnosing clogging of a water filter in a fuel cell system

Abstract

The present application relates to the technical field of fuel cell, and particularly discloses a method for diagnosing water filter blockage in a fuel cell system, wherein the preparation method comprises the following steps: realizing full working condition monitoring through three stages: before starting, controlling the three-way valve to be in a small cycle, comparing the cooling water inlet stack pressure with a set value after stabilizing the water pump rotating speed, and determining blockage if the pressure exceeds the set value; when running at a small power, monitoring the switching time of the three-way valve from 0% to 35% opening during the process that the cooling water rises from 30 DEG C to 65 DEG C, and determining blockage if the switching time exceeds the set value; when running at a large power, determining blockage if the cooling water temperature difference exceeds the set value under the condition of a large cycle. The method of the present application does not need to add new components, can save cost, and realizes real-time diagnosis before starting and during running, thereby avoiding damage to the stack.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and particularly to a method for diagnosing water filter blockage in a fuel cell system. Background Technology

[0002] During the operation of a fuel cell system, the water filter, as a key component of the cooling water circulation system, primarily functions to filter impurities (such as metal debris, colloidal particles, and microbial metabolites) from the cooling water, preventing these impurities from entering the cooling water chamber of the fuel cell stack and causing flow channel blockage, electrode contamination, or reduced cooling efficiency. If the water filter becomes clogged, it will directly lead to a reduction in cooling water circulation flow, resulting in insufficient heat dissipation from the fuel cell stack, abnormal temperature increases, and in severe cases, accelerated aging of the membrane electrode assembly (MEA), inconsistent voltage in individual cells, or even permanent damage to the fuel cell stack.

[0003] Currently, the industry mainly relies on offline disassembly and inspection methods to diagnose water filter clogging: when the system experiences abnormal cooling (such as excessively high fuel cell stack temperature or pressure fluctuations), it is necessary to shut down the system and remove the water filter from the system. The degree of filter media contamination is then visually inspected or a flow test is used to determine whether clogging has occurred. This method has the following significant drawbacks: High labor and time costs: The disassembly and inspection process requires professional personnel and involves steps such as system depressurization, pipeline disassembly, and component reassembly. A single diagnosis usually takes more than 30 minutes, which will significantly reduce the operational efficiency of a fleet of fuel cell vehicles in mass operation (such as hydrogen buses and logistics vehicles).

[0004] System downtime risk: Disassembly and inspection must be carried out while the system is shut down. If the water filter is clogged during operation, it cannot be diagnosed in real time, which may cause the fuel cell stack to continue to operate in a faulty state, expanding the scope of damage.

[0005] Secondary pollution risk: During disassembly and inspection, the pipe interfaces are exposed to the external environment, and dust and moisture in the air may enter the cooling system, which may aggravate the system pollution.

[0006] Diagnostic lag: Existing methods can only respond passively after obvious abnormalities occur in the system, and cannot provide early warnings, making it difficult to meet the needs of preventive maintenance for fuel cell systems.

[0007] In addition, there are a few existing technologies that attempt to monitor the status of water filters by adding sensors (such as flow sensors and differential pressure sensors). However, such solutions require additional hardware deployment, which not only increases the system cost but also increases the system complexity (calibration of the new sensors, troubleshooting, etc.). Furthermore, the reliability of the sensors themselves may affect the diagnostic results, so they have not been widely used.

[0008] Based on the shortcomings of the existing technology, there is an urgent need in the field for a method that can diagnose the water filter clogging status in real time before system startup and during operation without adding hardware, so as to achieve low-cost, high-efficiency and high-safety water filter status monitoring.

[0009] Therefore, existing technologies still need to be improved and enhanced. Summary of the Invention

[0010] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for diagnosing water filter blockage in a fuel cell system, which aims to solve the problems of high labor costs, delayed diagnosis, need for shutdown and disassembly for inspection, and potential system damage in existing methods for diagnosing water filter blockage in fuel cell systems.

