A method and system for recovering a dry state of a membrane of a fuel cell engine

Abstract

The application belongs to the technical field of fuel cells, and specifically relates to a fuel cell engine membrane dry state recovery method and system, an electrochemical impedance value is obtained and a deviation from a target value is calculated, based on a deviation threshold range, combined with a dynamic weight, a pressure drop rate and a historical trend, membrane dryness is diagnosed as normal, slight, moderate or severe; after secondary confirmation, a hierarchical regulation strategy is executed, and regulation parameters at least include operating temperature and current; from slight to severe membrane dryness, the types of regulation parameters increase, the temperature regulation amplitude increases and the duration is shortened, and the impedance is continuously monitored and adaptively terminated during regulation. The application realizes accurate identification and hierarchical active recovery of the membrane dry state by replacing a humidity sensor through multi-parameter fusion diagnosis, avoids misjudgment and excessive regulation, and guarantees efficient and stable operation of the fuel cell.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, specifically a method and system for restoring the dry state of a fuel cell engine membrane. Background Technology

[0002] The statements in this section pertain only to the background technology related to this invention and do not necessarily constitute prior art.

[0003] During operation, proton exchange membrane fuel cells (PEMFCs) require sufficient hydration to maintain high proton conductivity. However, due to the complex and variable operating conditions of fuel cells, deviations in environmental temperature and humidity, and operating conditions (such as temperature, pressure, and metering ratio), the proton exchange membrane is prone to dehydration, resulting in "membrane drying." Membrane drying directly increases the membrane's proton conduction resistance, raises the cell's internal resistance, and degrades output performance. Prolonged operation or continuous operation in a dry state can lead to irreversible physical damage (such as cracking) and chemical degradation of the membrane, causing permanent performance degradation and severely shortening its lifespan.

[0004] To address the membrane dryness problem, existing technologies typically utilize humidity sensors for humidity monitoring and humidification control. By installing humidity sensors at the inlet and / or outlet of the fuel cell, the relative humidity of the gas is monitored, thereby inferring the hydration state of the membrane and controlling the operation of an external humidifier accordingly.

[0005] However, humidity sensors measure the humidity of the channels in the battery system, not the water content of the proton exchange membrane (PEM) itself. Whether the membrane is dry depends on a combination of factors, including channel humidity, current density, temperature, and water transfer kinetics within the membrane. It's possible for the channel gas humidity to be normal, but the membrane to be dry. Furthermore, high-precision, high-stability humidity sensors that meet automotive-grade requirements are expensive, increasing the overall system cost.

[0006] To avoid using expensive humidity sensors, some systems employ conservative control using fixed parameters calibrated based on experience (such as setting high inlet humidity, limiting maximum operating temperature, and setting minimum current threshold). This method cannot precisely adjust according to the actual membrane condition. Over-humidification when unnecessary may lead to "water flooding," while insufficient adjustment when needed may fail to effectively alleviate membrane dryness. Summary of the Invention

[0007] This invention provides a method and system for restoring the membrane dryness of a fuel cell engine, solving the problem of irreversible performance degradation caused by proton exchange membrane drying. Without relying on high-cost, low-reliability physical humidity sensors, a control strategy diagnoses the membrane dryness and performs active, graded environmental adjustments to significantly improve the fuel cell's durability and operational reliability, while controlling the overall system cost to meet application requirements.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention discloses a method for restoring the dry state of a fuel cell engine membrane, comprising the following steps: The electrochemical impedance value of the fuel cell is obtained, and the deviation between it and the preset target impedance value is calculated. Based on the preset threshold range to which the deviation belongs, combined with the dynamic weight of the operating parameters, the rate of change of pressure drop and the historical membrane dryness trend, the membrane dryness status of the fuel cell is diagnosed as normal, slight membrane dryness, moderate membrane dryness or severe membrane dryness. Based on the membrane dryness state obtained from the diagnosis, after verification by the secondary confirmation mechanism, the corresponding graded adjustment strategy is executed. The adjustment parameters in the graded adjustment strategy include at least the operating temperature and operating current of the fuel cell. Among them, from the slight membrane dryness state to the severe membrane dryness state, the types of adjustment parameters included in the graded adjustment strategy increase, the adjustment range of the operating temperature dynamically calculated based on the impedance deviation value increases, and the adjustment duration is shortened. During the adjustment process, the impedance is continuously monitored and adaptive termination is achieved.

[0009] Furthermore, the secondary confirmation mechanism is as follows: When initially diagnosed with mild, moderate, or severe membrane dryness, the pre-calibrated differential monitoring duration is... t conf Within, with a preset data collection step size △t col Simultaneously and continuously, parameters such as electrochemical impedance, monomer voltage, and air / hydrogen path pressure changes corresponding to each membrane dry state were collected; among them, the monitoring duration for severe membrane dryness was... t conf a Medium membrane dry monitoring duration t conf b Mild membrane dryness monitoring duration t conf c satisfy t conf a < t conf b < t conf c ; If the percentage of valid data meeting the corresponding membrane dryness determination criteria within the monitoring period is greater than or equal to the preset threshold. or If the second confirmation is successful, it indicates a true membrane dry state; if the percentage of valid data is less than [a certain percentage], then [the second confirmation is successful]. or If the second confirmation fails, it is considered a false membrane dryness signal. The adjustment strategy will be abandoned and normal operation will be maintained.

[0010] Furthermore, based on the preset threshold range to which the deviation belongs, combined with the dynamic weights of operating parameters, the rate of change of pressure drop, and historical membrane dryness trends, the membrane dryness status of the fuel cell is diagnosed as normal, slight membrane dryness, moderate membrane dryness, or severe membrane dryness, specifically: When the deviation value is greater than or equal to the first threshold (△E) a Furthermore, the fuel cell cell voltage is less than or equal to the target voltage, and the air path pressure drop is less than or equal to the target air path pressure drop, and the air path pressure drop rate is greater than or equal to the preset pressure drop rate threshold (V). p ), or the hydrogen pressure drop is less than or equal to the target hydrogen pressure drop and the rate of decrease in hydrogen pressure drop is greater than or equal to the preset pressure drop rate threshold (V). p When the fuel cell is in a state of severe membrane dryness, it is diagnosed as being in a state of severe membrane dryness. When the deviation value is less than the first threshold (△E) a And greater than or equal to the second threshold (ΔE) b Simultaneously, when the cell voltage of the fuel cell is less than or equal to the target voltage, the fuel cell is diagnosed as being in a moderate membrane dry state; if the number of slight membrane dryness occurrences in this range is greater than or equal to the preset threshold, it is directly determined to be a moderate membrane dry state. When the deviation value is less than the second threshold (△E) b And greater than or equal to the third threshold (ΔE) c When the fuel cell is in a state of slight membrane dryness, it is diagnosed that the fuel cell is in a state of slight membrane dryness. When the deviation value is less than the third threshold (△E) c When the fuel cell is in normal condition, the diagnosis is confirmed. Among them, the first threshold, the second threshold, and the third threshold satisfy: △E a >△E b >△E c The dynamic weighting coefficients of each judgment parameter are calculated in real time based on the current operating parameters, and the historical membrane drying trend is used as an auxiliary basis for judging the membrane drying status classification.

