A temperature self-regulating control system and method for a fuel cell system

Abstract

The application discloses a temperature self-adjusting control system and method for a fuel cell system, and the control system comprises a sensing and monitoring module, a control module and an actuator module; the sensing and monitoring module is used for collecting system state parameters in real time, and an output end of the sensing and monitoring module is connected to the control module; an output end of the control module is connected to the actuator module, and the control module controls the actuator module by adopting a multi-stage PID control mode so as to adjust the temperature. The application improves the temperature control stability of the SOFC system.

Description

Technical Field

[0001] This invention relates to the field of fuel cell temperature control, and in particular to a temperature self-regulating control method and system for fuel cell systems. Background Technology

[0002] Solid oxide fuel cells (SOFCs), as efficient and clean energy conversion devices, have shown great potential in distributed power generation, large-scale power plants, and special power sources. The fuel cell stack, as its core component, has an operating temperature that is a key parameter affecting its performance, efficiency, lifespan, and reliability. SOFCs typically operate in high-temperature environments of 600–1000°C, and their operating temperature is one of the most critical parameters determining battery performance, efficiency, long-term stability, and lifespan. Precise temperature control is essential for maintaining the stability of the electrolyte and electrode materials, preventing thermal stress damage, ensuring the conversion rate of reactant gases, and inhibiting carbon buildup.

[0003] The temperature control technology of existing SOFC systems faces more severe challenges than that of low-temperature fuel cells (such as PEMFC). Existing solutions are inadequate in dealing with inlet temperature disturbances and the large inertial characteristics of the system, and their stability and response speed cannot meet the requirements. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a temperature self-regulating control method and system for fuel cell systems. Given the high-temperature operating characteristics and stringent control requirements of SOFCs, there is an urgent need in the field for a control architecture capable of real-time sensing of inlet air temperature changes and using it as a feedforward signal, combined with an advanced control architecture that can overcome the large inertia of the system and achieve rapid and accurate response, to dynamically and adaptively adjust the stack operating temperature. The introduction of a multi-level PID control algorithm is precisely to effectively address the inherent limitations of single PID control when dealing with the complexities of SOFCs.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A temperature self-regulating control system for a fuel cell system, the control system comprising a sensing and monitoring module, a control module, and an actuator module;

[0007] The sensing and monitoring module is used to collect system status parameters in real time, and its output is connected to the control module.

[0008] The output of the control module is connected to the actuator module. The control module uses a multi-level PID control method to control the actuator module and thus regulate the temperature.

[0009] The sensing and monitoring module includes an intake air temperature sensor installed on the air intake duct, multiple fuel cell stack temperature sensors installed at the center of key locations on the fuel cell stack, a sensor for monitoring fuel cell stack current / voltage, and a fuel flow sensor.

[0010] The actuator module includes an air flow regulating device and / or a fuel flow regulating device for regulating the air flow and / or fuel flow entering the fuel cell stack.

[0011] The control module is a multi-level PID controller, which includes a main PID controller and a secondary PID controller. The main PID controller serves as the outer control loop, and its output serves as the input of the secondary PID controller. The output signal of the secondary PID controller acts on the actuator module.

[0012] The main PID controller has a setpoint of the target operating temperature of the fuel cell stack, T_target, and a feedback value of the measured average temperature of the fuel cell stack, T_stack_avg, from the fuel cell stack temperature sensor. The main PID controller calculates based on the deviation e1 between the two, and its output is used as the setpoint of the secondary PID controller, i.e., the desired intake air temperature value, T_in_air_demand.

[0013] The secondary PID controller: its setpoint comes from the output of the primary PID controller, and its feedback value is the actual T_in_air. The secondary PID controller calculates based on its own deviation e2 and generates the final control signal, which is output to the actuator module to drive the airflow regulating device to operate.

[0014] The control module also includes a feedforward compensator; the feedforward compensator obtains a preliminary air flow compensation signal based on the real-time intake air temperature T_in_air through a preset data model describing the dynamic relationship between intake air temperature change and air compensation flow rate, and superimposes it with the output signal of the secondary PID controller to jointly act on the actuator.

[0015] A control method for a temperature self-regulating control system for a fuel cell system, the method comprising the following steps:

[0016] S1: System initialization, setting the target operating temperature of the fuel cell stack, T_target;

[0017] S2: Real-time acquisition of inlet air temperature T_in_air and temperature at multiple measuring points on the fuel cell stack, and calculation of the measured average temperature of the fuel cell stack T_stack_avg;

[0018] S3: Main PID controller operation: Calculates the deviation e1 between T_target and T_stack_avg, and outputs the desired intake air temperature value T_in_air_demand after PID calculation;

[0019] S4: Feedforward compensator operation: Obtain the feedforward control quantity F_feedforward based on the real-time intake air temperature T_in_air;

[0020] S5: The secondary PID controller works as follows: using T_in_air_demand as the setpoint and the actual T_in_air as the feedback, it calculates the deviation e2, performs PID calculations, and outputs the feedback control quantity F_feedback.

