Bidirectional LLC converter resonance parameter particle swarm optimization method

Abstract

The invention relates to the technical field of converter parameter optimization, in particular to a bidirectional LLC converter resonance parameter particle swarm optimization method and system, and the method comprises the steps: building an LLC full-bridge converter loss model, and calculating the total loss power on the premise of introducing an inductance ratio and a quality factor; the inductance ratio and the quality factor are used as alternative variables of resonant inductance, excitation inductance and resonant capacitance; the gain of the LLC full-bridge converter is calculated, and the value range of the inductance ratio meeting the gain requirement and the value range of the quality factor meeting the soft switching condition are obtained through solving; and continuously updating the inductance ratio and the quality factor through a particle swarm optimization algorithm, and determining the resonant inductance, the excitation inductance and the resonant capacitance corresponding to the inductance ratio and the quality factor as optimal parameters. According to the LLC full-bridge converter, the design of complex resonance parameters in the LLC full-bridge converter can be realized on the premise of meeting the requirements of a user-side energy storage system on bidirectional energy flow and high-efficiency conversion.

Description

Technical Field

[0001] This application relates to the technical field of converter parameter optimization, and particularly to a particle swarm optimization method for resonant parameters of a bidirectional LLC converter. Background Art

[0002] In recent years, to meet the strict requirements of user-side energy storage systems in terms of safety, efficiency, and reliability, the DC-DC converters used not only need to achieve stable voltage conversion, but also must withstand moderate current and voltage stresses, and at the same time have a high energy transfer efficiency. As an efficient conversion technology that can achieve soft switching and reduce losses, the LLC resonant converter is widely used in such systems. Among them, the LLC full-bridge converter, as the most common structure in the LLC resonant converter, can better meet the above requirements for DC-DC converters, and thus has received widespread attention and application in the industry.

[0003] In the existing design of LLC full-bridge converters, the working efficiency of the LLC full-bridge converter is closely related to the resonant cavity parameters. The converter includes three resonant components: the resonant inductor Lr, the magnetizing inductor Lm, and the resonant capacitor Cr. The interaction among the three is not a simple linear relationship, and its coupling effect and influence mechanism are relatively complex, resulting in the optimization design of parameters being a major problem in hardware design for a long time. Currently, the LLC full-bridge converter mainly includes two types of parameter design methods: one is to establish the time-domain relationship between the resonant current Ir, the magnetizing current Im, and the dead time td, and then quantitatively calculate the working loss of the converter, and thus deduce the relationship between the loss and the dead time. Then, combined with the calculation formulas of the effective values of the primary and secondary side currents of the transformer, the appropriate resonant parameters are solved by simultaneous equations. The other is to select a set of parameters within the given parameter range, verify whether the converter operates in the PO mode through simulation, and check whether the gain meets the requirements. If not, the parameters are adjusted until all conditions are met.

[0004] However, the applicability of these methods has limitations: on the one hand, taking the time-domain loss model method as an example, when establishing the relationship between the resonant current Ir, the exciting current Im, and the dead time td, this method often assumes that the converter operates in a specific mode. However, in actual applications, the operating mode of the converter may change, resulting in a deviation between the loss model and the actual situation, affecting the accuracy of subsequent parameter solving. On the other hand, when using the method of parameter selection and simulation verification, it is necessary to repeatedly adjust the parameters within the given parameter range: first, verify whether the converter is in the PO mode through simulation; then, check whether the gain meets the requirements; if not, the parameters must be reselected and the verification repeated. This process not only makes the design process long and complex, but also because the existing solutions only target the LLC full-bridge converter with unidirectional energy flow, it is difficult to directly apply the parameter debugging to the bidirectional energy transmission system. Therefore, how to design the complex resonant parameters in the LLC full-bridge converter while meeting the requirements of the user-side energy storage system for bidirectional energy flow and high-efficiency conversion, so as to break through the limitations of unidirectional design, is a difficult problem currently faced. Summary of the Invention

[0005] This application provides a method and system for optimizing the resonant parameters of a bidirectional LLC converter, which can realize the design of complex resonant parameters in the LLC full-bridge converter while meeting the requirements of the user-side energy storage system for bidirectional energy flow and high-efficiency conversion. The present application provides the following technical solutions: In a first aspect, this application provides a method for optimizing the resonant parameters of a bidirectional LLC converter, and the method includes: Establish a loss model of the LLC full-bridge converter, which is used to calculate the total loss power of the forward and reverse operation of the LLC full-bridge converter on the premise of introducing the inductance ratio and the quality factor; Through the mathematical derivation of the resonant circuit, take the inductance ratio and the quality factor as the substitution variables of the resonant inductor, the exciting inductor, and the resonant capacitor; calculate the gain of the LLC full-bridge converter and solve the value range of the inductance ratio that meets the gain requirement and the value range of the quality factor that meets the soft-switching condition; Based on the LLC full-bridge converter loss model and the obtained value ranges of the inductance ratio and the quality factor, continuously update the inductance ratio and the quality factor through the particle swarm optimization algorithm until the loss of the LLC full-bridge converter is minimized and no longer changes, and determine the resonant inductor, the exciting inductor, and the resonant capacitor corresponding to the inductance ratio and the quality factor at this time as the optimal parameters.

