PEM fuel cell water status testing and adaptive management method

Abstract

The application relates to the technical field of fuel cells, and discloses a PEM fuel cell water state test system and a self-adaptive management method. The test system comprises an active diagnosis unit, which is used for applying a small, preset waveform and amplitude electrical disturbance to the fuel cell stack; a response analysis unit, which is used for collecting electrical response signals of the fuel cell stack under the electrical disturbance in real time; a water state decoupling module, which is used for decoupling and distinguishing characteristic parameters reflecting a membrane hydration state of the fuel cell stack and characteristic parameters reflecting a gas diffusion layer flooding state of the fuel cell stack; a water state quantification module, which is used for quantifying the decoupled characteristic parameters into a membrane hydration degree index and a gas diffusion layer flooding degree index; and a self-adaptive control unit, which is used for self-adaptively adjusting operation parameters of the fuel cell stack. The application can test the internal water state of the fuel cell in real time, in situ and non-invasively, and realizes self-adaptive management accordingly.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, specifically relating to a method for water state testing and adaptive management of PEM fuel cells. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are widely considered a key future direction in the clean energy field due to their high energy conversion efficiency, zero emissions, and low operating temperature, demonstrating enormous application potential in areas such as electric vehicles, distributed generation, and portable power supplies. However, the performance stability and long-term durability of PEMFCs are highly sensitive to their internal water management. Precise and stable water management is one of the key technological challenges in ensuring the efficient and reliable operation of fuel cells.

[0003] Currently, the testing and evaluation technologies for the internal water state of fuel cells, as well as corresponding management strategies, mainly face the following challenges and limitations: Existing water state testing methods generally fail to provide real-time, in-situ, accurate information on water distribution within the fuel cell. They often rely on external humidity sensors or dew point sensors to measure outlet gas humidity, or on electrochemical impedance spectroscopy (EIS) analysis to assess the overall water state of the fuel cell. These external or holistic measurement methods often cannot precisely distinguish between the hydration state of the proton exchange membrane (PEM) and the degree of flooding in the gas hydration layer (GDL). While EIS provides relatively comprehensive electrochemical information, its measurement is time-consuming, and the fitting analysis of the measurement results is complex, making it difficult to apply to real-time control under rapidly changing operating conditions in fuel cells. Current interruption methods are mainly used to measure ohmic impedance, but their ability to identify GDL flooding is limited, and they struggle to effectively differentiate between different water problems. Furthermore, while techniques such as neutron imaging can visually present the water distribution inside the fuel cell, their high cost and bulky equipment make them unsuitable for commercial fuel cell systems or online monitoring. The shortcomings of these methods result in delayed water state perception, limited accuracy, and a lack of ability to identify the root causes of different water problems.

[0004] Traditional fuel cell water management strategies generally lack the ability to finely perceive and differentiate the specific water state inside the cell, resulting in a rather crude management approach. These strategies typically employ empirical humidification and simple open-loop / closed-loop control, addressing potential flooding issues by adjusting humidifier power, increasing gas flow, or periodic purging. However, because it is impossible to know in real-time and accurately whether the problem is membrane dryness or GDL flooding, preventing flooding may lead to membrane dryness, or ensuring membrane hydration may cause GDL flooding. This crude management not only has poor management effectiveness, continuously impacting cell performance and lifespan, but also often requires additional auxiliary power, reducing the overall efficiency and economics of the fuel cell system.

[0005] Existing water management technologies struggle to adapt and implement the most targeted control measures in real time for two distinct water issues: membrane hydration and gas-depleted hydration (GDL) flooding. Because they cannot accurately identify and differentiate between these two water problems, traditional systems often fail to implement refined and differentiated management strategies, resulting in poor targeting and unsatisfactory effects. This lack of adaptive and differentiated management capabilities is a key obstacle to current fuel cell performance optimization and durability improvement.