[0021] S6: Synthetic control quantity: The feedforward control quantity F_feedforward and the feedback control quantity F_feedback are superimposed to generate the total control quantity u(t);

[0022] S7: Convert the total control quantity u(t) into an actuator command to drive the air flow regulating device, change the air flow entering the fuel cell stack, and thus regulate the fuel cell stack temperature.

[0023] The method further includes step S8: continuously outputting the total control quantity until a control cycle is completed, then returning to step S2 to achieve closed-loop continuous control.

[0024] In step S4, the preset data model describing the dynamic relationship between intake air temperature change and air compensation flow rate is used to query the instantaneous air compensation value of the fuel cell stack intake air temperature regulation based on the real-time intake air temperature T_in_air, and then convert it into a feedforward control quantity F_feedforward.

[0025] The advantages of this invention are: a) The cascaded PID structure effectively overcomes large inertia: the main loop is responsible for macroscopic temperature control and ensures steady-state accuracy; the secondary loop (with intake air thermal dynamics as the controlled object) has a fast response speed and can suppress secondary disturbances such as intake air temperature in a timely manner, which significantly improves the dynamic performance of the system, reduces overshoot, and speeds up the adjustment process.

[0026] b) Feedforward compensation enhances anti-disturbance capability: By introducing inlet air temperature as a feedforward signal, the system can "prepare for the worst" and adjust the air flow in advance to compensate for the disturbance of inlet air temperature before it affects the core temperature of the fuel cell stack, which greatly improves the anti-interference capability and predictability of the system.

[0027] c) Superior control quality and robustness: The multi-stage PID control structure decomposes a complex object into two relatively simple loops for control, resulting in better overall performance and robustness to parameter changes compared to a single-stage PID. It can better adapt to the dynamic characteristics of SOFC under different operating conditions such as startup and load variation, achieving optimal or suboptimal control across the entire operating range.

[0028] d) Ensuring stack safety and lifespan: Through faster and more stable temperature control, the internal temperature gradient and fluctuations of the stack are effectively reduced, greatly reducing the risk of material failure due to thermal stress, which is crucial for extending the service life of SOFC stacks. Attached Figure Description

[0029] The following is a brief explanation of the contents of each of the accompanying drawings and the markings in the drawings:

[0030] Figure 1 This is the physical structure of the SOFC system described in this invention.

[0031] Figure 2 This is the block diagram of the multi-level PID control of the present invention.

[0032] Figure 3 This is a logic flowchart of the multi-level PID control algorithm described in this invention.

[0033] The markings in the above diagrams are as follows: 1. Air intake pipe; 2. Air blower; 3. Air butterfly valve; 4. Heat exchanger; 5. Intake air temperature sensor; 6. Fuel intake pipe; 7. Fuel control valve; 8. Solid oxide fuel cell stack; 9. High-temperature exhaust pipe; 10. Temperature sensor one; 11. Temperature sensor two; 12. Temperature sensor three; 13. Main PID controller; 14. Sub-PID controller; 15. Feedforward compensator. Detailed Implementation

[0034] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and the description of the preferred embodiments.

[0035] The existing temperature control technology for SOFC systems mainly suffers from the following problems:

[0036] a) Control challenges arising from large system inertia and hysteresis: SOFC stacks have enormous heat capacity, resulting in slow temperature response and significant inertia and hysteresis characteristics. Traditional single-loop PID controllers, whether controlling airflow, fuel flow, or cooling medium, typically use the measured temperature at a single point on the stack as the sole feedback. This single-feedback control mode exhibits severe hysteresis in response to sudden load changes or inlet air temperature disturbances. When cold air enters the system, the internal temperature distribution of the stack has already begun to change, but by the time the sensor detects the deviation, the thermal disturbance has already occurred, and the controller only begins to act, easily leading to temperature overshoot or continuous oscillation. For SOFCs, frequent temperature fluctuations and excessive temperature gradients generate enormous thermal stress, which is a major cause of ceramic material cracking, seal failure, and stack structural damage.

[0037] b) The direct impact of inlet air temperature disturbances is overlooked: The temperature of the air (oxidant) entering the fuel cell stack is the core disturbance source affecting its thermal equilibrium. Changes in ambient temperature and fluctuations in the efficiency of upstream heat exchangers (such as regenerators) can lead to abrupt changes in inlet air temperature. This cooler airflow entering the high-temperature fuel cell stack directly absorbs a large amount of reaction heat, locally altering the electrochemical reaction rate and current density distribution. Most existing technologies do not use inlet air temperature as a core control input; the controller cannot predict such disturbances and can only passively perform "post-event remediation," making it difficult to guarantee control quality.

