Fuel cell system hydrogen pressure control method based on adaptive stepping PI control

Abstract

The invention discloses a fuel cell system hydrogen pressure control method based on adaptive stepping PI control, which comprises the steps of hydrogen path dynamic model construction, variable step size stepping modulation and dynamic parameter adjustment, and adopts a variable step size stepping modulation mechanism and a dynamic parameter correction strategy to optimize the problem of fuel cell hydrogen pressure control. The adjustment step length is dynamically switched by comparing the deviation between the feedback pressure and the target value in real time, the target value is quickly approached when the deviation is large, and the fine adjustment mode is switched when the deviation is approached to the threshold value. The step length coefficient is corrected online by combining the coupling parameters of the proportional valve front pressure and the electric pile current, and the pressure overshoot phenomenon is eliminated. The design ensures that the pressure response is smoothly converged in the whole process, and the stack structure damage caused by hydrogen pressure oscillation is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cell control systems, and in particular to a hydrogen pressure control method for a fuel cell system based on adaptive step-by-step PI control. Background Art

[0002] In fuel cell systems, the stability of the hydrogen inlet pressure directly affects the performance and life of the stack. Traditional PI control methods have a significant overshoot problem in hydrogen pressure control, especially under conditions such as shutdown and gas replenishment, pressure maintenance and leak detection. Overshoot may cause excessive hydrogen pressure or pressure difference failure, thereby damaging the stack membrane electrode. Traditional pressure feedback PI control adjusts the proportional valve opening by fixing PI parameters. Although the structure is simple, it is difficult to balance rapidity and stability. When the step load changes, the hydrogen pressure response is prone to overshoot and the stabilization time is relatively long. Existing methods have deficiencies in overshoot suppression and adaptability to working conditions. There is an urgent need for a hydrogen pressure control solution that can dynamically adjust the control parameters according to the real-time pressure difference and current to achieve a fast and overshoot-free response.

[0003] A Chinese patent document discloses a fuel cell reaction gas pressure control system and method [Application Number: 202210636289.0, Publication Number: CN114976122B] including: a switch valve, a proportional valve, a pressure relief valve, a pressure sensor, a controller and a fuel cell stack module. The switch valve, the proportional valve, the pressure relief valve, the pressure sensor and the fuel cell stack module are electrically connected in sequence, and the controller is electrically connected to the switch valve, the proportional valve, the pressure relief valve, the pressure sensor and the fuel cell stack module respectively. Although this patent achieves the purpose of fuel cell reaction gas pressure control, there are still obvious overshoot problems and insufficient response time. Summary of the Invention

[0004] A method for controlling hydrogen pressure in a fuel cell system based on adaptive step-by-step PI control, characterized by comprising the following steps: Construct a dynamic model of the hydrogen circuit: including a proportional valve flow model, a stack hydrogen consumption model, and a tail gas emission model; Variable step size modulation: According to the feedback pressure F (k-1) and the target value Z (k) The difference dynamically adjusts the step size coefficient k; Dynamic parameter adjustment: Calculate the step correction coefficient k′ based on the proportional valve upstream pressure P1 and the stack current I.

[0005] Preferably, the hydrogen path dynamic model includes the following transfer function: Hydrogen pressure transfer function: ; The proportional valve opening transfer function corresponding to the proportional valve flow model is: ; The stack current transfer function corresponding to the stack hydrogen consumption model is: ; The tail exhaust valve opening transfer function corresponding to the tail exhaust emission model is: .

[0006] Through the above technical solutions, the accuracy and dynamic response capability of hydrogen pressure control are improved. The hydrogen pressure transfer function establishes a direct mathematical relationship between pressure changes and hydrogen mass changes, enabling the controller to quantify the instantaneous impact of hydrogen flow fluctuations on pressure, laying the model foundation for suppressing overshoot. The proportional valve opening transfer function characterizes the linear control characteristics of the valve action on the hydrogen supply flow, ensuring a high degree of consistency between the flow regulation instructions and the execution results, and eliminating the regulation lag from the source. The stack current transfer function directly maps the load current change to hydrogen consumption, enabling the controller to predict the dynamic needs of the stack and compensate for the hydrogen supply gap in advance. The tail valve opening transfer function quantifies the impact intensity of the tail pulse interference on the pressure system, providing mathematical model support for actively offsetting interference.

[0007] Overall, the collaborative modeling of four transfer functions enables digital analysis of the dynamic characteristics of the entire hydrogen circuit. By converting physical mechanisms into computable control parameters, the system can decouple multivariable coupling in real time, maintaining precise tracking of hydrogen pressure under complex operating conditions, significantly improving the control quality and operating life of the fuel cell system.