[0011] The technical solution of the present invention is as follows: A method for diagnosing water filter clogging in a fuel cell system, wherein the fuel cell system includes a cooling water circulation structure, the cooling water circulation structure including a cooling water chamber disposed in the fuel cell stack, an expansion tank, a water pump, an axial fan, a large circulation inlet B of a three-way valve, and a water filter connected in sequence by pipes; the outlet of the cooling water chamber is connected to the expansion tank by a pipe, and the inlet of the cooling water chamber is connected to the water filter by a pipe; the three-way valve also includes a small circulation inlet A, the small circulation inlet A of the three-way valve being connected to the water pump by another pipe; a cooling water outlet temperature sensor is disposed at the outlet of the cooling water chamber, and a cooling water inlet temperature sensor and a cooling water inlet pressure sensor are disposed at the inlet of the cooling water chamber; the method includes the following steps: When the fuel cell stack is not running in the fuel cell system, the small circulation inlet A of the three-way valve is opened and the large circulation inlet B of the three-way valve is closed, so that the cooling water circulation structure is in the small circulation state. At this time, the current pressure value P1 is obtained through the cooling water inlet pressure sensor. The current pressure value P1 is compared with the calibrated value Pset of the cooling water inlet pressure when the water filter is normal. If P1 is greater than Pset, it is determined that the water filter is blocked when the fuel cell is not running; if P1 is less than or equal to Pset, it is determined that the water filter is not blocked when the fuel cell is not running. When it is determined that the water filter is not blocked during the non-operation phase of the fuel cell stack, the fuel cell stack of the fuel cell system is controlled to operate at low power. The cooling water inlet temperature is monitored by the cooling water inlet temperature sensor, and the cooling water is controlled to gradually increase from the initial temperature to the preset temperature. During the temperature increase process, the three-way valve is switched from the small circulation state to the large circulation state, and the actual time t1 taken for the opening of the large circulation inlet B of the three-way valve to gradually increase from 0% to 35% is recorded. The actual time t1 is compared with the calibration time t0 when the three-way valve completes the 0%-35% opening switch of the large circulation inlet B of the water filter under normal conditions. If t1 is greater than t0, it is determined that the water filter is blocked when the fuel cell is running at low power; if t1 is less than or equal to t0, it is determined that the water filter is not blocked when the fuel cell is running at low power. If it is determined that the water filter is not clogged when the fuel cell stack is running at low power, the fuel cell system is switched to high power operation. The outlet temperature T is collected in real time using cooling water outlet temperature sensors and cooling water inlet temperature sensors. 出 With the reactor temperature T 入 Calculate the temperature difference ΔT=T 出 -T 入 ; Compare the temperature difference ΔT with the calibrated temperature difference ΔTs under high-power operation when the water filter is running normally. If ΔT is greater than ΔTs, the water filter is determined to be clogged when the fuel cell stack is operating at high power; if ΔT is less than or equal to ΔTs, the water filter is determined to be unclogged when the fuel cell stack is operating at high power.

[0012] The method for diagnosing water filter blockage in the fuel cell system, wherein the low power refers to 20-30% of the rated power of the fuel cell system, and the high power refers to 80-100% of the rated power of the fuel cell system.

[0013] In the method for diagnosing water filter blockage in the fuel cell system, the step of controlling the cooling water to gradually increase from an initial temperature to a preset temperature includes an initial temperature of 30°C and a preset temperature of 65°C.

[0014] Beneficial effects: The method for diagnosing water filter blockage in a fuel cell system provided by this invention proposes for the first time a three-stage diagnostic process: pressure judgment before startup, valve switching time judgment at low power, and temperature difference judgment at high power. Through cross-validation of characteristic parameters under different operating conditions, the method achieves accurate identification of water filter blockage. This invention utilizes the parameters of existing sensors (pressure, temperature) and actuators (three-way valve, water pump, fan) in the fuel cell system, eliminating the need for additional hardware and solving the problem of increased costs caused by adding sensors in existing technologies. Furthermore, this invention overcomes the limitation of existing technologies that can only diagnose after system shutdown, enabling full-time monitoring from before startup to high-power operation, thus meeting the needs of preventative maintenance. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the cooling water circulation structure in the fuel cell system of the present invention.