[0006] In a specific feasible implementation, the establishment of the LLC full-bridge converter loss model includes: Normalize the switching frequency; Introduce the key current parameters of the LLC full-bridge converter at the forward resonant frequency point by calculating the inductance ratio and quality factor. The key current parameters include the effective value of the resonant current, the maximum value of the exciting current, and the effective value of the secondary side current. Calculate the total loss power of the converter during forward and reverse operations based on the calculated key current parameters.

[0007] In a specific implementable embodiment, the calculation of the total loss power of the converter during forward and reverse operations based on the calculated key current parameters includes: The total loss power of the converter during forward and reverse operations is the sum of the loss powers of the resonant side MOSFETs during forward and reverse operations, the loss powers of the non-resonant side MOSFETs during forward and reverse operations, the loss powers of the resonant cavity during forward and reverse operations, and the loss powers of the transformer during forward and reverse operations.

[0008] In a specific implementable embodiment, the calculation of the gain of the LLC full-bridge converter and the solution for the value range of the inductance ratio that meets the gain requirement and the value range of the quality factor that meets the soft-switching condition include: The gain satisfies: ; and The calculation formulas are as follows: ; Wherein, and are the highest and lowest voltages of the battery, is the DC bus voltage, is the turns ratio of the transformer; In the no-load case, the quality factor is 0, and the formula for the gain is as follows: .

[0009] In a specific implementable embodiment, the calculation of the gain of the LLC full-bridge converter and the solution for the value range of the inductance ratio that meets the gain requirement and the value range of the quality factor that meets the soft-switching condition further includes: To ensure that the gain of the LLC full-bridge converter can meet the minimum requirement, let the normalized frequency take the maximum value , at this time: ; Solve to obtain the range of the inductance ratio that meets the gain requirement.

[0010] In a specific feasible implementation, calculating the gain of the LLC full-bridge converter and solving for the value range of the inductance ratio that meets the gain requirement and the value range of the quality factor that meets the soft-switching condition further includes: To ensure that the LLC full-bridge converter can achieve soft switching, that is, to ensure that the main switching tubes turn on at zero voltage, it is necessary to make the imaginary part of the input impedance zero. The corresponding critical conditions are as follows: ; At full load, let , and substitute it into the above formula, combined with the following gain requirements: ;

[0011] Solve for the value range of the quality factor that meets the soft-switching condition.

[0012] In a specific feasible implementation, based on the LLC full-bridge converter loss model and the obtained value ranges of the inductance ratio and the quality factor, the inductance ratio and the quality factor are continuously updated through the particle swarm optimization algorithm until the loss of the LLC full-bridge converter is minimized and no longer changes. Determining the resonant inductor, magnetizing inductor, and resonant capacitor corresponding to the inductance ratio and the quality factor at this time as the optimal parameters includes: Establish an LLC full-bridge converter simulation model on MATLAB / SIMULINK, and define the design parameters of the LLC full-bridge converter and the model parameters of the LLC full-bridge converter loss model; After defining the design parameters of the LLC full-bridge converter and the model parameters of the LLC full-bridge converter loss model, substitute the loss model parameters into the LLC full-bridge converter loss model to obtain the sum of the forward operating loss and the reverse operating loss of the LLC full-bridge converter; Use the particle swarm algorithm for optimization, substitute it into the LLC full-bridge converter simulation model for simulation calculation, obtain the sum of the forward operating loss and the reverse operating loss of the LLC full-bridge converter, and continuously iterate until the loss of the LLC full-bridge converter is minimized and no longer changes. Determine the resonant inductor, magnetizing inductor, and resonant capacitor corresponding to the inductance ratio and the quality factor at this time and use them as the optimal parameters in the LLC full-bridge converter.

[0013] In a second aspect, the present application provides a particle swarm optimization system for the resonant parameters of a bidirectional LLC converter, adopting the following technical solution: A particle swarm optimization system for the resonant parameters of a bidirectional LLC converter includes: A loss model establishment module for establishing an LLC full-bridge converter loss model, which is used to calculate the total loss power of the forward and reverse operations of the LLC full-bridge converter on the premise of introducing the inductance ratio and the quality factor; A value range determination module, which is used to, through mathematical derivation of the resonant circuit, use the inductance ratio and quality factor as alternative variables for the resonant inductor, exciting inductor, and resonant capacitor; calculate the gain of the LLC full-bridge converter and solve to obtain the value range of the inductance ratio that meets the gain requirement and the value range of the quality factor that meets the soft-switching condition. A parameter update module, which is used to, based on the loss model of the LLC full-bridge converter and the obtained value ranges of the inductance ratio and quality factor, continuously update the inductance ratio and quality factor through the particle swarm optimization algorithm until the loss of the LLC full-bridge converter is minimized and no longer changes, and determine the resonant inductor, exciting inductor, and resonant capacitor corresponding to the inductance ratio and quality factor at this time as the optimal parameters.

