A hybrid vehicle energy management method based on auxiliary variable reconstruction and dynamic expansion non-singular backstepping control

Abstract

The application discloses a kind of based on auxiliary variable reconstruction and dynamic expansion non-singular backstepping control Hybrid Electric Vehicle energy management method, comprising the following steps: S1, establish the whole vehicle power balance relationship;S2, calculate the high-voltage DC bus load current;S3, set the SOC threshold of the power battery system;S4, the fuel cell system power is smoothed;S5, establish the Boost DC / DC converter average model;S6, auxiliary variable reconstruction;S7, dynamic expansion;S8, the high-voltage DC bus voltage error design;S9, non-singular backstepping control law design.The application based on auxiliary variable reconstruction and dynamic expansion non-singular backstepping control Hybrid Electric Vehicle energy management method, can be carried out while fuel cell and power battery power distribution, improve the stability of DC bus voltage, and avoid the singular problem caused by duty cycle close to 1 in traditional backstepping control.

Description

Technical Field

[0001] This invention relates to the field of energy management and intelligent control technology for new energy vehicles, and in particular to an energy management method for hybrid vehicles based on auxiliary variable reconstruction and dynamic extended nonsingular backstepping control. Background Technology

[0002] Fuel cells are favored by governments and companies worldwide due to their high energy conversion efficiency, environmental friendliness, quiet operation, and high reliability. They are considered the preferred clean and efficient power generation technology of the 21st century. However, for fuel cell vehicles, the inherent limitations of fuel cell stacks, such as their soft output characteristics and slow output response, prevent them from providing the vehicle with the necessary power in a timely manner. Furthermore, fuel cells are expensive and have a short lifespan, making them unsuitable as a standalone energy source. Therefore, current fuel cell vehicles utilize a dual power system consisting of a fuel cell and a power battery, with the power battery serving as the primary power output source to meet the vehicle's energy demands in real time.

[0003] In fuel cell-battery hybrid vehicles, the fuel cell is typically connected to a high-voltage DC bus via a Boost DC / DC converter, while the battery is connected to the same bus via a bidirectional DC / DC converter. The electric motor drive system is powered by the DC bus. The stability of the DC bus voltage directly affects the dynamic performance of the electric motor drive system and the overall vehicle safety. When the vehicle is starting, accelerating, climbing, or experiencing sudden load changes, the load power changes rapidly, which can easily cause fluctuations in the bus voltage. If the bus voltage fluctuations are too large, it may cause torque fluctuations in the drive system, overcurrent in the DC / DC converter, abnormal battery charging and discharging, and even affect the stability of the entire vehicle control system.

[0004] Fuel cells inherently possess characteristics such as slow dynamic response, limited output power variation rate, and the tendency for frequent power fluctuations to lead to reduced lifespan. Therefore, in fuel cell hybrid systems, energy management strategies not only need to meet the vehicle's power requirements but also need to avoid frequent and significant power fluctuations in the fuel cell and rationally utilize the power battery for peak power compensation and regenerative energy absorption.

[0005] On the one hand, existing energy management methods for fuel cell hybrid vehicles mainly include rule-based methods, optimization-based methods, and intelligent algorithm-based methods. Rule-based methods have simple structures and good real-time performance, but their adaptability to complex operating conditions is limited; optimization-based methods can achieve better energy allocation results, but the computational load is large, and real-time application is somewhat difficult; intelligent algorithm-based methods have strong learning capabilities, but they have high requirements for training data, computing resources, and engineering reliability.

[0006] On the other hand, in terms of DC bus voltage control, existing technologies typically employ methods such as proportional-integral control, sliding mode control, model predictive control, and traditional backstepping control. Proportional-integral control has a simple structure, but in Boost converter systems with strong nonlinearity and rapid load changes, it is prone to problems such as slow response speed and insufficient disturbance rejection. Sliding mode control has strong robustness, but it is prone to chattering, affecting the lifespan of the converter's switching devices. Model predictive control can handle constraints, but it involves a large amount of online computation. Traditional backstepping control can utilize the nonlinear structure of the Boost converter to improve control performance, but the controller derivation process usually requires division of (1-d), which can easily generate singular terms. Where d is the duty cycle of the Boost converter. When the vehicle is under high power demand or high boost ratio conditions, the duty cycle of the Boost converter may be close to 1. At this time, 1-d→0, which causes the controller output to tend to infinity, resulting in numerical instability, control input saturation, or even control failure.