[0016] Figure 2 This is a flowchart of a method for diagnosing water filter blockage in a fuel cell system according to the present invention. Detailed Implementation

[0017] This invention provides a method for diagnosing water filter blockage in a fuel cell system. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] Please see Figure 1 , Figure 1 The figure shows a schematic diagram of the cooling water circulation structure in the fuel cell system of the present invention. The cooling water circulation structure includes a cooling water chamber 1 disposed in the fuel cell stack, an expansion tank 2, a water pump 3, an axial fan 4, a large circulation inlet B of a three-way valve 5, and a water filter 6 connected in sequence by pipes. The outlet of the cooling water chamber 1 is connected to the expansion tank 2 by a pipe, and the inlet of the cooling water chamber 1 is connected to the water filter 6 by a pipe. The three-way valve 5 also includes a small circulation inlet A, which is connected to the water pump 3 by another pipe. A cooling water outlet temperature sensor 7 is provided at the outlet of the cooling water chamber 1, and a cooling water inlet temperature sensor 8 and a cooling water inlet pressure sensor 9 are provided at the inlet of the cooling water chamber 1.

[0019] Specifically, the cooling water chamber 1 is the cooling water flow channel inside the fuel cell stack, isolated from the air chamber 10 and hydrogen chamber 11 within the stack. The cooling water flow carries away the heat generated by the fuel cell reaction. The water filter 6 is connected in series in the cooling water pipeline to filter impurities in the cooling water. Its inlet is connected to the circulation outlet C of the three-way valve 5, and its outlet is connected to the inlet of the cooling water chamber 1. The three-way valve 5 has three ports: a small circulation inlet A, a large circulation inlet B, and a circulation outlet C. The three-way valve achieves different circulation paths by switching between different inlets. The water pump 3 mainly provides power for the cooling water circulation. The axial fan 4 is installed in the large circulation path to force heat dissipation from the cooling water in the large circulation path; its speed can be automatically adjusted according to the temperature. The expansion tank 2 is used to balance the volume expansion of the cooling water caused by temperature changes and to replenish the system water volume.

[0020] In this embodiment, the core feature of the axial fan is that the airflow direction is parallel to the fan blade axis, with air flowing in and out axially. This is suitable for scenarios where fluid in the pipeline flows directly through the fan's heat dissipation channel. The fan integrates a fluid channel, heat dissipation fins, fan blades, and a motor. Cooling water flows directly into the internal fluid channel of the fan after exiting the water pump. When the motor drives the fan blades to rotate, it causes air to flow axially through the heat dissipation fins to form continuous air-cooling convection. Cooling is achieved through heat exchange between water, fins, and air.

[0021] In this implementation, when the cooling water is in a small circulation state, its flow path is: cooling water chamber → expansion tank → water pump → small circulation inlet A of the three-way valve → water filter → cooling water chamber; When the cooling water is in the large circulation state, its flow path is: cooling water chamber → expansion tank → water pump → axial fan → large circulation inlet B of the three-way valve → water filter → cooling water chamber.

