Control method and system for double proportional valves and ejector of hydrogen path of fuel cell

Abstract

The invention relates to the technical field of fuel cell hydrogen supply system control, in particular to a control method and system for double proportional valves and an ejector of a fuel cell hydrogen path. Comprising a stop valve and a two-way parallel proportional valve, the stop valve is arranged at the front end of the two-way proportional valve, a first ejector is connected behind a main proportional valve, and the stop valve, a bypass proportional valve and a second ejector are connected into an electric pile in parallel. The input is that the controller collects the hydrogen entering pressure transmitted by the pressure sensor in real time, the main proportional valve is controlled preferentially, and the bypass proportional valve is controlled after the opening degree of the main proportional valve reaches the flow upper limit, so that the closed-loop control of the hydrogen entering pressure is realized, and meanwhile, the stoichiometric ratio of the hydrogen entering the reactor meets the operation requirement of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cell hydrogen supply system control, and in particular to a control method and system for a dual proportional valve and an ejector in a fuel cell hydrogen path. Background Art

[0002] Traditional internal combustion engines (such as gasoline engines and diesel engines) convert chemical energy into heat energy through the combustion of fuel, and then convert heat energy into mechanical energy through mechanical parts such as pistons and crankshafts. Its energy conversion process is limited by the Carnot cycle. Generally speaking, the thermal efficiency of traditional gasoline engines is about 30%, and the thermal efficiency of diesel engines can reach about 40%. In addition, the efficiency of traditional engines will drop significantly under partial load or idling conditions. This is because the combustion process of the engine is not ideal under these conditions, and the energy loss such as friction of mechanical parts accounts for a relatively large proportion. In addition, the combustion of gasoline and diesel will produce a large amount of pollutants, such as carbon monoxide, hydrocarbons, nitrogen oxides and particulate matter, which have a serious impact on the environment and air quality. Fuel cells are electrochemical devices that can directly convert chemical energy into electrical energy. Its energy conversion process is not limited by the Carnot cycle and theoretically has a very high energy conversion efficiency. For example, the theoretical energy conversion efficiency of proton exchange membrane fuel cells (PEMFCs) can reach about 83%. In practical applications, its efficiency can generally reach 40% to 60%, especially under partial load conditions, the efficiency can still be maintained at a high level. Moreover, when hydrogen is used as a fuel, its combustion product is water, which is pollution-free. It is a very clean energy carrier and is more environmentally friendly.

[0003] The anode hydrogen reflux of hydrogen fuel cells mainly depends on hydrogen circulation pumps or ejectors. The reliability of hydrogen circulation pumps is relatively low due to the presence of mechanical moving parts. And generally speaking, the efficiency of hydrogen circulation pumps may be lower than that of ejectors in some cases, especially under conditions of small flow and high pressure increase, where mechanical losses account for a larger proportion and the efficiency will be lower. The ejector has a simple structure and no moving parts, so it has high reliability. The ejector has no friction loss of mechanical moving parts during operation, and its efficiency mainly depends on the mixing and energy conversion process of the fluid. Under appropriate working conditions, the efficiency of the ejector can reach a high level.

[0004] The solution of a single-channel ejector is to adjust the flow rate of the ejected fluid by changing the parameters of the driving fluid. The adjustment method is relatively simple. The flexibility of its flow and pressure regulation is relatively low. When facing complex and changeable working conditions, it may not be able to meet the requirements quickly and accurately. In addition, the relationship between the opening of the proportional valve and the flow rate is usually nonlinear, so the control difficulty is greatly increased.

[0005] In the control scheme of the traditional dual-path ejector, whether to open the second proportional valve is often determined by the preset stack current. Two sets of control parameters are required to control the two proportional valves separately. In addition, the two proportional valves have coupling characteristics, which greatly increases the difficulty of control and is not conducive to stable and long-term operation of the system.

[0006] In summary, the mechanical components of the hydrogen circulation pump have low reliability and limited efficiency; the flow regulation flexibility of the single-way ejector is poor and the nonlinear control is complex; the two sets of control parameters of the traditional dual-way ejector are highly coupled and the system stability is poor. Therefore, how to optimize the hydrogen supply pressure and flow through the coordinated control of the dual proportional valve (main valve + bypass proportional valve) and the ejector is a technical problem to be solved. Summary of the invention

[0007] The problem to be solved by the present invention is to provide a control method and system for a dual proportional valve and an ejector in a hydrogen circuit of a fuel cell, which omits a hydrogen circulation pump, reduces the power consumption and volume inside the system, and at the same time, the dual proportional valve ejector scheme introduces a new linear control scheme, which can better cover various power points and improve the system fault tolerance.