[0011] Furthermore, based on the membrane dryness status obtained from the diagnosis, and after verification through a secondary confirmation mechanism, the corresponding graded adjustment strategy is executed, specifically as follows: The diagnosis was mild membrane dryness. After secondary confirmation that the membrane dryness was not a transient disturbance, the first-stage regulation was implemented: controlling the fuel cell operating temperature to decrease the first amplitude (ΔT) dynamically calculated based on the impedance deviation value. c ), and maintain the current operating current for the first time period (t) dry-c During the adjustment process, the impedance value is continuously monitored. If the impedance value drops below the target impedance value in advance, the adjustment is terminated and the state is switched after a period of stable operation. The diagnosis was moderate membrane dryness. After secondary confirmation that the membrane dryness was not a transient disturbance, the second-stage regulation was implemented: the fuel cell operating temperature was controlled by a second reduction in magnitude (ΔT) based on dynamic calculation of the impedance deviation value. b At the same time, control the air metering ratio to reduce the third amplitude (△S) b ), and maintain the current operating current for the second time period (t dry-b During the adjustment process, the impedance value is continuously monitored. If the impedance value drops below the target impedance value in advance, the adjustment is terminated immediately and the state is switched after a period of stable operation. The diagnosis was severe membrane dryness. After secondary confirmation that the membrane dryness was not a transient disturbance, the third-level regulation was implemented: controlling the fuel cell operating temperature to decrease by the fourth magnitude (ΔT). a At the same time, the air metering ratio is reduced by the fifth level (△S). a Increase air operating pressure to the sixth level (△P) a And reduce the opening time of the drain valve by the seventh amplitude (△t). a ), and maintain the current operating current for the third time period (t) dry-a During the adjustment process, the impedance value is continuously monitored. If the impedance value drops below the target impedance value in advance, the adjustment is terminated immediately and the state is switched after a period of stable operation.

[0012] Furthermore, the operating temperature adjustment range satisfies: △T a >△T b >△T c The air metering ratio adjustment range meets the following requirement: △S a >△S b The duration of the adjustment satisfies: t dry-a <t dry-b <t dry-c .

[0013] Furthermore, when the duration corresponding to each level of adjustment ends or the impedance value reaches the target ahead of schedule during the adjustment process, the electrochemical impedance value of the fuel cell is obtained again. If the impedance value drops below the target impedance value, the adjustment is deemed effective, and a state switch is executed. If the impedance value does not decrease below the target impedance value, the adjustment is deemed ineffective, and the system will switch to a higher-level adjustment strategy or enter a low-temperature operation state.

[0014] Furthermore, the state transition is a step-by-step state transition, specifically as follows: After the first-level adjustment is determined to be effective, normal operation mode is restored; After the second-level adjustment is deemed effective, the operating temperature (ΔT) is maintained after the preset step-by-step recovery gradient. b ), air metering ratio (△S) b At each preset gradient duration (Δt_grad), the parameters are restored to the preset gradient magnitude until the normal operating mode is fully restored. During the restoration process, the impedance value is continuously monitored. If the impedance value rises back to the membrane dryness judgment threshold range, the restoration is immediately stopped and the current parameters are maintained. After the third-level adjustment is deemed effective, the operating temperature (ΔT) is maintained after the preset step-by-step recovery gradient. a ), air metering ratio (△S) a ), air operating pressure (△P) a ) and drain valve opening time (△t) a At each preset gradient duration (Δt_grad), the parameters are restored to the preset gradient magnitude until the normal operating mode is fully restored. During the restoration process, the impedance value is continuously monitored. If the impedance value rises back to the membrane dryness judgment threshold range, the restoration is immediately stopped and the current parameters are maintained.

[0015] Furthermore, when the third-level regulation is deemed ineffective, the system enters a low-temperature operation state. In this state, based on a pre-calibrated amplitude, the operating temperature of the fuel cell is reduced at all current points, and a low-temperature state graded exit mechanism is implemented. The specific implementation method of this mechanism is as follows: After starting in low-temperature operation mode, the pre-calibrated stable operating time is continuously maintained. t low stb During this stage, the membrane dryness status is not determined and no heating operation is performed. Small-scale temperature rise and monitoring process: After the stable operation period ends, initiate the staged temperature rise exit process, and increase the operating temperature of all current points according to the pre-calibrated small-scale temperature rise range. △T up1 Increase monitoring duration after temperature rise t low mon Simultaneously collect the electrochemical impedance value of the fuel cell in real time. If the impedance value remains stable below the target impedance value within the monitoring period and there is no upward trend, the heating is deemed effective. The temperature after the heating is maintained and the operation continues, and the restriction that the operating conditions cannot be changed is lifted. Pre-calibrated cycle duration t low cycle Then, repeat the above small-scale heating and monitoring process; if the impedance value rises back to the membrane dryness judgment threshold range within the monitoring time after a certain heating, the heating is deemed invalid, the operating temperature is restored to the previous stable low temperature value, the heating process is paused, and the operation is maintained at that temperature. t low retry Then, try the same heating process again; If multiple attempts to raise the temperature are unsuccessful, the tiered exit process will be stopped, and the current lowest stable low temperature value will be maintained until the end of the current operating cycle; in this state, the restriction that no changes to the operating conditions are allowed must be maintained at all times.

[0016] Furthermore, the dynamic weighting of operating parameters is specifically as follows: based on the current density and operating temperature of the fuel cell, dynamic coefficients are calculated through a preset weighting function, including impedance weighting coefficient, cell voltage weighting coefficient, and voltage drop weighting coefficient. The sum of these three is 1, which is used to dynamically adjust the first threshold ΔE. a Second threshold △E b The third threshold △E c Target voltage and preset voltage drop rate threshold V p .

[0017] The second aspect of the present invention discloses a fuel cell engine membrane dry state recovery system, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the above-described fuel cell engine membrane dry state recovery method.

[0018] Compared with existing technologies, one or more of the above technical solutions have the following beneficial effects: 1. Using electrochemical impedance spectroscopy as the core, a "virtual sensor" is formed by fusing multiple parameters. Impedance is used as a parameter that directly reflects the membrane state for diagnosis, which is more accurate and timely than indirect humidity measurement. Furthermore, instead of outputting a simple "yes / no" judgment, it achieves a graded diagnosis from mild to moderate to severe, and subsequently adopts a progressively escalating adjustment strategy. This avoids dependence on high-cost, easily failing physical humidity sensors, significantly reducing system costs, and also improves the robustness and accuracy of condition monitoring.

[0019] 2. For membrane dryness of varying severity, a progressively enhanced regulation strategy was designed. The regulation parameters were expanded from a single temperature to a combination of multiple parameters such as metering ratio and pressure. The regulation amplitude and duration were dynamically matched with the fault level, realizing a leap from "coarse protection" to "fine regulation" and effectively avoiding under-regulation or over-regulation.

