A PEMFC stack voltage online reconstruction method based on two-state coupling

Abstract

This invention discloses an online voltage reconfiguration method for PEMFC stacks based on dual-state coupling. This invention can output non-sensor state quantities that cannot be directly measured by sensors, including the fast state of the effective cathode gas, the slow state of the liquid water net inventory, the liquid water compressibility factor, and additional mass transfer losses. This method can improve the voltage reconfiguration accuracy under dynamic operating conditions and provides a technical foundation for control correction, fault warning, and decision support in onboard PEMFC systems.

Description

Technical Field

[0001] This invention relates to the field of proton exchange membrane fuel cell system modeling and online state estimation technology, and particularly to an online real-time voltage reconstruction method for the operation of vehicle-mounted proton exchange membrane fuel cell (PEMFC) stacks. Based on a fundamental physical voltage model, a fixed common dynamic base, the fast state of the effective gas at the cathode, and the slow state of the net liquid water storage at the cathode, this method achieves online reconstruction of the stack voltage and the additional mass transfer losses at the cathode, and outputs internal state information that cannot be directly measured by sensors. Background Technology

[0002] Existing vehicle-mounted PEMFC systems are typically equipped with sensors for current, voltage, inlet pressure, some temperature, and actuator control quantities. However, key states such as the effective oxygen supply capacity near the fuel cell reaction interface, the degree of liquid water accumulation, additional mass transfer losses, and the resulting performance degradation trend are often not directly obtainable by sensors.

[0003] Traditional fuel cell stack voltage models often emphasize quasi-steady-state polarization characteristics, typically using a reversible voltage term superimposed with activation losses, ohmic losses, and concentration losses to describe the output voltage. While these models can describe the basic polarization framework, they struggle to characterize phenomena such as cathode gas supply lag, liquid water accumulation and release, and mass transfer improvement during the recovery phase under dynamic on-board conditions. Consequently, they often exhibit significant biases during rapid load changes, high current plateaus, and the recovery phase.

[0004] On the other hand, the difference in measured voltage and current can only indicate that "performance has changed", but it is difficult to provide non-sensor information that is truly valuable for control and decision-making, such as: whether the current deviation is more likely to be due to a decrease in the effective oxygen supply capacity of the cathode or an increase in mass transfer blockage caused by the accumulation of liquid water; whether the change requires adjustment of air supply, valve opening or other control variables; and whether the change has a continuous evolution trend and can be used for fault early warning.

[0005] Therefore, there is a need for an online reconfiguration method for PEMFC stack voltage that is geared towards automotive applications, has a clear physical meaning of state, can be updated online recursively, can output non-sensor internal state, and can provide a basis for control correction and fault diagnosis. Summary of the Invention

[0006] The purpose of this invention is to provide an online voltage reconfiguration method for PEMFC stacks based on the fast state of effective gas at the cathode and the slow state of net liquid water storage. This method addresses the problems of existing methods, such as difficulty in revealing the non-sensor-controlled internal state of the stack online, difficulty in effectively characterizing dynamic mass transfer loss at the cathode, and difficulty in directly supporting control correction and anomaly identification.