[0008] In view of the shortcomings of the prior art, the present invention solves the technical problems by adopting a technical solution: a control method for a dual proportional valve and an ejector in a hydrogen path of a fuel cell, comprising the following steps:

[0009] a. The opening and closing of the hydrogen passage is controlled by a stop valve, and the stop valve is located at the front end of the main proportional valve and the bypass proportional valve;

[0010] b. The pressure sensor collects the hydrogen pressure signal at the inlet of the fuel cell stack in real time and inputs it into the controller as the control target;

[0011] c. Calibrate the nonlinear relationship between the opening of the main proportional valve and the bypass proportional valve and the total flow;

[0012] d. Integrate the nonlinear characteristics of the two valves into a linear mapping relationship between the total opening percentage and the total flow rate;

[0013] e. The controller outputs the total opening percentage based on the PID algorithm, and distributes the actual opening of the main proportional valve and the bypass proportional valve according to the total opening percentage to achieve closed-loop control of the hydrogen pressure.

[0014] Preferably, the specific process in step c is as follows:

[0015] Prioritize the nonlinear relationship between the opening of the main proportional valve and the total flow rate;

[0016] After the opening of the main proportional valve reaches the upper threshold, the opening of the main proportional valve is maintained unchanged, and the nonlinear relationship between the opening of the bypass proportional valve and the total flow is calibrated;

[0017] Finally, the mapping relationship between the opening of the main proportional valve, bypass proportional valve and the total flow is obtained.

[0018] Preferably, in step d, the total opening percentage is calculated as follows: the sum of the calibrated maximum flow rates of the main proportional valve and the bypass proportional valve is set as the total opening maximum value, the total opening of each calibration point = current calibrated flow value / calibrated flow maximum value*100%, and each calibrated flow value corresponds to a different total opening, thereby obtaining a straight line of a linear relationship.

[0019] Preferably, the linear mapping relationship between the total opening percentage and the total flow rate is generated by piecewise interpolation or polynomial fitting, and the linearization error is less than 2%.

[0020] Preferably, in step e, the total opening percentage allocation rule is:

[0021] When the total opening percentage is ≤ the flow upper limit threshold of the main proportional valve, only the opening of the main proportional valve is adjusted;

[0022] When the total opening percentage is greater than the flow upper limit threshold of the main proportional valve, the main proportional valve maintains the maximum opening, and the bypass proportional valve is linearly adjusted according to the remaining demand.

[0023] Preferably, the controller uses a single set of PID parameters to adjust the total opening percentage, and controls the openings of the main proportional valve and the bypass proportional valve respectively through independent PWM signals.

[0024] Preferably, the opening flow calibration data of the main proportional valve and the bypass proportional valve are obtained through experimental testing and stored as a linearization conversion table of nonlinear data.

[0025] Preferably, the controller adopts an anti-integral windup mechanism when the pressure deviation exceeds the limit, limiting the accumulation of the integral term to avoid sudden changes in the control amount.

[0026] A fuel cell hydrogen supply system, comprising: a hydrogen tank, a stop valve, a main proportional valve, a bypass proportional valve, a first ejector, a second ejector, a pressure sensor, a fuel cell stack and a controller;

[0027] The front end of the stop valve is connected to the hydrogen tank, the main proportional valve and the bypass proportional valve are connected in parallel to the rear end of the stop valve and are respectively connected to the first ejector and the second ejector; the rear ends of the first ejector and the second ejector are connected in parallel and connected to the inlet of the fuel cell stack through a pressure sensor;

[0028] The controller is configured to execute the control method according to any one of claims 1-8.

[0029] Preferably, the first ejector and the second ejector are fluid dynamic devices without moving parts, which are used to improve the hydrogen reflux efficiency.

[0030] The beneficial effects of the present invention are as follows:

[0031] 1. The proportional valve characteristic itself is nonlinear. We linearize the process into the PID controller 9 to achieve linear control of the nonlinear proportional valve, simplify the control difficulty, and improve the system fault tolerance and stability.