[0020] 3. A secondary confirmation mechanism is set before adjustment to eliminate instantaneous interference; the adjustment range is dynamically calculated based on the impedance deviation value to achieve precise matching; the impedance is monitored in real time during the adjustment process and adaptive termination is supported; the state recovery adopts a step-by-step gradient mechanism to avoid secondary film drying; a graded exit mechanism is designed for low-temperature operation to reduce performance loss. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 A schematic diagram of the membrane dry state recovery process of a fuel cell engine provided in one or more embodiments of the present invention; Figure 2 This is a schematic diagram of the process for determining the dry state of a fuel cell engine membrane, provided in one or more embodiments of the present invention. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0025] As described in the background section, existing technologies typically employ a humidity sensor-based monitoring and humidification control method. This involves installing humidity sensors at the inlet and / or outlet of the fuel cell to monitor the relative humidity of the reactant gases, thereby inferring the hydration state of the membrane and controlling the operation of an external humidifier accordingly.

[0026] However, the sensor measures the humidity of the gas in the flow channel, not the water content of the proton exchange membrane itself. This indirect measurement method has an inherent hysteresis and cannot reflect the transient hydration state of the membrane in real time and accurately. Especially under dynamic operating conditions, the membrane may have dried out, but the change in gas humidity has not yet been captured by the sensor. At the same time, high-precision, high-stability humidity sensors that meet automotive-grade requirements are expensive, increasing the total system cost. Furthermore, in the complex gas environment of fuel cell operation, which is high in humidity and may contain trace amounts of ionic impurities, humidity sensors are prone to drift, poisoning, or damage. The measurement accuracy decreases rapidly over time, requiring frequent calibration or replacement, resulting in high maintenance costs.

[0027] To avoid using expensive humidity sensors, some systems employ conservative control using fixed parameters based on experience (such as setting high intake humidity, limiting maximum operating temperature, and setting minimum current thresholds). This approach, however, cannot precisely adjust according to the actual membrane condition. Over-humidification when unnecessary can lead to "flooding," while insufficient adjustment when needed may fail to effectively alleviate membrane dryness. Furthermore, an overly conservative strategy limits fuel cell operation in its high-efficiency range, sacrificing system performance and fuel economy.

[0028] In summary, existing technologies rely on high-cost, low-reliability physical sensors or employ non-adaptive control strategies, making it difficult to meet the comprehensive cost and performance requirements of commercial applications while ensuring the long lifespan and high reliability of fuel cell engines.

[0029] Therefore, this solution provides a method and system for restoring the membrane dryness of a fuel cell engine. Using electrochemical impedance as the core criterion, it integrates cell voltage and flow path voltage drop trends to construct a multi-parameter, software-based "virtual sensor" to replace the physical humidity sensor, directly diagnosing membrane dryness. Through a graded, closed-loop regulation strategy focused on reducing operating temperature, it promotes membrane "self-hydration" by altering the internal environment, upgrading from "passive protection" to "active maintenance and recovery."

[0030] This solution uses a combination of impedance value, cell voltage, and air / hydrogen path pressure drop to determine the membrane dry state, avoiding misjudgments caused by relying on a single factor.

[0031] This solution adjusts the membrane dryness state of different levels by adjusting conditions such as temperature, metering ratio, pressure, and drain valve frequency. No additional sensors or actuators are required, and the current change is limited during the state adjustment process to avoid misjudgment caused by current changes. It is easy to implement in products.

[0032] like Figure 1 As shown, a method for restoring the dry state of a fuel cell engine membrane includes the following steps: The electrochemical impedance value of the fuel cell is obtained, and the deviation between it and the preset target impedance value is calculated. Based on the preset threshold range to which the deviation belongs, combined with the dynamic weight of the operating parameters, the rate of change of pressure drop and the historical membrane dryness trend, the membrane dryness status of the fuel cell is diagnosed as normal, slight membrane dryness, moderate membrane dryness or severe membrane dryness. Based on the membrane dryness state obtained from the diagnosis, after verification by the secondary confirmation mechanism, the corresponding graded adjustment strategy is executed. The adjustment parameters in the graded adjustment strategy include at least the operating temperature and operating current of the fuel cell. Among them, from the slight membrane dryness state to the severe membrane dryness state, the types of adjustment parameters included in the graded adjustment strategy increase, the adjustment range of the operating temperature dynamically calculated based on the impedance deviation value increases, and the adjustment duration is shortened. During the adjustment process, the impedance is continuously monitored and adaptive termination is achieved.

[0033] This solution consists of two parts: "Fuel Cell Membrane Dryness Judgment Method" and "Fuel Cell Engine Humidity Adjustment Method". The specific process of each part is described below.

[0034] 1) Method for judging the dryness of fuel cell membranes.

[0035] The system performs real-time online assessments based on impedance values, dynamic weighting of operating parameters, individual cell voltage change trends, air path pressure drop and its rate of change, hydrogen path pressure drop and its rate of change, and historical membrane dryness trends. This is achieved by recording and storing data for a fixed duration T. run The operating current and various variables, when the cumulative operation at a single current point exceeds T run Then, the membrane dryness condition is determined. It is essential to ensure that the fuel cell is under relatively stable operating conditions when performing the membrane dryness assessment, avoiding unreliable diagnostics under transient conditions (such as acceleration or deceleration).

[0036] The sources and determination methods for each variable are as follows: a) Impedance value: Impedance values ​​are acquired in real time using the electrochemical impedance spectroscopy device of the fuel cell engine's DC / DC converter, with actual data at a given frequency and amplitude used as the basis for judgment. The target impedance value is calibrated using operating current and cumulative operating time. In a dry membrane state, the high-frequency impedance is relatively high.

[0037] b) Individual Cell Voltage: The stack voltage and individual cell voltage values ​​are acquired in real time via the fuel cell engine voltage acquisition module. The target individual cell voltage value is calibrated using the operating charge, cumulative operating time, and the voltage value of the previous operating cycle. In a dry membrane state, the individual cell voltage is lower than the target value and continues to decrease.

[0038] c) Hydrogen / air pressure drop and rate of change: The pressure drop and rate of change are calculated in real time using pressure sensors at the fuel cell inlet and outlet (rate of change = (current pressure drop - previous pressure drop) / time interval). The target pressure drop value is the calibration value under standard operating conditions, and a preset pressure drop rate threshold (V) is used. p Calibration was performed via bench testing. The membrane in its dry state is characterized by a pressure drop value lower than the target value and a pressure drop rate ≥ V. p .

[0039] d) Dynamic weighting coefficients and threshold dynamic adjustment: The judgment thresholds for impedance, individual cell voltage, and hydrogen / open circuit voltage drop are not fixed values, but are adjusted according to the current operating parameters (current density). J Operating temperature T The weights are calculated in real time using a preset weighting function, as shown in the following formula: W Z =k 1 ×J+k 2 ×(T 0 T)+k 3; W V =k 4 ×(1 J)+k 5 ×(T T 1 )+k 6; W P =1 W Z W V ; in, W Z For the dynamic weighting coefficient of impedance, W V This is the dynamic weighting coefficient for the individual unit voltage. W P The dynamic weighting coefficient for pressure drop; k 1~ k 6 is the calibration coefficient; T 0 and T 1 represents the calibrated temperature threshold; J The current density is normalized to 0~1.