[0007] Furthermore, in existing methods, energy management strategies and DC bus controllers are often designed separately. The energy management strategy only focuses on power distribution between the fuel cell and the power battery, while the underlying bus controller only focuses on bus voltage regulation. Although this hierarchical design is structurally clear, it may lead to difficulties in coordinating fuel cell lifetime protection, power battery SOC maintenance, bus voltage stability, and load disturbance suppression. Summary of the Invention

[0008] The purpose of this invention is to provide a hybrid vehicle energy management method based on auxiliary variable reconstruction and dynamic expansion non-singular backstepping control, which can improve the DC bus voltage stability while distributing power between the fuel cell and the power battery, and avoid the singularity problem caused by the duty cycle being close to 1 in traditional backstepping control.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A hybrid vehicle energy management method based on auxiliary variable reconstruction and dynamic extended nonsingular backstepping control, wherein the hybrid vehicle includes a fuel cell system, a power battery system, a high-voltage DC bus, a Boost DC / DC converter on the fuel cell system side, a bidirectional DC / DC converter on the power battery system side, a motor drive system, a vehicle load, an energy management controller, and a vehicle controller, comprising the following steps: S1, establish the power balance relationship of the whole vehicle; The overall vehicle power balance relationship is obtained through the following formula: (1); in: For the vehicle's required power, This refers to the output power of the fuel cell system. This refers to the output power of the power battery system. S2, Calculate the load current of the high-voltage DC bus; Parameters are collected in real time by the energy management controller. , , , , , , and Status information; in, The output voltage of the fuel cell system. The inductor current of the Boost DC / DC converter is... The voltage of the high-voltage DC bus is... The load current of the high-voltage DC bus is... The state of charge of the power battery system; The high-voltage DC bus load current is obtained by the following formula: (2); S3, setting the power battery system Threshold; The power battery system The threshold is obtained by the following formula: (3); in, This represents the lowest permissible state of charge for the power battery system. This represents the highest permissible state of charge for the power battery system. The desired state of charge of the power battery system. for Adjust the lower threshold, for Adjust the upper threshold; when At that time, the vehicle was operating under low load conditions; If satisfied Controlling the fuel cell system to operate at the minimum high-efficiency power level, i.e. (4) Simultaneously, excess power is supplied to charge the power battery system, i.e. (5); If satisfied The output power of the fuel cell system is reduced or the fuel cell system is put into an idling state, and the power battery system takes on part of the low power load. when At that time, the vehicle was operating under medium load conditions; At this time, the fuel cell system undertakes the main power demand, and according to The deviation is corrected, that is... (6); in, for Adjustment coefficient; If satisfied This increases the output power of the fuel cell system and replenishes the energy of the power battery system. If satisfied This reduces the output power of the fuel cell system, allowing the power battery system to bear part of the load. when At that time, the vehicle was under high load conditions; At this time, the output power of the fuel cell system is limited to (7) The power battery system provides peak power compensation as follows: (8), and satisfy ; If the power battery system Too low, that is At the same time, the discharge power of the power battery system is limited, and the vehicle controller limits the vehicle's drive power requirements; in, This represents the maximum output power of the fuel cell system. This represents the minimum high-efficiency power of the fuel cell system. This represents the maximum discharge power of the power battery system. This represents the maximum charging power of the power battery system. This is the reference power for the fuel cell system. This is the reference power of the power battery system; S4, smooth the power of the fuel cell system; The reference power of the fuel cell system satisfies: (9); The following discrete form is adopted: (10); in: This represents the maximum allowable power variation of the fuel cell system within one sampling period. This is the smoothed power command of the fuel cell system. This is a limiting function; The power command of the power battery system is obtained by the following formula: (11); in, This refers to the power command of the power battery system; S5, Establish the average model of the Boost DC / DC converter; The average state model of the Boost DC / DC converter is: (12); in, , , The inductor current of the Boost DC / DC converter is... Where L is the voltage of the high-voltage DC bus, C is the inductance of the Boost DC / DC converter, and d is the duty cycle of the Boost DC / DC converter. This refers to the equivalent bus current on the power battery system side. The equivalent bus current on the power battery system side is obtained by the following formula: (13); Wherein, the power battery system meets the following requirements when discharging: The power battery system meets the following requirements when charging: ; S6, Auxiliary variable reconstruction; Auxiliary variables are established using the following formula: (14); The dynamic equation for the high-voltage DC bus voltage is obtained from the following equation: (15); Substituting equation (14) into equation (15) yields the following: (16); S7, dynamic expansion; Introducing dynamic expansion variables and define ; Where u is the duty cycle change rate control quantity; According to equation (14), we can obtain: (17); Substituting into the dynamic equation of the inductor current of the Boost DC / DC converter: (18); get: (19); By dynamically expanding, the system can be represented as: (20); This system configuration can be used for non-singular backstepping control design; S8, the high-voltage DC bus voltage error design; The high-voltage DC bus voltage tracking error is established according to the following formula: (twenty one); in, This is the reference voltage for the high-voltage DC bus; From the aforementioned dynamic equation of the high-voltage DC bus voltage, we can obtain: (twenty two); Design virtual control variables: (twenty three); in, The first control gain; when When the reference voltage is constant, ; Establish auxiliary error: (twenty four); Substituting equation (24) into equation (22), we get: (25); Furthermore, we can obtain: (26); S9, non-singular backstep control law design; Constructing Lyapunov functions: (27); Its derivative is: (28); Substitute into the error dynamic equation: (29); Further construct extended Lyapunov functions: (30); but: (31); According to equation (24), we can obtain the following equation: (32); Then according to equation (20) We can obtain the following formula: (33); therefore: (34); Summarized as follows: (35); Design control law: (36); in, This is the second control gain; Substituting into the control law, we get: (37).

