Elastic performance constraint control method for air flow and pressure of hydrogen fuel cell

Abstract

The invention belongs to the technical field of fuel cells, and particularly relates to an elastic performance constraint control method for air flow and pressure of a hydrogen fuel cell, which comprises the following steps: considering the influence of load change and external interference on an air loop, and establishing a nonlinear dynamic model capable of reflecting air flow and pressure coupling characteristics; introducing a specified performance function and an error transformation function by combining transient and steady-state performance requirements of the peroxide ratio and the cathode pressure; aiming at the problems of large uncertainty fluctuation amplitude and fast load change of the system, designing a high-order interference observer and constructing a self-adaptive elastic performance boundary; and finally, designing control instructions of a back pressure valve and an air compressor based on an interference utilization mechanism and a dynamic surface method, and completing elastic performance constraint control of air flow and pressure. According to the invention, multivariable coordination control of the air loop of the hydrogen fuel cell is realized, and the system operation is safer and greener while transient and steady-state performance requirements of the system are met.

Description

Technical Field

[0001] The invention belongs to the technical field of fuel cells, and in particular relates to an elastic performance constraint control method for air flow and pressure of a hydrogen fuel cell. Background Art

[0002] Proton exchange membrane fuel cells have become a highly promising zero-carbon power generation solution in the aviation and automotive fields due to their advantages such as high efficiency, high power density and zero emissions. However, in practical applications, the fuel cell air supply system has problems such as nonlinear coupling, frequent load changes and external interference, which makes it difficult to determine the system parameters, and the flow / pressure fluctuates sharply under variable load conditions, and even causes stack oxygen deficiency, which seriously affects the performance of the fuel cell system. The decoupling method using traditional feedforward or feedback linearization not only ignores the inherent nonlinear dynamics, but also amplifies the linearization error sharply when the fuel cell operating point is offset on a large scale, generating a non-matching control input signal.

[0003] At present, in the research on elastic performance constraint control of air flow and pressure, Chinese patent application CN202410714810.7 (Decoupling optimization method for automotive fuel cell air system) uses data-driven methods to identify transfer functions and analyze coupling and gain effects, designs different decoupling controllers based on diagonal matrices and judges robustness, reduces the degree of coupling between flow and pressure, but does not consider the adaptability and stability of the decoupling controller when complex working conditions change. Chinese patent application CN202311097493.0 (A fuel cell air supply system and method adapted to different altitudes) distinguishes working modes according to empirical altitude values, and realizes adaptive adjustment of intake pressure at different altitudes, but the optimization of control accuracy and dynamic response performance of air flow and pressure is not comprehensive enough. Chinese patent application CN202310794951.X (An anti-disturbance fuel cell air supply system) designs an anti-disturbance control strategy, which calculates the motor according to the target value and the angular velocity of the observation point. Shaft current, suppressing electromagnetic and load disturbances, without considering the use of beneficial components of interference to improve system safety performance.

[0004] In summary, the existing fuel cell technology has insufficient operational safety in complex environments such as load mutations and external interference. Therefore, the study of multivariable elastic performance constraint control of fuel cell gas supply systems is still an urgent engineering problem to be solved. Summary of the invention

[0005] Aiming at the problems of nonlinear coupling, frequent load changes, and external disturbances in the air supply system of hydrogen fuel cells, to overcome the deficiencies of the existing technology and make full use of the beneficial components of the disturbances, the present invention provides an elastic performance constraint control method for the air flow and pressure of hydrogen fuel cells. Considering the influence of load changes and external disturbances on the air circuit, a nonlinear dynamic model reflecting the coupling characteristics of air flow and pressure is established, and a specified performance function is introduced in combination with transient and steady-state performance requirements; at the same time, aiming at the system uncertainty and load change problems, a high-order disturbance observer and an adaptive elastic performance boundary are designed, and control commands are designed based on the disturbance utilization mechanism and the dynamic surface method to achieve multivariable coordinated control of the air circuit of hydrogen fuel cells, meet the system performance requirements and ensure safe and green operation.

[0006] To achieve the above object, the present invention adopts the following technical solutions: An elastic performance constraint control method for the air flow and pressure of a hydrogen fuel cell, comprising the following steps: The first step is to consider the influence of load changes and external disturbances on the air circuit and establish a nonlinear dynamic model that can reflect the coupling characteristics of air flow and pressure; The second step is to introduce a specified performance function and an error transformation function based on the nonlinear dynamic model in the first step, in combination with the transient and steady-state performance requirements of the oxygen ratio and the cathode pressure; The third step is to design a high-order disturbance observer and construct an adaptive elastic performance boundary based on the specified performance function and the error transformation function in the second step, aiming at problems such as large amplitude of system uncertainty fluctuations and fast load changes; The fourth step is to design the control commands for the back pressure valve and the air compressor based on the high-order disturbance observer and the adaptive elastic performance boundary in the third step, according to the disturbance utilization mechanism and the dynamic surface method, and complete the elastic performance constraint control of the air flow and pressure.