[0040] Each weight coefficient satisfies 0 < W Z 、W V 、W P < 1, and W Z +W V +W P =1.

[0041] Based on the calculated dynamic weighting coefficients, the judgment thresholds for each parameter are adjusted in real time. Impedance deviation threshold adjustment: at high current density ( J Larger) or high operating temperature ( T Under higher operating conditions, impedance is more sensitive to the dry state of the membrane. In this case, it is appropriate to reduce the first threshold ΔE of the impedance deviation. a Second threshold △E b The third threshold △E c This makes the system more sensitive to impedance changes; conversely, under low current density or low temperature conditions, the impedance deviation threshold should be appropriately increased.

[0042] Individual voltage threshold adjustment: at low current density ( J Under relatively low current density conditions, the cell voltage is more sensitive to the dry state of the membrane. In this case, the target voltage value should be appropriately reduced or the voltage judgment condition should be relaxed. Conversely, under high current density conditions, the voltage judgment requirement should be appropriately increased.

[0043] Pressure drop threshold adjustment: Under medium and low temperature conditions, pressure drop changes better reflect the membrane drying trend. In this case, it is appropriate to reduce the pressure drop rate threshold V. p Or a target voltage drop value, making the system more sensitive to changes in voltage drop.

[0044] The specific adjustment range is calibrated through bench tests and pre-stored in the controller in the form of a mapping table (MAP) between weighting coefficients and threshold adjustment amounts. Through the above dynamic adjustment, it is ensured that the sensitivity of each parameter to the determination of the membrane dry state remains relatively consistent under different operating conditions, avoiding misjudgments or omissions caused by changes in operating conditions.

[0045] e) Historical Membrane Drying Trend: Real-time recording of membrane dryness diagnosis results and occurrence frequency to establish a historical membrane dryness trend database. When the number of mild membrane dryness occurrences within a preset time period (T_trend) is greater than or equal to a preset frequency threshold (N), the dryness trend is established. trend When the membrane dryness level is reached, the membrane dryness grade is adjusted upwards (slight → moderate) as an auxiliary judgment criterion.

[0046] f) Execution flow of dynamic threshold adjustment: After the cumulative running time at a single current point meets the requirement, the impedance, average single-cell voltage, and air / hydrogen circuit voltage drop within that time period are calculated in increments of Δt_mon. Simultaneously, based on the current current density... J and operating temperature T Calculate dynamic weight coefficients W Z , W V , W P Based on the weighting coefficients, the dynamic adjustment amount of each decision threshold is obtained from a pre-calibrated MAP table, and the baseline threshold is corrected in real time. The corrected threshold is then used for execution. Figure 2The membrane dryness assessment process is shown below. This mechanism ensures that the sensitivity of membrane dryness diagnosis remains relatively consistent under different operating conditions, capturing true changes in membrane dryness rather than fleeting fluctuations.

[0047] according to Figure 2 The process shown includes the following steps to determine membrane dryness: Obtain the deviation between the current impedance value and the target value of the fuel cell, based on the current current density J and operating temperature. T Calculate dynamic weighting coefficients, and dynamically adjust each judgment threshold (ΔE) based on the weighting coefficients. a ΔE b ΔE c Target voltage, V p (etc.), retrieve historical membrane drying trend data; Severe membrane dryness judgment: If the adjusted impedance deviation value is greater than or equal to the adjusted first threshold ΔE a Furthermore, the voltage of the fuel cell unit is less than or equal to the adjusted target voltage, and simultaneously meets any of the following voltage drop conditions: (1) The air path pressure drop is less than or equal to the air path target pressure drop and the air path pressure drop rate is greater than or equal to the adjusted pressure drop rate threshold V. p ; (2) The hydrogen pressure drop is less than or equal to the target hydrogen pressure drop and the rate of decrease of the hydrogen pressure drop is greater than or equal to the adjusted pressure drop rate threshold V. p ; The diagnosis is that the fuel cell is in a state of "severe membrane dryness".

[0048] Medium membrane dryness judgment: If the adjusted impedance deviation value meets ΔE a Deviation value ≥ ΔE b If the fuel cell cell voltage is ≤ the adjusted target voltage, then the fuel cell is diagnosed as being in a "moderate membrane dryness" state; if the number of occurrences of slight membrane dryness within this range is ≥ N, then the fuel cell is diagnosed as being in a "moderate membrane dryness" state. trend It was directly determined to be a medium-sized membrane dryness.

[0049] Slight membrane dryness assessment: If the adjusted impedance deviation value satisfies ΔEb>deviation value≥ΔEc, then the fuel cell is diagnosed as being in a "slight membrane dryness" state.

[0050] Normal state: If the adjusted impedance deviation value is less than ΔEc, the fuel cell is diagnosed as being in a "normal" state. The "target value" and threshold (△E) involved in the above judgment process a , △E b , △E c Target voltage, V p All values ​​(etc.) are based on the benchmark values ​​calibrated by bench tests, and then adjusted in real time according to dynamic weighting coefficients. The threshold satisfies ΔE. a >△Eb >△E c The larger the deviation value, the more severe the film drying condition.

[0051] During bench testing, standard values ​​at various current points and membrane dryness values ​​under different conditions are measured. In actual use, the MAP (Mean Amount Mapping) of current and deviation values ​​is checked. The bench testing also simultaneously measures three variables: impedance, cell voltage, and voltage drop, and establishes a database for judging membrane dryness. The database pre-stores impedance MAPs for different operating time stages, matching different MAPs based on engine operating time. Furthermore, a corresponding engine operating time coefficient can be added during subsequent adjustments to address state differences arising at different battery lifespans, achieving self-adaptation.

[0052] After the engine reaches any level of film dryness, it undergoes a secondary confirmation mechanism for verification before adjusting the engine humidity. During the humidity adjustment period, film dryness is not assessed; the film dryness assessment process is only performed during normal operation.

[0053] The above scheme constructs a "virtual sensor" by fusing multiple parameters (impedance + dynamic weighting + voltage + voltage drop and rate of change of voltage drop + historical membrane drying trend), overcoming the shortcomings of single physical sensors, such as susceptibility to failure and drift. Impedance, as an intrinsic parameter directly reflecting the membrane state, provides more accurate and timely diagnosis than indirect humidity measurement. Instead of simply outputting a "yes / no" judgment, it achieves a graded diagnosis from mild to moderate to severe, with corresponding progressively escalating adjustment strategies.

[0054] 2) Humidity regulation method for fuel cell engine.

[0055] Once membrane dryness is diagnosed, adjustments are not implemented immediately. Instead, a second confirmation is performed, with monitoring durations varying according to the specific membrane dryness state. t conf Internally, continuously monitor relevant parameters such as impedance, voltage, and voltage drop. t conf If all internal parameters still meet the criteria for determining the membrane dry state, then it is determined to be a true membrane dry state, and the corresponding adjustment strategy is executed; if t conf If the internal parameters return to the normal range, it is determined to be a transient disturbance. No adjustment is performed, and normal operation continues while monitoring is strengthened. After verification by the secondary confirmation mechanism, the corresponding tiered adjustment strategy is then executed.

