Backflow power optimized DAB converter sliding mode control method

Abstract

The invention discloses a DAB converter sliding mode control method for reflow power optimization, and relates to the technical field of reflow power optimization, and the method comprises the steps: building a state relation model of the input voltage, the output current and the reflow power of a converter; generating a sliding mode initial population according to the N control parameter combinations of the sliding mode controller; calculating a backflow power error, a current error and a voltage error; constructing a sliding mode control fitness function, and generating a sliding mode control parameter combination sequence; generating M updated control parameter combinations; performing performance evaluation by using a sliding mode control fitness function; updating and optimizing the M updating control parameter combinations; and obtaining an optimal control parameter combination to perform sliding mode control of the DAB converter. The technical problem that efficient and accurate energy transmission is difficult to achieve in sliding mode control of an existing DAB converter, and consequently the reflow power control optimization effect is poor is solved, fast response and high precision of sliding mode control are achieved, and the technical effect of reducing reflow power is achieved.

Description

Technical Field

[0001] The present application relates to the technical field related to reflux power optimization, and in particular to a sliding mode control method for a DAB converter with reflux power optimization. Background Art

[0002] With the rapid development of modern power electronics technology, the dual active bridge (DAB) converter, as an efficient and reliable power conversion device, has shown broad application prospects in power transmission, electric vehicle charging, renewable energy systems and other fields. The DAB converter achieves electrical isolation and voltage matching through a high-frequency transformer, and optimizes the return power by adjusting the input voltage and output current. Its performance optimization has become the key to improving the overall efficiency and stability of the system. The return power refers to the part of the energy that returns to the power supply in the reverse form during the power conversion process, thereby reducing the overall energy conversion efficiency. When optimizing the return power, traditional control methods (such as PI control or PID control) are difficult to deal with nonlinear factors and complex dynamic behaviors in the system, and thus it is difficult to achieve efficient and accurate energy transmission, especially in reducing the return power (i.e., invalid energy circulation). In the process of optimizing the return power of the DAB converter using sliding mode control, selecting appropriate control parameters (such as duty cycle, phase shift angle and switching gain) is crucial to achieving the best control effect. The traditional manual parameter adjustment method is difficult to meet the needs of different working conditions at the same time, which easily leads to unsatisfactory control performance and insufficient return power optimization.

[0003] At present, in the DAB converter sliding mode control related technologies for reflux power optimization, there is a technical problem that it is difficult to achieve efficient and accurate parameter control and energy transmission, resulting in poor reflux power control optimization effect. Summary of the invention

[0004] The present application provides a DAB converter sliding mode control method for reflux power optimization, thereby solving the technical problem that it is difficult to achieve efficient and accurate parameter control and energy transmission in the existing DAB converter sliding mode control, resulting in poor reflux power control optimization effect, and realizing fast response and high precision of sliding mode control, thereby achieving the technical effect of reducing reflux power.

[0005] The present application provides a DAB converter sliding mode control method for backflow power optimization, comprising: establishing a state relationship model of converter input voltage, converter output current and converter backflow power based on a circuit topology of the DAB converter; determining a sliding mode surface according to the state relationship model, defining a sliding mode controller, and generating a sliding mode initial population according to N control parameter combinations of the sliding mode controller, wherein N is a positive integer greater than 1; calculating the backflow power error, current error and voltage error of the N control parameter combinations in the sliding mode initial population; constructing a sliding mode control fitness function according to the sliding mode surface, evaluating the fitness value of the N control parameter combinations according to the sliding mode control fitness function, and calculating the backflow power error, current error and voltage error of the N control parameter combinations in the sliding mode initial population according to the evaluation results; The result generates a sliding mode control parameter combination sequence; the first M control parameter combinations are selected from the sliding mode control parameter combination sequence for update operation to generate M updated control parameter combinations, wherein M is a positive integer greater than 1, and M<N; the M updated control parameter combinations are applied to the sliding mode controller, and the performance is evaluated using the sliding mode control fitness function; based on the performance evaluation results, the M updated control parameter combinations are updated and optimized, and it is continuously iterated until a predetermined reflux power optimization target is met; according to the real-time operation data of the DAB converter, the performance evaluation results of the M updated control parameter combinations are optimized and adjusted to obtain the optimal control parameter combination for sliding mode control of the DAB converter.

[0006] In a possible implementation, the first M control parameter combinations are selected from the sliding mode control parameter combination sequence for update operation to generate M updated control parameter combinations, and the following processing is also performed: based on the calculation result of the sliding mode control fitness function, the fitness values ​​of the N control parameter combinations are sorted from low to high to obtain a sliding mode control parameter combination sequence, and M control parameter combinations with fitness values ​​lower than a preset fitness threshold are selected from the sequence; a crossover operation is performed on the M control parameter combinations to generate M crossover control parameter combinations; a mutation operation is performed on the M crossover control parameter combinations to obtain the M updated control parameter combinations and generate a sliding mode update population; and the sliding mode control fitness function is used to perform performance evaluation on the updated control parameter combinations of the sliding mode update combination to obtain an initial sliding mode control evaluation result.

[0007] In a possible implementation, the obtaining of the optimal control parameter combination and the sliding mode control of the DAB converter further performs the following processing: acquiring the real-time operating data, including the real-time input voltage, the real-time output current and the real-time reflux power; feeding back the real-time operating data to the sliding mode controller, and optimizing and adjusting the M updated control parameter combinations by using the sliding mode controller; recalculating the fitness of the M updated control parameter combinations by using the sliding mode control fitness function, and selecting the control parameter combination with the largest fitness value as the optimal control parameter combination in combination with the initial sliding mode control evaluation result; and performing an external interference test on the optimal control parameter combination. If the test passes, the optimal control parameter combination is used for the sliding mode control of the DAB converter.