[0006] In summary, existing technologies still have significant shortcomings in the accurate sensing and refined management of water conditions in fuel cells, severely hindering further performance improvements and commercialization of PEMFCs. Therefore, there is an urgent need to develop a technology capable of real-time and accurate identification of the membrane hydration state and GDL flooding state within PEMFCs, and based on this, to achieve adaptive and differentiated water management. This aims to significantly improve fuel cell performance, efficiency, and durability, reduce operating costs, and thus accelerate the widespread application of PEMFCs. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for testing and adaptively managing the water state of a PEM fuel cell. By solving the technical problems of difficulty in accurately distinguishing between membrane hydration and GDL flooding states and the lack of adaptive differentiated management strategies in the testing and management of the water state of a PEM fuel cell, this invention provides a method and approach that can accurately test the internal water state of a fuel cell in real time, in situ, and non-invasively, and thereby implement an adaptive differentiated management system.

[0008] To achieve the goal of real-time, in-situ, non-invasive, and precise testing of the internal water state of a fuel cell, and to realize adaptive differentiated management accordingly, this invention provides the following technical solution: A PEM fuel cell water state testing system, characterized in that: the testing system includes: a fuel cell stack, an active diagnostic unit, a response analysis unit, a water state decoupling module, and a water state quantification module; An active diagnostic unit, connected to the positive and negative terminals of the fuel cell, is used to apply small electrical disturbances of preset waveforms and amplitudes to the fuel cell stack. A response analysis unit, also connected to the positive and negative terminals of the fuel cell, is used to acquire the electrical response signals of the fuel cell stack under electrical disturbances in real time. A water state decoupling module, connected to the response analysis unit, is used to analyze and process the electrical response signals to decouple and distinguish characteristic parameters reflecting the membrane hydration state of the fuel cell stack and characteristic parameters reflecting the flooding state of the gas diffusion layer. A water state quantification module, connected to the water state decoupling module, is used to quantify the decoupled characteristic parameters into membrane hydration level indicators and gas diffusion layer flooding level indicators. Furthermore, the system also includes an adaptive control unit, connected to the water state quantification module, which adopts differentiated control strategies based on the membrane hydration level indicators and the gas diffusion layer flooding level indicators to adaptively adjust the operating parameters of the fuel cell stack.

[0009] An adaptive water state management method for PEM fuel cells, the method being implemented based on the aforementioned PEM fuel cell water state testing system, is characterized by the following steps: S1: Applying a small electrical disturbance of preset waveform and amplitude to the PEM fuel cell; S2: Real-time acquisition of the electrical response signal of the fuel cell under the electrical disturbance; S3: Analyzing and processing the electrical response signal, decoupling and extracting characteristic parameters reflecting the hydration state of the fuel cell membrane and characteristic parameters reflecting the flooding state of the fuel cell gas diffusion layer; S4: Quantifying the decoupled membrane hydration state characteristic parameters and gas diffusion layer flooding state characteristic parameters into membrane hydration degree index and gas diffusion layer flooding degree index; S5: Adaptively adjusting the operating parameters of the fuel cell by adopting differentiated control strategies based on the membrane hydration degree index and the gas diffusion layer flooding degree index.

[0010] As one possible implementation, the electrical disturbance includes: a short-duration, small-amplitude current pulse or an AC signal within a specific frequency range.

[0011] In some embodiments, when the electrical disturbance is a short-duration, small-amplitude current pulse, the water state decoupling module evaluates the characteristic parameters of the membrane hydration state by analyzing the instantaneous drop amplitude of the voltage response curve of the electrical response signal, and evaluates the characteristic parameters of the gas diffusion layer flooding state by analyzing the slow decay or recovery portion of the voltage response curve.

[0012] In other embodiments, when the electrical disturbance is an AC signal within a specific frequency range, the water state decoupling module evaluates the characteristic parameters of the membrane hydration state by analyzing the high-frequency impedance spectrum data of the electrical response signal, and evaluates the characteristic parameters of the gas diffusion layer flooding state by analyzing the low-frequency impedance spectrum data of the electrical response signal.