[0056] The secondary verification mechanism is a validity verification process after membrane dryness diagnosis. It is used to eliminate false diagnostic results caused by non-membrane dryness factors such as transient operating condition fluctuations, sensor acquisition errors, and electromagnetic interference. Specifically: When the initial diagnosis indicates mild, moderate, or severe membrane dryness, a secondary confirmation should be initiated immediately, within the pre-calibrated differential monitoring duration. tconf Inside, with △t col (0.1~0.5s) is the acquisition step size for synchronous and continuous acquisition of core parameters such as electrochemical impedance, monomer voltage, and air / hydrogen path voltage drop. Among them, severe membrane dryness t conf a (e.g., 20-40 seconds) is used for quick confirmation and early intervention for recovery; Medium membrane dry t conf b (For example, 40~60s); Mild membrane dryness t conf c (For example, 60~80s); The above monitoring duration meets the requirements. t conf a < t conf b < t conf c .

[0057] The calculation method for "percentage of effective data": over the entire monitoring period... t conf Within, based on the step size of the data collection △t col Each sampling point is checked to determine whether the parameters at each sampling time meet the criteria for the corresponding membrane dry state. The proportion of sampling points that meet the criteria out of the total number of sampling points is the percentage of valid data. The statistical window is the entire monitoring time (e.g., 30 seconds), rather than a single 0.5-second step, thus having sufficient statistical significance.

[0058] If the percentage is greater than or equal to the preset threshold or If the percentage of effective data is 80%~95%, the secondary confirmation is deemed successful, confirming a true membrane dry state, and the corresponding graded adjustment strategy is then implemented; if the percentage of effective data is < or If the second confirmation fails, it is considered a false membrane dry signal (such as caused by transient operating condition fluctuations or electromagnetic interference), and the adjustment strategy is abandoned and normal operation is maintained.

[0059] The above calibration parameters ( t conf , △t col , orAll parameters (etc.) were determined through bench tests combined with actual working conditions.

[0060] For different degrees of membrane dryness, after secondary confirmation, the humidity was adjusted in stages by adjusting the following operating conditions. All adjustment ranges were dynamically calculated based on the current impedance deviation value, rather than fixed values. The dynamic calculation function is shown in the following formula: ΔX=k X ×(ΔE ΔEmin) / (ΔEmax) ΔEmin)×ΔXmax ; in, ΔX To adjust the dynamic adjustment range of the parameters (△T, △S, △P, △ta, etc.); k X These are the calibration coefficients for each parameter; DE This is the current impedance deviation value; ΔEmin This represents the minimum deviation value corresponding to the membrane dryness grade; ΔEmax This represents the maximum deviation value corresponding to the membrane dryness grade; ΔXmax This represents the maximum calibration adjustment range corresponding to the membrane dryness level. This function achieves a positive correlation between the adjustment range and the impedance deviation value; the larger the deviation, the larger the adjustment range. Calibration based on the stack characteristics is required. DE ΔEmin The minimum deviation value is taken as the standard value. When this deviation value exceeds the calibration value, it indicates that the current deviation is still near the boundary of the membrane dryness grade. Adjusting too small an adjustment is meaningless. In this case, take... ΔX=0 That is, this parameter is not adjusted to avoid unnecessary disturbances to the system caused by ineffective adjustments. The specific value of the deviation is determined by bench testing for different fuel cell stacks.

[0061] a) Adjustment state during "slight membrane dryness": The diagnosis was mild membrane dryness. After secondary confirmation that the membrane dryness was not a transient disturbance, the first-stage regulation was implemented: controlling the fuel cell operating temperature to decrease the first amplitude (ΔT) dynamically calculated based on the impedance deviation value. c ), and maintain the current operating current for the first time period (t) dry-c During the adjustment process, the impedance value is continuously monitored with a step size of Δt_mon (Δt_mon is the calibration monitoring step size, usually 0.5~2s). If t dry-c If the impedance value drops below the target impedance value before the end, the adjustment will be terminated and the system will switch to normal operation mode after a set period of time. If t dry-c If the impedance value has not decreased below the target impedance by the end of the test, the system will switch to the "medium film dryness" adjustment state and restart the timing.

[0062] b) Conditioning state during "medium membrane dryness": The diagnosis was moderate membrane dryness. After secondary confirmation that the membrane dryness was not a transient disturbance, the second-stage regulation was implemented: the fuel cell operating temperature was controlled by a second reduction in magnitude (ΔT) based on dynamic calculation of the impedance deviation value. b At the same time, control the air metering ratio to reduce the third amplitude (△S) b ), and maintain the current operating current for the second time period (t dry-b ); During the adjustment process, the impedance value is continuously monitored with a step size of Δt_mon. If t dry-b If the impedance value drops below the target impedance value before the end, the adjustment is immediately terminated and step-by-step gradient recovery is performed. If t dry-b If the impedance value does not decrease below the target impedance at the end, the system will switch to the "severe membrane dryness" adjustment state and restart the timing.

[0063] c) Adjustment state during "severe membrane dryness": The diagnosis was severe membrane dryness. After secondary confirmation that the membrane dryness was not a transient disturbance, the third-level regulation was implemented: controlling the fuel cell operating temperature to decrease by the fourth magnitude (ΔT). a At the same time, the air metering ratio is reduced by the fifth level (△S). a Increase air operating pressure to the sixth level (△P) a And reduce the opening time of the drain valve by the seventh amplitude (△t). a ), and maintain the current operating current for the third time period (t) dry-a ); During the adjustment process, the impedance value is continuously monitored with a step size of Δt_mon. If t dry-a If the impedance value is reduced to below the target impedance value before the end, the adjustment is immediately terminated and step-by-step gradient recovery is performed. If t dry-a If the impedance value does not drop below the target impedance at the end, the system enters a low-temperature operating state, and other conditions return to normal. Furthermore, membrane dryness judgment is no longer performed during the initial startup of the low-temperature operating state.

[0064] d) Low-temperature operation: When the "severe film dryness" condition cannot be adjusted to a normal state, the operating temperature at each current point is reduced through calibration to increase the relative humidity of the fuel cell stack operation and prevent film dryness from worsening; at the same time, a graded exit mechanism for the low-temperature condition is designed, specifically as follows: The "severe membrane dryness" state was regulated by the third stage (t) dry-a If the impedance value still does not decrease below the target impedance after a certain period of time, the system enters a cryogenic operating state. This state is a safety protection mechanism set up by the system to protect the fuel cell from irreversible membrane dry damage.

[0065] The initial operating temperature for cryogenic operation needs to be calibrated for the specific fuel cell stack through bench testing. The calibration principle is to ensure that the membrane drying is effectively alleviated (i.e., the relative humidity inside the fuel cell stack) while avoiding excessively low temperatures that could lead to liquid water accumulation and cause a "flooding" fault. The calibrated initial temperature value is pre-stored in the controller, and this calibration value is directly called when the system enters cryogenic operation.