[0007] This invention further introduces a fast state of effective cathode gas on top of the fundamental physical Nernst piecewise voltage model and a fixed common dynamic base. With cathode liquid water net storage slow state The additional mass transfer loss at the cathode is reconstructed online to obtain a final reconstructed voltage that more closely approximates the actual operating conditions. It also outputs non-sensor information related to the internal state that cannot be directly observed by the sensor.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a PEMFC stack voltage online reconfiguration method based on dual-state coupling, comprising the following steps: S1 collects data from vehicle-mounted sensors and controllers, including at least time, fuel cell current, fuel cell voltage, cathode inlet pressure, anode inlet pressure, and temperature-related data. S2 constructs a basic voltage model based on the collected data, wherein the basic voltage model is preferably a piecewise polarization model based on the physical Nernst mechanism; S3 constructs a fixed common dynamic base on the basic voltage model to reflect the impact of supply-consumption mismatch on the equivalent reaction interface pressure, and obtains the basic reconfiguration voltage. ; S4 updates the fast state of the effective gas at the cathode online based on the change in current and the rate of change in current. The transient deviation of the effective oxygen supply capacity of the cathode reaction interface is used to characterize the behavior. S5 updates the cathode liquid water net inventory status online based on production water, continuous flow drainage, enhanced drainage during the recovery phase, and background discharge. To characterize liquid water accumulation and mass transfer blockage memory effect; S6 constructs liquid water compressibility factor The compressibility factor is used to correct the intensity of the fast state of the cathode effective gas to obtain the equivalent state of the cathode effective gas. S7 calculates the additional mass transfer loss at the cathode based on the equivalent state of the effective gas at the cathode, and compares it with the basic reconstruction voltage. Superimposed, the final reconstructed voltage is obtained. ; S8 outputs the final reconfiguration voltage. Cathode effective gas fast state The cathode liquid water net storage is slow. Liquid water compressibility factor Additional mass transfer losses at the cathode and related diagnostic or control correction results.

[0009] Beneficial effects Compared with existing voltage estimation methods that rely solely on quasi-steady-state polarization models, this invention can better characterize the cathode-added mass transfer losses during the high-current stage, dynamic load switching stage, and recovery stage, thereby improving the accuracy of online reconfiguration of the stack voltage.

[0010] Compared to traditional methods that only output voltage errors, this invention can output non-sensor state quantities with clear engineering interpretations, including the fast state of the cathode effective gas, the slow state of the liquid water net inventory, and additional mass transfer losses, thereby improving state interpretability.

[0011] The non-sensor state variables output by this invention can be further used for air supply regulation, valve opening correction, performance degradation monitoring, anomaly identification, and subsequent lifespan trend analysis, facilitating the formation of a digital reconstruction system oriented towards control and decision-making services.

[0012] This invention adopts a hierarchical structure of "basic model + fixed common dynamic base + fast state + slow state", which has good scalability. New states, fault modes or control correction logic can be added later without changing the overall framework.

[0013] This invention can output non-sensor state quantities that cannot be directly measured by sensors, including the fast state of effective gas at the cathode, the slow state of net liquid water inventory, the liquid water compressibility factor, and additional mass transfer losses. In application, when a vehicle is accelerating or experiencing a rapid increase in load, and a momentary drop in the fuel cell stack voltage occurs, the fast state can be used to identify insufficient effective oxygen supply to the cathode, providing a basis for increasing air supply and correcting control parameters of relevant actuators. When a vehicle is on a high-current platform or recovering from a load drop, and voltage recovery is delayed or fluctuates abnormally, the slow state can be used to determine liquid water accumulation and drainage recovery status, providing a basis for drainage strategy optimization, anomaly identification, and performance degradation analysis. This method can improve the voltage reconstruction accuracy under dynamic operating conditions and provides a technical foundation for control correction, fault warning, and decision support in onboard PEMFC systems. Attached Figure Description

[0014] Figure 1. Overall flowchart of the PEMFC stack voltage online reconfiguration method based on dual-state coupling.

[0015] Figure 2 is a schematic diagram of the principle structure of the three-layer recursive architecture and dual-state coupling of the present invention.

[0016] Figure 3 shows the logic diagram of the fast and slow dual-state coupling and compression factor correction of the present invention.

[0017] Figure 4 A block diagram of the voltage online reconfiguration system of the present invention. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. The overall process of the present invention is as follows: Figure 1 As shown.

[0019] To clarify the source of each variable in this invention, this embodiment first distinguishes the quantities involved in the reconstruction into measured quantities and calculated quantities. The measured quantities are directly provided by the onboard sensors and / or controllers; the calculated quantities are obtained recursively by substituting the measured quantities into the basic model, the fixed common dynamic base model, and the dual-state online update model.

[0020]

[0021] The three-layer recursive architecture and dual-state coupling relationship of this invention are as follows: Figure 2 As shown.