[0038] c) Limitations of Single-Stage PID Control: In complex, nonlinear, and highly coupled thermodynamic systems like SOFCs, traditional single-stage PID controllers typically have fixed parameters or are obtained through simple table lookups. These fixed control parameters struggle to simultaneously meet the optimal control requirements of the system under different operating conditions, such as startup, steady-state operation, and variable load. Rapid temperature rise is needed during startup, precise stability maintenance is required in steady state, and rapid disturbance suppression is necessary under variable load. Single-stage PID controllers cannot adaptively adjust their control strategy across a wide operating range, often sacrificing response speed for stability, or vice versa, failing to achieve the optimal balance between speed and stability.

[0039] This invention discloses a temperature self-regulating control method suitable for fuel cell systems. By real-time acquisition of the SOFC stack inlet temperature, the method adjusts actuator valves to adapt to the uncertainties in temperature changes caused by the fuel cell stack reaction, ensuring that the stack operates within a stable and efficient temperature range. This control method is based on a fuel cell temperature control system model built on the Matlab / Simulink platform. Combined with intelligent control algorithms (multi-level PID control), it achieves flexible adjustment of the system's operating temperature, effectively solving problems such as unstable system temperature control during SOFC system startup and under changing operating conditions, leading to fuel flow oscillations and stack performance fluctuations. This design not only improves the temperature control stability of the SOFC system but also enhances the system's adaptability to different operating conditions, possessing significant engineering application value for improving the lifespan and robustness of SOFC systems.

[0040] This embodiment provides a temperature self-regulating control system for a fuel cell system. The system hardware includes a sensing and monitoring module, a control module, and an actuator module.

[0041] The sensing and monitoring module is used to collect system status parameters in real time, and its output is connected to the control module.

[0042] The output of the control module is connected to the actuator module. The control module uses a multi-level PID control method to control the actuator module and thus regulate the temperature.

[0043] The sensing and monitoring module includes an intake air temperature sensor mounted on the air intake duct, multiple stack temperature sensors positioned at key locations on the stack, sensors for monitoring stack current / voltage, and a fuel flow sensor. Both the intake air temperature sensor and the stack temperature sensor can use contact-type temperature sensors to acquire corresponding temperature data, providing basic parameter information for subsequent temperature control.

[0044] The actuator module includes air flow regulators and / or fuel flow regulators to regulate the air and / or fuel flow entering the fuel cell stack. In the temperature control system, the actuator module, as the final execution unit connecting control decisions with the physical world, mainly consists of air flow regulators (air butterfly valves) and fuel flow regulators (fuel valves). The level of cooperation between the two directly determines the accuracy, response speed, and stability of temperature control.

[0045] An air butterfly valve is an airflow regulating actuator. Its core structure consists of a circular valve body and a valve plate that can rotate around an axis. The airflow area is adjusted by changing the angle between the valve plate and the pipeline axis. When the valve plate is parallel to the pipeline, it is fully open; when it is perpendicular, it is fully closed. The actuator receives a 4-20mA or 0-10V standard analog signal from the controller, driving the valve plate to precisely position itself between 0-90°, achieving continuous proportional regulation of airflow. Depending on the power source, air butterfly valves are mainly divided into pneumatic and electric types. Pneumatic butterfly valves consist of a pneumatic actuator and a valve positioner, converting electrical signals into air pressure to drive the valve plate to rotate. They have advantages such as simple structure, large output torque, fire and explosion resistance, and are suitable for harsh environments or occasions with readily available air sources. Electric butterfly valves are driven by a servo motor, offering high control precision and easy installation, making them suitable for locations without an air source. In temperature control, air butterfly valves typically have near-quick-opening flow characteristics, an adjustable range of up to 50:1, and a basic error of ±2% of the full stroke. They have high flow capacity, low flow resistance coefficient, and self-cleaning function, making them suitable for air pipelines with high flow rates and low pressure differentials. These parameters determine the temperature range and accuracy that the system can stably control.

[0046] The fuel flow regulating device is responsible for accurately measuring the amount of fuel entering the burner. It is the direct regulating unit for energy input in temperature control. Its core working principle is valve-controlled throttling regulation. By changing the flow cross-sectional area between the valve core and the valve seat, the fuel flow is controlled by the throttling effect. This regulation method is characterized by fast response and high control accuracy. Modern fuel regulating valves have continuously evolved according to drive technology: proportional control uses a proportional electromagnet to drive the valve core, making the valve core displacement proportional to the input signal, achieving linear regulation of fuel flow. It has a simple structure and low cost. Digital control uses a stepper motor or servo motor to drive the valve, combined with a digital optical encoder for position feedback. The repeatability can reach ±0.3%, and the regulation ratio can be as high as 500:1. A single valve can cover the entire temperature control range from ignition to full load. Under high-temperature conditions, the fuel valve needs to consider the isolation design of materials and actuators. By lengthening the valve stem or using heat insulation structures, the actuator, whose operating temperature is usually no more than 150°C, is isolated from the high-temperature valve body, which can reach 400-700°C, to ensure accurate regulation in extreme environments.