[0010] Preferably, it further includes: S10, duty cycle limiting and control input implementation; The duty cycle of the Boost DC / DC converter is physically constrained by the following formula: (38); In practical controllers, the duty cycle is discretely integrated and limited using the following formula: (39); in, The sampling period of the actual controller. This represents the upper limit of the duty cycle change rate. The amplitude of u is limited by the following formula: (40); The final output PWM duty cycle is: (41); The duty cycle is used to control the switching devices of the Boost DC / DC converter.

[0011] Preferably, Step S3 also includes the braking energy recovery condition: when At this time, the vehicle is in regenerative braking mode: At this point, the reference power of the fuel cell system is reduced to the off state, i.e. (42); The power battery system absorbs regenerative braking energy: (43); in, ; Simultaneously satisfying the maximum charging power constraint of the power battery system: (44); like This limits the regenerative braking charging power to prevent the power battery system from overcharging.

[0012] Preferably, In step S1, based on the efficiency of the Boost DC / DC converter and the bidirectional DC / DC converter, the vehicle power balance relationship is obtained by the following formula: (45); in: The power conversion efficiency of the fuel cell system. The power conversion efficiency of the power battery system is given.

[0013] More preferably, In step S4, based on the efficiency of the Boost DC / DC converter and the bidirectional DC / DC converter, the power command of the power battery system is obtained by the following formula: (46).

[0014] Preferably, In step S2, when When the current is too small, the load current of the high-voltage DC bus is obtained by the following formula: (47); in: .

[0015] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: By defining auxiliary variables Dynamically reconstruct the bus voltage to This avoids the direct occurrence of problems in traditional reverse step control. The problem of singular terms is addressed by maintaining good numerical stability even when the Boost duty cycle d is close to 1. Using the DC bus voltage error as the control target, a Lyapunov function and a non-singular backstepping control law are constructed to enable the bus voltage to quickly track the reference value and remain stable under conditions such as load change, vehicle acceleration and regenerative braking, resulting in good DC bus voltage stability. Introducing a power change rate constraint into the energy management layer of the fuel cell helps to reduce frequent and large power changes in the fuel cell, thereby reducing membrane electrode degradation, gas supply shocks, and output voltage fluctuations, and increasing the service life by about 20%. The power distribution between the fuel cell and the power battery is dynamically adjusted based on the SOC status of the power battery. When the SOC is too low, the output power of the fuel cell is increased to charge the power battery. When the SOC is too high, the output power of the fuel cell is reduced and the power battery is used first, thereby maintaining the SOC within a reasonable range. The real-time feedback rate is 10% higher than that of traditional methods. Attached Figure Description

[0016] AppendixFigure 1 This is a schematic diagram of the energy management system structure for a fuel cell-power battery hybrid vehicle according to the present invention; Appendix Figure 2 This is a control flowchart of the energy management method according to the present invention; Appendix Figure 3 This is a block diagram of the non-singular backstepping control structure for auxiliary variable reconstruction and dynamic expansion according to the present invention; Appendix Figure 4 This is a schematic diagram of the power distribution between the fuel cell and the power battery in Example 1; Appendix Figure 5 This is a simulation comparison chart of the power demand, fuel cell output power, power battery power, and SOC of the method of the present invention and the rule control method in Example 1 under a typical bus cycle operating condition. Appendix Figure 6 This is a simulation comparison of the fuel cell power change rate and cumulative hydrogen consumption of the method of the present invention and the rule control method in Example 1 under typical bus cycle conditions. Detailed Implementation

[0017] The technical solution of the present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0018] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the embodiments of the invention. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0019] In the description of the embodiments of the present invention, it should be understood that the terms "length", "inner", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the embodiments of the present invention.