[0013] Compared with existing technologies, the present invention provides a method for water state testing and adaptive management of PEM fuel cells, which has the following beneficial effects: First, this invention enables real-time, in-situ, and non-invasive testing. By applying minute electrical disturbances and analyzing the battery's own response, it achieves real-time monitoring of the water state inside the fuel cell without the need for additional physical sensors, thus avoiding damage to the battery structure and additional installation space requirements.

[0014] Secondly, this invention can refine the decoupling of water states. It innovatively decouples the two distinct water problems of membrane hydration state and GDL flooding state by analyzing the transient ohmic impedance change and steady-state mass transfer impedance change in different frequency domains of the battery response signal under specific electrical disturbances. This overcomes the drawbacks of traditional methods that are confusing or difficult to distinguish.

[0015] Third, this invention enables differentiated adaptive management. Based on finely decoupled water state information, it can adopt different control strategies specifically, rather than simply adjusting a single parameter to address all problems, thus achieving more precise and efficient water management. Precise water management effectively avoids membrane drying and GDL flooding, significantly reduces ohmic losses and concentration polarization, improves battery output performance and efficiency, while reducing irreversible damage to the MEA caused by dry-wet cycling or localized over-wetting, extending the lifespan of the fuel cell, avoiding unnecessary auxiliary power consumption such as over-humidification or frequent purging, and improving the overall energy efficiency of the system. Attached Figure Description

[0016] Figure 1 Diagram of the PEM fuel cell water state testing system; Figure 2 This is a flowchart illustrating the steps of a PEM fuel cell water state testing and adaptive management method.

[0017] In the diagram: 1. Fuel cell stack; 2. Active diagnostic unit; 3. Response analysis unit; 4. Water state decoupling module; 5. Water state quantification module; 6. Adaptive control unit. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] A PEM fuel cell water state testing system includes a fuel cell stack 1, an active diagnostic unit 2, a response analysis unit 3, a water state decoupling module 4, a water state quantification module 5, and an adaptive control unit 6. The fuel cell stack 1 is the core component of the PEM fuel cell system, with its anode and cathode connected to hydrogen and air supply systems respectively, and equipped with auxiliary devices such as a humidifier, flow controller, temperature sensor, and heater. The active diagnostic unit 2 is connected to the positive and negative terminals of the fuel cell stack. It includes a signal generator and a power coupler, capable of applying a small electrical disturbance with a preset waveform and amplitude to the fuel cell stack 1. This disturbance is either a current pulse with a duration of 10-100 ms and an amplitude of approximately 0.1%-1% of the normal operating current; or an AC sine wave signal with a frequency range from 0.1 Hz to 10 kHz and an effective amplitude of 5-50 mV. These disturbances are designed to have minimal impact on the normal operation of the fuel cell. Power couplers are devices used to distribute input power to multiple output ports or combine power from multiple input ports, achieving efficient power distribution and synthesis while maintaining signal integrity and low loss. In the test system, they are used for signal sampling and monitoring. The response analysis unit 3, also connected to the positive and negative terminals of fuel cell stack 1, includes a high-speed data acquisition card and an analog-to-digital converter. It acquires the voltage response signal of the fuel cell in real time at a high sampling rate when disturbances are applied by the active diagnostic unit. For current pulses, it acquires the transient voltage response; for AC signals, it acquires transient voltage and current for impedance spectrum calculation. When the electrical disturbance is a short-duration, small-amplitude current pulse, the water state decoupling module 4 evaluates the characteristic parameters of the membrane hydration state by analyzing the instantaneous drop amplitude of the voltage response curve of the electrical response signal, and evaluates the characteristic parameters of the gas diffusion layer flooding state by analyzing the slow decay or recovery portion of the voltage response curve.