[0014] In a third aspect, the present application provides an electronic device, and the device includes a processor and a memory; a program is stored in the memory, and the program is loaded and executed by the processor to implement a particle swarm optimization method for the resonant parameters of a bidirectional LLC converter as described in the first aspect.

[0015] In a fourth aspect, the present application provides a computer-readable storage medium, and a program is stored in the storage medium, and when the program is executed by a processor, it is used to implement a particle swarm optimization method for the resonant parameters of a bidirectional LLC converter as described in the first aspect.

[0016] In summary, the beneficial effects of the present application at least include: (1) By constructing an accurate loss model based on the resonant circuit theory, in the design of the present application, the traditional inductor and capacitor parameters are converted into two dimensionless parameters, namely the inductance ratio and the quality factor, thereby reducing the dimension of multiple complex variables of the system, making the current distribution and loss calculation of the converter in the forward and reverse operating states more accurate.

[0017] (2) After using the inductance ratio and quality factor to replace the original resonant inductor, exciting inductor, and resonant capacitor, not only the number of design variables is greatly reduced, but also the coupling relationship between parameters becomes more intuitive and easy to understand. Combined with the particle swarm optimization algorithm, the designer can automatically search for the optimal solution within the predetermined parameter range without cumbersome manual parameter adjustment and multiple simulation verifications. Through this optimized design process, engineers can quickly obtain the optimal parameter set that meets the requirements of gain, soft switching, and power loss, thereby greatly reducing the difficulty of hardware design and system debugging, and shortening the product R & D and iteration cycle.

[0018] A loss model of the LLC full-bridge converter is established using circuit theory and resonance principle. The key current parameters at the forward resonance frequency point are calculated through the normalized switching frequency, and the inductance ratio and quality factor are introduced as the characteristic variables of the resonant inductor, exciting inductor, and resonant capacitor. Through the mathematical derivation of the resonant circuit, these dimensionless parameters are used to calculate the gain of the converter, and further the value ranges of the inductance ratio and quality factor that meet the gain and soft-switching conditions are solved. On the MATLAB / SIMULINK simulation platform, the particle swarm optimization algorithm is used to iteratively update the inductance ratio and quality factor until the optimal solution that minimizes and stabilizes the total forward and reverse losses of the converter is found, and the optimal resonant inductor, resonant capacitor, and exciting inductor are deduced therefrom. This solution not only reduces the complexity of parameter solving but also realizes high-efficiency conversion under bidirectional energy flow, solving the deficiencies of the existing design methods in hardware parameter optimization.

[0019] The above description is only an overview of the technical solution of this application. In order to be able to understand the technical means of this application more clearly and implement it according to the content of the specification, the following takes the preferred embodiment of this application and describes it in detail with the accompanying drawings as follows. Brief Description of the Drawings

[0020] Figure 1 It is a schematic flow chart of the particle swarm optimization method for the resonant parameters of the bidirectional LLC converter in the embodiment of this application.

[0021] Figure 2 It is a schematic flow chart of using the particle swarm algorithm to find the optimal parameter solution in the embodiment of this application.

[0022] Figure 3 It is a relationship diagram between the optimal loss of the particle swarm algorithm and the number of iterations in the embodiment of this application.

[0023] Figure 4 It is a forward waveform diagram comparing the parameters obtained by using the current common design method in the embodiment of this application to obtain three other groups of parameters, substituting them into the simulation, and comparing them with the parameters obtained by the optimization calculation of this application.

[0024] Figure 5 It is a reverse waveform diagram comparing the parameters obtained by using the current common design method in the embodiment of this application to obtain three other groups of parameters, substituting them into the simulation, and comparing them with the parameters obtained by the optimization calculation of this application.

[0025] Figure 6 It is a block diagram of the electronic device for the particle swarm optimization of the resonant parameters of the bidirectional LLC converter in the embodiment of this application. Detailed Description of the Embodiment

[0026] The following further describes in detail the specific implementation manners of the present application in conjunction with the accompanying drawings and embodiments. The following embodiments are used to illustrate the present application, but are not used to limit the scope of the present application.