[0020] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0021] In this embodiment of the invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a communication connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this embodiment of the invention according to the specific circumstances.

[0022] In embodiments of the present invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0023] The following disclosure provides many different implementations or examples for carrying out different structures of the embodiments of the present invention. To simplify the disclosure of the embodiments of the present invention, specific examples of components and arrangements are described below. Of course, these are merely examples and are not intended to limit the embodiments of the present invention. Furthermore, reference numerals and / or reference letters may be repeated in different examples of the embodiments of the present invention; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various implementations and / or arrangements discussed.

[0024] This embodiment provides a hybrid vehicle energy management method based on auxiliary variable reconstruction and dynamic extended nonsingular backstepping control. (See also...) Figure 1 As shown, the fuel cell-power battery hybrid vehicle in this embodiment includes a fuel cell system, a power battery system, a high-voltage DC bus, a Boost DC / DC converter (i.e., a unidirectional DC / DC converter) on the fuel cell system side, a bidirectional DC / DC converter on the power battery system side, a motor drive system (i.e., a drive motor), a vehicle load (i.e., accessory load), an energy management controller, and a vehicle controller.

[0025] When the vehicle starts, the power battery system supplies power to the fuel cell system. The fuel cell system is connected to the high-voltage DC bus via a unidirectional DC / DC converter, while the power battery system is connected to the high-voltage DC bus via a bidirectional DC / DC converter. The motor drive system is powered by the high-voltage DC bus and drives the vehicle. The vehicle controller is connected to the fuel cell system, power battery system, motor drive system, unidirectional DC / DC converter, and bidirectional DC / DC converter, respectively. It is used to collect vehicle operating status parameters and, based on the vehicle's power demand, the power battery system's state of charge (SOC), and the fuel cell system's operating constraints, calculates the fuel cell system's output power command and the power battery system's charge / discharge power command in real time.

[0026] See Figure 2 The diagram illustrates the specific energy management method control process. The aforementioned vehicle energy management method includes the following steps: S1, establish the power balance relationship of the whole vehicle; The vehicle's operating status parameters are collected. The vehicle controller collects vehicle speed, vehicle acceleration, accelerator pedal opening, brake pedal signal, drive motor speed, drive motor torque, high voltage DC bus voltage, fuel cell system output voltage, fuel cell system output current, power battery system voltage, power battery system current, and power battery system SOC value to establish the vehicle power balance relationship.

[0027] When the transient energy storage of the high-voltage DC bus is ignored or treated as a bounded disturbance, the power balance relationship of the entire vehicle is obtained by the following formula: (1); in: For the vehicle's required power, To provide power output for the fuel cell system; This refers to the output power of the power battery system; during power battery discharge... When the power battery is charging .

[0028] Equation (1) is used for subsequent calculation of the fuel cell reference power. Fuel cell power command and power battery power command .

[0029] Furthermore, in step S1, considering the efficiency of the Boost DC / DC converter on the fuel cell system side and the efficiency of the bidirectional DC / DC converter on the power battery system side, the vehicle power balance relationship is obtained by the following formula: (45); in: For the power conversion efficiency of the fuel cell system, This refers to the power conversion efficiency of the power battery system.

[0030] S2, calculate the load current of the high-voltage DC bus; Collect vehicle operating status and electrical status parameters, and collect these parameters in real time through the energy management controller. , , , , , , and Status information; in, For the output voltage of the fuel cell system, For the inductor current of the Boost DC / DC converter, This is the voltage of the high-voltage DC bus. This refers to the load current of the high-voltage DC bus. This refers to the state of charge of the power battery system.

[0031] The high-voltage DC bus load current is obtained by the following formula: (2).

[0032] Furthermore, in step S2, to avoid To address the division-to-zero issue caused by small noise or sampling noise, a regularization approach is used in practical control. The high-voltage DC bus load current is obtained using the following formula: (47); in: .

[0033] S3, based on vehicle power requirements Power battery state of charge (SOC), fuel cell maximum output power Minimum high-efficiency power of fuel cells Maximum discharge power of the power battery Maximum charging power of the power battery Determine the reference power of the fuel cell and power battery reference power Setting up the power battery system Threshold; Power battery system The threshold is obtained by the following formula: (3); in, This represents the lowest permissible state of charge for the power battery system. This represents the highest permissible state of charge for the power battery system. The desired state of charge of the power battery system. for Adjust the lower threshold, for Adjust the upper threshold.