[0020] When the electrical disturbance is an AC signal within a specific frequency range, the water state decoupling module 4 evaluates the characteristic parameters of the membrane hydration state by analyzing the high-frequency impedance spectrum data of the electrical response signal, and evaluates the characteristic parameters of the gas diffusion layer flooding state by analyzing the low-frequency impedance spectrum data of the electrical response signal. The water state decoupling module 4 is a processing core, which is an embedded controller, DSP, or industrial control computer. It receives data collected by the response analysis unit 3 and executes a preset algorithm to decouple the water state characteristic parameters. When a current pulse is applied, the water state decoupling module 4 analyzes the voltage response curve. The initial rapid drop of the curve mainly reflects the ohmic impedance (R_ohmic) of the battery, which is closely related to the ionic conductivity of the membrane, and thus reflects the degree of membrane hydration. The subsequent slow decay or recovery of the curve mainly reflects the mass transfer impedance (R_mt), which is related to the diffusion resistance of the reactant gas in the GDL, and thus reflects the degree of GDL flooding. When an AC signal is applied for impedance spectrum measurement, the water state decoupling module 4 calculates the impedance spectrum. It extracts the real intercept of the impedance in the high-frequency region as the ohmic impedance R_ohmic, characterizing the hydration state of the membrane. It analyzes the diffusion arc characteristics in the low-frequency region as the mass transfer impedance R_mt, characterizing the flooding state of the GDL. The water state quantification module 5 receives the R_ohmic and R_mt values ​​from the decoupling module 4. It has a built-in water state database or empirical model, maps these impedance values ​​to specific membrane hydration and GDL flooding indicators, and makes judgments based on the preset optimal operating range, outputting an accurate water state report. The adaptive control unit 6 is the system's decision center. It receives the report from the water state quantification module 5 and, according to preset control logic, sends instructions to the fuel cell auxiliary equipment for differentiated adjustments.

[0021] If the report shows that the membrane hydration is too low or R_ohmic is too high, the adaptive control unit 6 will increase the humidifier's operating power or reduce the reactive gas flow rate to increase the water vapor residence time.

[0022] If the report indicates that the GDL flooding level is too high (i.e., R_mt is too high), the adaptive control unit 6 will increase the cathode gas flow rate, initiate a short purging procedure, or increase the operating temperature to accelerate the evaporation of liquid water.

[0023] If both dryness and flooding tendencies exist simultaneously, the adaptive control unit 6 will weigh the options based on preset priorities or current load conditions. Under the premise of ensuring output power under high load, it will prioritize solving the flooding problem and under low load, it will prioritize solving the membrane dryness problem to protect the membrane.

[0024] An adaptive water state management method for PEM fuel cells first involves system initialization, including sensor calibration and control parameter loading. During normal fuel cell operation, basic operating parameters such as cell voltage, current, and temperature should also be monitored.

[0025] The method includes the following steps: S1: The active diagnostic unit periodically or as needed applies specific electrical disturbances to the fuel cell. This step involves non-continuous disturbances, which are brief and intermittent, ensuring normal operation. S2: The response analysis unit acquires the fuel cell's electrical response signal under disturbance in real time. S3: The water state decoupling module analyzes and processes the acquired response signal, decoupling it to obtain the ohmic impedance R_ohmic, characterizing the membrane hydration state, and the mass transfer impedance R_mt, characterizing the GDL flooding state. S4: The water state quantification module quantifies R_ohmic and R_mt into specific membrane hydration and GDL flooding level indicators. S5: The adaptive control unit determines whether the quantified water state is within the optimal operating range. If the membrane hydration level is too low, the adaptive control unit adjusts the humidifier power to increase humidification; or reduces the gas flow rate; or lowers the operating temperature. If the GDL flooding level is too high, the adaptive control unit increases the gas flow rate to promote water discharge; or initiates a brief purging; or increases the operating temperature to accelerate water evaporation. If the water condition is good or there is a tendency for both drying and flooding (handled according to a preset strategy), then keep the current operating parameters unchanged or make minor adjustments. Finally, continue monitoring the fuel cell operation and proceed to the next test-management cycle.