[0027] Optionally, the present application takes the particle swarm optimization method for the resonant parameters of the bidirectional LLC converter provided in each embodiment as an example for illustration in an electronic device. The electronic device is a terminal or a server. The terminal can be a mobile phone, a computer, a tablet computer, etc. The type of the electronic device is not limited in this embodiment.

[0028] Referring to Figure 1 , which is a schematic flowchart of the particle swarm optimization method for the resonant parameters of the bidirectional LLC converter provided in an embodiment of the present application. The method at least includes the following steps: Step S101: Establish a loss model of the LLC full-bridge converter. The loss model of the LLC full-bridge converter is used to calculate the total loss power of the forward and reverse operation of the LLC full-bridge converter on the premise of introducing the inductance ratio and the quality factor.

[0029] In step S101, first, the actually used switching frequency is normalized to f n =1, and the key current parameters of the LLC full-bridge converter at the forward resonant frequency point are calculated, including the effective value of the resonant current , the maximum value of the magnetizing current and the effective value of the secondary current . Based on the circuit theory and the working principle of the resonant circuit, the inductance ratio and the quality factor are introduced, and the calculation formula is obtained through mathematical derivation as follows: ; Among them, represents the total loss power in the forward and reverse rated operating states, is the turns ratio of the transformer, is the secondary voltage, is the secondary rated current, is the inductance ratio, which is used to reflect the coupling ratio between the resonant inductor and the magnetizing inductor, is the quality factor, which is used to measure the balance between the energy storage and loss of the resonant circuit.

[0030] Subsequently, the total loss power of the forward and reverse operation of the converter is calculated based on the calculated key current parameters. Specifically, first, the loss power when the resonant-side MOSFET operates forward and reverse and the loss power when the non-resonant-side MOSFET operates forward and reverse are calculated respectively.

[0031] Specifically, the loss power The calculation method is as follows: ; Among them, is the conduction loss of the MOS transistor on the resonant side during forward operation, is the turn-off loss of the MOS transistor on the resonant side during forward operation, is the conduction loss of the MOS transistor on the resonant side during reverse operation, is the turn-on loss of the MOS transistor when the switch on the resonant side is turned on.

[0032] ; ; ; ; Among them, represents the effective value of the resonant current of the MOS transistor on the resonant side in the forward operation state, represents the equivalent resistance of the MOS transistor in the conduction state, represents the DC bus voltage, represents the resonant frequency, represents the time required for the internal capacitance of the MOS transistor to be charged, represents a complete switching cycle, represents the energy loss generated by the conduction voltage and current on the MOS transistor, represents the effective value of the resonant current of the resonant side in the reverse operation state, represents the current value of the MOS transistor during reverse operation, represents the impedance in the conduction state, represents the output capacitance of the MOS transistor.

[0033] Specifically, the power losses of the non-resonant side MOS transistor during forward and reverse operations are calculated as follows: ; Among them, is the conduction loss of the non-resonant side MOS transistor during forward operation, is the turn-on loss of the non-resonant side MOS transistor during forward operation, is the conduction loss of the non-resonant side MOS transistor during reverse operation, is the turn-off loss of the non-resonant side MOS transistor during reverse operation.

[0034] ; ; ; ; Among them, represents the rated output power, which is the power output target of the system under rated conditions, represents the voltage drop when the MOS transistor is conducting, that is, the voltage loss of the device in the conducting state, represents the turns ratio of the transformer, represents the equivalent resistance when the MOS transistor is conducting, represents the effective value of the resonant current of the non-resonant side MOS transistor during forward operation, represents the current flowing through the non-resonant side MOS transistor during reverse operation, represents the equivalent resistance of the MOS transistor in the conducting state, represents the output capacitance of the MOS transistor, represents the resonant frequency, represents the secondary voltage.

[0035] Subsequently, calculate the loss power of the resonant cavity during forward and reverse operations and the loss power of the transformer during forward and reverse operations , and the calculation formula is obtained through mathematical derivation based on circuit theory and the working principle of the resonant circuit as follows: ; Among them, and are the equivalent resistances of the resonant inductor and resonant capacitor respectively, represents the effective value of the resonant current on the resonant side in the reverse operation state, represents the effective value of the resonant current of the MOS transistor on the resonant side in the forward operation state.

[0036] ; Among them, and are the equivalent resistances of the primary and secondary sides of the transformer respectively, represents the effective value of the resonant current on the resonant side in the reverse operation state, represents the effective value of the resonant current of the MOS transistor on the resonant side in the forward operation state.

[0037] Finally, the total loss power of the converter during forward and reverse operations is the sum of the loss power of the MOS transistor on the resonant side during forward and reverse operations, the loss power of the MOS transistor on the non-resonant side during forward and reverse operations, the loss power ; It should be noted that in this application, the total loss power under the forward and reverse rated operating conditions is usually used as a rated or reference value, while is the detailed total loss power calculated according to the model. That is to say, as a design parameter or target index, it is used for normalization and as an input for calculating other current parameters in the formula, while is the total loss obtained by summing up each part (such as the switching and conduction losses of the MOS transistors on the resonant side and non-resonant side, the losses of the resonant cavity and the transformer). In short, is a preset or desired loss value, while is the result calculated by the model, reflecting the summary of actual various losses.