[0034] when At that time, the vehicle was operating under low load conditions; If satisfied To control the fuel cell system to operate at the minimum high-efficiency power level, i.e. (4) At the same time, the excess power is supplied to charge the power battery system, that is... (5); If satisfied This involves reducing the output power of the fuel cell system or putting the fuel cell system into an idling state, so that the power battery system can bear part of the low-power load, in order to avoid overcharging of the power battery system.

[0035] when At that time, the vehicle was operating under medium load conditions; At this point, the fuel cell system undertakes the main power demand, and according to The deviation is corrected, that is... (6); in, for Adjustment coefficient; If satisfied ,but For positive, Increase the output power of the fuel cell system appropriately to replenish the energy of the power battery system; If satisfied If necessary, the output power of the fuel cell system should be appropriately reduced, and the power battery system should bear part of the load.

[0036] when At that time, the vehicle was under high load conditions; At this point, the output power of the fuel cell system is constrained by the maximum power limit, i.e., limited to... (7) The power battery system provides peak power compensation for (8), and satisfy ; If the power battery system Too low, that is At that time, the discharge power of the power battery system is limited, and the vehicle controller limits the vehicle's drive power requirements. in, This represents the maximum output power of the fuel cell system. For the minimum high-efficiency power of the fuel cell system, This represents the maximum discharge power of the power battery system. This represents the maximum charging power of the power battery system. This is the reference power for the fuel cell system. This is the reference power for the power battery system.

[0037] S4 smooths the reference power of the fuel cell system to reduce power fluctuations and extend its lifespan. Apply power change rate constraints, and assume Let be the maximum allowable power change of the fuel cell system within one sampling period. Then, the reference power of the fuel cell system satisfies: (9); In actual control, the following discrete form is used: (10); in: This represents the maximum allowable power variation of a fuel cell system within one sampling period. The power command of the fuel cell system after smoothing. This is the amplitude limiting function.

[0038] The power command of the power battery system is obtained by the following formula: (11); in, This is the power command for the power battery system.

[0039] Furthermore, considering the efficiency of the Boost DC / DC converter and the bidirectional DC / DC converter, the power command of the power battery system is obtained by the following formula: (46).

[0040] S5. Establish the average model of the Boost DC / DC converter and define the state variables. and ;in, For the inductor current of the Boost DC / DC converter, This is the voltage of the high-voltage DC bus.

[0041] The average state model of the Boost DC / DC converter is: (12); Where L is the inductance of the Boost DC / DC converter, C is the high-voltage DC bus capacitance, and d is the duty cycle of the Boost DC / DC converter. This is the equivalent bus current on the power battery system side.

[0042] The equivalent bus current on the power battery system side is obtained by the following formula: (13); Among them, the power battery system meets the following requirements when discharging. The power battery system meets the charging requirements. .

[0043] S6, Auxiliary variable reconstruction, is prone to problems in the backstep control of traditional Boost DC / DC converters. Regarding the related singular terms, when the duty cycle d approaches 1, the controller may experience numerical divergence. To avoid this problem, an auxiliary variable is established using the following formula: (14); The dynamic equation for the high-voltage DC bus voltage is obtained from the following equation: (15); Substituting equation (14) into equation (15) yields the following: (16); By reconstructing this auxiliary variable, the bus voltage control design no longer needs to directly adjust the parameters. Finding the reciprocal eliminates the problem in traditional backstep control. Type singularity.

[0044] S7, Dynamic Expansion, due to auxiliary variables The duty cycle d is included, and a dynamic expansion variable is introduced to further construct a strict feedback form. and define ; Where u is the new control input, namely the duty cycle rate of change control quantity; According to equation (14), we can obtain: (17); Substituting into the dynamic equation of the inductor current of the Boost DC / DC converter: (18); get: (19); Therefore, the system after reconstruction and dynamic expansion using auxiliary variables can be represented as: (20); This system form avoids taking the reciprocal of 1-d and is suitable for non-singular backstep control design.

[0045] S8, High Voltage DC Bus Voltage Error Design; The high-voltage DC bus voltage tracking error is established according to the following formula: (twenty one); in, This is the reference voltage for the high-voltage DC bus. From the dynamic equation of the high-voltage DC bus voltage, we can obtain: (twenty two); Design virtual control variables: (twenty three); in, The first control gain; when When the reference voltage is constant, ; Establish auxiliary error: (twenty four); Substituting equation (24) into equation (22), we get: (25); Furthermore, we can obtain: (26).