[0007] Specifically, the first step includes: considering the influence of load changes and external disturbances on the air circuit, and obtaining the air compressor speed , the supply manifold pressure , the cathode field pressure , and the back pressure valve opening according to the dynamic characteristics of the air supply system; the air flow rate at the outlet of the air compressor is fitted as a nonlinear function of and , and the nonlinear dynamic model of the multi-input multi-output air supply system is established as: ; Among them, the system state variables are , is the first derivative of , is the input voltage of the air compressor, is the opening control command of the back pressure valve, is the system uncertainty, is the load current of the fuel cell, are the system model parameters.

[0008] Specifically, the second step includes: Based on the non-linear dynamic model in the first step, combined with the transient and steady-state performance requirements of the peroxide ratio and the cathode pressure, the following specified performance function is introduced: , where, and are preset constants, is the adaptive boundary term to be designed, ; Define the error transformation function as follows: , where, and are preset constants, is the tracking error of the th element, .

[0009] Specifically, in the third step, based on the specified performance function and the error transformation function in the second step, aiming at the problems of large fluctuations in system uncertainty and fast load changes, a high-order disturbance observer is designed as: , where, and are the estimated values of and respectively, and are the first-order derivatives of and respectively, , is the design parameter, ; Define the adaptive performance boundary term as: , where, is the positive design parameter, is the performance boundary adjustment factor designed to cope with disturbances and load changes, and the corresponding update rate is as follows: , where, , , , and are positive design parameters, , and are the derivatives of the reference inputs, .

[0010] Specifically, in the fourth step, based on the disturbance utilization mechanism and the dynamic surface method, the following first-order filters and error variables are introduced: , wherein, is the time constant, is the filter output, and the virtual controlled variable is selected as and , is 's target value, , , , and are respectively , and 's first-order derivatives, is the process calculation formula, , , , is the disturbance utilization function, is the disturbance estimation error, , and the superscript T is the matrix transpose symbol; Design the back pressure valve opening control command and the air compressor input voltage as follows: , wherein, , is the design parameter.

[0011] The beneficial effects of the present invention compared with the prior art are as follows: (1) Around the flow / pressure coupling characteristics under load changes and the presence of external disturbances, a multi-input multi-output nonlinear dynamic model of the air supply system is established. While overcoming the poor adaptability of traditional methods to complex working conditions, it avoids control deviations caused by the failure to consider nonlinear coupling characteristics, and the control effect is better.

[0012] (2) Aiming at the problems of large system uncertainty fluctuation amplitude and fast load change, a high-order disturbance observer is designed to accurately and real-time monitor the system uncertainty, construct an adaptive elastic performance boundary, realize flexible adjustment of the boundary, and improve the stability and reliability of the system under complex working conditions.

[0013] (3) For the situation where the beneficial components of interference are not considered in the multivariable control of the air supply system, control instructions are designed based on the interference utilization mechanism and the dynamic surface method. While achieving the elastic performance constraints, the control energy consumption is reduced, ensuring the safe and green operation of the system. Description of the Drawings

[0014] Figure 1 It is a flowchart of an elastic performance constraint control method for the air flow and pressure of a hydrogen fuel cell according to the present invention; Figure 2 It is a comparison result diagram of the cathode pressure and flow tracking errors of an elastic performance constraint control method for the air flow and pressure of a hydrogen fuel cell according to the present invention; Figure 3 It is an elastic performance constraint effect diagram under external interference of an elastic performance constraint control method for the air flow and pressure of a hydrogen fuel cell according to the present invention. Detailed Embodiment

[0015] Next, the technical solutions in the embodiments of the present invention will be clearly, elaborately and comprehensively explained in combination with the corresponding drawings. It should be clearly pointed out that the embodiments described herein are only a part of the embodiments of the present invention, not all of them. Based on the embodiments presented by the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

