A high-efficiency control method for a hydrogen supply system of a fuel cell engine

Abstract

The application discloses a high-efficiency control method for a hydrogen supply system of a fuel cell engine and belongs to the technical field of fuel cells. The method comprises the following steps: adopting fuzzy control to control the rotating speed of a hydrogen circulating pump, including taking the difference AV between the target difference V_tar of the average single-piece voltage and the lowest single-piece voltage of the hydrogen fuel cell stack and the actual difference V_real, and the change rate dAV of the difference AV as system input; and adopting fuzzy PI control to control the opening of a hydrogen proportional valve, including taking the difference AP between the target value P_tar of the anode hydrogen inlet pressure of the hydrogen fuel cell stack and the actual pressure P_real collected by the hydrogen low-pressure sensor, and the change rate dAP of the difference AP as system input. The application can solve the technical problems of control overshoot, oscillation, slow response and high parasitic power consumption existing in the hydrogen supply system of the hydrogen fuel cell in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell technology, and specifically relates to a high-efficiency control method for a hydrogen supply system of a fuel cell engine. Background Technology

[0002] With the energy crisis and environmental pollution becoming increasingly serious, the development of low-pollution energy technologies has become a research focus. Hydrogen fuel cells, as a highly efficient and clean energy conversion device, use hydrogen and oxygen as raw materials, with water as the only byproduct. They are considered the ultimate environmentally friendly vehicle power source and have broad application prospects.

[0003] To maintain stable anode pressure in fuel cells, existing hydrogen fuel cell anode inlet proportional valves are typically controlled using PID control. The negative feedback regulation in the PID control system continuously adjusts the valve opening until it reaches the desired level. While this method performs well under steady-state conditions, PID control struggles to provide stable performance when faced with dynamic changes in stack conditions, easily leading to overshoot and oscillations, resulting in degraded system performance. Furthermore, for the hydrogen flow demand at the fuel cell anode, using only the ejector is insufficient to actively regulate the flow rate, easily resulting in excessive or insufficient flow, leading to gas waste or failure to meet the system's normal hydrogen supply requirements. While the circulation pump can actively control the flow rate, improper speed settings increase parasitic power consumption, affecting the system's output power. Moreover, fuel cell reactions exhibit hysteresis, and conventional control methods are slow and lack stability.

[0004] Therefore, how to provide a control method that can achieve efficient and stable control of the hydrogen proportional valve and hydrogen circulation pump in the hydrogen supply system is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This invention addresses the aforementioned problems and overcomes the shortcomings of existing technologies by providing a highly efficient control method for a hydrogen supply system of a fuel cell engine. This invention can solve the technical problems of control overshoot, oscillation, slow response, and high parasitic power consumption in existing hydrogen fuel cell supply systems.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] This invention provides a high-efficiency control method for a hydrogen supply system of a fuel cell engine. The method is applied to a hydrogen supply system comprising a hydrogen cylinder bank, a hydrogen medium-pressure sensor, a hydrogen main line solenoid valve, a hydrogen proportional valve, an ejector, a hydrogen circulation pump, a hydrogen low-pressure sensor, a hydrogen fuel cell stack, a hydrogen discharge valve, a drain valve, a gas-liquid separator, and a check valve. The ejector and the hydrogen circulation pump are connected in parallel, and each branch is equipped with a check valve. The method comprises: S1. The rotational speed of the hydrogen circulation pump is controlled by fuzzy control, including using the difference ΔV between the target difference V_tar and the actual difference V_real of the average single-cell voltage and the lowest single-cell voltage of the hydrogen fuel cell stack, and the rate of change dΔV of the difference ΔV as system input, outputting the adjusted rotational speed through fuzzy control rules, and setting different rotational speed thresholds under different electrical density conditions to output the final rotational speed. S2. The opening of the hydrogen proportional valve is controlled by fuzzy PI control, including using the difference ΔP between the target value of the anode hydrogen inlet pressure P_tar of the hydrogen fuel cell stack and the actual pressure P_real collected by the hydrogen low-pressure sensor, and the rate of change dΔP of the difference ΔP as system input, and adjusting the proportional gain K of the PI controller through fuzzy control rules. p and integral gain K i This is to control the opening degree of the hydrogen proportional valve.

[0008] Further, step S1 specifically includes: S1.1 Calculate the difference ΔV = V_tar - V_real and its rate of change dΔV; S1.2 Set fuzzy control parameters, take the difference ΔV and the rate of change dΔV as inputs, perform fuzzy processing and fuzzy inference through the fuzzy control rule table, and obtain fuzzy quantity output; S1.3 Defuzzify the fuzzy output to obtain the current speed adjustment amount. Add the current speed adjustment amount to the speed at the previous moment to obtain the current hydrogen pump speed. Then, perform feedback adjustment based on the actual difference V_real to adjust the speed in the next step.