[0022] The calculated quantity is determined according to the following formula: First layer: Basic quasi-steady-state voltage model layer

[0023]

[0024]

[0025]

[0026]

[0027] Second layer: Fixed common dynamic reconstruction layer

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034] Third layer: Dual-state coupling additional reconstruction layer 1. Fast-state reference and driving quantities

[0035]

[0036]

[0037] 2. Fast state of effective gas at the cathode

[0038]

[0039] 3. Definition of voltage residual

[0040] 4. Cathode liquid water net storage slow state

[0041]

[0042]

[0043]

[0044]

[0045] 5. Fast and slow state coupling

[0046]

[0047]

[0048]

[0049] 6. Additional mass transfer correction and final reconstructed voltage

[0050]

[0051] To further illustrate the coupling relationship between fast states, slow states, and the compressibility factor, Figure 3 The fast and slow dual-state coupling and compression factor correction logic of the present invention is shown.

[0052] The first layer, the basic quasi-steady-state voltage model layer, is used to provide the reference framework for the stack voltage. The specific input-output relationship is shown in the aforementioned formula, and will not be elaborated further here.

[0053] Building upon the first layer, a second layer of fixed common dynamic reconfiguration is constructed. This layer utilizes the dynamic mismatch between supply and consumption to form a shared dynamic state, and obtains the base reconfiguration voltage through equivalent pressure correction. This layer primarily reflects the impact of the common dynamic mismatch between gas supply and reaction consumption.

[0054] Building upon the second layer, a third dual-state coupled additional reconstruction layer is constructed. This layer includes the fast state of the cathode effective gas. and cathode liquid water net storage slow state .in, Transient deviation used to characterize the effective oxygen supply capacity of the cathode reaction interface; Used to characterize the accumulation of liquid water and the resulting mass transfer blockage memory effect.

[0055] By liquid water compressibility factor The effect intensity of the fast state of the effective gas at the cathode is corrected to obtain the equivalent state of the effective gas at the cathode, and the additional mass transfer loss at the cathode is further calculated. The additional mass transfer loss at the cathode is superimposed on the base reconstruction voltage. The final reconstructed voltage is obtained. .

[0056] In practical applications, the , , as well as All of these are non-sensor state variables, which cannot be directly measured by a single onboard sensor, but are calculated recursively from the measured quantities using a model. These non-sensor state variables can be used to characterize changes in the effective oxygen supply capacity of the cathode, the degree of liquid water accumulation, and its inhibitory effect on mass transfer, and are further used for control correction, anomaly identification, performance degradation analysis, and subsequent decision support. The block diagram of the voltage online reconfiguration system of this invention is as follows: Figure 4 As shown.

[0057] The states and parameters in this invention can be configured with boundary and continuity constraints according to the requirements of automotive applications to ensure the interpretability and numerical stability of the online reconstruction results. If new component states, new fault modes, or new control corrections need to be introduced in the future, the hierarchical framework of this invention can be further expanded.

Claims

1. A method for online voltage reconfiguration of a PEMFC stack based on dual-state coupling, characterized in that, By further introducing the fast state of the effective gas at the cathode on top of the fundamental physics Nernst piecewise voltage model and a fixed common dynamic base. With cathode liquid water net storage slow state The additional mass transfer loss at the cathode is reconstructed online to obtain a final reconstructed voltage that more closely approximates the actual operating conditions. Simultaneously, it outputs non-sensor information related to the internal state; Specifically, the steps include the following: S1. Collect data from vehicle-mounted sensors and / or controllers, including time, fuel cell current, fuel cell voltage, cathode inlet pressure, anode inlet pressure, and temperature-related data; S2. Construct a basic voltage model based on the collected data to obtain the basic voltage; S3. Construct a fixed common dynamic base on the basic voltage model to obtain the basic reconfigured voltage. ; S4. Update the fast state of the effective gas at the cathode online based on the change in current and the rate of change in current. And calculate the fast additional mass transfer loss caused by the fast state of the effective gas at the cathode; S5. Update the net inventory status of cathode liquid water online based on the production water, continuous flow drainage, enhanced drainage during the recovery phase, and background discharge. ; S6. Construct the liquid water compressibility factor based on the slow state of the cathode liquid water net storage. The fast state of the cathode effective gas is corrected by the liquid water compressibility factor to obtain the equivalent state of the cathode effective gas. S7. Calculate the additional mass transfer loss at the cathode based on the equivalent state of the effective gas at the cathode, and compare it with the basic reconstruction voltage. Superimposed, the final reconstructed voltage is obtained. ; S8 outputs the final reconfigured voltage and the corresponding non-sensor state quantity, which are used for stack performance evaluation, fault diagnosis or control correction. The non-sensor state variables are obtained online by steps S3 to S7 based on the measured quantities and model recursive equations.