[0016] As Figure 1 shown, an elastic performance constraint control method for the air flow and pressure of a hydrogen fuel cell according to the present invention includes the following steps: First step, considering the influence of load changes and external interference on the air circuit, establish a nonlinear dynamic model that can reflect the coupling characteristics of air flow and pressure; Second step, based on the nonlinear dynamic model in the first step, combined with the transient and steady-state performance requirements of the oxygen ratio and cathode pressure, introduce a specified performance function and an error transformation function; Third step, based on the specified performance function and error transformation function in the second step, aiming at problems such as large fluctuations in system uncertainty and fast load changes, design a high-order disturbance observer and construct an adaptive elastic performance boundary; Fourth step, based on the high-order disturbance observer and adaptive elastic performance boundary in the third step, according to the interference utilization mechanism and the dynamic surface method, design the control instructions for the back pressure valve and the air compressor to complete the elastic performance constraint control of the air flow and pressure; Specifically, the first step includes: Considering the influence of load changes and external interference on the air circuit, obtain the air compressor speed according to the dynamic characteristics of the air supply system , supply manifold pressure , cathode field pressure , and back pressure valve opening ; The air compressor outlet gas flow is fitted as a non - linear function of and . The non - linear dynamic model of the multi - input multi - output air supply system is established as: ; Among them, the system state variables are , is 's first - order derivative, is the air compressor input voltage, is the back pressure valve opening control command, is the system uncertainty, is the fuel cell load current, are the system model parameters.

[0017] Specifically, the second step includes: Based on the non - linear dynamic model in the first step, combined with the transient and steady - state performance requirements of the oxygen - to - fuel ratio and cathode pressure, the following specified performance function is introduced: , Among them, and are preset constants, is the adaptive boundary term to be designed, ; Define the error transformation function as follows: , Among them, and are preset constants, is the tracking error 's th element, .

[0018] Specifically, the third step includes: Based on the specified performance function and error transformation function in the second step, aiming at problems such as large system uncertainty fluctuation amplitude and fast load change, a high - order disturbance observer is designed as: , Among them, and are the estimated values of and respectively, and are and respectivelyThe first derivative of , is a design parameter, ; Define the adaptive performance boundary term as: , where is a positive design parameter, is a performance boundary adjustment factor designed to cope with disturbances and load changes, and the corresponding update rate is as follows: , where , , , and are positive design parameters, , and are the derivatives of the reference input, .

[0019] Specifically, the fourth step includes: Based on the disturbance utilization mechanism and the dynamic surface method, introduce the following first-order filter and error variables: , where is the time constant, is the filter output, select the virtual controlled variable as and , is 's target value, , , , and are respectively , and 's first derivatives, is the process calculation formula, , , , is the disturbance utilization function, is the disturbance estimation error, , the superscript T is the matrix transpose symbol.

[0020] Design the back pressure valve opening control command and the air compressor input voltage as follows: , where , are design parameters. Thus, the elastic performance constraint control of air flow and pressure is completed.

[0021] Embodiment 1: Taking the air supply system of a hydrogen fuel cell as an example, considering the problems such as the influence of load changes and external disturbances on the air circuit during actual operation, large fluctuations in system uncertainty, and fast load changes, an elastic performance constraint control strategy for the air flow and pressure of a hydrogen fuel cell is designed to achieve the efficient and stable operation of the air supply system of a hydrogen fuel cell under complex working conditions.

[0022] The specific steps of this embodiment are as follows: First step, considering the influence of load changes and external disturbances on the air circuit, according to the dynamic change laws of key components such as the air compressor, supply manifold, and cathode flow field, a nonlinear multi-input multi-output dynamic model is established. The specific model parameter values are shown in Table 1; Table 1

[0023] Second step, combining the performance requirements of the system for the oxygen excess ratio and cathode pressure, determine the reference oxygen excess ratio and cathode pressure , introduce the specified performance function to determine the transient and steady-state performance constraints of the tracking error , define the output and its reference signal , and then convert the performance constraint problem into a signal bounded problem through the error transformation function . The preset constants are set as follows: , , , , , , , ; Third step, estimate the uncertainty in the system by designing a high-order disturbance observer to provide effective compensation information for the control system. At the same time, construct an adaptive elastic performance boundary , and flexibly adjust the performance boundary function according to the actual operating conditions and uncertainty degree of the system. The relevant design parameters are , , , , , , , , , , , , , , , , ; Step 4: Based on the interference utilization mechanism and the dynamic surface method, design the opening control command of the backpressure valve and the input voltage of the air compressor , design , , thus completing the elastic performance constraint control of air flow and pressure; To verify the flow-pressure coordination control effect of the fuel cell under the elastic performance constraint designed by the present invention, experimental verification was carried out based on the hardware test platform of the high-power water-cooled fuel cell air supply system. First, without considering external interference, the proposed method was compared with the active disturbance rejection decoupling controller. The tracking error results of the cathode pressure and flow under the elastic performance constraint are as Figure 2 shown. The dashed line represents the designed non-linear controller under the elastic performance constraint, the solid line represents the active disturbance rejection decoupling controller, and the dash-dotted line and dotted line represent the upper and lower bounds of the performance constraint respectively. The experimental results show that when the load current changes from 150 A to 330 A, the tracking errors of the flow and pressure under the designed control method can meet the specified performance constraints. While under the active disturbance rejection decoupling control method, the tracking error exceeds the performance constraint boundary at the moment of load change, and the average absolute errors of the flow and pressure under the proposed method are 0.97% and 3.78% lower than those of the active disturbance rejection decoupling control method respectively. To further verify the control effect of the elastic performance constraint under the condition of interference, a disturbance signal was injected into the cathode pressure channel, and the experimental results are as Figure 3 shown. When the disturbance signal triggers the threshold designed by the adaptive elastic boundary function, the tracking error can meet the transient and steady-state performance requirements under the designed control method. While in the conventional specified performance control without considering the elastic constraint, due to the tracking error touching the performance boundary, a singular phenomenon occurs in the system.