[0008] Preferably, the variable step size step modulation rule is specifically as follows: when hour: ; when hour: .

[0009] Through the above technical solution, the stability and response efficiency of hydrogen pressure control are coordinated and optimized. The variable step size step modulation rule constructs a dynamic convergence mechanism. The design defines the control stage by the threshold Δ: when the deviation is large, it is gradually adjusted according to the proportional coefficient to avoid pressure oscillations caused by step mutations; when approaching the target, it switches to the precise locking mode to eliminate the inertia overshoot caused by the traditional PI integral accumulation. The dynamic correction coefficient in the proportional adjustment amount further enhances the adaptive capability. This coefficient is calculated in real time based on the coupling relationship between the pressure before the proportional valve and the stack current, so that the adjustment step size automatically matches the changes in the system operating conditions. This dual synergy of threshold triggering and parameter self-tuning enables the hydrogen pressure to maintain a smooth transition under interference such as sudden load and tail exhaust pulses, and achieves compatibility between overshoot zeroing and response acceleration from the control logic level.

[0010] Preferably, the step length correction coefficient calculation formula is specifically as follows: ; in: , .

[0011] The above technical solution significantly reduces overshoot in the fuel cell hydrogen pressure control system, effectively minimizing the risk of stack structural damage. A variable-step-size step modulation mechanism ensures smooth and controllable pressure regulation, significantly extending the life of the membrane electrode. The device maintains hydrogen pressure stability during on / off operation, mitigating the pressure oscillation inherent in traditional control methods. A dynamic parameter correction design optimizes system response efficiency. The control core adaptively matches load changes and pressure fluctuations, maintaining regulation accuracy even during sudden current changes. This solution shortens pressure convergence time and improves fuel cell operating efficiency. Full-process digital modeling enhances adaptability to operating conditions. Exhaust interference is compensated, allowing the system to maintain control accuracy despite hydrogen supply pressure fluctuations. This design reduces downtime and enhances the device's continuous operation capability. A modular control architecture simplifies operation and maintenance. The adaptive mechanism reduces the need for manual commissioning, and real-time pressure status monitoring improves diagnostic efficiency. The overall solution reduces the lifecycle maintenance cost of the fuel cell system.

[0012] Preferably, the hydrogen pressure transfer function satisfies: ; Where V is the volume of the hydrogen circuit.

[0013] This technical solution precisely matches the hydrogen circuit volume parameters with the dynamic pressure response, allowing the controller to adapt to piping systems of varying specifications. This design eliminates the regulation delay caused by volume parameter mismatches. The pressure transfer function improves control accuracy. The system dynamically adjusts its response speed based on actual gas characteristics, maintaining stable regulation performance under high-pressure conditions. Pressure fluctuations are significantly reduced, maintaining consistent proximity to the target setpoint. Control parameters automatically adjust to environmental changes. When hydrogen temperature or pressure fluctuates, the system automatically adjusts the regulation force, effectively reducing control errors. This mechanism ensures stability under diverse operating conditions.

[0014] The overall design simplifies the commissioning process. After the engineer enters basic piping parameters, the system automatically generates matching control parameters, significantly shortening commissioning time.

[0015] Preferably, the system comprises: Hydrogen supply module: includes high-pressure hydrogen storage tank, pressure reducing valve, and proportional valve, used to adjust the hydrogen flow; Sensing module: including pressure sensor (monitoring P, P1, P3, P4), current sensor (monitoring I), temperature sensor (monitoring T); Control module: includes an adaptive step-by-step PI controller, which dynamically adjusts the opening of the proportional valve and tail exhaust valve according to the model and feedback signals; the proportional valve and tail exhaust valve execute the opening command output by the controller.

[0016] Preferably, the controller is configured to implement the hydrogen mass conservation equation: .

[0017] Through this technical solution, the mass conservation equation is embedded in the controller's core execution process, enabling real-time tracking of changes in hydrogen inventory within the pipeline. This design ensures a dynamic balance between hydrogen supply and consumption, eliminates pressure fluctuations caused by mass imbalance, and improves system operational stability. It also significantly improves adaptability to liquid water operating conditions.

[0018] The overall solution significantly improves fuel utilization and system reliability.

[0019] Preferably, the tail valve opening D The value of 2 is 0 or 1.