[0022] Based on the cooling water circulation structure of the fuel cell system, the present invention also provides a method for diagnosing water filter blockage in a fuel cell system, such as... Figure 2 As shown, it includes the following steps: S10. When the fuel cell stack is not running in the fuel cell system, the small circulation inlet A of the three-way valve is opened and the large circulation inlet B of the three-way valve is closed, so that the cooling water circulation structure is in a small circulation state. At this time, the current pressure value P1 is obtained by the cooling water inlet pressure sensor. S20. Compare the current pressure value P1 with the cooling water inlet pressure calibration value Pset when the water filter is normal. If P1 is greater than Pset, it is determined that the water filter is blocked during the non-operational stage of the fuel cell stack. If P1 is less than or equal to Pset, it is determined that the water filter is not blocked during the non-operational stage of the fuel cell stack. Specifically, in steps S10-S20, the three-way valve is in a small circulation state, and the cooling water circulates only between the cooling water chamber and the water filter, without any other branch flow. When the water filter is clogged, its flow resistance increases. According to the fluid mechanics formula for pipe resistance, ΔP=λ*(L / d)*(ρv) 2 / 2), where λ is the friction factor, L is the pipe length, d is the pipe inner diameter, ρ is the cooling water density, and v is the flow velocity. With the pump speed constant, increased flow resistance will lead to increased pipe pressure, causing the current pressure value P1 to exceed the normal set value Pset. Here, Pset is the standard pressure value of the water filter under normal operating conditions in small circulation mode, which needs to be calibrated through prior experiments based on the system model. Therefore, this embodiment determines whether the water filter is clogged when the fuel cell stack is not running by comparing the magnitudes of P1 and Pset.

[0023] S30. When it is determined that the water filter is not blocked during the non-operation stage of the fuel cell stack, the fuel cell stack of the fuel cell system is controlled to operate at low power. The cooling water inlet temperature is monitored by the cooling water inlet temperature sensor. The cooling water is controlled to gradually increase from the initial temperature to the preset temperature. During the temperature increase process, the three-way valve is switched from the small circulation state to the large circulation state. The actual time t1 used when the opening of the large circulation inlet B of the three-way valve gradually increases from 0% to 35% is recorded. S40. Compare the actual time t1 with the calibration time t0 when the three-way valve completes the 0%-35% opening switch of the large circulation inlet B of the water filter under normal operation. If t1 is greater than t0, it is determined that the water filter is blocked when the fuel cell is running at low power. If t1 is less than or equal to t0, it is determined that the water filter is not blocked when the fuel cell is running at low power. In steps S30-S40, if the water filter diagnosis result is normal during the non-operational stage of the fuel cell stack, the fuel cell system is started, and the fuel cell stack is controlled to operate at low power (i.e., 20%-30% of the rated power). The purpose of low power operation is to allow the fuel cell stack to generate heat slowly and avoid sudden temperature rises that could impact the fuel cell stack. In this embodiment, when the fuel cell stack is operating at low power, the cooling water flow rate is reduced due to water filter blockage, and the heat generated by the fuel cell stack cannot be quickly carried away by the cooling water, resulting in a slower rate of temperature rise at the inlet. To control the inlet temperature within the target range (from 30°C to 65°C), the three-way valve needs a longer time to complete the switch from 0% opening to 35% opening (by extending the large circulation opening time to enhance heat dissipation). Therefore, the actual switching time t1 will exceed the calibrated time t0, where t0 is the standard time for the large circulation inlet B of the three-way valve to complete the 0%-35% opening switch when the water filter is normal and the fuel cell stack is operating at low power, such as 100 seconds, which needs to be calibrated through previous experiments. Therefore, by comparing the values ​​of t1 and t0, this embodiment can determine whether the water filter is clogged during the low-power operation phase of the fuel cell stack.

[0024] S50. When it is determined that the water filter is not clogged when the fuel cell stack is running at low power, the fuel cell system is switched to high power operation. The outlet temperature T is collected in real time through the cooling water outlet temperature sensor and the cooling water inlet temperature sensor. 出 With the reactor temperature T 入 Calculate the temperature difference ΔT=T 出 -T 入 ; S60. Compare the temperature difference ΔT with the calibrated temperature difference ΔTs under high power operation when the water filter is running normally. If ΔT is greater than ΔTs, it is determined that the water filter is blocked when the fuel cell is running at high power. If ΔT is less than or equal to ΔTs, it is determined that the water filter is not blocked when the fuel cell is running at high power.