[0024] Although the above describes the illustrative specific embodiments of the present invention for the understanding of those skilled in the art in this technical field, and it should be clear that the present invention is not limited to the scope of the specific embodiments. For those ordinary skilled in the art in this technical field, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

Claims

1. A method for controlling the elastic performance of air flow and pressure in a hydrogen fuel cell, characterized in that: The following steps are involved: The first step is to consider the impact of load changes and external disturbances on the air circuit and establish a nonlinear dynamic model that can reflect the coupling characteristics of air flow and pressure; In the second step, based on the nonlinear dynamic model in the first step, combined with the transient and steady-state performance requirements of the excess oxygen ratio and cathode pressure, the specified performance function and the error transformation function are introduced; In the third step, based on the specified performance function and error transformation function in the second step, a high-order disturbance observer is designed and an adaptive elastic performance boundary is constructed to address the problems of large fluctuations in system uncertainty and rapid load changes. In the fourth step, based on the high-order disturbance observer and adaptive elastic performance boundary in the third step, according to the disturbance utilization mechanism and dynamic surface method, the back pressure valve and air compressor control instructions are designed to complete the elastic performance constraint control of air flow and pressure.

2. The method for controlling the elastic performance of the air flow and pressure of a hydrogen fuel cell according to claim 1, characterized in that: The first step includes: considering the impact of load changes and external interference on the air circuit, and obtaining the air compressor speed according to the dynamic characteristics of the air supply system , Supply manifold pressure , cathode field pressure , and back pressure valve opening ;Air compressor outlet gas flow Fitting to and The nonlinear function of the multi-input and multi-output air supply system is established as: ； The system state variables are: , for The first derivative of Input voltage for air compressor, is the back pressure valve opening control instruction, is the system uncertainty, is the fuel cell load current, are system model parameters.

3. The method for controlling the elastic performance of the air flow and pressure of a hydrogen fuel cell according to claim 2, characterized in that: The second step includes: based on the nonlinear dynamic model in the first step, combined with the transient and steady-state performance requirements of the excess oxygen ratio and the cathode pressure, introducing the following specified performance function: ， in, and is the preset constant, is the adaptive boundary term to be designed, ; The error transformation function is defined as follows: ， in, and is the preset constant, Tracking error No. elements, .

4. The method for controlling the elastic performance of the air flow and pressure of a hydrogen fuel cell according to claim 3, characterized in that: In the third step, based on the specified performance function and error transformation function in the second step, a high-order disturbance observer is designed to solve the problems of large fluctuation amplitude of system uncertainty and fast load change: ， in, and They are and The estimated value of and They are and The first derivative of , is the design parameter, ; Defining Adaptive Performance Boundary Terms for: ， in, is a positive design parameter, The performance boundary adjustment factor designed to cope with interference and load changes has the following update rates: ， in, , , , and is a positive design parameter, , and is the derivative of the reference input, .

5. The method for controlling the elastic performance constraint of the air flow and pressure of a hydrogen fuel cell according to claim 4, characterized in that: In the fourth step, based on the interference utilization mechanism and the dynamic surface method, the following first-order filter and error variable are introduced: ， in, is the time constant, is the filter output, and the virtual controlled variable is selected as and , for The target value of , , , and They are , and The first derivative of is the process calculation formula, , , , is the interference utilization function, is the interference estimation error, , superscript T is the matrix transpose symbol; Design back pressure valve opening control command And air compressor input voltage as follows: ， in, , is the design parameter.

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