[0066] Once the system enters cryogenic operation, it initially prohibits changes in operating conditions (i.e., operating current). The fuel cell must be maintained at the current point at which it entered cryogenic operation until the condition is adjusted to a reasonable range before any changes in operating conditions are permitted. This restriction aims to eliminate the interference of current fluctuations on the membrane dry state recovery process and ensure the effectiveness of cryogenic regulation measures.

[0067] In this state, the operating temperature at each current point is reduced by calibration (based on the calibrated initial low-temperature temperature) to increase the relative humidity of the fuel cell stack operation and prevent film deterioration; at the same time, a graded exit mechanism for the low-temperature state is designed, specifically as follows: After starting the low-temperature operation, the pre-calibrated stable operating time will be maintained. t low stb (For example, 5~15min), this stage is the initial stage of low temperature start-up, during which the membrane dryness status is not judged and the heating operation is not performed; After the stable operation period ends, initiate the graded temperature rise exit process, gradually increasing the operating temperature of all current points by a pre-calibrated small amount. △T up1 (For example, 2~5℃) Increase the temperature and maintain monitoring duration after the temperature rise. t low mon (For example, 3~8 minutes) The electrochemical impedance value of the fuel cell is collected simultaneously. If the impedance value remains stable below the target impedance value within the monitoring time and there is no upward trend, the heating is deemed effective. The system continues to operate at the temperature after the heating. At this time, the restriction of "not allowing changes in operating conditions" is lifted, allowing the system to adjust the operating conditions according to actual needs. Pre-calibrated cycle duration t low cycle After (e.g., 8-15 minutes), repeat the above small-amplitude heating and monitoring process; if, after a certain heating, the impedance value rises back to the membrane dryness judgment threshold range within the monitoring time, then the heating is deemed invalid, the operating temperature is immediately restored to the previous stable low temperature value, the heating process is paused, and the operation is maintained at that temperature. t low retryAfter (e.g., 10-20 minutes), try the same temperature increase again; If three consecutive attempts to raise the temperature are unsuccessful, the step-by-step exit process will be stopped, and the current lowest stable low temperature value will be maintained until the end of the current operating cycle. In this state, the restriction of "no change of operating conditions" will be maintained until the end of the current operating cycle or the system is powered on and off again.

[0068] All calibration durations and temperature ranges (including initial low-temperature temperature, t low stb , △T up1 , t low mon , t low cycle , t low retry All parameters (e.g., [specific parameters]) were determined through bench tests combined with actual operating conditions, and different fuel cell stacks need to be calibrated separately. During the initial startup phase of low-temperature operation, membrane dryness assessment is no longer required.

[0069] Step-by-step gradient recovery mechanism: After effective adjustment for moderate and severe membrane dryness, the adjustment parameters are not directly restored to normal. Instead, a step-by-step gradient recovery method is used to avoid rapid loss of membrane moisture due to rapid parameter restoration, which could trigger secondary membrane dryness. The specific recovery rules are as follows: Set the gradient recovery step number n, the single-step gradient magnitude ΔX_grad, and the gradient interval duration Δt_grad. All parameters are recovered in the same number of steps. After the adjustment is effective, maintain the adjusted parameters for Δt_grad for a period of time. After monitoring the impedance value and finding no abnormalities, restore each adjusted parameter to the normal parameter ΔX_grad. Each recovery step maintains the duration of Δt_grad and monitors the impedance value. If the impedance value remains normal, the next recovery step continues. If the impedance value rises back to the membrane dryness determination threshold range (i.e., the membrane dryness determination condition is met again), the recovery is stopped immediately, and the current parameters are maintained until the end of this running cycle or the impedance value returns to normal (i.e., it exits the membrane dryness determination threshold range) before trying again. After completing n steps of recovery, the parameters are restored to normal and the system enters normal operating mode.

[0070] There are two main sources of moisture within the fuel cell membrane: Water is produced by the reaction: The electrochemical reaction itself produces water.

[0071] Gas humidification: Moisture carried by the air and hydrogen entering the fuel cell stack.

[0072] When membrane drying occurs, it is often because operating conditions (such as excessively high temperature or excessive airflow) cause the rate of water evaporation and removal to exceed the rate of generation and input.

[0073] Therefore, the adjustment strategy in this scheme is to reverse the above process.

[0074] The lower the temperature, the more drastically the maximum amount of water vapor (saturation humidity) that air can hold decreases. This makes it easier for existing water vapor within the fuel cell stack to exceed its saturation point and condense into liquid water. Lower temperatures can increase the hydrophilicity of proton exchange membranes such as Nafion, making them more effective at absorbing and retaining moisture. By reducing the saturated vapor pressure of water and increasing the hydrophilicity of the membrane, the amount of moisture evaporating from the membrane and electrodes is reduced at its source. This is reflected in specific control strategies such as "reducing the air metering ratio," "increasing the air operating pressure," and "reducing the duration of drain valve opening."

[0075] Reduce air metering ratio (△S) b ,△S a This reduces excessive, dry intake air. With reduced airflow, less moisture is "blown away" from the fuel cell stack. Increased relative humidity of the fuel cell outlet gas makes the water vapor environment within the flow channels more conducive to moisture back-diffusion into the membrane, rather than extraction from it.

[0076] Increase air operating pressure (△P) a Physically, this is equivalent to increasing the partial pressure capacity of water vapor in the gas, while simultaneously raising the water level inside the fuel cell stack (because the drainage pressure is higher), allowing more liquid water to remain near the membrane electrode assembly for absorption.

[0077] Reduce the duration of drain valve opening (△t) a This means retaining more liquid water inside the system, extending the time for water to contact the membrane and hydrate it.

[0078] Meanwhile, from slight membrane dryness to severe membrane dryness, the adjustment parameters increase progressively (slight membrane dryness requires only temperature adjustment; moderate membrane dryness requires temperature and air metering ratio adjustment; severe membrane dryness requires temperature, air metering ratio adjustment, air pressure adjustment, and drain valve opening duration adjustment). This tiered design follows the "principle of minimal intervention," the specific principle of which is as follows: When the membrane dries slightly, the problem is not serious. Simply lowering the operating temperature can change the saturated vapor pressure inside the fuel cell stack, promoting membrane self-hydration. At this time, parameters such as air metering ratio and pressure should not be adjusted to avoid unnecessary additional impact on fuel cell stack durability.

[0079] When the membrane is moderately dry, temperature adjustment alone is insufficient to effectively alleviate the dryness. In this case, in addition to cooling, an auxiliary measure of "reducing the air metering ratio" is added to reduce the moisture carried away by airflow. Although this adjustment will slightly affect the oxygen supply, the benefits outweigh the risks at moderate membrane dryness levels.