[0046] S9, non-singular backstep control law design; Constructing Lyapunov functions: (27); Its derivative is: (28); Substitute into the error dynamic equation: (29); Further construct extended Lyapunov functions: (30); but: (31); According to equation (24), we can obtain the following equation: (32); Then according to equation (20) We can obtain the following formula: (33); therefore: (34); Summarized as follows: (35); To ensure system error convergence, the control input u is designed as follows: (36); in, For the second control gain, it can avoid When the value is small, new singular problems arise, thus enabling non-singular backstep control.

[0047] Substituting into the control law, we get: (37); Substituting the control law into the error system allows for... Satisfying the negative or semi-negative conditions ensures the voltage error of the high-voltage DC bus. and auxiliary error It is bounded and converges to the expected range.

[0048] Furthermore, this energy management method also includes: S10, duty cycle limiting and PWM input implementation; The duty cycle of a Boost DC / DC converter is physically constrained by the following formula: (38); In practical controllers, the duty cycle is discretely integrated and limited using the following formula: (39); in, The sampling period of the actual controller. This represents the upper limit of the duty cycle change rate. The amplitude of u is limited by the following formula: (40); The final output PWM duty cycle is: (41); This duty cycle is used to control the switching devices of the Boost DC / DC converter on the fuel cell system side, so that the high-voltage DC bus voltage... Stable tracking reference voltage .

[0049] Furthermore, step S3 also includes a braking energy recovery condition: when At this time, the vehicle is in regenerative braking mode: At this point, the reference power of the fuel cell system drops to the off state, i.e. (42); The power battery system absorbs regenerative braking energy: (43); in, ; Simultaneously meet the maximum charging power constraint of the power battery system: (44); like This limits the regenerative braking charging power to prevent the power battery system from overcharging.

[0050] See Figure 3 The diagram shown is a flowchart of the auxiliary variable reconstruction and dynamic expansion nonsingular backstepping control structure, including the steps S6 and S7 mentioned above.

[0051] Example 1: To verify the effectiveness of the method of this invention, a simulation model of a fuel cell-power battery hybrid vehicle was established. The simulation objects include the fuel cell system, the power battery system, the high-voltage DC bus, the drive motor, and the vehicle load model. The simulation conditions adopt typical urban bus cycle conditions, which include frequent starts, accelerations, braking, short-term stops, and load changes during uphill climbing.

[0052] The simulation parameters are set as follows: the fuel cell output power range is 5kW to 90kW, the initial SOC of the power battery is 0.58, the SOC reference value is 0.60, the allowable SOC range is 0.45 to 0.75, the maximum power change rate of the fuel cell is 0.18kW / s, the rated voltage of the power battery is 600V, and the rated capacity of the power battery is 180Ah.

[0053] The method of this invention is compared with the rule-based control method, which adjusts the output power of the fuel cell based on the SOC deviation and the demand power threshold. The method of this invention compensates for sudden changes in demand power and model uncertainty by reconstructing auxiliary variables, and generates fuel cell power commands by dynamically expanding non-singular backstepping control.

[0054] See Figure 4 It is known that when the power demand of the vehicle fluctuates rapidly, the output power of the fuel cell does not directly follow the instantaneous peak value, but mainly undertakes the average power output; the power battery undertakes the transient peak power during high power demand phases such as acceleration and hill climbing, and absorbs regenerative energy during braking or negative power conditions. The corresponding advantages are: it achieves a reasonable division of labor between the fuel cell and the power battery, preventing frequent and large power surges in the fuel cell, reducing dynamic shock and aging risks, and improving the ability to recover and utilize braking energy. The method of this invention enables the fuel cell output power to change smoothly, with the power battery undertaking the transient peak power, thereby avoiding drastic fluctuations in fuel cell power with the power demand of the vehicle.

[0055] See Figure 5As shown in the figure above, compared to the rule-based method, the fuel cell output power curve in this invention is smoother and can follow changes in the vehicle's average power demand, rather than responding drastically to peak power demands. The corresponding advantages are: it helps suppress sudden power fluctuations in the fuel cell, improves output stability, and thus extends the fuel cell's lifespan.

[0056] See Figure 5 As shown in the figure, the charging and discharging power amplitude of the power battery in this invention can better cover the rapid changes in power demand, providing compensation under high load and absorbing regenerative energy during braking. The corresponding advantages are: enhanced adaptability of the hybrid power system to transient operating conditions, improved peak load support capacity, and improved regenerative braking energy recovery effect.