[0009] Furthermore, in step S1.2, the membership functions of the elements within the fuzzy subsets of the input and output parameters are triangular functions and Gaussian distribution functions, respectively; in step S1.3, the centroid method is used for defuzzification.

[0010] Further, step S2 specifically includes: S2.1 Calculate the difference ΔP = P_tar - P_real and its rate of change dΔP; S2.2. Set fuzzy control parameters, taking the difference ΔP and the rate of change dΔP as system inputs, performing fuzzy processing and fuzzy inference through the fuzzy control rule table, and outputting the result to adjust the proportional gain K. p and integral gain K i The fuzzy quantity; S2.3 Defuzzify the fuzzy quantity to obtain the adjusted proportional gain K. p and integral gain K iThe system calculates and outputs a control signal based on the PI control formula to control the opening degree of the hydrogen proportional valve.

[0011] Furthermore, in step S2.2, the membership functions of the elements within the fuzzy subsets of both the input and output parameters are set to Gaussian distribution functions; in step S2.3, the centroid method is used for defuzzification.

[0012] Furthermore, in step S1, setting different speed thresholds under different electrical density conditions includes setting an initial speed threshold to shorten the hydrogen pump response time, and setting a maximum speed threshold to avoid damage to the fuel cell.

[0013] Furthermore, step S2 also includes: during the process of hydrogen discharge and drainage of the fuel cell system through the hydrogen discharge valve and the drainage valve, the opening degree of the hydrogen proportional valve is compensated through a calibration test to meet the hydrogen inlet pressure requirements on the anode side.

[0014] Furthermore, the difference ΔV and rate of change dΔV in step S1, and the difference ΔP and rate of change dΔP in step S2, are all divided into five levels of linguistic variables in their respective domains: negative large (NB), negative small (NS), zero (ZO), positive small (PS), and positive large (PB).

[0015] The beneficial effects of the present invention.

[0016] This invention employs fuzzy PI control instead of traditional PID control for the hydrogen proportional valve. It adaptively adjusts the PI parameters based on pressure error and its rate of change, effectively avoiding overshoot and oscillation, and achieving rapid and stable tracking of the anode feed pressure. Fuzzy control is used to dynamically adjust the hydrogen circulation pump speed, ensuring it operates at near-optimal speeds under various conditions. This avoids energy waste associated with fixed-speed control, reducing pump parasitic power consumption and improving the overall efficiency of the engine system. By setting speed thresholds under different electrical densities, reasonable initial and limit values ​​are provided for hydrogen pump control, shortening response time. Simultaneously, proportional valve opening compensation is incorporated during hydrogen and water discharge processes to quickly suppress pressure fluctuations. Precise control of the single-chip voltage difference and feed pressure ensures uniform hydrothermal management and reactant gas distribution within the fuel cell stack, contributing to extended stack lifespan. Attached Figure Description

[0017] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0018] Figure 1This is a schematic diagram of the hydrogen supply system of the fuel cell engine in this invention.

[0019] Figure 2 This is a schematic diagram of the fuzzy control principle of the hydrogen circulation pump speed in this invention.

[0020] Figure 3 This is a schematic diagram of the fuzzy PI control principle for the hydrogen proportional valve opening in this invention.

[0021] The markings in the diagram are as follows: 1 is the hydrogen cylinder assembly, 2 is the hydrogen medium pressure sensor, 3 is the hydrogen main line solenoid valve, 4 is the hydrogen proportional valve, 5 is the ejector, 6 is the hydrogen circulation pump, 7 is the hydrogen low pressure sensor, 8 is the hydrogen fuel cell stack, 9 is the hydrogen discharge valve, 10 is the drain valve, 11 is the gas-water separator, and 12 is the one-way valve. Detailed Implementation