[0032] 2. Integrate the control of the two-way proportional valves into a set of PID control parameters, and use the performance upper limit of the main proportional valve as the switching condition of the two-way proportional valves, which greatly reduces the control amount and control difficulty and improves the system fault tolerance.

[0033] 3. The solution of the present invention can replace the traditional hydrogen circulation pump solution, reduce system power consumption and volume, and improve reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the working process of the proportional valve and the ejector of the method of the present invention;

[0035] Figure 2 It is a hardware structure diagram involved in the present invention;

[0036] Figure 3 The proportional valve calibration flow data of the present invention;

[0037] Figure 4 It is a nonlinear curve between the opening degree and the total flow rate of the proportional valve involved in the present invention;

[0038] Figure 5 is the relationship between the opening percentage of the total proportional valve and the flow rate of the present invention;

[0039] Figure 6 It is the relationship between the total proportional valve opening percentage and the actual opening of the two-way proportional valves of the present invention;

[0040] Figure 7 It is a schematic diagram of the system structure of the present invention;

[0041] Figure 8 It is a schematic diagram of the anti-integral saturation method involved in the present invention;

[0042] Fig. 9 It is the pressure fluctuation curve under the rated working condition involved in the present invention;

[0043] Fig.10 The pressure fluctuation curve from half load to rated load involved in the present invention;

[0044] Explanation of the reference numerals: 1. Hydrogen tank; 2. Shut-off valve; 3. Main proportional valve; 4. First ejector; 5. Bypass proportional valve; 6. Second ejector; 7. Pressure sensor; 8. Fuel cell stack; 9. Controller. DETAILED DESCRIPTION

[0045] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments of the present invention are provided for the purpose of illustration and description, and are not intended to be exhaustive or to limit the present invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention, and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

[0046] like Figure 1 The figure shows the working process of the proportional valve and the ejector of the present invention. After the system is started, the total opening is adjusted by the pressure feedback from the stack pressure sensor 7. At the same time, the opening of the main proportional valve 3 and the opening of the bypass proportional valve 5 corresponding to the total opening are respectively sent to the two proportional valves, and the main proportional valve 3 is opened first. When the opening of the main proportional valve 3 reaches the upper limit threshold, the opening of the main proportional valve 3 is fixed at the threshold, and the bypass proportional valve 5 is adjusted to meet the different power requirements of the system. A control method for a dual proportional valve and an ejector in a hydrogen path of a fuel cell, the specific steps are as follows:

[0047] a. The opening and closing of the hydrogen passage is controlled by the stop valve 2, and the stop valve 2 is located at the front end of the main proportional valve 3 and the bypass proportional valve 5;

[0048] b. The pressure sensor 7 collects the hydrogen pressure signal at the inlet of the fuel cell stack 8 in real time and inputs it into the controller 9 as a control target;

[0049] c. Calibrate the nonlinear relationship between the opening of the main proportional valve 3 and the bypass proportional valve 5 and the total flow rate; during calibration, give priority to calibrating the nonlinear relationship between the opening of the main proportional valve 3 and the total flow rate;

[0050] After the opening of the main proportional valve 3 reaches the upper limit threshold, the opening of the main proportional valve 3 is maintained unchanged, and the nonlinear relationship between the opening of the bypass proportional valve 5 and the total flow is calibrated;

[0051] Finally, the mapping relationship between the opening of the main proportional valve 3 and the bypass proportional valve 5 and the total flow is obtained. The opening flow calibration data of the main proportional valve 3 and the bypass proportional valve 5 are obtained through experimental testing and stored as a linear conversion table of nonlinear data.

[0052] d. Integrate the non-linear characteristics of the two valves into a linear mapping relationship between the total opening percentage and the total flow rate; the calculation method of the total opening percentage is as follows: set the sum of the calibrated maximum flow rates of the main proportional valve 3 and the bypass proportional valve 5 as the maximum total opening (100%), and the total opening at each calibration point = the current calibrated flow rate value / the maximum calibrated flow rate * 100%. Corresponding different total openings to the calibrated flow rate values, a straight line with a linear relationship can be obtained. The linear mapping relationship between the total opening percentage and the total flow rate is generated by piecewise interpolation or polynomial fitting, and the linearization error is less than 2%.