[0057] See Figure 5 As shown in the figure below, under the method of this invention, the SOC of the power battery is consistently maintained within a reasonable range and gradually stabilizes near the reference value; the simulated final SOC is approximately 0.60096, closer to the reference value of 0.60, while the final SOC of the rule-based method is approximately 0.61075. The corresponding advantage is that this invention demonstrates a better ability to maintain the state of charge of the power battery, avoiding prolonged periods of excessively high or low SOC, thus improving the health of the power battery and ensuring the continuous operation of the vehicle.

[0058] See Figure 6 As shown in the figure above, the method of this invention has a significant suppressive effect on the power change rate of fuel cells, and can significantly reduce the peak power change rate of fuel cells. Under the method of this invention, the maximum power change rate of fuel cells is approximately 0.18 kW / s, while under the rule-based control method, the maximum power change rate is approximately 3.2 kW / s, a reduction of approximately 94.37%. This invention can effectively suppress frequent and rapid load changes in fuel cells, significantly reduce the mechanical and electrochemical shocks caused by frequent load changes in fuel cell operation, make fuel cell operation more stable and reliable, and help extend the service life of fuel cells.

[0059] See Figure 6 As shown in the figure below, the cumulative hydrogen consumption of the method of this invention is lower than that of the rule-based control method. At the end of the simulation, the cumulative hydrogen consumption of this invention is approximately 0.646 kg, while that of the rule-based method is approximately 0.684 kg, representing a reduction of approximately 5.54%. The method of this invention can improve the energy utilization efficiency of the entire vehicle and reduce the cost of hydrogen fuel consumption by rationally allocating the power of the fuel cell and the power battery, allowing the fuel cell to operate more within its optimal efficiency range.

[0060] In summary, the energy management method of the present invention can take into account the power requirements of the whole vehicle, the state of charge of the power battery, the suppression of fuel cell load changes and the reduction of hydrogen consumption, and is suitable for application scenarios in urban vehicles with frequent start-stop, large load changes and complex operating conditions.