[0047] In a complete temperature control system, the air butterfly valve and fuel valve do not operate independently but work collaboratively according to a specific air-fuel ratio control strategy. A cascade control structure is typically used: the main loop (temperature controller) calculates the required total energy input based on the deviation between the current temperature and the setpoint; the secondary loop (fuel controller) receives instructions from the main loop to adjust the fuel valve opening and change the fuel flow; the air butterfly valve must be linked with the fuel valve, adjusting synchronously according to a pre-set functional relationship. Combined with the principle of temperature prediction, the actuator's actions directly affect the future temperature trend: when the controller predicts that the temperature will deviate from the setpoint, it will send a signal in advance to change the opening of the fuel valve and air butterfly valve, overcoming the system's large inertia through proactive adjustment; in the event of a sudden failure, the fuel valve needs to have a rapid closing function (e.g., 350 milliseconds full stroke), while the air butterfly valve can close as needed with a delayed closing time to purge residual combustible gas in the furnace. Modern integrated control systems, through unified scheduling by a central controller, overcome the shortcomings of traditional manual control and asynchronous adjustment of dual butterfly valves, achieving synchronous proportional adjustment, which not only improves the response speed of temperature control but also optimizes combustion efficiency.

[0048] The air butterfly valve achieves precise control of the combustion air volume with its large flow rate and low flow resistance, while the fuel valve achieves high-precision metering of fuel flow rate by means of proportional electromagnet or digital motor technology. Under the coordination of the controller, the two stabilize the temperature near the target value by dynamically adjusting the air-fuel ratio. The accuracy, linearity and response speed of the actuator directly determine whether the temperature control system can effectively overcome hysteresis and suppress interference, and finally achieve stable and accurate temperature control.

[0049] The control module is a multi-stage PID controller, which includes a main PID controller and a secondary PID controller. The main PID controller serves as the outer control loop, and its output serves as the input of the secondary PID controller. The output signal of the secondary PID controller acts on the actuator module.

[0050] The main PID controller has a setpoint of T_target (target operating temperature of the fuel cell stack) and a feedback value of T_stack_avg (measured average temperature of the fuel cell stack from the fuel cell stack temperature sensor). The main PID controller calculates the value based on the deviation e1 between the two values ​​and outputs the setpoint of the secondary PID controller, which is the desired intake air temperature value T_in_air_demand.

[0051] The secondary PID controller's setpoint comes from the output of the primary PID controller, and its feedback value is the actual T_in_air. The secondary PID controller calculates based on its own deviation e2 and generates the final control signal, which is then output to the actuator module to drive the airflow regulating device. This dual PID control approach achieves precise airflow regulation, thereby enabling precise temperature control.

[0052] In a preferred embodiment of this application, the control module further includes a feedforward compensator. The feedforward compensator obtains a preliminary airflow compensation signal based on the real-time intake air temperature T_in_air using a preset data model describing the dynamic relationship between intake air temperature changes and airflow compensation. This signal is superimposed on the output signal of the secondary PID controller and acts together on the air butterfly valve of the actuator module to achieve intake airflow regulation and control, thereby regulating the temperature. In this embodiment, the air butterfly valve and the fuel valve do not operate independently but work collaboratively according to a specific air-fuel ratio control strategy. The optimal air-fuel ratio of the fuel cell at different load points is determined in advance through experiments, and the corresponding air butterfly valve opening and fuel valve opening data are recorded. Then, a curve is fitted and stored in the control module's memory as a reference relationship MAP between the air butterfly valve opening and the fuel valve opening. When the control signal acting on the air butterfly valve is obtained from the multi-level PID controller, the corresponding fuel valve opening is obtained by querying the MAP based on the adjusted opening of the air butterfly valve, and then the fuel valve is controlled. This achieves the linkage control of the air butterfly valve and the fuel valve, realizing accurate temperature control. The interlocking control of two valves ensures precise temperature control, essentially achieving a precise energy flow ratio. In steady state, a constant air-fuel ratio eliminates the interference of efficiency fluctuations on temperature control, ensuring a linear relationship between heat input and fuel quantity, allowing the controller to calculate accurately and control stably. Dynamically, synchronized action and dynamic compensation eliminate instantaneous disturbances caused by the inertia of medium flow during regulation, resulting in a smooth temperature change curve without overshoot. Globally, a wider controllability ratio and built-in safety interlocks ensure good controllability and safety across the entire operating range. Therefore, the interlocking control is not a simple mechanical connection, but rather integrates two physical valves into a logical "energy regulating valve" through control algorithms, achieving a leap from extensive to intensive control of the thermal process.

[0053] This embodiment also provides a control method for a temperature self-regulating control system of a fuel cell system, the method comprising the following steps:

[0054] S1: System initialization, setting the target operating temperature T_target of the fuel cell stack; system initialization refers to the initialization of the temperature control system, including confirming that all actuators and sensors are in a ready state, and establishing safe initial conditions for subsequent automatic control. This includes:

[0055] 1) Controller Module and Communication Self-Test: The system first performs a self-test on the core controller, including memory verification and program integrity checks. Then, it checks the communication links with the host computer and remote monitoring unit to ensure they are functioning correctly. Simultaneously, the controller scans all expansion modules (such as analog input modules and thermocouple acquisition modules) to confirm that the module configuration matches the physical hardware and that there are no board detachments or fault alarms.