[0053] e. The controller 9 outputs the total opening percentage based on the PID algorithm and distributes the actual openings of the main proportional valve 3 and the bypass proportional valve 5 according to the total opening percentage to achieve the closed-loop control of the hydrogen pressure;

[0054] The distribution rule of the total opening percentage is as follows:

[0055] When the total opening percentage ≤ the flow upper limit threshold of the main proportional valve 3, only adjust the opening of the main proportional valve 3;

[0056] When the total opening percentage > the flow upper limit threshold of the main proportional valve 3, the main proportional valve 3 maintains the maximum opening, and the bypass proportional valve 5 is linearly adjusted according to the remaining demand.

[0057] The controller 9 uses a single set of PID parameters to adjust the total opening percentage and controls the openings of the main proportional valve 3 and the bypass proportional valve 5 respectively through independent PWM signals. When the pressure deviation exceeds the limit, the controller 9 adopts an anti-integral saturation mechanism to limit the accumulation of the integral term to avoid sudden changes in the control quantity.

[0058] It should be noted that the opening of the main proportional valve 3 is simply referred to as the main opening, and the opening of the bypass proportional valve 5 is simply referred to as the secondary opening or bypass opening. The calibration process of integrating the non-linear relationship between the calibrated opening flow rates of the main proportional valve 3 and the bypass proportional valve 5 into a linear mapping relationship between the total opening percentage and the flow rate is carried out in a laboratory environment. The flow rate data of the main proportional valve 3 and the bypass proportional valve 5 at different openings are collected through a high-precision flow meter and a pressure sensor 7; the flow rate data at different openings are collected through a flow meter. The flow meter is placed on the gas source side. First, the main proportional valve 3 is calibrated. After the flow rate of the main proportional valve 3 reaches the upper limit, the bypass proportional valve 5 is calibrated while keeping the opening of the main proportional valve 3 unchanged; in order to test the consistency of the equipment performance, we adopt a repeatability test method. Through multiple tests and comparisons, the deviation of the flow meter values at the same opening is within 2%.

[0059] Such as Figure 7The figure shows a schematic diagram of the system structure of the present invention, where the stop valve 2 is at the front end of the two-way proportional valve, the main proportional valve 3 is connected to the first ejector 4, and the bypass proportional valve 5 is connected to the second ejector 6. The rear end of the first ejector 4 is connected in parallel with the rear end of the second ejector 6 and then connected to the fuel cell stack 8 through the pressure sensor 7. The controller 9 collects the hydrogen inlet pressure transmitted by the pressure sensor 7 in real time, and preferentially controls the main proportional valve 3; when the opening of the main proportional valve 3 reaches the upper limit of the flow rate, the bypass proportional valve 5 is controlled to achieve closed-loop control of the hydrogen inlet pressure while ensuring that the hydrogen metering ratio of the inlet meets the system operation requirements. After the hydrogen gas source enters and is turned on, the controller 9 preferentially opens the stop valve 2, and then opens the main proportional valve 3. When the opening of the main proportional valve 3 reaches the upper limit threshold, the bypass proportional valve 5 is opened. The control input of the two-way proportional valve is the hydrogen inlet pressure fed back by the inlet pressure sensor 7. The functions of each structure are as follows:

[0060] Stop valve 2: Located at the front end of the dual proportional valve, it serves as the main switch to control the total flow of hydrogen;

[0061] Main proportional valve 3: connected to the first ejector 4, to adjust the hydrogen flow rate first;

[0062] Bypass proportional valve 5: connected to the second ejector 6, connected in parallel with the main proportional valve 3, enabled after the main proportional valve 3 is saturated, to supplement the flow;

[0063] Pressure sensor 7: monitors the inlet pressure of the fuel cell stack 8 in real time and feeds back to the controller 9;

[0064] Controller 9: Based on the PID algorithm, it outputs the total opening percentage and distributes it to the two valves in proportion.