[0061] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A hybrid vehicle energy management method based on auxiliary variable reconstruction and dynamic extended nonsingular backstepping control, the hybrid vehicle comprising a fuel cell system, a power battery system, a high-voltage DC bus, a Boost DC / DC converter on the fuel cell system side, a bidirectional DC / DC converter on the power battery system side, a motor drive system, a vehicle load, an energy management controller, and a vehicle controller, characterized in that, Includes the following steps: S1, establish the power balance relationship of the whole vehicle; The overall vehicle power balance relationship is obtained through the following formula: （1）； in: For the vehicle's required power, This refers to the output power of the fuel cell system. This refers to the output power of the power battery system. S2, Calculate the load current of the high-voltage DC bus; Parameters are collected in real time by the energy management controller. , , , , , , and Status information; in, The output voltage of the fuel cell system. The inductor current of the Boost DC / DC converter is... The voltage of the high-voltage DC bus is... The load current of the high-voltage DC bus is... The state of charge of the power battery system; The high-voltage DC bus load current is obtained by the following formula: （2）； S3, setting the power battery system Threshold; The power battery system The threshold is obtained by the following formula: （3）； in, This represents the lowest permissible state of charge for the power battery system. This represents the highest permissible state of charge for the power battery system. The desired state of charge of the power battery system. for Adjust the lower threshold, for Adjust the upper threshold; when At that time, the vehicle was operating under low load conditions; If satisfied Controlling the fuel cell system to operate at the minimum high-efficiency power level, i.e. (4) Simultaneously, excess power is supplied to charge the power battery system, i.e. (5); If satisfied The output power of the fuel cell system is reduced or the fuel cell system is put into an idling state, and the power battery system takes on part of the low power load. when At that time, the vehicle was operating under medium load conditions; At this time, the fuel cell system undertakes the main power demand, and according to The deviation is corrected, that is... (6); in, for Adjustment coefficient; If satisfied This increases the output power of the fuel cell system and replenishes the energy of the power battery system. If satisfied This reduces the output power of the fuel cell system, allowing the power battery system to bear part of the load. when At that time, the vehicle was under high load conditions; At this time, the output power of the fuel cell system is limited to (7) The power battery system provides peak power compensation as follows: (8), and satisfy ; If the power battery system Too low, that is At the same time, the discharge power of the power battery system is limited, and the vehicle controller limits the vehicle's drive power requirements; in, This represents the maximum output power of the fuel cell system. This represents the minimum high-efficiency power of the fuel cell system. This represents the maximum discharge power of the power battery system. This represents the maximum charging power of the power battery system. This is the reference power for the fuel cell system. This is the reference power of the power battery system; S4, smooth the power of the fuel cell system; The reference power of the fuel cell system satisfies: （9）； The following discrete form is adopted: （10）； in: This represents the maximum allowable power variation of the fuel cell system within one sampling period. This is the smoothed power command of the fuel cell system. This is a limiting function; The power command of the power battery system is obtained by the following formula: （11）； in, This refers to the power command of the power battery system; S5, Establish the average model of the Boost DC / DC converter; The average state model of the Boost DC / DC converter is: （12）； in, , , The inductor current of the Boost DC / DC converter is... Where L is the voltage of the high-voltage DC bus, C is the inductance of the Boost DC / DC converter, and d is the duty cycle of the Boost DC / DC converter. This refers to the equivalent bus current on the power battery system side. The equivalent bus current on the power battery system side is obtained by the following formula: （13）； Wherein, the power battery system meets the following requirements when discharging: The power battery system meets the following requirements when charging: ; S6, Auxiliary variable reconstruction; Auxiliary variables are established using the following formula: （14）； The dynamic equation for the high-voltage DC bus voltage is obtained from the following equation: （15）； Substituting equation (14) into equation (15) yields the following: （16）； S7, dynamic expansion; Introducing dynamic expansion variables and define ; Where u is the duty cycle change rate control quantity; According to equation (14), we can obtain: （17）； Substituting into the dynamic equation of the inductor current of the Boost DC / DC converter: （18）； get: （19）； By dynamically expanding, the system can be represented as: （20）； This system configuration can be used for non-singular backstepping control design; S8, the high-voltage DC bus voltage error design; The high-voltage DC bus voltage tracking error is established according to the following formula: （21）； in, This is the reference voltage for the high-voltage DC bus; From the aforementioned dynamic equation of the high-voltage DC bus voltage, we can obtain: （22）； Design virtual control variables: （23）； in, The first control gain; when When the reference voltage is constant, ; Establish auxiliary error: （24）； Substituting equation (24) into equation (22), we get: （25）； Furthermore, we can obtain: （26）； S9, non-singular backstep control law design; Constructing Lyapunov functions: （27）； Its derivative is: （28）； Substitute into the error dynamic equation: （29）； Further construct extended Lyapunov functions: （30）； but: （31）； According to equation (24), we can obtain the following equation: （32）； Then according to equation (20) We can obtain the following formula: （33）； therefore: （34）； Summarized as follows: （35）； Design control law: （36）； in, This is the second control gain; Substituting into the control law, we get: （37）。 2. The hybrid vehicle energy management method based on auxiliary variable reconstruction and dynamic expansion nonsingular backstepping control according to claim 1, characterized in that, Also includes: S10, duty cycle limiting and control input implementation; The duty cycle of the Boost DC / DC converter is physically constrained by the following formula: （38）； In practical controllers, the duty cycle is discretely integrated and limited using the following formula: （39）； in, The sampling period of the actual controller. This represents the upper limit of the duty cycle change rate. The amplitude of u is limited by the following formula: （40）； The final output PWM duty cycle is: （41）； The duty cycle is used to control the switching devices of the Boost DC / DC converter.

3. The hybrid vehicle energy management method based on auxiliary variable reconstruction and dynamic expansion nonsingular backstepping control according to claim 1, characterized in that: Step S3 also includes the braking energy recovery condition: when At this time, the vehicle is in regenerative braking mode: At this point, the reference power of the fuel cell system is reduced to the off state, i.e. (42); The power battery system absorbs regenerative braking energy: （43）； in, ; Simultaneously satisfying the maximum charging power constraint of the power battery system: （44）； like This limits the regenerative braking charging power to prevent the power battery system from overcharging.

4. The hybrid vehicle energy management method based on auxiliary variable reconstruction and dynamic expansion nonsingular backstepping control according to claim 1, characterized in that: In step S1, based on the efficiency of the Boost DC / DC converter and the bidirectional DC / DC converter, the vehicle power balance relationship is obtained by the following formula: （45）； in: The power conversion efficiency of the fuel cell system. The power conversion efficiency of the power battery system is given.

5. The hybrid vehicle energy management method based on auxiliary variable reconstruction and dynamic expansion nonsingular backstepping control according to claim 4, characterized in that: In step S4, based on the efficiency of the Boost DC / DC converter and the bidirectional DC / DC converter, the power command of the power battery system is obtained by the following formula: （46）。 6. The hybrid vehicle energy management method based on auxiliary variable reconstruction and dynamic expansion nonsingular backstepping control according to claim 1, characterized in that: In step S2, when When the current is too small, the load current of the high-voltage DC bus is obtained by the following formula: （47）； in: .

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