[0080] In cases of severe membrane dryness, the membrane is already in a state of severe water loss, and irreversible damage will occur if intervention is not initiated promptly. At this point, a multi-pronged approach is needed. In addition to cooling and reducing the air metering ratio, more forceful measures should be taken, such as increasing air pressure (enhancing water vapor partial pressure to promote water retention within the membrane) and reducing the duration of the drain valve opening (extending the residence time of liquid water within the fuel cell stack). Although these adjustments have some impact on fuel cell stack durability, compared to the permanent degradation caused by membrane dryness, this short-term, controlled intervention is necessary and worthwhile.

[0081] Therefore, in the parameter of "fixed duration", t dry-a <t dry-b <t dry-c To achieve humidity regulation by intervening in the shortest possible time; Among the parameters for "reduced operating temperature", △T a >△T b >△T c Intervention should be carried out within the largest possible range of temperature reduction. In the parameter "air metering ratio decreases", △S b <△S a It significantly reduces the air metering ratio under severely dry membrane conditions, maximizing moisture retention and creating a highly favorable environment for membrane rehydration.

[0082] While reducing the air metering ratio can maintain moisture, it sacrifices the system's oxygen supply and reaction efficiency, and may lead to risks such as localized flooding. Therefore, this strategy is only used in the "moderate membrane dryness" and "severe membrane dryness" levels, and the application intensity is precisely controlled dynamically based on impedance deviation values.

[0083] In the early stages, cooling measures with no side effects should be prioritized. Only when the problem escalates should more effective air volume reduction measures, which come at a performance cost, be introduced, and the intensity of these measures should increase with the severity of the problem.

[0084] This solution eliminates the need for costly and interference-prone humidity sensors and their associated calibration and maintenance processes. Although an impedance measurement circuit is added, its hardware cost in mass production applications is typically lower than that of multiple automotive-grade humidity sensors.

[0085] All adjustments in this solution (cooling, reducing the air metering ratio, pressure regulation, and controlling the drain valve) are achieved by modifying the existing subsystems of the fuel cell engine (cooling system, air compressor, back pressure valve, and drain valve). This eliminates the need for complex external humidifiers or other new hardware, significantly improving the feasibility of the solution. By replacing external sensors with reliable software algorithms, and combining optimized designs such as dynamic weighting, secondary confirmation, dynamic adjustment range, real-time monitoring adaptive termination, step-by-step gradient recovery, and low-temperature graded exit, the system's failure points are reduced, meeting the high robustness requirements of automotive systems.

[0086] Accordingly, a fuel cell engine membrane dry state recovery system includes a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the above-mentioned fuel cell engine membrane dry state recovery method.

[0087] The processor is configured to: acquire the electrochemical impedance value of the fuel cell, calculate the deviation between it and the preset target impedance value, and based on the preset threshold range to which the deviation belongs, combined with the dynamic weight of the operating parameters, the rate of change of pressure drop and the historical membrane dryness trend, diagnose the membrane dryness status of the fuel cell as normal, slightly dry, moderately dry or severely dry. The processor is also configured to: based on the membrane dryness state obtained from the diagnosis, and after verification by a secondary confirmation mechanism, execute the corresponding graded adjustment strategy. The adjustment parameters in the graded adjustment strategy include at least the operating temperature and operating current of the fuel cell. Specifically, from the slight membrane dryness state to the severe membrane dryness state, the graded adjustment strategy includes more types of adjustment parameters, and the adjustment range of the operating temperature dynamically calculated based on the impedance deviation value is increased, while the adjustment duration is shortened. During the adjustment process, the impedance is continuously monitored and adaptive termination is achieved.

[0088] This solution determines membrane dryness status by combining impedance value, dynamic weighting of operating parameters, individual cell voltage, air / hydrogen path pressure drop and rate of change of pressure drop, and historical membrane dryness trends, avoiding misjudgments caused by single-factor judgments. A secondary confirmation mechanism is set up before adjustment to eliminate instantaneous interference. The adjustment range is dynamically calculated based on impedance deviation value to achieve precise matching. Impedance is monitored in real time during the adjustment process, supporting adaptive termination. A step-by-step gradient mechanism is adopted for state recovery to avoid secondary membrane dryness. A graded exit mechanism is designed for low-temperature operation to reduce performance loss.

[0089] This solution adjusts the membrane dryness for different levels by adjusting conditions such as temperature, metering ratio, pressure, and drain valve frequency. No additional sensors or actuators are required, and current changes are limited during the adjustment process to avoid misjudgments caused by current variations. It is easy to implement in products.

[0090] The above are merely preferred embodiments of the present invention and are not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for restoring the dry state of a fuel cell engine membrane, characterized in that, Includes the following steps: The electrochemical impedance value of the fuel cell is obtained, and the deviation between it and the preset target impedance value is calculated. Based on the preset threshold range to which the deviation belongs, combined with the dynamic weight of the operating parameters, the rate of change of pressure drop and the historical membrane dryness trend, the membrane dryness status of the fuel cell is diagnosed as normal, slight membrane dryness, moderate membrane dryness or severe membrane dryness. The dynamic weighting of the operating parameters specifically refers to dynamic coefficients calculated using a preset weighting function based on the current density and operating temperature of the fuel cell. These coefficients include impedance weighting coefficients, cell voltage weighting coefficients, and voltage drop weighting coefficients, the sum of which is 1. These coefficients are used to dynamically adjust the first threshold ΔE. a Second threshold △E b The third threshold △E c Target voltage and preset voltage drop rate threshold V p ; Based on the membrane dryness obtained from the diagnosis, after verification by the secondary confirmation mechanism, the corresponding graded adjustment strategy is executed. The adjustment parameters in the graded adjustment strategy include at least the operating temperature and operating current of the fuel cell. Among them, from slight membrane dryness to severe membrane dryness, the graded regulation strategy includes more types of regulation parameters, and the regulation range of operating temperature dynamically calculated based on impedance deviation value is increased. At the same time, the regulation duration is shortened, and impedance is continuously monitored during the regulation process and adaptive termination is achieved. Based on the membrane dryness status obtained from the diagnosis, and after verification through a secondary confirmation mechanism, the corresponding graded adjustment strategy is implemented, specifically as follows: The diagnosis was mild membrane dryness. After secondary confirmation and verification, the first-stage adjustment was implemented, specifically: the fuel cell operating temperature was reduced by the first magnitude ΔT. c Maintain the current operating current for the first time period t dry-c During the adjustment process, the impedance value is continuously monitored. If the impedance value drops below the target impedance value ahead of schedule, the adjustment is terminated. The diagnosis was moderate membrane dryness. After secondary confirmation and verification, the second-stage adjustment was implemented, specifically: the fuel cell operating temperature was reduced by the second magnitude ΔT. b The air metering ratio decreased by the third magnitude △S b Maintain the current operating current for the second time period t dry-b During the adjustment process, the impedance value is continuously monitored. If the impedance value drops below the target impedance value prematurely, the adjustment is terminated immediately. The diagnosis was severe membrane dryness. After secondary confirmation and verification, the third-level adjustment was implemented, specifically: the fuel cell operating temperature was reduced by the fourth magnitude ΔT. a The air metering ratio decreased by the fifth magnitude △S a Increase air operating pressure by the sixth magnitude △P a And reduce the duration of the drain valve opening by the seventh amplitude △t a Maintain the current operating current for the third time period t dry-a During the adjustment process, the impedance value is continuously monitored. If the impedance value drops below the target impedance value prematurely, the adjustment is terminated immediately. In the graded regulation strategy, the electrochemical impedance value of the fuel cell is obtained again when the duration corresponding to each level of regulation ends or when the impedance value reaches the target ahead of schedule during the regulation process. If the impedance value drops below the target impedance value, the adjustment is deemed effective, and a state switch is executed. The state transition is a step-by-step state transition, specifically as follows: After the first level of adjustment in the tiered adjustment strategy is determined to be effective, the normal operation mode is restored. After the second stage of the graded adjustment strategy is deemed effective, the reduced operating temperature T will be... b Air metering ratio S b According to the preset step-by-step gradient recovery, first maintain the adjusted parameters to run for a preset gradient duration Δt_grad, then restore the normal parameters to a preset gradient magnitude. For each recovery step, maintain the parameters for that step to run for Δt_grad. During the recovery process, continuously monitor the impedance value. If the impedance value rises back to the membrane dryness judgment threshold range, immediately stop the recovery and maintain the current parameters. Repeat the above process until the normal operation mode is fully restored. After the third level of regulation in the graded regulation strategy is determined to be effective, the reduced operating temperature T will be... a Air metering ratio S a Air operating pressure P a and drain valve opening time t a According to the preset step-by-step gradient recovery, first maintain the adjusted parameters to run for a preset gradient duration Δt_grad, then restore the normal parameters to a preset gradient magnitude. For each recovery step, maintain the parameters for that step to run for Δt_grad. During the recovery process, continuously monitor the impedance value. If the impedance value rises back to the membrane dryness judgment threshold range, immediately stop the recovery and maintain the current parameters. Repeat the above process until the normal operation mode is fully restored.