[0065] The controller 9 controls the opening of the main proportional valve 3 and the bypass proportional valve 5 by outputting two independent PWM signals. The opening working range of the main proportional valve 3 and the bypass proportional valve 5 can be obtained by calibration, and the relationship between the opening of the main proportional valve 3, the bypass proportional valve 5 and the hydrogen flow rate is calibrated. Figure 3 As shown in the figure, the upper threshold of the opening of the main proportional valve 3 is determined by calibration at 60, and the lower threshold is about 30. When the main proportional valve reaches the upper threshold, the opening of the main proportional valve is kept unchanged, and the bypass proportional valve is calibrated. The upper threshold of the opening of the bypass proportional valve 5 is 65, and the lower threshold is about 28. Figure 4 From the fitting curves of the two figures, we can find that the opening and flow of the main proportional valve 3 and the bypass proportional valve 5 are not in a linear relationship. The closer to the upper limit of the proportional valve capacity, the smaller the Y-axis change rate of the fitting curve. The nonlinear relationship between the proportional valve opening and flow makes our PI control more complicated. In addition, two sets of different proportional valves require two sets of control parameters for control, and there is coupling interference between them, which makes control more difficult. Therefore, here we first linearize the sum of the two proportional valve flows and the total opening percentage.

[0066] Its control strategy is to integrate the capabilities of two proportional valves in control, convert the relationship between the opening of the main proportional valve 3 and the bypass proportional valve 5 and the flow rate into the relationship between the total opening percentage of the proportional valve and the flow rate, so as to achieve overall linear control of the flow rate, such as Figure 5 As shown, we set the sum of the calibrated maximum flow of the two-way proportional valve as the total opening maximum value (100%), the total opening of each calibration point = current calibrated flow value / maximum calibrated flow value * 100%, and correspond each calibrated flow value to a different total opening. A linear fitting curve of total opening and total flow can be obtained, y = 16.83x + 1E-12, where x is the total opening percentage and y is the flow value. At the same time, through the calibrated total opening and total flow, the correspondence between the total flow and the opening of the two-way proportional valve, we can also derive the relationship between the total opening percentage and the opening of the two-way proportional valve. In this way, we only need one set of control parameters to control the total opening, and because there is a linear relationship between the total opening and the total flow, compared with the original nonlinear control, the difficulty of PI control is relatively simple.

[0067] After linearizing the total opening of the proportional valve and the flow rate, we use the hydrogen inlet pressure as the control target and output the total opening of the proportional valve through PID control. However, the total opening of the proportional valve we output at this time is not the actual opening of the two-way proportional valve. We also need to convert the total opening into the actual opening of the two-way proportional valve.

[0068] In the specific control strategy, through the previous calibration data, the calculation formula of total opening and total flow, we will allocate the corresponding total opening to the main proportional valve 3 and the bypass proportional valve 5 according to the flow ratio of the two proportional valves. The main proportional valve 3 is opened first. When the opening of the main proportional valve 3 reaches the maximum flow opening, the bypass proportional valve 5 is opened to achieve accurate control of the target stack pressure. The relationship between the total proportional valve opening percentage and the actual opening of the two proportional valves is as follows: Figure 6 As shown, the total opening is distributed to the two proportional valves, the maximum flow of the main proportional valve 3 accounts for the first 24.6% of the total opening, and the flow of the bypass proportional valve 5 accounts for the last 75.4% of the total maximum flow.

[0069] The PID control formula is in the form of:

[0070]

[0071] Among them, u(t) is the output of controller 9, which is the total opening;

[0072] e(t) is the system error, which is the target value of hydrogen inlet pressure minus the actual value fed back by the hydrogen inlet pressure sensor 7;

[0073] Kp is the proportional term: the output is adjusted directly according to the current error. When the error is large, proportional control can respond quickly, but it may cause oscillation or static error.

[0074] Ki is the integral term: it is used to process the accumulated error of the system, adjust the output by integrating the error, and eliminate the static error;

[0075] Kd is the differential term: predict future trends based on the error change rate and appropriately reduce the overshoot and oscillation of the system;

[0076] The parameter tuning method adopts a compact method: a set of PID parameters is first given based on experience, and then the controller 9 is put into operation to observe the response curve of the system (such as step response). According to the performance indicators of the response (such as overshoot, adjustment time, steady-state error, etc.), the parameters are adjusted according to certain rules until a satisfactory control effect is obtained.

[0077] (1) First use only proportional control, adjust Kp from small to large, observe the system response, and make the system have a certain degree of rapidity and a small steady-state error.

[0078] (2) Add integral control, appropriately reduce Kp, and adjust Ki to eliminate steady-state error.