[0022] Referring to the accompanying drawings, this embodiment provides a high-efficiency control method for a hydrogen supply system of a fuel cell engine, applied to a hydrogen supply system of a fuel cell engine. First, refer to... Figure 1 The hydrogen supply system structure used in this method is as follows: Hydrogen cylinder group 1 serves as the hydrogen source, which is then connected in sequence to a hydrogen medium-pressure sensor 2 and a hydrogen main line solenoid valve 3. The main line hydrogen enters the hydrogen fuel cell stack 8 after passing through a hydrogen proportioning valve 4. One branch passes through an ejector 5, and the other branch passes through a hydrogen circulation pump 6 and a one-way valve 12. A low-pressure hydrogen sensor 7 is installed at the inlet of the stack 8 to monitor the inlet pressure in real time. The anode outlet pipe of the stack 8 is connected to a gas-liquid separator 11, whose bottom outlet is connected to a hydrogen discharge valve 9 to discharge hydrogen and nitrogen to ensure hydrogen purity, and a drain valve 10 to discharge the generated water. The top outlet of the gas-liquid separator 11 splits into two parallel branches entering the hydrogen fuel cell stack 8. One branch flows back to the inlet of the ejector 5 through a one-way valve 12, and the other branch forms a hydrogen circulation loop through the one-way valve 12 and the hydrogen circulation pump 6.

[0023] The control method in this embodiment includes two parallel and complementary steps.

[0024] Step S1: High-efficiency control of hydrogen pump speed based on fuzzy control. This step aims to meet the system's demand for anode hydrogen circulation flow rate with the lowest power consumption.

[0025] like Figure 2 As shown, first, step S1.1 is executed: calculate the difference ΔV = V_tar - V_real between the target difference V_tar and the actual difference V_real between the average single cell voltage and the lowest single cell voltage of the fuel cell, and the rate of change of this difference dΔV.

[0026] Next, step S1.2 is executed: ΔV and dΔV are input into the fuzzy controller. The fuzzy controller first fuzzifies these two precise quantities. In this embodiment, the universes of discourse for both ΔV and dΔV are divided into five linguistic variable levels: {negative large (NB), negative small (NS), zero (ZO), positive small (PS), positive large (PB)}. The membership function for the input quantity is a trigonometric function, and the membership function for the output quantity (speed adjustment quantity) is a Gaussian distribution function. Then, inference is performed according to the fuzzy rules shown in Table 1 below. This rule table is based on expert experience and a large amount of experimental data.

[0027] Then, step S1.3 is executed: the fuzzy output obtained from the inference is defuzzified using the "center of gravity method" to obtain a precise current speed adjustment. This adjustment is added to the hydrogen pump speed at the previous moment to obtain the target hydrogen pump speed at the current moment. Finally, to prevent damage to the fuel cell stack due to slow response or excessive speed, the system sets different speed thresholds under different electrical density conditions (e.g., limiting the maximum speed at low electrical density and increasing the base speed at high electrical density), and outputs the final command after limiting the calculated speed.

[0028] Step S2: Efficient control of hydrogen proportional valve opening based on fuzzy PI control. This step aims to achieve fast response and stable control of the hydrogen proportional valve, avoiding overshoot and oscillation.

[0029] like Figure 3 As shown, first, step S2.1 is performed: calculate the difference ΔP = P_tar - P_real between the target value of the anode hydrogen inlet pressure P_tar and the actual pressure P_real collected by the hydrogen low-pressure sensor 7, and the rate of change of this difference dΔP.

[0030] Next, step S2.2 is executed: ΔP and dΔP are input into the fuzzy PI controller. Similarly, the universes of discourse for both are divided into five levels: {NB, NS, ZO, PS, PB}, and all membership functions are set to Gaussian distribution functions. Inference is performed according to the fuzzy rules shown in Table 2 below, and the fuzzy quantities used to adjust the PI controller parameters are output.

[0031] Then, perform step S2.3: after defuzzification using the centroid method, obtain the accurate K. p and K i Adjust the value to obtain the current optimal K. p and K i Parameters. Finally, substituting the pressure error e(t)=ΔP into the PI controller formula (a well-known formula), the calculated control quantity u(t) is the opening command of the hydrogen proportional valve 4.

[0032] The formula for the PI controller is: , In the above formula, u(t) is the calculated output control signal, e(t) is the error between the target value and the measured value, t is the system running time, and k p For proportional gain, k i This is the integral gain.

[0033] Furthermore, when the system needs to perform hydrogen venting or drainage operations (i.e., opening hydrogen venting valve 9 or drainage valve 10), the anode pressure will experience severe disturbances. To address this, this method uses pre-calibration tests to obtain the proportional valve opening compensation amount required for hydrogen venting / draining under different operating conditions. When the operation occurs, this compensation amount is directly superimposed on the opening command output by the fuzzy PI controller, achieving feedforward compensation and thus quickly stabilizing the reactor feed pressure.

[0034] Through the coordinated operation of steps S1 and S2 described above, this embodiment can achieve efficient and stable control of the hydrogen supply system of the fuel cell engine, effectively solving the shortcomings of the prior art.

[0035] It is understood that the above specific description of the present invention is only for illustrating the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention to achieve the same technical effect; as long as the use needs are met, they are all within the protection scope of the present invention.