[0056] 2) Sensor Zero Point and Range Verification: The accuracy of temperature control directly depends on the precision of the temperature sensor. During initialization, the system reads the initial values ​​of the stack inlet temperature, outlet temperature, internal key point temperatures, and ambient temperature. Reasonableness Check: The readings at each temperature measurement point are compared with the ambient temperature. If a reading deviates abnormally (e.g., the internal temperature of the stack shows 200°C when not heated), the system will determine that the sensor is faulty or disconnected and will report an error and shut down. Cold State Confirmation: Typically, the initial temperature at which the stack starts up must be below a certain safety threshold (e.g., below 100°C for high-temperature SOFCs, and consistent with ambient temperature for low-temperature PEMFCs) to ensure that the startup procedure begins from a "cold state" and avoids thermal stress shock.

[0057] 3) Actuator Mechanism Initialization: After a power outage and restart, the actual mechanical position of actuators such as air butterfly valves and fuel valves may become out of sync with the last position signal stored in the controller. Therefore, during initialization, a "valve self-tuning" or "zero-point finding" procedure is executed: the controller sends a closing command to the valve and continuously monitors the feedback signal. When the valve reaches the mechanical limit (fully closed position), the feedback signal stops changing, and the controller calibrates this position as 0%. Subsequently, the valve will briefly open to a certain angle to verify the flexibility of action and return to a safe position (usually the "standby opening" before ignition, such as fully closed or slightly open). For fans and pumps, status checks will be performed to confirm that there is no overload or stall.

[0058] 4) Safety Interlock Logic Activation: In the final stage of initialization, the system checks all safety conditions, including: whether the gas leak detection signal is normal, whether the exhaust system is started, whether the cooling water pressure meets the standard, and whether the emergency stop button is reset. Only when all safety interlock conditions are met will the system allow the next step—target temperature setting and heating start-up.

[0059] The target temperature can be dynamically set based on the fuel cell's optimal temperature. A pre-calibrated target temperature model can automatically acquire the target temperature that matches the current optimal operating state of the fuel cell, thus providing a basis for subsequent control. The target temperature model can be pre-calibrated to establish a comparison curve between the fuel cell's current operating parameters and the target temperature, enabling rapid and dynamic setting of the target temperature to meet the needs of different operating environments.

[0060] S2: Real-time acquisition of intake air temperature T_in_air and multiple measuring points of the fuel cell stack, and calculation of the measured average temperature of the fuel cell stack T_stack_avg; Multiple temperature data can be measured through pre-set temperature sensors, and the measured average temperature value is obtained by averaging the acquired temperature data.

[0061] S3: Main PID controller operation: Calculates the deviation e1 between the target operating temperature T_target of the fuel cell stack and the measured average temperature T_stack_avg of the fuel cell stack, and outputs the desired inlet air temperature value T_in_air_demand after PID calculation.

[0062] S4: Feedforward compensator operation: Obtain the feedforward control quantity F_feedforward based on the real-time intake air temperature T_in_air;

[0063] S5: The secondary PID controller works as follows: it takes the desired intake air temperature value T_in_air_demand output by the main PID controller as the set value, and the actual T_in_air as the feedback. It calculates the deviation e2, performs PID calculations, and outputs the feedback control quantity F_feedback.

[0064] S6: Synthetic control quantity: The feedforward control quantity F_feedforward and the feedback control quantity F_feedback are superimposed to generate the total control quantity u(t);

[0065] S7: Convert the total control quantity u(t) into an actuator command to drive the air flow regulating device, change the air flow entering the fuel cell stack, and thus regulate the fuel cell stack temperature.

[0066] Step S8: Continuously output the total control quantity until a control cycle is completed, then return to step S2 to achieve closed-loop continuous control.