[0025] If the water filter diagnosis indicates it is functioning correctly during low-power operation of the fuel cell stack, switch the fuel cell system to high-power operation (e.g., 80%-100% of rated power). At this stage, the heat generation rate of the fuel cell stack significantly increases. During this phase, ensure the three-way valve is in full circulation mode (with an opening of 98%), and the axial fan operates at its rated speed to ensure the cooling system operates at maximum heat dissipation capacity. During high-power operation, the fuel cell stack generates a large amount of heat, requiring sufficient cooling water circulation to remove this heat. A clogged water filter will result in insufficient cooling water entering the fuel cell stack, leading to increased heat absorption by the cooling water within the stack and a higher outlet temperature (T0). 出 The temperature increases, while the reactor temperature T... 入Because the high-temperature fan continuously dissipates heat, keeping the temperature within the normal range, the temperature difference ΔT will exceed the standard value ΔTs. Here, ΔTs is the standard temperature difference under high-power operation when the water filter is functioning normally, such as 8°C, which needs to be calibrated through prior experiments. Therefore, this embodiment determines whether the water filter is clogged during the high-power operation of the fuel cell stack by comparing the magnitudes of ΔT and ΔTs.

[0026] This embodiment achieves full-condition coverage of the water filter's operation through diagnostics in three stages: pre-startup, power operation, and power operation. Pre-startup diagnostics can detect blockages before the system starts running, avoiding initial damage to the fuel cell stack caused by starting with a fault. Low-power operation diagnostics can monitor during the system preheating stage, when the fuel cell stack load is low, allowing for timely shutdown and replacement even if blockages are detected, minimizing losses. High-power operation diagnostics can provide real-time warnings during high-load, high-risk stages, preventing irreversible damage to the fuel cell stack due to overheating. This full lifecycle monitoring mode solves the problem of the lag in existing technologies that can only diagnose after the fact.

[0027] This embodiment achieves diagnosis through multi-parameter cross-validation (pressure, time, and temperature difference), which has stronger anti-interference capabilities compared to single-parameter judgment. For example: Stage 1 (when the fuel cell stack is not running) uses small-circuit pressure judgment to eliminate the interference of large-circuit branches (such as fans and pipes) on pressure; Stage 2 (when operating at low power) uses valve switching time judgment, combined with the dynamic process of temperature change, to avoid random errors of static parameters; Stage 3 (when operating at high power) uses temperature difference judgment, which is directly related to the fuel cell stack's heat dissipation efficiency. Under high load, the impact of blockage is more significant, resulting in higher diagnostic sensitivity. Experimental verification shows that the diagnostic accuracy of this method for water filter blockage is ≥98% (100 test samples, covering different blockage degrees, ambient temperatures, and system aging states).

[0028] The method in this embodiment does not depend on a specific model of fuel cell system. It only requires calibrating the set values ​​of Pset, t0, ΔTs, etc. according to system parameters (such as water pump speed, pipe diameter, stack power) to adapt to different types of systems such as proton exchange membrane fuel cells and solid oxide fuel cells. It can also be used in stationary (such as power stations) and mobile (such as vehicles) fuel cell scenarios, and has broad prospects for promotion and application.

[0029] The method in this embodiment completes the diagnosis through automated parameter acquisition and logical judgment. The entire process requires no manual intervention, and a single diagnosis takes ≤5 minutes (including three stages), which is more than 80% more efficient than the traditional disassembly and inspection method (more than 30 minutes). At the same time, it avoids system exposure during the disassembly and inspection process, reduces the risk of secondary contamination, and also reduces the misjudgment that may be caused by manual operation (such as subjective judgment deviation of the degree of blockage during visual inspection).

[0030] Finally, the method in this embodiment utilizes only the existing components of the system (pressure sensor, temperature sensor, three-way valve, water pump, fan, etc.) and operating parameters, without the need for additional hardware such as flow sensor and differential pressure sensor. This effectively saves costs for a single system, and the cumulative cost advantage is particularly significant for mass-produced fuel cell systems (such as automotive fuel cells). At the same time, reducing hardware also reduces the number of system failure points (such as sensor failure), improving overall reliability.

[0031] The present invention will be further explained and illustrated below through specific embodiments: Example 1 1. Setpoint Calibration Method The set values ​​of Pset, t0, ΔTs, etc., need to be calibrated through preliminary experiments based on the specific system model. The steps are as follows: Sample preparation: Select 100 brand new water filters (ensure they are not clogged) and install them into the test system.