[0008] In a possible implementation, an external interference test is performed on the optimal control parameter combination. If the test passes, the optimal control parameter combination is used for the sliding mode control of the DAB converter, and the following processing is also performed: by simulating external interference conditions of different intensities, multiple sliding mode control scenarios of the DAB converter are simulated, wherein the external interference conditions include input voltage fluctuations, load changes, and ambient temperature changes; the simulated return power errors under the multiple sliding mode control scenarios are calculated respectively, the simulated return power errors are compared with the return power errors, and it is determined whether the external interference test is passed according to the comparison result; if the optimal control parameter combination passes the external interference test, it is used as the final optimal control parameter combination of the DAB converter; if the optimal control parameter combination fails to pass the external interference test, the control parameters are readjusted according to the real-time operation data, and the return power optimization target is achieved through multiple iterations to obtain the final optimal control parameter combination.

[0009] In a possible implementation, an initial sliding mode population is generated according to N control parameter combinations of the sliding mode controller, and the following processing is also performed: adjusting the weight of the sliding mode control fitness function according to the real-time environmental parameters of the DAB converter; randomly initializing the duty cycle, phase shift angle and switching gain; optimizing and adjusting the switching gain of the sliding mode controller based on the adjusted sliding mode control fitness function; generating N control parameter combinations based on the duty cycle, the phase shift angle and the switching gain to obtain the initial sliding mode population.

[0010] In a possible implementation, the constructing of a sliding mode control fitness function according to the sliding surface further performs the following processing: establishing a sliding surface error function based on a combination of the return power error, the current error and the voltage error; based on the sliding surface error function, taking the maximum allowable return power threshold, the current fluctuation range and the phase shift angle limit as constraints of the sliding mode control fitness function, establishing the sliding mode control fitness function with the goal of minimizing the weighted sum of the return power error, the current error and the voltage error.

[0011] In a possible implementation, the state relationship model of the converter input voltage, the converter output current and the converter return power is established, and the following processing is also performed: determining the current transmission direction according to the circuit topology of the DAB converter; obtaining the voltage of the input bridge arm and the current of the output bridge arm in the DAB converter according to the current transmission direction; defining the state variables of the DAB converter, including the state variables of the input voltage, the output current and the return power; and constructing the state relationship model according to the differential equation established by the state variables.

[0012] In a possible implementation, the reflux power is obtained and the following processing is also performed: the bridge arm input power and the bridge arm output power are calculated by analyzing the bridge arm forward transmission waveform and the bridge arm reverse transmission waveform; and the reflux power of the DAB converter is calculated based on the bridge arm input power and the bridge arm output power.

[0013] The invention proposes a sliding mode control method for a DAB converter with reflux power optimization proposed in the present application. Based on the circuit topology of the DAB converter, a state relationship model of the converter input voltage, the converter output current and the converter reflux power is established; a sliding surface is determined according to the state relationship model, a sliding mode controller is defined, and a sliding mode initial population is generated according to N control parameter combinations of the sliding mode controller, wherein N is a positive integer greater than 1; the reflux power error, current error and voltage error of the N control parameter combinations in the sliding mode initial population are calculated; a sliding mode control fitness function is constructed according to the sliding surface, and the fitness value of the N control parameter combinations is evaluated according to the sliding mode control fitness function. The results of the evaluation are used to generate a sliding mode control parameter combination sequence; the first M control parameter combinations are selected from the sliding mode control parameter combination sequence for update operation to generate M updated control parameter combinations, wherein M is a positive integer greater than 1, and M<N; the M updated control parameter combinations are applied to the sliding mode controller, and the sliding mode control fitness function is used to perform performance evaluation; based on the performance evaluation results, the M updated control parameter combinations are updated and optimized, and continuous iteration is performed until the predetermined reflux power optimization target is met; according to the real-time operation data of the DAB converter, the performance evaluation results of the M updated control parameter combinations are optimized and adjusted to obtain the optimal control parameter combination for sliding mode control of the DAB converter. The technical problem that it is difficult to achieve efficient and accurate parameter control and energy transmission in the existing DAB converter sliding mode control, resulting in poor optimization effect of reflux power control, is solved, and fast response and high precision of sliding mode control are achieved, so as to achieve the technical effect of reducing reflux power. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solution of the embodiment of the present invention, the accompanying drawings of the embodiment of the present invention will be briefly introduced below. A flow chart is used in the present application to illustrate the operations performed by the system according to the embodiment of the present application. It should be understood that the preceding or following operations are not necessarily performed accurately in order. On the contrary, various steps can be processed in reverse order or simultaneously as needed. At the same time, other operations can also be added to these processes, or one or more operations can be removed from these processes.

[0015] Figure 1 A schematic flow chart of a sliding mode control method for a DAB converter with optimized reflux power provided in an embodiment of the present application;

[0016] Figure 2 A schematic diagram of a flow chart for obtaining an optimal control parameter combination in a sliding mode control method for a DAB converter with reflux power optimization provided in an embodiment of the present application. DETAILED DESCRIPTION

[0017] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below.

[0018] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application will be further described in detail below in conjunction with the accompanying drawings. The described embodiments should not be regarded as limiting the present application. All other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of this application.

[0019] In the following description, reference is made to "some embodiments", which describe a subset of all possible embodiments, but it is understood that "some embodiments" may be the same subset or different subsets of all possible embodiments, and may be combined with each other without conflict, and the terms "first\second" involved are merely to distinguish similar objects and do not represent a specific ordering of objects. The terms "including" and "having" and any variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product, or server that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or modules that are not clearly listed or inherent to these processes, methods, products, or devices. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by technicians in the technical field of this application. The terms used herein are for the purpose of describing the embodiments of the present application only.