Claims

1. A high-efficiency control method for a hydrogen supply system of a fuel cell engine, the method being applied to a hydrogen supply system, the system comprising a hydrogen cylinder group (1), a hydrogen medium-pressure sensor (2), a hydrogen main line solenoid valve (3), a hydrogen proportional valve (4), an ejector (5), a hydrogen circulation pump (6), a hydrogen low-pressure sensor (7), a hydrogen fuel cell stack (8), a hydrogen discharge valve (9), a drain valve (10), a gas-water separator (11), and a check valve (12), wherein, The ejector (5) and the hydrogen circulation pump (6) are connected in parallel, and each branch is equipped with the one-way valve (12). The method is characterized by comprising: S1. The rotational speed of the hydrogen circulation pump (6) is controlled by fuzzy control, including: taking the target difference V_tar and the actual difference V_real of the average single-cell voltage and the lowest single-cell voltage of the hydrogen fuel cell stack (8) as the system input, the adjusted rotational speed is output through fuzzy control rules, and different rotational speed thresholds are set under different electrical density conditions to output the final rotational speed; S2. The opening of the hydrogen proportional valve (4) is controlled by fuzzy PI control, including: using the difference ΔP between the target value of the anode hydrogen inlet pressure P_tar of the hydrogen fuel cell stack (8) and the actual pressure P_real collected by the hydrogen low-pressure sensor (7), and the rate of change dΔP of the difference ΔP as system input, and adjusting the proportional gain K of the PI controller through fuzzy control rules. p and integral gain K i To control the opening degree of the hydrogen proportional valve (4).

2. The efficient control method for a hydrogen supply system of a fuel cell engine according to claim 1, characterized in that, Step S1 specifically includes: S1.1 Calculate the difference ΔV = V_tar - V_real and its rate of change dΔV; S1.2 Set fuzzy control parameters, take the difference ΔV and the rate of change dΔV as inputs, perform fuzzy processing and fuzzy inference through the fuzzy control rule table, and obtain fuzzy quantity output; S1.3 Defuzzify the fuzzy output to obtain the current speed adjustment amount. Add the current speed adjustment amount to the speed at the previous moment to obtain the current hydrogen pump speed. Then, perform feedback adjustment based on the actual difference V_real to adjust the speed in the next step.

3. The efficient control method for a hydrogen supply system of a fuel cell engine according to claim 2, characterized in that, In step S1.2, the membership functions of the elements within the fuzzy subsets of the input and output parameters are triangular functions and Gaussian distribution functions, respectively; in step S1.3, the centroid method is used for defuzzification.

4. The efficient control method for a hydrogen supply system of a fuel cell engine according to claim 1, characterized in that, Step S2 specifically includes: S2.1 Calculate the difference ΔP = P_tar - P_real and its rate of change dΔP; S2.

2. Set fuzzy control parameters, taking the difference ΔP and the rate of change dΔP as system inputs, performing fuzzy processing and fuzzy inference through the fuzzy control rule table, and outputting the result to adjust the proportional gain K. p and integral gain K i The fuzzy quantity; S2.3 Defuzzify the fuzzy quantity to obtain the adjusted proportional gain K. p and integral gain K i The output control signal is calculated according to the PI control formula to control the opening degree of the hydrogen proportional valve (4).

5. The efficient control method for a hydrogen supply system of a fuel cell engine according to claim 4, characterized in that, In step S2.2, the membership functions of the elements within the fuzzy subsets of the input and output parameters are both set to Gaussian distribution functions; in step S2.3, the centroid method is used for defuzzification.

6. The efficient control method for a hydrogen supply system of a fuel cell engine according to claim 1, characterized in that, In step S1, setting different speed thresholds under different electrical density conditions includes setting an initial speed threshold to shorten the hydrogen pump response time and setting a maximum speed threshold to avoid damage to the fuel cell.

7. The efficient control method for a hydrogen supply system of a fuel cell engine according to claim 1, characterized in that, Step S2 further includes: during the process of hydrogen discharge and drainage of the fuel cell system through the hydrogen discharge valve and the drainage valve, the opening degree of the hydrogen proportional valve is compensated through a calibration test to meet the hydrogen inlet pressure requirements on the anode side.

8. The efficient control method for a hydrogen supply system of a fuel cell engine according to claim 1, characterized in that, The difference ΔV and rate of change dΔV in step S1, and the difference ΔP and rate of change dΔP in step S2, are all divided into five levels of linguistic variables in their respective domains: negative large (NB), negative small (NS), zero (ZO), positive small (PS), and positive large (PB).

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