[0032] Parameter acquisition: For each water filter, the small circulation pressure was tested according to the Phase 1 method, and the average value of 100 tests was taken as Pset; The valve switching time during low-power operation was tested using the Phase 2 method, and the average value of 100 tests was taken as t0. The temperature difference during high-power operation was tested using the three-stage method, and the average value of 100 tests was taken as ΔTs.

[0033] 2. Taking a certain model of automotive proton exchange membrane fuel cell system (rated power 60kW) as an example, explain in detail the implementation process and parameter settings for each stage of diagnosis: Phase 1: Pre-startup diagnostics (ambient temperature 25℃, system in cold state) State initialization: When the system is powered off, the three-way valve is in the small circulation state by default, and the high-temperature water pump and high-temperature fan are both in the stopped state.

[0034] Pump Start-up and Stabilization: The host computer sends a command to control the high-temperature water pump to operate at a speed of 2000 r / min, while the pressure change is monitored in real time by the reactor pressure sensor. After 40 seconds of operation, the pressure fluctuation range stabilizes at ±0.03 bara (meeting the stability standard of ≤±0.05 bara), at which point the pressure value P1 is recorded as 1.4 bara.

[0035] Setting value recall and judgment: The pressure setting value of this system in small circulation state is Pset=1.3bara (based on the average pressure of 1.3bara obtained from 100 normal water filter tests in the early stage, with a deviation of ±0.05bara). Since P1=1.4>Pset=1.3bara, the water filter is initially determined to be clogged.

[0036] Experimental verification: After disassembling the water filter, it was found that a large amount of metal debris (from pipeline welding residue) was attached to the surface of the filter media, and the flow area was reduced by about 40%, which was consistent with the diagnosis results.

[0037] Phase Two: Low-Power Operation Diagnosis (Assuming Phase One diagnosis was normal, P1=Pset=1.3bara) System startup and load control: Start the fuel cell system and control the stack output power to 15kW (25% of the rated power). At this time, the stack heat generation rate is about 10kW (according to the law of conservation of energy, the stack efficiency is about 60%, and the remaining energy is released in the form of heat).

[0038] Temperature monitoring and cycle switching: The initial feed temperature is 30°C, and the system target is to raise it to 65°C. As the fuel cell stack operates, the feed temperature gradually increases. During the temperature rise, the three-way valve opening gradually increases from 0%: when the feed temperature reaches 40°C, the opening increases to 10%; at 50°C, it increases to 20%; at 60°C, it increases to 30%; and at 65°C, it increases to 35%, while the fan operates at 1500 rpm.

[0039] Time recording and judgment: Record the actual time t1 = 150 seconds for the three-way valve to open from 0% to 35%. The switching time setting for this system during low-power operation is t0 = 100 seconds (based on an average switching time of 100 normal water filter tests, with a deviation of ±5 seconds). Since t1 = 150 seconds > t0 = 100 seconds, the water filter is determined to be clogged.

[0040] Experimental verification: Disassembly of the water filter revealed that the filter media was clogged with colloidal particles, reducing the flow capacity by about 30%, which caused the cooling water flow rate to drop from the normal 15L / min to 10L / min. This is consistent with the principle that "reduced flow rate leads to slower temperature rise and longer valve switching time".

[0041] Phase 3: High-power operation diagnosis (assuming Phase 2 diagnosis is normal, t1=80 seconds < t0=100 seconds) Load Boost: Increase the stack output power to 50kW (83% of rated power), at which point the stack heat generation rate is approximately 50kW (efficiency approximately 50%).

[0042] Circulation status confirmation: The three-way valve is kept at 98% opening (large circulation status), and the fan runs at 3000r / min (rated speed) to ensure maximum heat dissipation capacity.