[0020] The present application embodiment provides a sliding mode control method for a DAB converter with optimized reflux power, such as Figure 1 As shown, the method includes:

[0021] Step S100: establishing a state relationship model of converter input voltage, converter output current and converter return power based on the circuit topology of the DAB converter.

[0022] Preferably, based on the circuit topology of the DAB converter, the dynamic behavior between the input voltage, output current and return power of the DAB converter is described as a set of equations by mathematical modeling, so as to accurately reflect the interaction and influence relationship between these variables. Specifically, the circuit topology of the DAB converter is composed of two full-bridge inverters, which are respectively located between the input and output ends and coupled by a high-frequency transformer in the middle. The power flow can be controlled by adjusting the phase shift angle between the input and output ends, so as to achieve efficient energy conversion. The bidirectional characteristics of the power flow lead to the generation of return power. The input voltage is the main input signal of the DAB converter, which comes from the power supply end. The change of the input voltage will directly affect the power transmission of the DAB converter. The output current is the current output by the converter to the load, which reflects the energy demand of the load. The return power is the phenomenon that part of the power flows back to the input end due to phase shift or improper control during the power transmission process of the converter. The return power will cause energy loss and reduce the system efficiency. It also includes other state variables such as the leakage inductance current and the bridge arm current of the transformer. In the DAB converter, the relationship between the input voltage and the output current mainly depends on the coupling coefficient and phase shift control of the transformer. The DAB converter controls the power flow by adjusting the phase shift angle between the input and output. The dynamic relationship between the input voltage and the output current can be described by the following formula:

[0023]

[0024] Output current I out The relationship between the output power is:

[0025]

[0026] Among them, P out is the output power, V in is the input voltage, V out is the output voltage, φ is the phase shift angle, L is the leakage inductance of the transformer, f s is the switching frequency. In the DAB converter, the reflux power changes with the phase shift angle φ. When the phase shift angle is small, the reflux power increases, resulting in reduced system energy efficiency. By optimizing control parameters such as the phase shift angle, the generation of reflux power can be effectively reduced.

[0027] In a possible implementation, step S100 further includes step S110, determining the current transmission direction according to the circuit topology of the DAB converter; step S120, obtaining the voltage of the input bridge arm and the current of the output bridge arm in the DAB converter according to the current transmission direction; step S130, defining the state variables of the DAB converter, including the state variables of the input voltage, the output current and the return power; step S140, constructing the state relationship model according to the differential equation established by the state variables.

[0028] Preferably, the DAB converter is a bidirectional power converter, usually composed of two full-bridge inverters and a high-frequency transformer. The input end and the output end can transmit power to each other. In the DAB converter, the direction of power transmission can be achieved by adjusting the phase shift angle between the input bridge arm and the output bridge arm. When the phase shift angle is positive, the power is transmitted from the input end to the output end; when the phase shift angle is negative, the power is transmitted from the output end back to the input end. Through the phase shift control of the DAB converter, the current transmission direction can be from the input side to the output side, or from the output side back to the input side. The current transmission direction directly affects the return power and the overall energy conversion efficiency of the system; according to the current transmission direction, the voltage of the input bridge arm and the current of the output bridge arm are measured in real time. The input bridge arm voltage of the DAB converter is determined by the switching state of the full-bridge inverter on the input side. By adjusting the duty cycle of the input bridge arm switch, the input voltage can be controlled, thereby affecting the current on the output side. The current of the output bridge arm is a direct reflection of the power transmission to the load, which is determined by the current of the secondary winding of the high-frequency transformer and the state of the output bridge arm switch and is used to power the load; define the state variables of the DAB converter, including input voltage, output current and return power. Through these state variables, the operating state of the DAB converter can be controlled and optimized to minimize the return power and improve efficiency; derive the differential equation of the DAB converter based on the voltage, current and power relationship of the circuit:

[0029]

[0030] Among them, f represents the relationship function between the state variables in the system, P reflow is the return power, V in is the input voltage, I out is the output current. Finally, according to the differential equation of the DAB converter, a state relationship model is constructed to describe the dynamic relationship between the input voltage, output current and return power of the DAB converter, which is used for the design and optimization of the sliding mode controller. The expression is as follows:

[0031]

[0032] in, is the state variable vector (including input voltage, output current and return power), u(t) is the control input (such as phase shift angle and duty cycle), A and B are the state matrix and input matrix of the system.

[0033] Step S200, determining a sliding mode surface according to the state relationship model, defining a sliding mode controller, and generating a sliding mode initial population according to N control parameter combinations of the sliding mode controller, wherein N is a positive integer greater than 1.

[0034] Preferably, the sliding surface is determined according to the state relationship model. The sliding surface is the core control design part in the sliding mode controller, which reflects the deviation between the state variables of the system and the desired state, and is used to guide the state of the system to converge to a predetermined target and maintain stability on the sliding surface. Specifically, the established state relationship model of the DAB converter is used to determine the relationship between the state variables of the system (such as input voltage, output current, return power, etc.) to describe the dynamic behavior of the system. The sliding surface is usually defined based on the error of the system. For example, the state error e (return power error, current error or voltage error) can be defined by the following sliding surface equation:

[0035] s(t)=α·e P +β·e I +γ·e V ;

[0036] Among them, e P is the return power error, e I is the current error, e V is the voltage error, α, β, γ are weight coefficients, reflecting the importance of each error in the sliding mode control. The sliding surface is used to determine whether the system has reached the desired state and guide the controller to adjust the system. The sliding mode controller is used to ensure that the system state reaches and remains on the sliding surface as soon as possible. The definition of the sliding mode controller specifically includes that the sliding mode controller uses the control law to make the system state move along the sliding surface and gradually reduce the error. The control law is as follows:

[0037] u(t) = -K·sign(s(t));

[0038] Among them, u(t) is the control input (such as phase shift angle, duty cycle, etc.), s(t) is the sliding surface equation, K is the control gain, and sign(s(t)) represents the sign function of the sliding surface, which is used to determine the convergence direction of the system state to the sliding surface. The control effect of the sliding mode controller is highly dependent on key control parameters, such as duty cycle, phase shift angle and switching gain, which affect the dynamic response, steady-state error and reflux power optimization effect of the system; when generating the initial population, N different control parameter combinations are selected, N is a positive integer greater than 1, indicating the number of control parameter combinations in the population, and each control parameter combination consists of parameters such as duty cycle, phase shift angle and switching gain, representing different sliding mode control strategies. For example, the duty cycle can be randomly selected within a certain range, and the phase shift angle and switching gain can also be set to a reasonable range according to the system characteristics.

[0039] In a possible implementation, step S200 further includes step S210, adjusting the weight of the sliding mode control fitness function according to the real-time environmental parameters of the DAB converter; step S220, randomly initializing the duty cycle, phase shift angle and switching gain; step S230, optimizing and adjusting the switching gain of the sliding mode controller based on the adjusted sliding mode control fitness function; step S240, generating N control parameter combinations based on the duty cycle, the phase shift angle and the switching gain to obtain the sliding mode initial population.

[0040] Preferably, the real-time environmental parameters of the DAB converter may include input voltage, output current, reflux power, load change, temperature, etc. According to the real-time environmental parameters, the weight coefficient in the fitness function is adjusted. For example, if the ambient temperature fluctuation has a greater impact on the voltage, the weight γ is adjusted to stabilize the voltage; the duty cycle refers to the ratio of the on-time of the bridge arm switch in one cycle to the total cycle, which affects the rate and efficiency of power conversion. The randomly initialized duty cycle can generate different values ​​within a certain range, such as a random number between 0 and 1. The phase shift angle controls the phase difference between the input and output ends of the DAB converter, determines the power transmission direction and reflux power, and the randomly initialized phase shift angle can be performed within a certain phase shift range. The switching gain affects the response speed and stability of the sliding mode controller, and the control system How to respond at the switching point. The purpose of randomly initializing the switching gain is to evaluate its impact on system performance under different gain values. By randomly generating different combinations of duty cycle, phase shift angle and switching gain, multiple control parameter combinations are generated; according to the evaluation results of the adjusted fitness function, the value of the switching gain is adjusted using an optimization algorithm (such as genetic algorithm or gradient descent method) to find an optimal gain value that can minimize the return power error and other errors. According to the previously randomly initialized duty cycle, phase shift angle and optimized and adjusted switching gain, N different control parameter combinations are generated, representing different strategies of the sliding mode controller. Each combination will have different effects on the system's return power, current and voltage, and finally generate an initial sliding mode population as the starting point for subsequent optimization.

[0041] Step S300, calculating the return power error, current error and voltage error of N control parameter combinations in the sliding mode initial population.

[0042] Preferably, in the sliding mode control optimization process, the performance of each control parameter combination is evaluated, and the effect of each combination is evaluated by measuring and calculating the error value generated under different system states. Each combination will affect the behavior of the system's return power, output current and voltage. Specifically, the return power error refers to the difference between the return power actually measured in the converter and the expected return power (usually minimum or zero). The existence of return power will cause energy loss. The goal is to minimize the return power through control; the return power is usually calculated by measuring the current waveform and voltage waveform in the DAB converter. Specifically, the return power is related to the phase shift angle, input voltage, output current and system The return power will change with the change of the control parameter combination. The return power is calculated and compared for each combination. The smaller the return power error is, the better the optimization effect of the control parameter combination is. The current error refers to the difference between the actual output current and the expected output current. The actual output current is measured at the output end of the DAB converter by a current sensor. The current error reflects the deviation of the system in responding to load demand. The control parameter combination will directly affect the size of the current error. The voltage error refers to the difference between the actual value and the expected value of the output voltage. The voltage error is measured in real time at the output end of the converter by a voltage sensor. Voltage errors are usually caused by changes in the control parameters inside the system and external loads. Therefore, dynamic measurements are required under different parameter combinations. The smaller the voltage error, the better the response to the voltage demand of the load. The controller needs to dynamically adjust the control parameters to keep the voltage error within a low range to ensure the stability of the system output voltage. In the sliding mode control optimization, each control parameter combination in the initial population represents a set of different control strategies (such as duty cycle, phase shift angle, switching gain, etc.). For each control parameter combination, the return power error, current error and voltage error need to be calculated to evaluate its performance.

[0043] Step S400: constructing a sliding mode control fitness function according to the sliding mode surface, evaluating the fitness values ​​of the N control parameter combinations according to the sliding mode control fitness function, and generating a sliding mode control parameter combination sequence according to the evaluation result.

[0044] Preferably, the sliding mode control fitness function is used to evaluate the impact of each control parameter combination on the system performance. The goal is to minimize the return power error while maintaining the stability of current and voltage. It is usually constructed by weighted summing of various errors (such as return power error, current error and voltage error), reflecting the overall performance of each control parameter combination. The expression of the sliding mode control fitness function is as follows:

[0045] F(θ)=α·(e P ) 2 +β·(e I )2 +γ·(e V ) 2 ;

[0046] Where θ is a combination of control parameters, including duty cycle, phase shift angle and switching gain, e P is the return power error, e I is the current error, e V is the voltage error, α, β, γ are weight coefficients, which are used to adjust the relative importance of different errors in the evaluation. Each control parameter combination generated in the initial population represents a different control strategy. The control parameters include duty cycle, phase shift angle and switching gain. N different control parameter combinations, each combination will have different effects on the system's return power, current and voltage. Through simulation or experiment, each control parameter combination is applied to the sliding mode controller of the DAB converter, and the return power, current and voltage response caused by it in the system are measured. For each control parameter combination, its fitness value is calculated according to the sliding mode control fitness function. The smaller the fitness value, the better the control parameter combination performs in terms of return power optimization and output performance stability. Then the fitness values ​​of the N control parameter combinations are sorted from the smallest to the largest fitness value. The sorted control parameter combinations form a sequence, which is arranged from the best performance (i.e., the smallest fitness value) to the worst.