[0038] Through the above steps, based on the resonant current parameters of the LLC full-bridge converter, the calculation formulas for each loss item are derived, and finally the LLC full-bridge converter loss model is obtained. The LLC full-bridge converter loss model can be used to calculate the total loss power of the converter in the forward and reverse operations and is applicable to various working conditions.

[0039] Step S102: Through the mathematical derivation of the resonant circuit, the inductance ratio and quality factor are used as alternative variables for the resonant inductor, magnetizing inductor, and resonant capacitor; calculate the gain of the LLC full-bridge converter and solve for the value range of the inductance ratio that meets the gain requirement and the value range of the quality factor that meets the soft-switching condition.

[0040] In step S102, the gain refers to the ratio of the output voltage to the input voltage of the converter. In the LLC resonant converter, the gain is not fixed but changes with the switching frequency. To ensure that the converter can adjust the gain to maintain its output voltage within a reasonable range, the gain must satisfy: ; and The calculation formulas of ; where and are the maximum and minimum voltages of the battery, is the DC bus voltage, is the turns ratio of the transformer.

[0041] In practice, the normalized frequency is used to represent the operating frequency of the converter: ; where is the actual switching frequency, is the resonant frequency.

[0042] Since the gain is affected by frequency it is necessary to calculate as well as to ensure that when the converter operates within this frequency range, the gain requirement is met. Under no-load conditions, the quality factor is 0, and the formula for the gain is as follows: ; Secondly, in an LLC resonant converter, the parameter combination of the inductor and capacitor determines the operating characteristics of the converter. If the resonant inductor , the magnetizing inductor and the resonant capacitor are directly used for calculation, involving multiple variables, the calculation is complex and it is also difficult to adjust the parameters. Therefore, through mathematical derivation of the resonant circuit, two variable inductance ratios and the quality factor are used as alternative variables for the resonant inductor, magnetizing inductor and resonant capacitor, as follows: ; where is the equivalent load impedance of the converter.

[0043] Subsequently, in order to ensure that the gain of the LLC full-bridge converter can meet the minimum requirement, let the normalized frequency take the maximum value , at this time: ; From this, the range of the inductance ratio that meets the gain requirement is solved. Specifically, when the normalized frequency reaches the highest, the gain of the LLC converter will drop to the lowest. To ensure that even in this most unfavorable operating condition, the gain is still not lower than the minimum value required by the system, compare the gain at the highest frequency with the allowable minimum gain and observe their relationship as the inductance ratio changes. The specific method is: first determine the position where the gain is the lowest at the highest frequency, then analyze the trend of the gain increasing or decreasing with increasing, and find the k value that makes the gain exactly reach the lower limit; then combined with must be positive physical constraint, an upper and lower bound can be obtained, thus clarifying the value range of that meets the gain requirement.

[0044] Subsequently, in order to ensure that the LLC full-bridge converter can achieve soft switching, that is, to ensure that the main switch tube conducts at zero voltage, it is necessary to make the imaginary part of the input impedance 0, and the corresponding critical conditions are as follows: ; At full load, let , and substitute it into the above formula, combined with the following gain requirements: ; Thus, the quality factor satisfying the soft-switching condition is solved to obtain its value range. Specifically, when the converter operates at the heaviest load and the lowest normalized frequency, to achieve zero-voltage switching, the imaginary part of the input impedance at this time must be exactly zero, so that the main switch can conduct at the moment when the voltage drops to zero. For this reason, the lowest frequency is taken as the observation point to observe the influence of the quality factor on the phase of the input impedance: when adjusting from small to large, the imaginary part of the input impedance will experience a change from inductive to capacitive or reverse. Find those value intervals where the imaginary part just crosses zero, that is, the range satisfying the soft-switching condition. Then, at the same lowest frequency, it is also necessary to ensure that the converter gain is not lower than the highest output demand. By analyzing the trend of the gain changing with , the values that can achieve both zero-voltage switching and meet the gain lower limit are screened out. The intersection of the two is the final value range of the quality factor that ensures both soft-switching and meets the gain requirements.

[0045] Step S103: Based on the loss model of the LLC full-bridge converter and the obtained range of the inductance ratio and the quality factor, continuously update the inductance ratio and the quality factor through the particle swarm optimization algorithm until the loss of the LLC full-bridge converter is minimized and no longer changes, and determine the resonant inductor, magnetizing inductor, and resonant capacitor corresponding to the inductance ratio and the quality factor at this time as the optimal parameters.