[0067] In step S4, a preset data model describing the dynamic relationship between intake air temperature changes and air compensation flow rate is used to query the instantaneous air compensation value for fuel cell stack intake air temperature regulation based on the real-time intake air temperature T_in_air, and convert it into a feedforward control quantity F_feedforward. The feedforward compensator, based on the real-time intake air temperature T_in_air, obtains a preliminary air flow compensation signal through a preset data model describing the dynamic relationship between intake air temperature changes and air compensation flow rate. This signal is superimposed on the output signal of the secondary PID controller and acts together on the air butterfly valve of the actuator module to achieve intake air flow rate regulation and control, thereby regulating the temperature. In this embodiment, the air butterfly valve and the fuel valve do not operate independently but work collaboratively according to a specific air-fuel ratio control strategy. The optimal air-fuel ratio for the fuel cell at different load points was pre-determined through experiments, and the corresponding air butterfly valve opening and fuel valve opening data were recorded. A curve was then fitted and stored in the control module's memory as a MAP (map) of the relationship between the air butterfly valve and fuel valve openings. When a control signal acting on the air butterfly valve is received by a multi-stage PID controller, the corresponding fuel valve opening is retrieved from the MAP based on the adjusted opening of the air butterfly valve. This allows for the coordinated control of the air butterfly valve and fuel valve, achieving accurate temperature control. The coordinated control of the two valves ensures precise temperature control, essentially achieving a precise energy flow ratio. In steady state, a constant air-fuel ratio eliminates the interference of efficiency fluctuations on temperature control, ensuring a linear relationship between heat input and fuel quantity, allowing the controller to calculate accurately and control stably. In dynamic states, synchronous action and dynamic compensation eliminate instantaneous disturbances caused by the inertia of the medium flow during adjustment, resulting in a smooth temperature change curve without overshoot. Globally, by widening the adjustment ratio and incorporating built-in safety interlocks, the system ensures good controllability and safety across the entire operating range. Therefore, the linkage control is not a simple mechanical connection, but rather integrates two physical valves into a logical "energy regulating valve" through control algorithms, achieving a leap from extensive to intensive control of the thermal process.

[0068] This invention discloses a temperature self-regulating control method suitable for fuel cell systems. By real-time acquisition of the SOFC stack inlet temperature, the method adjusts actuator valves to adapt to the uncertainties in temperature changes caused by the fuel cell stack reaction, ensuring that the stack operates within a stable and efficient temperature range. This control method is based on a fuel cell temperature control system model built on the Matlab / Simulink platform. Combined with intelligent control algorithms (multi-level PID control), it achieves flexible adjustment of the system's operating temperature, effectively solving problems such as unstable system temperature control during SOFC system startup and under changing operating conditions, leading to fuel flow oscillations and stack performance fluctuations. This design not only improves the temperature control stability of the SOFC system but also enhances the system's adaptability to different operating conditions, possessing significant engineering application value for improving the lifespan and robustness of SOFC systems.

[0069] Firstly, the control method mainly includes the following system modules:

[0070] Sensing and monitoring module: used to collect system status parameters in real time, including an intake air temperature sensor installed on the air intake duct, multiple fuel cell stack temperature sensors installed at the center of key locations on the fuel cell stack, sensors for monitoring fuel cell stack current and voltage, and a fuel flow sensor.

[0071] Actuator modules: air flow regulating device (air butterfly valve), fuel flow regulating device (fuel valve).

[0072] Multi-level PID controller: It is signal-connected to the sensing and monitoring module and the actuator module. The multi-level PID controller is configured to execute a cascade PID control structure, specifically including: a) Main PID controller (outer loop): Its setpoint is the target operating temperature of the fuel cell stack T_target, and its feedback value is the measured average temperature of the fuel cell stack T_stack_avg from the fuel cell stack temperature sensor. The main PID controller calculates based on the deviation e1 between the two, and its output serves as the setpoint of the secondary PID controller, i.e., the desired inlet air temperature value T_in_air_demand. b) Secondary PID controller (inner loop): Its setpoint comes from the output of the main PID controller, and its feedback value is the actual T_in_air. The secondary PID controller calculates based on its own deviation e2 and generates the final control signal, which is output to the actuator module to drive the airflow regulating device.

[0073] c) The method further includes a feedforward compensator, which obtains a preliminary air flow compensation signal based on the real-time intake air temperature T_in_air through a preset data model describing the dynamic relationship between intake air temperature change and air compensation flow rate. This signal is then superimposed on the output signal of the secondary PID controller and acts together on the actuator.

[0074] Secondly, this invention provides a temperature control method based on the above system, comprising the following steps: S1: System initialization, setting the target operating temperature T_target of the fuel cell stack. S2: Real-time acquisition of the inlet air temperature T_in_air and the temperature of multiple measuring points on the fuel cell stack, calculating the measured average temperature T_stack_avg of the fuel cell stack. S3: The main PID controller operates: calculating the deviation e1 between T_target and T_stack_avg, and outputting the desired inlet air temperature value T_in_air_demand after PID calculation. S4: The feedforward compensator operates: based on the real-time inlet air temperature T_in_air, querying its instantaneous air compensation value for regulating the fuel cell stack inlet air temperature, and converting it into a feedforward control quantity F_feedforward. S5: The secondary PID controller operates: using T_in_air_demand as the setpoint and the actual T_in_air as feedback, calculating the deviation e2, and outputting the feedback control quantity F_feedback after PID calculation. S6: Synthesize the control quantity: Superimpose the feedforward control quantity F_feedforward and the feedback control quantity F_feedback to generate the total control quantity u(t). S7: Convert the total control quantity u(t) into an actuator command to drive the airflow regulating device, changing the airflow entering the fuel cell stack, thereby regulating the stack temperature. S8: Wait for one control cycle, then return to step S2 to achieve closed-loop continuous control.