[0047] In a possible implementation, step S400 further includes step S410, establishing a sliding surface error function based on a combination of the return power error, the current error and the voltage error; step S420, based on the sliding surface error function, using the maximum allowable return power threshold, current fluctuation range and phase shift angle limit as constraints of the sliding mode control fitness function, to establish the sliding mode control fitness function with the goal of minimizing the weighted sum of the return power error, current error and voltage error.

[0048] Preferably, the sliding surface error function combines the return power error, current error and voltage error to form an error function that comprehensively describes the system state, which is used to guide the system state to converge toward the ideal state, and reduce the overall error of the system by adjusting the input of the controller; in the optimization process, in order to ensure the safety and effectiveness of the system, it is necessary to set a series of constraints for the sliding mode control fitness function to ensure that the control parameters do not exceed the limit range of the system, and the maximum allowable return power is set as a threshold value P max, that is, the return power should not exceed this threshold. The output current may fluctuate under load, but it should be controlled within an allowable range. The phase shift angle is a key parameter affecting power transmission and return power. In order to ensure system stability, the phase shift angle should also be limited to a reasonable range. The core goal of the optimization is to minimize the weighted sum of the return power error, current error and voltage error in the sliding surface error function, which means that by adjusting the control parameters, the system can achieve the best performance in multiple aspects (return power, current, voltage) at the same time. The weighting coefficient is used to balance the relative importance of various errors in the fitness function. For example, if the return power has a greater impact on the system performance, the weight of α can be increased to give priority to reducing the return power error. The goal of the sliding mode control fitness function is to find the optimal control parameter combination by minimizing the weighted sum of the return power error, current error and voltage error.

[0049] Step S500, selecting the first M control parameter combinations from the sliding mode control parameter combination sequence for update operation, generating M updated control parameter combinations, wherein M is a positive integer greater than 1, and M<N.

[0050] Preferably, from the N control parameter combinations initially generated, based on the result of the fitness function calculation, the top M control parameter combinations with the best performance (i.e., the combinations with the smallest fitness values) are selected, and then the M combinations are further optimized and updated. Specifically, according to the sorting of the fitness values, the top M combinations with the smallest fitness values ​​are selected from the N control parameter combinations, where M is a positive integer greater than 1 and less than N, to ensure that subsequent optimization operations are performed only on the combinations that are most likely to obtain good control effects, thereby reducing the computational burden and improving the optimization efficiency. When selecting the M control parameter combinations, the optimal retention strategy can be adopted, that is, the combination with the smallest current fitness value is directly retained for the next round to prevent the current optimal solution from being lost during the crossover and mutation process. Through the crossover operation, different parts of the top M control parameter combinations are optimized. Recombination to generate a new control parameter combination, specifically, from two control parameter combinations, select a crossover point, exchange some parameters of the two combinations, for example, exchange the duty cycle of one combination with the phase shift angle of another combination to generate a new control parameter combination, select multiple crossover points from multiple control parameter combinations, exchange different parts of the parameters to generate more diversified combinations; the mutation operation further increases the diversity of control parameter combinations by randomly changing the values ​​of certain control parameters, and then randomly changes the duty cycle, phase shift angle or switching gain in a certain combination to ensure that more potential optimization parameter combinations can be explored; after crossover and mutation operations, M new control parameter combinations are generated, i.e., M updated control parameter combinations, which have better diversity and can be searched and optimized in a wider parameter space.

[0051] In a possible implementation, step S500 further includes step S510, based on the calculation result of the sliding mode control fitness function, sorting the fitness values ​​of N control parameter combinations from low to high to obtain a sliding mode control parameter combination sequence, and selecting M control parameter combinations whose fitness values ​​are lower than a preset fitness threshold; step S520, performing a crossover operation on the M control parameter combinations to generate M crossover control parameter combinations; step S530, performing a mutation operation on the M crossover control parameter combinations to obtain the M updated control parameter combinations and generate a sliding mode update population; step S540, using the sliding mode control fitness function to perform a performance evaluation on the updated control parameter combination of the sliding mode update combination to obtain an initial sliding mode control evaluation result.

[0052] Preferably, the calculation result of the sliding mode control fitness function refers to the performance of each control parameter combination, which is judged by calculating the error (such as reflux power error, current error, voltage error). The lower the fitness value, the better the control effect of the combination. N refers to the number of initially generated control parameter combinations. By calculating the fitness value of each combination, they are arranged in order from low to high. The combination with the lowest fitness value represents the best control effect. A fitness value threshold (i.e., a preset fitness target) is set. From the sorted N combinations, M control parameter combinations with fitness values ​​lower than the threshold are selected; a new control parameter combination is generated by exchanging some parameters in two or more parameter combinations, which can be a single-point crossover or a multi-point crossover. Two control parameter combinations are selected, and some of their parameters (such as duty cycle, phase shift angle, switching angle) are extracted respectively. gain) are alternately combined to generate a new parameter combination, and a new control parameter combination equal to the original M control parameter combinations is generated; the mutation operation is to introduce randomness to avoid the optimization process from falling into a local optimal solution. By randomly changing the values ​​of certain control parameters, the diversity of parameter combinations can be expanded. Certain control parameters (such as phase shift angle, duty cycle, switching gain, etc.) are randomly selected and changed in small amplitudes. For example, the value of a certain control parameter is increased or decreased by a small random amount to generate a new parameter combination. After the mutation operation, the original M cross control parameter combinations are converted into M updated control parameter combinations to obtain a sliding mode update population; the fitness value of each updated control parameter combination is calculated through the fitness function to obtain their performance in optimizing the return power, output current and voltage stability, that is, to obtain the initial sliding mode control evaluation result.