[0079] Allocation logic:

[0080] Through calibration calculation, we obtain the total flow corresponding to the total opening. The total flow corresponds to the opening of the two proportional valves. The main proportional valve 3 is opened first. After the main proportional valve 3 reaches the upper limit threshold a, the bypass proportional valve is opened.

[0081] When the total opening percentage is ≤ a%, only the main proportional valve 3 works;

[0082] When the total opening is greater than a%, the main proportional valve 3 maintains the maximum opening, and the bypass proportional valve 5 opens linearly according to the remaining demand.

[0083] The dynamic response optimization adopts the anti-integral saturation mechanism: when the pressure deviation continues to exceed the limit, the integral term accumulation is limited to avoid sudden changes in the control amount. In practical applications, in order to avoid excessive accumulation of integral terms, we use the limit-weakened integral method: when it is detected that the control amount u(t) enters the saturation zone, the integral term is no longer accumulated, but the integral weakening operation is performed. This will not produce too much overshoot, and when reverse adjustment is required, it can respond faster to avoid the output staying in the saturation zone for a long time. Figure 8 It is the anti-integral windup method.

[0084] Pressure fluctuation suppression: When bypass proportional valve 5 intervenes, a smooth transition algorithm is used to ensure that the pressure overshoot is less than 5%. The pressure fluctuation curve is as follows Fig.10 As shown, the hydrogen pressure fluctuation range is within ±3%.

[0085] The experimental data related to the method of the present invention are as follows:

[0086] 1. Rated power test:

[0087] Target pressure: 2.5 bar, actual fluctuation range: 2.475~2.525 bar (±1%).

[0088] Compared with traditional hydrogen circulation pump solutions, energy consumption is reduced by 7% and volume is reduced by 5%.

[0089] like Fig. 9 The figure shows the pressure fluctuation curve under rated working conditions, and the pressure fluctuation range is within ±1%.

[0090] 2. Low temperature start (20℃):

[0091] The system achieves pressure stabilization within 30 seconds with no hydrogen condensation issues.

[0092] 3. High load mutation (50% → 100%):

[0093] Pressure overshoot <3%, stabilization time <1 second.

[0094] like Figure 7 As shown, a fuel cell hydrogen supply system includes a hydrogen tank 1, a stop valve 2, a main proportional valve 3, a bypass proportional valve 5, a first ejector 4, a second ejector 6, a pressure sensor 7, a fuel cell stack 8 and a controller 9;

[0095] The front end of the stop valve 2 is connected to the hydrogen tank 1, and the main proportional valve 3 and the bypass proportional valve 5 are connected in parallel to the rear end of the stop valve 2 and are respectively connected to the first ejector 4 and the second ejector 6; the first ejector 4 and the second ejector 6 are connected in parallel at the rear ends and connected to the inlet of the fuel cell stack 8 through the pressure sensor 7; the first ejector 4 and the second ejector 6 are fluid power devices without moving parts, which are used to improve the hydrogen reflux efficiency.

[0096] The controller 9 is configured to execute the control method of the dual proportional valve and the ejector of the hydrogen circuit of the fuel cell.

[0097] The present invention solves the problems of complex control and low efficiency of the traditional hydrogen supply system through the coordinated control of the dual proportional valve and the ejector, linearization of nonlinear characteristics and integration of single PID parameters. It has the significant advantages of high precision, low energy consumption and wide adaptability to working conditions, which is in line with the development trend of high efficiency and intelligentization of fuel cell technology. Compared with the traditional hydrogen circulation pump solution, the energy consumption of the solution of the present invention is reduced by about 7% and the volume is reduced by about 5%. The present invention can be widely used in the field of vehicle-mounted fuel cell systems, distributed power stations and backup power supplies, especially in scenarios with strict requirements on system volume, energy consumption and reliability. By simplifying the control logic and improving fault tolerance, the maintenance cost and failure rate of the fuel cell system can be significantly reduced.