[0046] In step S103, first establish an LLC full-bridge converter simulation model on MATLAB / SIMULINK, and then define the design parameters of the LLC full-bridge converter and the model parameters of the LLC full-bridge converter loss model. The design parameters of the LLC full-bridge converter and the model parameters of the LLC full-bridge converter loss model in this application are shown in Table 1 and Table 2 respectively:

[0047]

[0048] After defining the design parameters of the LLC full-bridge converter and the model parameters of the LLC full-bridge converter loss model, substitute the loss model parameters into the loss model of the LLC full-bridge converter to obtain the sum of the forward operating loss and the reverse operating loss of the LLC full-bridge converter, as shown below: ; Finally, the particle swarm optimization algorithm is used for optimization. The parameter settings of the algorithm are shown in Table 3. Combining Figure 2 , the iteration number t, the particle population number N, and the learning factors c 1 and c 2 are defined, and the initial position x i and the initial velocity v i of each particle are randomly set. Calculate the fitness of each particle, substitute it into the LLC full-bridge converter simulation model for simulation calculation, obtain the sum of the forward working loss and the reverse working loss of the LLC full-bridge converter, and then start continuous iteration and update the particle position, calculate the new fitness, compare the individual optimal solution and the global optimal solution of each particle, and judge whether to update until the loss of the LLC full-bridge converter is minimized and no longer changes. Determine the resonant inductor, exciting inductor, and resonant capacitor corresponding to the inductance ratio and quality factor at this time as the optimal parameters in the LLC full-bridge converter.

[0049]

[0050] In this application, after 50 iterations, the relationship curve between the total loss and the iteration number is as shown in the appendix Figure 3 . As the number of iterations increases, the total loss of the parameter group found by the particle swarm optimization algorithm shows a decreasing trend, indicating that the algorithm continuously updates the optimal LLC parameters in multiple iterations. When the number of iterations reaches 35, the total loss no longer changes, indicating that the algorithm has found the optimal solution. The corresponding total forward and reverse operation losses are 382 W and 498 W, the inductance ratio k is 0.3, and the quality factor Q is 0.63. By calculation, the resonant inductor Lr is 86.7 μH, the resonant capacitor Cr is 81.1 nF, and the exciting inductor Lm is 289 μH.

[0051] To verify the optimality of the optimization results of the particle swarm optimization algorithm, three other groups of parameters are obtained using common current design methods, substituted into the simulation, and compared with the parameters obtained by the optimization calculation of the present invention. For Parameter 1, the resonant inductor Lr is 71.6 μH, the resonant capacitor Cr is 98.3 nF, and the exciting inductor Lm is 194 μH. For Parameter 2, the resonant inductor Lr is 60.5 μH, the resonant capacitor Cr is 116 nF, and the exciting inductor Lm is 209 μH. For Parameter 3, the resonant inductor Lr is 67.4 μH, the resonant capacitor Cr is 104 nF, and the exciting inductor Lm is 193 μH. Substitute them into the forward and reverse simulations, and record the output voltage V o , resonant current i r , exciting current i m , primary and secondary side switch tube voltages u g and currenti g The waveforms, the forward and reverse simulation waveforms are as attached Figure 4 Attached Figure 5 as shown. The simulation data corresponding to the four groups of resonance parameters are shown in Table 4

[0052]

[0053] In summary, this application uses circuit theory and resonance principle to establish a loss model of LLC full-bridge converter. By normalizing the switching frequency, the key current parameters at the forward resonance frequency point are calculated, and the inductance ratio and quality factor are introduced as characteristic variables of the resonant inductor, exciting inductor and resonant capacitor. Through the mathematical derivation of the resonant circuit, these dimensionless parameters are used to calculate the gain of the converter, and further the value ranges of the inductance ratio and quality factor that meet the gain and soft-switching conditions are solved. On the MATLAB / SIMULINK simulation platform, the particle swarm optimization algorithm is used to iteratively update the inductance ratio and quality factor until the optimal solution that minimizes and stabilizes the total forward and reverse losses of the converter is found, and then the optimal resonant inductor, resonant capacitor and exciting inductor are deduced from this. This solution not only reduces the complexity of parameter solving, but also realizes high-efficiency conversion under bidirectional energy flow, and solves the deficiencies of existing design methods in hardware parameter optimization