[0053] Step S600: Apply the M updated control parameter combinations to the sliding mode controller, and use the sliding mode control fitness function to perform performance evaluation.

[0054] Preferably, the M control parameter combinations generated by crossover and mutation operations are applied to the sliding mode controller, and the influence of these parameter combinations on the system performance is evaluated again through actual testing or simulation, that is, the performance is evaluated using the sliding mode control fitness function. Each combination will obtain a new fitness value, indicating its performance in optimizing the return power and ensuring the stability of current and voltage. Specifically, under each control parameter combination, the sliding mode controller is started and the DAB converter is allowed to enter the normal working mode, and the operating state of the system is adjusted in real time. The fitness value of each control parameter combination is calculated through the measured return power, current and voltage data, reflecting the influence of the combination on the system performance. The smaller the value, the better the optimization effect of the combination. Ideally, the optimal control parameter combination should have the smallest return power error, and the output current and voltage errors should also be as small as possible to ensure the stable operation of the system.

[0055] Step S700: update and optimize the M update control parameter combinations based on the performance evaluation result, and continue to iterate until a predetermined reflux power optimization target is met.

[0056] Preferably, in each iteration, after evaluating the updated control parameter combination based on the sliding mode control fitness function, the parameter combination with the best performance is selected, and a new parameter combination is generated through optimization operations such as crossover and mutation, and the performance is evaluated again. This process is continuously optimized through multiple rounds of iterations, and the control parameter combination of the sliding mode controller is continuously improved and adjusted until the system's return power, output current and voltage reach the predetermined optimization target, and finally the optimal control parameter combination that can meet the predetermined target (such as minimizing the return power, stabilizing the output current and voltage) is found. Specifically, a performance evaluation is performed for each control parameter combination to calculate the fitness value. Based on these performance evaluation results, the goal of updating the optimization is to further improve the control parameter combination so that the return power is minimized, the output current and voltage are stabilized at the expected values, and the update through crossover and mutation is completed. Operation, generate new control parameter combinations and apply sliding mode control fitness function for performance evaluation. After each update optimization, continue to select the top M control parameter combinations with the best performance according to the ranking results of the fitness values, and perform a new round of crossover and mutation operations. According to the actual system feedback data, the weight coefficient of the fitness function can be dynamically adjusted to focus on the aspects that need to be optimized most. For example, if the return power error is large, the weight of the return power error can be increased to give priority to optimizing this part. The iterative process will continue until the following conditions are met. When the return power error, current error and voltage error of the control parameter combination generated by a certain round of iteration all reach the predetermined optimization target (for example, the return power is lower than the set threshold, and the current and voltage errors are within an acceptable range), the optimization is considered to be completed and the iteration is stopped.

[0057] Step S800: optimizing and adjusting the performance evaluation results of the M updated control parameter combinations according to the real-time operation data of the DAB converter to obtain the optimal control parameter combination for sliding mode control of the DAB converter.

[0058] Preferably, during the actual operation of the DAB converter, the key operating parameters of the system (such as input voltage, output current, return power, etc.) are monitored in real time, and the control parameters of the sliding mode controller are dynamically adjusted and optimized according to these real-time data. During the actual operation of the DAB converter, the key operating parameters of the system (such as input voltage, output current, return power, etc.) are monitored in real time, and the control parameters of the sliding mode controller are dynamically adjusted and optimized according to these real-time data. Specifically, the real-time operating data of the DAB converter include input voltage, output voltage, output current and return power. Sensors (such as current sensors and voltage sensors) are used to collect these key parameters in real time and feed them back to the controller. The performance of each combination has been obtained by evaluating the performance of M updated control parameter combinations with a fitness function. However, in an actual system, the operating environment and load of the DAB converter may change continuously. Therefore, it is necessary to dynamically adjust the performance evaluation results according to the real-time operating data. Specifically, based on Real-time data is used to dynamically adjust the weight coefficients α, β, and γ in the fitness function, thereby changing the relative importance of different errors (return power error, current error, and voltage error) in performance evaluation; the fitness value of each control parameter combination is re-evaluated according to the real-time data, and the fitness result of the combination is adjusted according to the new data. For example, if the load increase causes the output current error to increase, the sliding mode controller should reduce the current error by dynamically adjusting the phase shift angle or the duty cycle; the real-time data collected by the sensor is fed back to the sliding mode controller to form a closed-loop control system. The sliding mode controller uses these real-time data to adjust the control parameters. After multiple rounds of iterations and real-time optimization, the control parameter combination with the smallest fitness value and the best performance is selected as the final control strategy of the DAB converter sliding mode controller. This optimal control parameter combination is applied to the sliding mode controller of the DAB converter to ensure efficient and stable operation under different loads and different working conditions, minimize the return power, and ensure the stability of current and voltage output.

[0059] In one possible implementation, Figure 2As shown, step S800 further includes step S810, obtaining the real-time operation data, including real-time input voltage, real-time output current and real-time reflux power; step S820, feeding back the real-time operation data to the sliding mode controller, and using the sliding mode controller to optimize and adjust the M updated control parameter combinations; step S830, using the sliding mode control fitness function to recalculate the fitness of the M updated control parameter combinations, combining the initial sliding mode control evaluation result, and selecting the control parameter combination with the largest fitness value as the optimal control parameter combination; step S840, performing an external interference test on the optimal control parameter combination, and if the test passes, the optimal control parameter combination is used for the sliding mode control of the DAB converter.