2. The method for restoring the dry state of a fuel cell engine membrane as described in claim 1, characterized in that, The two-factor confirmation mechanism is as follows: When initially diagnosed with mild, moderate, or severe membrane dryness, the pre-calibrated differential monitoring duration should be used. t conf Within, with a preset data collection step size △t col Simultaneously and continuously, parameters such as electrochemical impedance, monomer voltage, and air / hydrogen path pressure changes corresponding to each membrane dry state were collected; among them, the monitoring duration for severe membrane dryness was... t conf a Medium membrane dry monitoring duration t conf b and duration of mild membrane dryness monitoring t conf c satisfy t conf a < t conf b < t conf c ; If the percentage of valid data meeting the corresponding membrane dryness determination criteria within the monitoring period is greater than or equal to the preset threshold. η If the second confirmation is successful, it indicates a true membrane dry state; if the percentage of valid data is less than [a certain percentage], then [the second confirmation is successful]. η If the second confirmation fails, it is considered a false membrane dryness signal. The adjustment strategy will be abandoned and normal operation will be maintained.

3. The method for restoring the dry state of the membrane in a fuel cell engine as described in claim 1, characterized in that, Based on the preset threshold range to which the deviation belongs, and combined with the dynamic weights of operating parameters, the rate of change of pressure drop, and historical membrane dryness trends, the membrane dryness state of the fuel cell is diagnosed, specifically as follows: When the deviation value is greater than or equal to the first threshold ΔE a Furthermore, the fuel cell cell voltage is less than or equal to the target voltage, and the air path pressure drop is less than or equal to the target air path pressure drop, with the air path pressure drop rate ≥ the preset pressure drop rate threshold V. p At that time, or the hydrogen pressure drop is less than or equal to the target hydrogen pressure drop and the rate of decrease of the hydrogen pressure drop is ≥ V p At that time, the fuel cell was diagnosed as being in a state of severe membrane dryness; When the deviation value is less than the first threshold ΔE a And greater than or equal to the second threshold ΔE b Meanwhile, when the voltage of a single fuel cell cell is less than or equal to the target voltage, the fuel cell is diagnosed as being in a moderate membrane dry state. When the deviation value is less than the second threshold ΔE b And greater than or equal to the third threshold ΔE c At that time, the fuel cell was diagnosed as being in a state of slight membrane dryness; When the deviation value is less than the third threshold ΔEc, the fuel cell is diagnosed as being in normal condition. Among them, the first threshold, the second threshold, and the third threshold satisfy: △E a >△E b >△E c .

4. The method for restoring the dry state of the membrane in a fuel cell engine as described in claim 1, characterized in that, In a graded regulation strategy, the adjustment range of the operating temperature satisfies: ΔT a >△T b >△T c The adjustment range of the air metering ratio satisfies: △S a >△S b The duration of the adjustment satisfies: t dry-a <t dry-b <t dry-c .

5. The method for restoring the dry state of the membrane in a fuel cell engine as described in claim 1, characterized in that, In the graded regulation strategy, the electrochemical impedance value of the fuel cell is obtained again when the duration corresponding to each level of regulation ends or when the impedance value reaches the target ahead of schedule during the regulation process. If the impedance value does not decrease below the target impedance value, the adjustment is deemed ineffective, and the system will switch to a higher-level adjustment strategy or enter a low-temperature operation state.

6. The method for restoring the dry state of a fuel cell engine membrane as described in claim 5, characterized in that, When the third-level regulation of the graded regulation strategy is deemed ineffective, the system enters a low-temperature operation state. Based on a pre-calibrated amplitude, the operating temperature of the fuel cell at all current points is reduced, and a graded exit mechanism for the low-temperature state is implemented, including: After starting in low-temperature operation mode, the pre-calibrated stable operating time is continuously maintained. t low stb During this stage, the membrane dryness status is not determined and no heating operation is performed. The small-scale temperature increase and monitoring process is as follows: After the stable operation period ends, initiate the graded temperature increase exit process, and increase the operating temperature of all current points according to the pre-calibrated small-scale temperature increase range. △T up1 Increase monitoring duration after temperature rise t low mon Simultaneously collect the electrochemical impedance value of the fuel cell in real time. If the impedance value remains stable below the target impedance value within the monitoring period and there is no upward trend, the heating is deemed effective. The temperature after the heating is maintained and the operation continues, and the restriction that the operating conditions cannot be changed is lifted. Pre-calibrated cycle duration t low cycle Then, repeat the above small-scale heating and monitoring process; if the impedance value rises back to the membrane dryness judgment threshold range within the monitoring time after a certain heating, the heating is deemed invalid, the operating temperature is restored to the previous stable low temperature value, the heating process is paused, and the operation is maintained at that temperature. t low retry Then, try the same heating process again; If multiple attempts to raise the temperature are unsuccessful, the tiered exit process will be stopped, and the current lowest stable low temperature value will be maintained until the end of the current operating cycle; in this state, the restriction that no changes to the operating conditions are allowed must be maintained at all times.

7. A fuel cell engine membrane dry state recovery system, characterized in that, It includes at least one processor and a memory connected to the processor, the memory being used to store a computer program; when the processor executes the computer program, it implements a method for restoring the dry state of a fuel cell engine membrane as described in any one of claims 1-6.

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