2. The online voltage reconfiguration method for PEMFC stacks according to claim 1, characterized in that, The basic voltage model in step S2 is a piecewise polarization model based on the physical-Nernst mechanism, which includes at least three or four of the following terms: reversible voltage term, activation loss term, ohmic loss term, and concentration loss term. The model is then calculated in segments according to the current density range to obtain the quasi-steady-state voltage framework.

3. The online voltage reconfiguration method for PEMFC stacks according to claim 1, characterized in that, The fixed common dynamic base in step S3 is constructed by a shared dynamic state characterizing the supply and consumption mismatch. This shared dynamic state is related at least to the cathode gas input, the stack current consumption, and the pressure correction process. It is used to correct the measured pressure to the equivalent reaction interface pressure and thereby form the basic reconstruction voltage. .

4. The online voltage reconfiguration method for PEMFC stacks according to claim 1, characterized in that, The fast state of the cathode effective gas in step S4 To characterize the transient deviation of the effective oxygen supply capacity of the cathode reaction interface, the fast state of the effective gas at the cathode is recursively updated based on the difference between the current low-pass reference value and the real-time current, as well as the filtered current change rate, and online correction is performed in conjunction with the voltage residual to obtain the additional mass transfer loss caused by the fast state.

5. The online voltage reconfiguration method for PEMFC stacks according to claim 1, characterized in that, The cathode liquid water in step S5 is in a slow storage state. To characterize the accumulation of liquid water in the cathode channel and / or diffusion layer and the mass transfer blockage memory effect, the slow state of the net liquid water in the cathode is recursively updated through the net effects of liquid water generation drive, continuous flow drainage drive, recovery phase enhanced drainage drive, and background discharge drive. The recovery phase enhanced drainage drive is activated by release qualification logic with hysteresis threshold and holding time.

6. The online voltage reconfiguration method for PEMFC stacks according to claim 1, characterized in that, The liquid water compressibility factor in step S6 The value range is limited to between a preset lower limit and 1. It is used to compress the effect of the fast state of the effective gas in the cathode when the net liquid water in the cathode increases, so as to reflect the inhibitory effect of liquid water accumulation on the cathode mass transfer capacity. Finally, the additional mass transfer loss of the cathode is calculated from the corrected equivalent state of the effective gas in the cathode.

7. The online voltage reconfiguration method for PEMFC stacks according to claim 1, characterized in that, The non-sensor state quantity output in step S8 includes at least one of the following: fast state of effective gas at cathode, slow state of net liquid water at cathode, liquid water compressibility factor, additional mass transfer loss at cathode, and incremental additional loss due to coupling of slow state. All non-sensor state quantities are obtained by online recursive calculation from measured quantities through steps S3 to S7. The changing trends of the non-sensor state quantities and the final reconstructed voltage are used to generate performance degradation indications, abnormal alarm information, or control correction basis.

8. A system for implementing the online voltage reconfiguration method for PEMFC stacks according to any one of claims 1 to 7, characterized in that, include: The system comprises a data access module, a parameter loading module, a basic calculation module, an intermediate dynamic reconstruction module, an online update module, a cathode additional mass transfer loss calculation module, a result output module, and a data management module. The basic calculation module generates the base voltage and a fixed common dynamic base. The online update module updates the fast state of the cathode effective gas. and cathode liquid water net storage slow state The cathode additional mass transfer loss calculation module is used to calculate based on... , and Calculate the final cathode additional mass transfer loss; The result output module is used to output the final reconstructed voltage and non-sensor state results; the data management module is used to record the historical evolution information of state variables and parameters.

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