[0060] Preferably, these data are acquired in real time through voltage and current sensors. The change of real-time data reflects the operating state of the DAB converter under different working conditions, such as load change, voltage fluctuation, etc. The real-time input voltage represents the input voltage of the DAB converter, reflecting the input energy change. The real-time output current refers to the output current of the converter, which affects the power supply performance of the load. The real-time reflux power represents the reflux phenomenon of energy. The reflux power needs to be reduced as much as possible to improve the energy conversion efficiency. Through the closed-loop control system, the real-time operation data (input voltage, output current, reflux power, etc.) will be fed back to the sliding mode controller to help the controller dynamically adjust the control strategy according to the current operation state and optimize the parameters in the M updated control parameter combinations. These control parameter combinations include duty cycle, phase shift angle, and switching gain. Among them, phase shift angle adjustment refers to adjusting the phase difference between input and output to optimize power transmission, duty cycle adjustment refers to controlling the switching time of the bridge arm to affect the output current, and switching gain adjustment refers to adjusting the switching frequency parameter to improve the response speed and stability of the controller. After the real-time data is fed back, the fitness of the M updated control parameter combinations is recalculated, and the new fitness value is compared with the initial sliding mode control. The control parameter combination can be combined with the control evaluation results to comprehensively consider the performance of historical data and real-time data, ensuring that the selected control parameter combination has good stability and optimization effect in long-term operation. The control parameter combination with the largest fitness value (i.e., the optimal) is selected from the M updated control parameter combinations. This combination can show good control effect in real-time operation and historical operation, and can minimize the return power while ensuring current and voltage stability. In order to ensure the stability of the optimal control parameter combination under actual complex working conditions, an external interference test is required. The external interference test simulates the performance of the DAB converter under different loads, input voltage fluctuations or environmental changes, and verifies the robustness and anti-interference ability of the selected control parameter combination. Possible external interferences include rapid fluctuations in input voltage, sudden changes in load, changes in ambient temperature, etc. If the optimal control parameter combination can effectively maintain stability under external interference conditions, minimize the return power, and maintain the stability of current and voltage output, the test is considered to have passed. When the external interference test passes, the optimal control parameter combination finally selected will be applied to the sliding mode control of the DAB converter to ensure the best system performance under actual operating conditions.

[0061] In a possible implementation, step S840 further includes step S841, simulating multiple sliding mode control scenarios of the DAB converter by simulating external interference conditions of different intensities, wherein the external interference conditions include input voltage fluctuations, load changes, and ambient temperature changes; step S842, respectively calculating the simulated return power errors under the multiple sliding mode control scenarios, comparing the simulated return power error with the return power error, and judging whether the external interference test is passed according to the comparison result; step S843, if the optimal control parameter combination passes the external interference test, it is used as the final optimal control parameter combination of the DAB converter; step S844, if the optimal control parameter combination fails to pass the external interference test, readjusting the control parameters according to the real-time operation data, iterating multiple times to achieve the return power optimization target, and obtaining the final optimal control parameter combination.

[0062] Preferably, by simulating external interference conditions, it is tested whether the sliding mode controller can effectively control the return power and maintain system stability under complex and changing working conditions, including simulating grid voltage fluctuations, sudden increase or decrease of load, ambient temperature changes, and possible fluctuations in the performance of circuit components (such as inductance, capacitance, etc.). Through these different external interference conditions, multiple sliding mode control scenarios are simulated to observe whether the sliding mode controller can effectively control the performance of the DAB converter under external interference of different intensities; in different external interference scenarios, the DAB converter is operated and its return power error is calculated to understand whether the control parameter combination can maintain a lower return power under voltage fluctuations, load changes or temperature fluctuations; by comparing the return power error in the simulated scenario with the return power error measured in the current actual operation, the effect of the sliding mode controller in dealing with external interference can be judged. If the return power error in the simulated scenario is close to or lower than the current actual error, it means that the control parameter combination performs well in dealing with external interference; if the control parameter combination can maintain a low return power error in all external interference scenarios, and the error value is acceptable If the control parameter combination is within the range of , it means that the control parameter combination can effectively cope with external interference. If the test passes, the control parameter combination is identified as the final optimal control parameter combination of the DAB converter and is applied to the actual sliding mode controller to ensure stability and efficiency in complex environments. If the control parameter combination generates a large return power error in certain external interference scenarios, and cannot maintain stability or energy efficiency decreases, the test is considered to have failed. By real-time monitoring of the input voltage, output current and return power of the DAB converter, the shortcomings of the current control parameter combination are dynamically analyzed, and the control parameter combination is re-optimized, including adjusting the duty cycle, phase shift angle and switching gain, etc., and optimization and adjustment are performed for specific interference problems. After multiple iterations, a control parameter combination that can perform well under all external interference conditions is finally found to minimize the return power while maintaining the stability of the output current and voltage, and the final optimal control parameter combination is obtained. The return power error and system performance in different scenarios are good, and it is applied to the sliding mode controller of the DAB converter to ensure efficient and stable operation under complex environments and dynamic load changes.