[0020] The above technical solution achieves more efficient state switching by using a binary value for the tailgate valve opening D2. This design simplifies the control logic, enabling the system to quickly respond to demand changes while avoiding the complexity and latency associated with traditional multi-stage control. Furthermore, this binary control approach improves system reliability and predictability, ensuring operational precision. In practical applications, this simple on-off control method can better adapt to different operating conditions and achieve more efficient flow regulation.

[0021] Preferably, when the target hydrogen pressure is 200 kPa and the stack current is 200 A, the overshoot is controlled to be less than 1%.

[0022] This precise control, achieved through the aforementioned technical solution, benefits from the system's rapid response, ensuring stable operation under high hydrogen pressure and high current conditions. Furthermore, this enhanced control precision effectively mitigates the impact of pressure fluctuations on fuel cell stack performance, improving the system's overall operational efficiency and reliability.

[0023] Specifically, an overshoot of less than 1% means that when the system reaches the target hydrogen pressure of 200kPa, the maximum pressure fluctuation will not exceed 2kPa. This small fluctuation range ensures a stable hydrogen supply to the fuel cell stack under high current conditions of 200A, avoiding performance fluctuations or damage risks caused by sudden pressure changes. This precise control capability not only improves the system's operational stability but also extends the life of the fuel cell stack.

[0024] In practical applications, this high-precision control strategy can better adapt to the dynamic changes of the fuel cell system, especially during rapid load changes or startup / shutdown processes, quickly stabilizing the hydrogen pressure and ensuring that the fuel cell stack always operates at its optimal state. This improvement in control accuracy is of great significance for improving the overall performance and reliability of the fuel cell system.

[0025] Compared with the prior art, the present invention has the following advantages: 1. This invention optimizes the hydrogen pressure control problem of fuel cells by adopting a variable step-size step modulation mechanism and a dynamic parameter correction strategy. By comparing the deviation between the feedback pressure and the target value in real time, the adjustment step size is dynamically switched: when the deviation is large, the target value is quickly approached, and when it approaches the threshold, the fine adjustment mode is switched. The step size coefficient is corrected online by combining the coupling parameters of the pressure before the proportional valve and the stack current to eliminate pressure overshoot. This design ensures smooth convergence of the pressure response throughout the entire process, effectively improving the stack structure damage caused by hydrogen pressure oscillation.

[0026] 2. This invention constructs a mathematical model of the entire hydrogen flow path, integrating the proportional valve flow characteristics, fuel cell stack consumption patterns, and tailpipe emission parameters. Based on the synergistic mechanism of the physical model and the adaptive step-by-step PI algorithm, the system automatically analyzes the coupled effects of proportional valve differential pressure fluctuations and load current changes on the control process, achieving steady-state pressure control under multivariable interference. This solution maintains pressure stability in a variety of complex operating conditions, significantly improving the system's anti-interference capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the structure of the hydrogen supply system of the present invention; Figure 2 It is a schematic diagram of the adaptive step-by-step PI control flow chart of the present invention; Figure 3 It is a schematic diagram of the test bench of the present invention; Figure 4 This is a schematic diagram of the traditional PI pressure-maintaining hydrogen pressure response curve; Figure 5 Schematic diagram of the adaptive step-by-step PI pressure-maintaining hydrogen pressure response curve of the present invention; Figure 6 It is a schematic diagram of the traditional PI control simulation curve; Figure 7 It is a schematic diagram of the adaptive step-by-step PI control simulation curve of the present invention. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] In order to solve the problems of large overshoot and slow response in traditional PI control in hydrogen pressure regulation, especially the defects that easily lead to excessive hydrogen pressure or pressure difference failure under special working conditions such as shutdown gas replenishment, pressure maintenance and leak detection, the present invention proposes an innovative technical solution. The schematic diagram of the hydrogen supply system is shown in Figure 1 , the schematic diagram of the adaptive step-by-step PI control flow chart is shown in Figure 2 , the test bench diagram is shown in Figure 3 The specific plan is as follows: Dynamic modeling: Build a complete dynamic model of the hydrogen circuit, including: proportional valve flow model; fuel cell hydrogen consumption model; tail exhaust emission model; these models accurately describe the dynamic characteristics of the system through transfer functions.

[0030] Variable step size step modulation: Dynamically adjust the step size coefficient according to the difference between the feedback pressure and the target value to achieve: In the early stage, a large step size is used to quickly approach the target value; in the later stage, the step size is reduced to suppress overshoot; when the difference is less than the threshold, the target value is directly set.

[0031] Dynamic parameter adjustment: Real-time calculation of step correction coefficient based on proportional valve upstream pressure and stack current: ; This correction mechanism enables the control parameters to adapt to different working conditions.