Claims

1. A control method for a dual proportional valve and an ejector in a fuel cell hydrogen circuit, characterized in that: The following steps are involved: a. The opening and closing of the hydrogen passage is controlled by a stop valve (2), wherein the stop valve (2) is located at the front end of the main proportional valve (3) and the bypass proportional valve (5); b. The pressure sensor (7) collects the hydrogen pressure signal at the inlet of the fuel cell stack (8) in real time and inputs it into the controller (9) as a control target; c. calibrate the nonlinear relationship between the opening of the main proportional valve (3) and the bypass proportional valve (5) and the total flow rate; d. Integrate the nonlinear characteristics of the two valves into a linear mapping relationship between the total opening percentage and the total flow rate; e. The controller (9) outputs the total opening percentage based on the PID algorithm, and distributes the actual openings of the main proportional valve (3) and the bypass proportional valve (5) according to the total opening percentage, thereby realizing closed-loop control of the hydrogen pressure.

2. The control method of the dual proportional valve and ejector of the fuel cell hydrogen circuit according to claim 1, characterized in that: The specific process in step c is as follows: Prioritize the nonlinear relationship between the opening of the main proportional valve (3) and the total flow rate; After the opening of the main proportional valve (3) reaches the upper limit threshold, the opening of the main proportional valve (3) is maintained unchanged, and the nonlinear relationship between the opening of the bypass proportional valve (5) and the total flow rate is calibrated; Finally, the mapping relationship between the opening degree of the main proportional valve (3), the bypass proportional valve (5) and the total flow rate is obtained.

3. The control method of the dual proportional valve and ejector of the fuel cell hydrogen circuit according to claim 1, characterized in that: In step d, the total opening percentage is calculated as follows: the sum of the calibrated maximum flow rates of the main proportional valve (3) and the bypass proportional valve (5) is set as the total opening maximum value (100%), the total opening of each calibration point = current calibrated flow value / calibrated flow maximum value*100%, and each calibrated flow value is corresponded to a different total opening, thereby obtaining a straight line of a linear relationship.

4. The control method of the dual proportional valve and ejector of the fuel cell hydrogen circuit according to claim 3 is characterized in that: The linear mapping relationship between the total opening percentage and the total flow rate is generated by piecewise interpolation or polynomial fitting, and the linearization error is less than 2%.

5. The control method of the dual proportional valve and ejector of the fuel cell hydrogen circuit according to claim 1, characterized in that: In step e, the total opening percentage allocation rule is: When the total opening percentage is ≤ the flow upper limit threshold of the main proportional valve (3), only the opening of the main proportional valve (3) is adjusted; When the total opening percentage is greater than the flow upper limit threshold of the main proportional valve (3), the main proportional valve (3) maintains the maximum opening, and the bypass proportional valve (5) is linearly adjusted according to the remaining demand.

6. The control method of the dual proportional valve and ejector of the fuel cell hydrogen circuit according to claim 5, characterized in that: The controller (9) uses a single set of PID parameters to adjust the total opening percentage, and controls the openings of the main proportional valve (3) and the bypass proportional valve (5) respectively through independent PWM signals.

7. The control method of the dual proportional valve and ejector of the hydrogen path of a fuel cell according to claim 1, characterized in that: The opening flow calibration data of the main proportional valve (3) and the bypass proportional valve (5) are obtained through experimental testing and stored as a linear conversion table of non-linear data.

8. The control method of the dual proportional valve and ejector of the fuel cell hydrogen circuit according to claim 1, characterized in that: The controller (9) adopts an anti-integral windup mechanism when the pressure deviation exceeds the limit, limiting the accumulation of the integral term to avoid sudden changes in the control amount.

9. A fuel cell hydrogen supply system, characterized in that: include: A hydrogen tank (1), a stop valve (2), a main proportional valve (3), a bypass proportional valve (5), a first ejector (4), a second ejector (6), a pressure sensor (7), a fuel cell stack (8) and a controller (9); The front end of the stop valve (2) is connected to the hydrogen tank (1), and the main proportional valve (3) and the bypass proportional valve (5) are connected in parallel to the rear end of the stop valve (2) and are respectively connected to the first ejector (4) and the second ejector (6); the rear ends of the first ejector (4) and the second ejector (6) are connected in parallel and connected to the inlet of the fuel cell stack (8) through the pressure sensor (7); The controller (9) is configured to execute the control method according to any one of claims 1 to 8.

10. The fuel cell hydrogen supply system according to claim 9, characterized in that: The first ejector (4) and the second ejector (6) are fluid dynamic devices without moving parts and are used to improve the hydrogen reflux efficiency.

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