[0063] The above specific implementation manner does not constitute a limitation to the protection scope of the present application. It should be understood by those skilled in the art that various modifications, combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application. In some cases, the actions or steps recorded in the present application can be performed in an order different from that in the embodiment and can still achieve the desired results. In addition, the process depicted in the accompanying drawings does not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

Claims

1. A sliding mode control method for a DAB converter with optimized reflux power, characterized in that: The method comprises: Based on the circuit topology of the DAB converter, a state relationship model of the converter input voltage, converter output current and converter return power is established; Determine a sliding surface according to the state relationship model, define a sliding mode controller, and generate a sliding mode initial population according to N control parameter combinations of the sliding mode controller, wherein N is a positive integer greater than 1; Calculating the return power error, current error and voltage error of N control parameter combinations in the sliding mode initial population; constructing a sliding mode control fitness function according to the sliding mode surface, evaluating the fitness values ​​of the N control parameter combinations according to the sliding mode control fitness function, and generating a sliding mode control parameter combination sequence according to the evaluation result; Selecting the first M control parameter combinations from the sliding mode control parameter combination sequence for update operation to generate M updated control parameter combinations, where M is a positive integer greater than 1, and M<N; Applying the M updated control parameter combinations to the sliding mode controller, and using the sliding mode control fitness function to perform performance evaluation; Based on the performance evaluation results, the M update control parameter combinations are updated and optimized, and the iteration is continued until a predetermined reflux power optimization target is met; According to the real-time operation data of the DAB converter, the performance evaluation results of the M updated control parameter combinations are optimized and adjusted to obtain the optimal control parameter combination for sliding mode control of the DAB converter.

2. A sliding mode control method for DAB converter with reflux power optimization as claimed in claim 1, characterized in that: Selecting the first M control parameter combinations from the sliding mode control parameter combination sequence for updating operation to generate M updated control parameter combinations, further comprising: Based on the calculation result of the sliding mode control fitness function, the fitness values ​​of N control parameter combinations are sorted from low to high to obtain a sliding mode control parameter combination sequence, and M control parameter combinations whose fitness values ​​are lower than a preset fitness threshold are selected from the sequence; Performing a crossover operation on the M control parameter combinations to generate M crossover control parameter combinations; Performing a mutation operation on the M crossover control parameter combinations to obtain the M update control parameter combinations and generate a sliding mode update population; The sliding mode control fitness function is used to perform a performance evaluation on the update control parameter combination of the sliding mode update combination to obtain an initial sliding mode control evaluation result.

3. A sliding mode control method for DAB converter with reflux power optimization as claimed in claim 2, characterized in that: The obtaining of the optimal control parameter combination and performing sliding mode control of the DAB converter also includes: Acquiring the real-time operation data, including real-time input voltage, real-time output current and real-time reflux power; Feeding back the real-time operation data to the sliding mode controller, and optimizing and adjusting the M updated control parameter combinations by using the sliding mode controller; Recalculate the fitness of the M updated control parameter combinations using the sliding mode control fitness function, and select the control parameter combination with the largest fitness value as the optimal control parameter combination in combination with the initial sliding mode control evaluation result; An external interference test is performed on the optimal control parameter combination. If the test passes, the optimal control parameter combination is used for sliding mode control of the DAB converter.

4. A sliding mode control method for DAB converter with optimized reflux power as claimed in claim 3, characterized in that: Performing an external interference test on the optimal control parameter combination, and if the test passes, using the optimal control parameter combination for sliding mode control of the DAB converter, further comprising: Simulating multiple sliding mode control scenarios of the DAB converter by simulating external interference conditions of different intensities, wherein the external interference conditions include input voltage fluctuations, load changes, and ambient temperature changes; Respectively calculating the simulated return power errors under the multiple sliding mode control scenarios, comparing the simulated return power errors with the return power errors, and judging whether the external interference test is passed according to the comparison results; If the optimal control parameter combination passes the external interference test, it is used as the final optimal control parameter combination of the DAB converter; If the optimal control parameter combination fails to pass the external interference test, the control parameters are readjusted according to the real-time operation data, and the reflux power optimization goal is achieved through multiple iterations to obtain the final optimal control parameter combination.

5. The sliding mode control method for DAB converter with optimized reflux power according to claim 1, characterized in that: According to the N control parameter combinations of the sliding mode controller, an initial sliding mode population is generated, which also includes: According to the real-time environmental parameters of the DAB converter, adjusting the weight of the sliding mode control fitness function; By randomly initializing the duty cycle, phase shift angle and switching gain; Optimizing and adjusting the switching gain of the sliding mode controller based on the adjusted sliding mode control fitness function; Based on the duty cycle, the phase shift angle and the switching gain, N control parameter combinations are generated to obtain the sliding mode initial population.

6. A sliding mode control method for DAB converter with optimized reflux power as claimed in claim 2, characterized in that: The constructing a sliding mode control fitness function according to the sliding mode surface comprises: Establishing a sliding surface error function based on a combination of the return power error, the current error and the voltage error; Based on the sliding surface error function, the maximum allowed reflux power threshold, current fluctuation range and phase shift angle limit are used as constraints of the sliding mode control fitness function, and the sliding mode control fitness function is established with the goal of minimizing the weighted sum of the reflux power error, current error and voltage error.

7. A sliding mode control method for DAB converter with optimized reflux power as claimed in claim 1, characterized in that: The step of establishing a state relationship model of the converter input voltage, the converter output current and the converter return power also includes: Determine the current transmission direction according to the circuit topology of the DAB converter; According to the current transmission direction, obtaining the voltage of the input bridge arm and the current of the output bridge arm in the DAB converter; Define the state variables of the DAB converter, including the state variables of input voltage, output current and return power; The state relationship model is constructed according to the differential equation established by the state variables.

8. A sliding mode control method for DAB converter with optimized reflux power as claimed in claim 7, characterized in that: Obtaining the reflux power also includes: By analyzing the forward transmission waveform of the bridge arm and the reverse transmission waveform of the bridge arm, the input power of the bridge arm and the output power of the bridge arm are calculated; The reflux power of the DAB converter is calculated according to the bridge arm input power and the bridge arm output power.

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