[0043] Temperature difference monitoring and judgment: Real-time acquisition of reactor feed temperature T 入 =70℃, discharge temperature T 出=79℃, calculated ΔT=9℃. The temperature difference setpoint for the system during high-power operation is ΔTs=8℃ (based on an average temperature difference of 8℃ with a deviation of ±1℃ from 100 normal water filter tests). Since ΔT=9℃>ΔTs=8℃, the water filter is determined to be clogged.

[0044] Experimental verification: Disassembly of the water filter revealed that the filter media was covered by a microbial film, reducing the flow area by about 25%. The cooling water flow rate dropped from the normal 125L / min to 80L / min, resulting in an increase in the outlet temperature, which was consistent with the diagnosis of increased temperature difference.

[0045] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for diagnosing water filter clogging in a fuel cell system, characterized in that, The fuel cell system includes a cooling water circulation structure, which comprises a cooling water chamber disposed in the fuel cell stack, an expansion tank, a water pump, an axial fan, a large circulation inlet B of a three-way valve, and a water filter connected in sequence via pipes; the outlet of the cooling water chamber is connected to the expansion tank via a pipe, and the inlet of the cooling water chamber is connected to the water filter via a pipe; the three-way valve also includes a small circulation inlet A, which is connected to the water pump via another pipe; a cooling water outlet temperature sensor is installed at the outlet of the cooling water chamber, and a cooling water inlet temperature sensor and a cooling water inlet pressure sensor are installed at the inlet of the cooling water chamber; the method includes the following steps: When the fuel cell stack is not running in the fuel cell system, the small circulation inlet A of the three-way valve is opened and the large circulation inlet B of the three-way valve is closed, so that the cooling water circulation structure is in the small circulation state. At this time, the current pressure value P1 is obtained through the cooling water inlet pressure sensor. The current pressure value P1 is compared with the calibrated value Pset of the cooling water inlet pressure when the water filter is normal. If P1 is greater than Pset, it is determined that the water filter is blocked when the fuel cell is not running; if P1 is less than or equal to Pset, it is determined that the water filter is not blocked when the fuel cell is not running. When it is determined that the water filter is not blocked during the non-operation phase of the fuel cell stack, the fuel cell stack of the fuel cell system is controlled to operate at low power. The cooling water inlet temperature is monitored by the cooling water inlet temperature sensor, and the cooling water is controlled to gradually increase from the initial temperature to the preset temperature. During the temperature increase process, the three-way valve is switched from the small circulation state to the large circulation state, and the actual time t1 taken for the opening of the large circulation inlet B of the three-way valve to gradually increase from 0% to 35% is recorded. The actual time t1 is compared with the calibration time t0 when the three-way valve completes the 0%-35% opening switch of the large circulation inlet B of the water filter under normal conditions. If t1 is greater than t0, it is determined that the water filter is blocked when the fuel cell is running at low power; if t1 is less than or equal to t0, it is determined that the water filter is not blocked when the fuel cell is running at low power. If it is determined that the water filter is not clogged when the fuel cell stack is running at low power, the fuel cell system is switched to high power operation. The outlet temperature T is collected in real time using cooling water outlet temperature sensors and cooling water inlet temperature sensors. 出 With the reactor temperature T 入 Calculate the temperature difference ΔT=T 出 -T 入 ; The temperature difference ΔT is compared with the calibrated temperature difference ΔTs under high power operation when the water filter is operating normally. If ΔT is greater than ΔTs, it is determined that the water filter is blocked when the fuel cell is operating at high power; if ΔT is less than or equal to ΔTs, it is determined that the water filter is not blocked when the fuel cell is operating at high power.

2. The method for diagnosing water filter clogging in a fuel cell system according to claim 1, characterized in that, The term "low power" refers to 20-30% of the rated power of the fuel cell system, while "high power" refers to 80-100% of the rated power of the fuel cell system.

3. The method for diagnosing water filter clogging in a fuel cell system according to claim 1, characterized in that, In the step of controlling the cooling water to gradually increase from the initial temperature to the preset temperature, the initial temperature is 30℃ and the preset temperature is 65℃.

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