[0075] In step S4, a preset data model describing the dynamic relationship between intake air temperature changes and air compensation flow rate is used to query the instantaneous air compensation value for fuel cell stack intake air temperature regulation based on the real-time intake air temperature T_in_air, and convert it into a feedforward control quantity F_feedforward. The feedforward compensator, based on the real-time intake air temperature T_in_air, obtains a preliminary air flow compensation signal through a preset data model describing the dynamic relationship between intake air temperature changes and air compensation flow rate. This signal is superimposed on the output signal of the secondary PID controller and acts together on the air butterfly valve of the actuator module to achieve intake air flow rate regulation and control, thereby regulating the temperature. In this embodiment, the air butterfly valve and the fuel valve do not operate independently but work collaboratively according to a specific air-fuel ratio control strategy. The optimal air-fuel ratio of the fuel cell at different load points was determined in advance through experiments, and the corresponding air butterfly valve opening and fuel valve opening data were recorded. Then, a curve was fitted and stored in the memory of the control module as a reference relationship between the air butterfly valve opening and the fuel valve opening. When the control signal acting on the air butterfly valve is obtained according to the multi-level PID controller, the corresponding fuel valve opening is obtained by querying the MAP according to the opening of the air butterfly valve after control adjustment, and then the fuel valve is controlled. This achieves the linkage control of the air butterfly valve and the fuel valve, and realizes accurate temperature control.

[0076] refer to Figure 1 This control method includes an SOFC system physical structure consisting of an air intake pipe 1, an air blower 2, an air butterfly valve 3, a heat exchanger 4, an intake air temperature sensor 5, a fuel intake pipe 6, a fuel control valve 7, a solid oxide fuel cell stack 8, a high-temperature exhaust pipe 9, and multiple temperature sensors (temperature sensor 10, temperature sensor 21, and temperature sensor 32) distributed in the stack.

[0077] refer to Figure 2 This control method includes a multi-stage PID controller consisting of a main PID controller 13, a secondary PID controller 14, and a feedforward compensator 15.

[0078] As attached Figure 1 , 2 As shown, a temperature self-regulating control method suitable for fuel cell systems mainly consists of the following parts:

[0079] The physical architecture of the SOFC system is as follows: Figure 1 The hardware components shown are as follows. The multi-stage PID controller implements, for example... Figure 2 The cascaded PID control algorithm is shown.

[0080] The multi-level controller receives signals (average value T_stack_avg) from intake air temperature sensor 5 (T_in_air) and fuel cell stack temperature sensors 10, 11, and 12.

[0081] The main PID controller uses a set target temperature of 750℃ (T_target) and feedback (T_stack_avg). Its output is the desired intake air temperature compensation (T_in_air_demand).

[0082] Sub-PID controller: With T_in_air_demand as the setpoint and the current actual intake air temperature T_in_air as the feedback, its output is F_feedback, which is the air compensation amount derived based on the difference between the actual and set temperatures.

[0083] Feedforward compensator: Real-time monitoring of intake air temperature T_in_air. Assuming the intake air temperature suddenly drops from 300℃ to 250℃, the feedforward compensator immediately calculates a feedforward airflow increment F_feedforward based on a pre-stored model (for every 10℃ decrease in temperature, the reference airflow needs to be increased by 2% to compensate for heat loss).

[0084] Control synthesis: F_feedforward and F_feedback are added together to obtain the final control command u(t), which is sent to the air butterfly valve to control the valve opening and adjust the feed air flow.

[0085] With this control method, when the intake air temperature drops sharply, the feedforward channel immediately increases the airflow to offset part of the cooling effect. At the same time, a slight drop in the fuel cell stack temperature is detected by the main loop, which further instructs the secondary loop to increase the airflow. This synergistic effect of "feedforward + cascade feedback" allows the fuel cell stack temperature to withstand disturbances very smoothly, avoiding the significant temperature drop and subsequent oscillations that may occur under traditional single PID control.

[0086] In a preferred embodiment of this application, in step S3, if the difference e1 is greater than the set threshold E, an intermediate target value is introduced for adjustment. This is because if the difference is too large, direct PID adjustment may cause a large overshoot. This scheme designs segmented adjustment. When the difference e1 is less than or equal to the threshold E, it directly proceeds to step S4; otherwise, it is greater than the threshold E. At this time, the average of the current temperature and the target temperature is taken as the intermediate target value. The difference between the real-time temperature and the intermediate target value is calculated to obtain e3. After PID calculation, the expected intake air temperature value T_in_air_demand1 in the segmented process is output. The intake air temperature value T_in_air_demand1 is substituted into steps S4-S8 until the temperature adjustment reaches the intermediate target value. After that, the intermediate target value is modified to the target value. e1 is calculated in step S3, and after PID calculation, the expected intake air temperature value T_in_air_demand is output. The temperature is then controlled in steps S4-S8 until the set target temperature is reached. This approach first sets an intermediate target (the average of the current temperature and the final target temperature). Once the system reaches this intermediate point, it switches to the final target. This method falls under setpoint programming or step approximation. It avoids problems such as integral saturation and large overshoot caused by directly applying full control under large deviations. Because the target in the first stage is close to the current value, the control process is relatively smooth; in the second stage, starting from the intermediate point, the deviation has decreased, allowing for more precise PID control.