[0032] System integration: includes hydrogen supply module, sensor module and control module, and realizes closed-loop control through hydrogen mass conservation equation: .

[0033] Example (target hydrogen pressure 200 kPa, stack current 200 A) 1. Test conditions Target hydrogen pressure Z (k) =200kPa Stack current I=200A Tail exhaust valve control: duty cycle 80%, cycle 5s.

[0034] 2. System initialization Hydrogen supply module: The high-pressure hydrogen storage tank outputs hydrogen, which is regulated by the pressure reducing valve and then controlled by the proportional valve (opening D1); Sensor module: Real-time monitoring of the pressure P2 before the proportional valve, the stack current I2, and the temperature T; Controller parameters: Initialize the step size coefficient k=0.3; The difference threshold Δt is set to 5% of the target value.

[0035] 3. Dynamic control process (1) Calculation of hydrogen mass conservation: ; m sup Calculated by the proportional valve flow model: ; m sta Calculated by the stack consumption model: ; m pur Calculated by the tailpipe emission model: ; Tail exhaust valve opening D2 = 0 or 1; (2) Variable step size step modulation: Feedback hydrogen pressure F (k−1) =50kPa, target value Z (k) =200kPa Judgment: |F(k−1)−Z(k)|=150kPa>Δt, dynamic adjustment is adopted: ; The step length correction coefficient k′ is calculated by dynamic parameter adjustment; (3) Dynamic parameter adjustment: Calculated based on the pressure P1 before the proportional valve and the stack current I: ; in: , ; Calibration conditions: P1=10bar, I1=200A.

[0036] 4. Control effect The hydrogen pressure stabilizes to 200 kPa within 10 seconds, with an overshoot of <1%; Compared with traditional PI control: stabilization time 15s, overshoot 11.5%; The control curve diagrams refer to Figure 4 Schematic diagram of the traditional PI pressure-maintaining hydrogen pressure response curve, Figure 5 Schematic diagram of the adaptive step-by-step PI pressure-maintaining hydrogen pressure response curve of the present invention.

[0037] 5. Simulation Verification The simulation verification results refer to Figure 6 Schematic diagram of traditional PI control simulation curve, Figure 7 Schematic diagram of the adaptive step-by-step PI control simulation curve of the present invention.

[0038] The above is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A hydrogen pressure control method for a fuel cell system based on adaptive step-by-step PI control, characterized in that The following steps are involved: Construct a dynamic model of the hydrogen circuit: including a proportional valve flow model, a stack hydrogen consumption model, and a tail gas emission model; Variable step size modulation: According to the feedback pressure F (k-1) and the target value Z (k) The difference dynamically adjusts the step size coefficient k; Dynamic parameter adjustment: Calculate the step correction coefficient k′ based on the proportional valve upstream pressure P1 and the stack current I.

2. The control method according to claim 1, wherein: The hydrogen path dynamic model includes the following transfer functions: Hydrogen pressure transfer function: ； The proportional valve opening transfer function corresponding to the proportional valve flow model is: ； The stack current transfer function corresponding to the stack hydrogen consumption model is: ； The tail exhaust valve opening transfer function corresponding to the tail exhaust emission model is: 。 3. The control method according to claim 1, wherein: The variable step size step modulation rule is specifically as follows: when hour: ; when hour: .

4. The control method according to claim 1, wherein: The step length correction coefficient calculation formula is specifically: ； in: , .

5. The control method according to claim 1, wherein: The hydrogen pressure transfer function satisfies: ； Where V is the volume of the hydrogen circuit.

6. The fuel cell system according to claim 1, wherein: The system comprises: Hydrogen supply module: includes high-pressure hydrogen storage tank, pressure reducing valve, and proportional valve, used to adjust the hydrogen flow; Sensing module: including pressure sensor (monitoring P, P1, P3, P4), current sensor (monitoring I), temperature sensor (monitoring T); Control module: includes an adaptive step-by-step PI controller, which dynamically adjusts the opening of the proportional valve and tail exhaust valve according to the model and feedback signals; the proportional valve and tail exhaust valve execute the opening command output by the controller.

7. The system according to claim 6, characterized in that: The controller is configured to implement the hydrogen mass conservation equation:

8. The system according to claim 6, characterized in that: The tail valve opening D The value of 2 is 0 or 1.

9. Application of the method according to claim 1 in a fuel cell pressure-maintaining leak detection operation, characterized in that: When the target hydrogen pressure is 200kPa and the stack current is 200A, the control overshoot is less than 1%.

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