[0054] An embodiment of this application also provides a particle swarm optimization system for the resonance parameters of a bidirectional LLC converter. The system at least includes the following modules A loss model establishment module, which is used to establish a loss model of LLC full-bridge converter. The loss model of LLC full-bridge converter is used to calculate the total loss power of the forward and reverse operation of LLC full-bridge converter on the premise of introducing the inductance ratio and quality factor A value range determination module, which is used to, through the mathematical derivation of the resonant circuit, use the inductance ratio and quality factor as substitution variables of the resonant inductor, exciting inductor and resonant capacitor; calculate the gain of LLC full-bridge converter and solve the value range of the inductance ratio that meets the gain requirement and the value range of the quality factor that meets the soft-switching condition A parameter update module, which is used to, based on the loss model of LLC full-bridge converter and the obtained value ranges of the inductance ratio and quality factor, continuously update the inductance ratio and quality factor through the particle swarm optimization algorithm until the loss of LLC full-bridge converter is minimized and no longer changes, and determine the resonant inductor, exciting inductor and resonant capacitor corresponding to the inductance ratio and quality factor at this time as the optimal parameters

[0055] For relevant details, refer to the above method embodiment

[0056] Figure 6It is a block diagram of an electronic device provided by an embodiment of the present application. The device at least includes a processor 401 and a memory 402.

[0057] The processor 401 may include one or more processing cores, such as: a 4-core processor, an 8-core processor, etc. The processor 401 may be implemented in at least one hardware form of DSP (Digital Signal Processing), FPGA (Field-Programmable Gate Array), or PLA (Programmable Logic Array). The processor 401 may also include a main processor and a coprocessor. The main processor is a processor for processing data in the wake state, also known as the CPU (Central Processing Unit); the coprocessor is a low-power processor for processing data in the standby state. In some embodiments, the processor 401 may be integrated with a GPU (Graphics Processing Unit), and the GPU is responsible for rendering and drawing the content to be displayed on the display screen. In some embodiments, the processor 401 may further include an AI (Artificial Intelligence) processor, and the AI processor is used to process computational operations related to machine learning.

[0058] The memory 402 may include one or more computer-readable storage media, and the computer-readable storage media may be non-transitory. The memory 402 may further include high-speed random access memory and non-volatile memory, such as one or more disk storage devices and flash storage devices. In some embodiments, the non-transitory computer-readable storage media in the memory 402 is used to store at least one instruction, and the at least one instruction is used to be executed by the processor 401 to implement the particle swarm optimization method for the resonance parameters of the bidirectional LLC converter provided in the method embodiment of the present application.

[0059] In some embodiments, the electronic device may further optionally include: a peripheral device interface and at least one peripheral device. The processor 401, the memory 402, and the peripheral device interface may be connected through a bus or signal lines. Each peripheral device may be connected to the peripheral device interface through a bus, signal lines, or a circuit board. Schematically, the peripheral devices include but are not limited to: a radio frequency circuit, a touch display screen, an audio circuit, and a power supply, etc.

[0060] Of course, the electronic device may also include fewer or more components, and this embodiment does not limit this.

[0061] Optionally, the present application also provides a computer-readable storage medium storing a program that is loaded and executed by a processor to implement the bidirectional LLC converter resonant parameter particle swarm optimization method in the above method embodiment.

[0062] Optionally, the present application also provides a computer product including a computer-readable storage medium storing a program that is loaded and executed by a processor to implement the bidirectional LLC converter resonant parameter particle swarm optimization method in the above method embodiment.

[0063] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0064] The above embodiments only represent several implementation manners of the present application, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several deformations and improvements can be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A particle swarm optimization method for resonant parameters of a bidirectional LLC converter, characterized in that: The method comprises: Establish the LLC full-bridge converter loss model, which is used to calculate the total power loss of the LLC full-bridge converter in forward and reverse operation under the premise of introducing the inductance ratio and quality factor; Through mathematical derivation of the resonant circuit, the inductance ratio and quality factor are used as substitute variables for the resonant inductance, excitation inductance and resonant capacitance; the gain of the LLC full-bridge converter is calculated and the range of inductance ratio that meets the gain requirement and the range of quality factor that meets the soft switching condition are obtained; Based on the loss model of LLC full-bridge converter and the obtained value range of inductance ratio and quality factor, the inductance ratio and quality factor are continuously updated by particle swarm optimization algorithm until the loss of LLC full-bridge converter is minimized and no longer changes. The resonant inductance, excitation inductance and resonant capacitance corresponding to the inductance ratio and quality factor at this time are determined as the optimal parameters.

2. The particle swarm optimization method for resonant parameters of a bidirectional LLC converter according to claim 1, characterized in that: The establishment of the LLC full-bridge converter loss model includes: Normalization sets the switching frequency; Inductance ratio and quality factor are introduced to calculate key current parameters of LLC full-bridge converter at forward resonant frequency point, wherein the key current parameters include effective value of resonant current, maximum value of excitation current and effective value of secondary current; The total power loss of the converter in forward and reverse operation is calculated based on the calculated key current parameters.