[0087] Obviously, the specific implementation of this invention is not limited to the above-described methods. Any non-substantial improvements made using the inventive concept and technical solution of this invention are within the protection scope of this invention.

Claims

1. A temperature self-regulating control system for a fuel cell system, characterized in that: The control system includes a sensing and monitoring module, a control module, and an actuator module; The sensing and monitoring module is used to collect system status parameters in real time, and its output is connected to the control module. The output of the control module is connected to the actuator module. The control module uses a multi-level PID control method to control the actuator module and thus regulate the temperature.

2. The temperature self-regulating control system for a fuel cell system as described in claim 1, characterized in that: The sensing and monitoring module includes an intake air temperature sensor installed on the air intake duct, multiple fuel cell stack temperature sensors installed at the center of key locations on the fuel cell stack, a sensor for monitoring fuel cell stack current / voltage, and a fuel flow sensor.

3. The temperature self-regulating control system for a fuel cell system as described in claim 1, characterized in that: The actuator module includes an air flow regulating device and / or a fuel flow regulating device for regulating the air flow and / or fuel flow entering the fuel cell stack.

4. A temperature self-regulating control system for a fuel cell system as described in claim 1, characterized in that: The control module is a multi-level PID controller, which includes a main PID controller and a secondary PID controller. The main PID controller serves as the outer control loop, and its output serves as the input of the secondary PID controller. The output signal of the secondary PID controller acts on the actuator module.

5. A temperature self-regulating control system for a fuel cell system as described in claim 4, characterized in that: The main PID controller has a setpoint of the target operating temperature of the fuel cell stack, T_target, and a feedback value of the measured average temperature of the fuel cell stack, T_stack_avg, from the fuel cell stack temperature sensor. The main PID controller calculates based on the deviation e1 between the two, and its output is used as the setpoint of the secondary PID controller, i.e., the desired intake air temperature value, T_in_air_demand.

6. A temperature self-regulating control system for a fuel cell system as described in claim 4, characterized in that: The secondary PID controller: its setpoint comes from the output of the primary PID controller, and its feedback value is the actual T_in_air. The secondary PID controller calculates based on its own deviation e2 and generates the final control signal, which is output to the actuator module to drive the airflow regulating device to operate.

7. A temperature self-regulating control system for a fuel cell system as described in any one of claims 4-6, characterized in that: The control module also includes a feedforward compensator; the feedforward compensator obtains a preliminary air flow compensation signal based on the real-time intake air temperature T_in_air through a preset data model describing the dynamic relationship between intake air temperature change and air compensation flow rate, and superimposes it with the output signal of the secondary PID controller to jointly act on the actuator.

8. A control method for a temperature self-regulating control system for a fuel cell system as described in any one of claims 1-6, characterized in that: The method includes the following steps: S1: System initialization, setting the target operating temperature of the fuel cell stack, T_target; S2: Real-time acquisition of inlet air temperature T_in_air and temperature at multiple measuring points on the fuel cell stack, and calculation of the measured average temperature of the fuel cell stack T_stack_avg; S3: Main PID controller operation: Calculates the deviation e1 between T_target and T_stack_avg, and outputs the desired intake air temperature value T_in_air_demand after PID calculation; S4: Feedforward compensator operation: Obtain the feedforward control quantity F_feedforward based on the real-time intake air temperature T_in_air; S5: The secondary PID controller works as follows: using T_in_air_demand as the setpoint and the actual T_in_air as the feedback, it calculates the deviation e2, performs PID calculations, and outputs the feedback control quantity F_feedback. S6: Synthetic control quantity: The feedforward control quantity F_feedforward and the feedback control quantity F_feedback are superimposed to generate the total control quantity u(t); S7: Convert the total control quantity u(t) into an actuator command to drive the air flow regulating device, change the air flow entering the fuel cell stack, and thus regulate the fuel cell stack temperature.

9. The control method for a temperature self-regulating control system for a fuel cell system as described in claim 8, characterized in that: The method further includes step S8: continuously outputting the total control quantity until a control cycle is completed, then returning to step S2 to achieve closed-loop continuous control.

10. The control method for a temperature self-regulating control system for a fuel cell system as described in claim 8, characterized in that: In step S4, the preset data model describing the dynamic relationship between intake air temperature change and air compensation flow rate is used to query the instantaneous air compensation value of the fuel cell stack intake air temperature regulation based on the real-time intake air temperature T_in_air, and then convert it into a feedforward control quantity F_feedforward.

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