[0026] This invention innovatively achieves real-time, in-situ, and non-invasive decoupled diagnosis of the membrane hydration state and GDL flooding state within the fuel cell by applying specific electrical disturbances with minimal impact on normal operation and precisely analyzing their responses. Based on this refined diagnostic result, the system can adaptively adopt targeted water management strategies, effectively avoiding the limitations of single control methods, thereby significantly improving the performance, efficiency, and durability of the fuel cell.

[0027] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0028] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A PEM fuel cell water state testing system, characterized in that: The test system includes: a fuel cell stack (1), an active diagnostic unit (2), a response analysis unit (3), a water state decoupling module (4), and a water state quantification module (5). An active diagnostic unit is connected to the positive and negative terminals of the fuel cell (1) and is used to apply small electrical disturbances with preset waveforms and amplitudes to the fuel cell stack (1). A response analysis unit is connected to the positive and negative terminals of the fuel cell (1) and is used to collect the electrical response signals of the fuel cell stack (1) under electrical disturbances in real time. A water state decoupling module is connected to the response analysis unit (3) and is used to analyze and process the electrical response signals to decouple and distinguish the characteristic parameters reflecting the membrane hydration state of the fuel cell stack (1) and the characteristic parameters reflecting the flooding state of the gas diffusion layer of the fuel cell stack (1). A water state quantification module is connected to the water state decoupling module (4) and is used to quantify the decoupled characteristic parameters into membrane hydration degree indicators and gas diffusion layer flooding degree indicators.

2. The PEM fuel cell water state testing system according to claim 1, characterized in that: The system also includes an adaptive control unit (6), which is connected to the water state quantification module (5). Based on the membrane hydration index and the gas diffusion layer flooding index, the adaptive control unit (6) adopts a differentiated control strategy to adaptively adjust the operating parameters of the fuel cell stack (1).

3. A PEM fuel cell water state adaptive management method, said method being implemented based on the PEM fuel cell water state testing system according to claim 1 or any one of the claims, characterized in that, Includes the following steps: S1: Apply a small electrical disturbance of preset waveform and amplitude to the PEM fuel cell; S2: Real-time acquisition of the electrical response signal of the fuel cell under the electrical disturbance; S3: Analysis and processing of the electrical response signal, decoupling and extracting characteristic parameters reflecting the hydration state of the fuel cell membrane and the flooding state of the fuel cell gas diffusion layer; S4: Quantification of the decoupled membrane hydration state characteristic parameters and gas diffusion layer flooding state characteristic parameters into membrane hydration degree index and gas diffusion layer flooding degree index; S5: Adaptive adjustment of the fuel cell operating parameters by adopting differentiated control strategies based on the membrane hydration degree index and the gas diffusion layer flooding degree index.

4. The PEM fuel cell water state adaptive management method according to claim 3, characterized in that: The electrical disturbances include: short-duration, small-amplitude current pulses or AC signals within a specific frequency range.

5. The PEM fuel cell water state adaptive management method according to claim 3, characterized in that, When the electrical disturbance is a short-duration small-amplitude current pulse, the water state decoupling module (4) evaluates the characteristic parameters of the membrane hydration state by analyzing the instantaneous drop amplitude of the voltage response curve of the electrical response signal, and evaluates the characteristic parameters of the gas diffusion layer flooding state by analyzing the slow decay or recovery part of the voltage response curve.

6. The system according to claim 3, characterized in that, When the electrical disturbance is an AC signal in a specific frequency range, the water state decoupling module (4) evaluates the characteristic parameters of the membrane hydration state by analyzing the high-frequency impedance spectrum data of the electrical response signal, and evaluates the characteristic parameters of the gas diffusion layer flooding state by analyzing the low-frequency impedance spectrum data of the electrical response signal.

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