3. The particle swarm optimization method for resonant parameters of a bidirectional LLC converter according to claim 2, characterized in that: The method of calculating the total power loss of the converter in forward and reverse operation based on the calculated key current parameters includes: The total power loss of the converter in forward and reverse operation is the sum of the power loss of the resonant side MOS tube in forward and reverse operation, the power loss of the non-resonant side MOS tube in forward and reverse operation, the power loss of the resonant cavity in forward and reverse operation, and the power loss of the transformer in forward and reverse operation.

4. The particle swarm optimization method for resonant parameters of a bidirectional LLC converter according to claim 1, characterized in that: The calculation of the gain of the LLC full-bridge converter and the solution to obtain the value range of the inductance ratio that meets the gain requirement and the value range of the quality factor that meets the soft switching condition include: Gain satisfies: ; and The calculation formula is as follows: ; in, and is the highest and lowest voltage of the battery, is the DC bus voltage, is the turns ratio of the transformer; Under no-load conditions, the quality factor is 0, the gain formula is as follows: 。 5. The particle swarm optimization method for resonant parameters of a bidirectional LLC converter according to claim 4, characterized in that: The calculation of the gain of the LLC full-bridge converter and the solution to obtain the value range of the inductance ratio that meets the gain requirement and the value range of the quality factor that meets the soft switching condition also include: In order to ensure that the gain of the LLC full-bridge converter can meet the minimum requirement, the normalized frequency Take the maximum value ,at this time: ； Solve to obtain the inductance ratio that meets the gain requirements range.

6. The particle swarm optimization method for resonant parameters of a bidirectional LLC converter according to claim 4, characterized in that: The calculation of the gain of the LLC full-bridge converter and the solution to obtain the value range of the inductance ratio that meets the gain requirement and the value range of the quality factor that meets the soft switching condition also include: In order to ensure that the LLC full-bridge converter can achieve soft switching, that is, to ensure that the main switch is turned on at zero voltage, the imaginary part of the input impedance needs to be 0. The corresponding critical conditions are as follows: ； At full load, , and bring it into the above formula, combined with the following gain requirements: ； Solve to obtain the quality factor that satisfies the soft switching condition The value range of .

7. The particle swarm optimization method for resonant parameters of a bidirectional LLC converter according to claim 1, characterized in that: Based on the LLC full-bridge converter loss model and the obtained inductance ratio and quality factor value range, the inductance ratio and quality factor are continuously updated by the particle swarm optimization algorithm until the loss of the LLC full-bridge converter is minimized and no longer changes, and the resonant inductance, excitation inductance and resonant capacitance corresponding to the inductance ratio and quality factor at this time are determined as optimal parameters, including: Establish a simulation model of LLC full-bridge converter on MATLAB / SIMULINK, define the design parameters of LLC full-bridge converter and the model parameters of LLC full-bridge converter loss model; After defining the design parameters of the LLC full-bridge converter and the model parameters of the LLC full-bridge converter loss model, the loss model parameters are introduced into the loss model of the LLC full-bridge converter to obtain the sum of the forward working loss and the reverse working loss of the LLC full-bridge converter; The particle swarm algorithm is used to find the optimal solution and the LLC full-bridge converter simulation model is substituted for the simulation calculation to obtain the sum of the forward working loss and the reverse working loss of the LLC full-bridge converter. The algorithm is continuously iterated until the loss of the LLC full-bridge converter is minimized and no longer changes. The resonant inductance, excitation inductance and resonant capacitance corresponding to the inductance ratio and quality factor at this time are determined and used as the optimal parameters in the LLC full-bridge converter.

8. A particle swarm optimization system for resonant parameters of a bidirectional LLC converter, characterized in that: include: The loss model establishment module is used to establish the LLC full-bridge converter loss model. The LLC full-bridge converter loss model is used to calculate the total power loss of the LLC full-bridge converter in forward and reverse operation under the premise of introducing the inductance ratio and quality factor; A value range determination module, used for using the inductance ratio and the quality factor as substitute variables for the resonant inductance, the excitation inductance and the resonant capacitance through mathematical deduction of the resonant circuit; Calculate the gain of the LLC full-bridge converter and solve the range of inductance ratios that meet the gain requirements and the range of quality factors that meet the soft switching conditions; The parameter updating module is used to continuously update the inductance ratio and quality factor through the particle swarm optimization algorithm based on the LLC full-bridge converter loss model and the obtained inductance ratio and quality factor value range until the loss of the LLC full-bridge converter is minimized and no longer changes, and determine the resonant inductance, excitation inductance and resonant capacitance corresponding to the inductance ratio and quality factor at this time as the optimal parameters.

9. An electronic device, characterized in that: The device includes a processor and a memory; a program is stored in the memory, and the program is loaded and executed by the processor to implement a particle swarm optimization method for resonant parameters of a bidirectional LLC converter as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The storage medium stores a program, and when the program is executed by the processor, it is used to implement a particle swarm optimization method for resonant parameters of a bidirectional LLC converter as described in any one of claims 1 to 7.

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