Stepless voltage regulation method and device with bidirectional voltage regulation function

Abstract

The invention provides a stepless voltage regulation method and device with a bidirectional voltage regulation function, and the method comprises the steps: constructing the relation between the input voltage of the input end of a first full-bridge circuit and the output voltage of the output end of a second full-bridge circuit through the turn ratio of an isolation transformer and the duty ratio of a full-bridge switching tube, and achieving the stepless voltage regulation of the output voltage, power transmission control is realized through combination of phase shift control and dynamic duty ratio modulation; after a bidirectional voltage regulation mathematical model is established, the output voltage of the output end of the second full-bridge circuit is further accurately controlled; detecting the output voltage of the output end of the second full-bridge circuit in real time, comparing the output voltage with the target voltage to generate an error signal, and adjusting a control parameter through a parameter adjusting law according to the error signal; when the boost mode and the buck mode are switched, smooth transition of the phase shift angle is realized by adopting a transition strategy to avoid voltage jump, and the dead time is dynamically adjusted based on a change value during smooth transition of the phase shift angle. Through the method and the corresponding device, the energy conversion efficiency of the circuit can be improved.

Description

Technical Field

[0001] The present invention provides a stepless voltage regulation method and device with bidirectional voltage regulation function, which relates to the technical field of stepless voltage regulation. Background Art

[0002] Traditional voltage regulation schemes usually adopt a fixed dead time to avoid simultaneous conduction of the upper and lower switching tubes on the same bridge arm to prevent short - circuit faults. However, the fixed dead time cannot adapt to different working conditions and circuit parameter changes. In some cases, too long fixed dead time will increase switching losses and reduce system efficiency; in other cases, too short fixed dead time may not ensure the safe operation of the switching tubes, and there is a risk of bridge arm through - conduction. When switching between boost and buck modes, traditional voltage regulation schemes are prone to voltage jump phenomena. This is because during the mode - switching process, the conduction states of the switching tubes and circuit parameters change suddenly, resulting in the output voltage deviating from the target value instantaneously. Voltage jumps may damage the load, especially for some devices sensitive to voltage changes. When the load changes, the output voltage of traditional voltage regulation schemes is prone to fluctuations. Due to changes in circuit parameters and different load characteristics, when the load current increases or decreases, the output voltage may deviate from the set value, affecting the stability and reliability of the system. Traditional voltage regulation methods are difficult to compensate for the impact of load changes on voltage in real - time and accurately. Summary of the Invention

[0003] The present invention provides a stepless voltage regulation method and device with bidirectional voltage regulation function to solve the above - mentioned problems: A stepless voltage regulation method with bidirectional voltage regulation function proposed by the present invention is based on a symmetric topology of a dual - active bridge. The symmetric topology of the dual - active bridge includes two full - bridge circuits and an isolation transformer, and supports bidirectional energy flow. The specific steps include: Construct the relationship between the input voltage at the input end of the first full - bridge circuit and the output voltage at the output end of the second full - bridge circuit through the turns ratio of the isolation transformer and the duty cycle of the full - bridge switching tubes to achieve stepless voltage regulation of the output voltage, and then combine phase - shift control with dynamic duty - cycle modulation to achieve power transfer control; After establishing a bidirectional voltage regulation mathematical model, further achieve precise control of the output voltage at the output end of the second full - bridge circuit; Real - time detect the output voltage at the output end of the second full - bridge circuit, compare it with the target voltage to generate an error signal, and adjust the control parameters according to the error signal through a parameter adjustment law; When switching between boost and buck modes, adopt a transition strategy to achieve smooth transition of the phase - shift angle to avoid voltage jumps, and dynamically adjust the dead time based on the change value during the smooth transition of the phase - shift angle.

[0004] Furthermore, the relationship between the input voltage at the input end of the first full-bridge circuit and the output voltage at the output end of the second full-bridge circuit is constructed by the turns ratio of the isolation transformer and the duty cycle of the full-bridge switching tubes to achieve stepless voltage regulation of the output voltage. Then, power transfer control is achieved by combining phase-shift control and dynamic duty-cycle modulation, including: Controlling the amplitude of the output voltage at the output end of the second full-bridge circuit through the input-output voltage relationship model. Specifically, the input-output voltage relationship model is:

[0005] Where, represents the output voltage at the output end of the second full-bridge circuit, n represents the turns ratio of the isolation transformer, D represents the duty cycle of the switching tubes in the first full-bridge circuit, represents the input voltage at the input end of the first full-bridge circuit; Then, based on the power transfer model, the power transfer is controlled by adjusting the phase difference between the first full-bridge circuit and the second full-bridge circuit and the output voltage at the output end of the second full-bridge circuit. Specifically, the power transfer model is:

[0006] Where, P represents the magnitude of the active power between the first full-bridge circuit and the second full-bridge circuit in the dual-active-bridge circuit, f represents the switching frequency, L represents the leakage inductance of the isolation transformer, represents the phase difference between the first full-bridge circuit and the second full-bridge circuit.

[0007] Furthermore, a bidirectional voltage regulation mathematical model is established to further precisely control the output voltage at the output end of the second full-bridge circuit, including: When the boost mode is preset, , energy is transferred from the input side of the first full-bridge circuit to the output side of the second full-bridge circuit. When in the buck mode, , energy is transferred from the output side of the second full-bridge circuit to the input side of the first full-bridge circuit; After achieving power transfer control, then the output voltage at the output end of the second full-bridge circuit is controlled through the bidirectional voltage regulation mathematical model. Specifically, the bidirectional voltage regulation mathematical model is:

[0008] Where, R represents the equivalent resistance value presented by the load connected to the output end of the second full-bridge circuit in the dual-active-bridge circuit.

[0009] The output voltage at the output end of the second full-bridge circuit is detected in real time, compared with the target voltage to generate an error signal, and the control parameters are adjusted according to the error signal through the parameter adjustment law, including: Detect the output voltage at the output terminal of the second full-bridge circuit in real time, compare it with the target output voltage to generate an error signal: , where e represents the error signal, represents the target output voltage of the second full-bridge circuit, represents the actual detected output voltage at the output terminal of the second full-bridge circuit; Based on the error signal, adjust the duty cycle and phase shift angle of the switching tubes of the full-bridge circuit through the parameter adjustment rate. Specifically, the parameter adjustment law is:

[0010] where, represents the duty cycle of the switching tubes of the full-bridge circuit at the k-th time step, represents the duty cycle of the switching tubes of the full-bridge circuit at the (k + 1)-th time step, represents the proportionality coefficient, represents the integral coefficient, represents the discrete control period, represents the error signal at the i-th time step;

[0011] where, represents the phase shift angle between the driving signals of the switching tubes of the first full-bridge circuit and the second full-bridge circuit in the dual-active-bridge circuit at the (k + 1)-th time step, represents the phase shift angle between the driving signals of the switching tubes at the input terminal of the first full-bridge circuit and the output terminal of the second full-bridge circuit in the dual-active-bridge circuit at the k-th time step, represents the sign function, which is used to judge the positive and negative of the error signal e.

[0012] Further, when switching between the boost and buck modes, adopt a transition strategy to achieve smooth transition of the phase shift angle to avoid voltage jumps, and dynamically adjust the dead time based on the change value during the smooth transition of the phase shift angle, including: When switching between the boost and buck modes, adopt a transition strategy to achieve smooth transition of the phase shift angle. Specifically, the transition strategy is:

[0013] where, represents the phase shift angle between the driving signals of the switching tubes of the full-bridge circuits on the input side and the output side in the dual-active-bridge circuit at time t, represents the initial value of the phase shift angle, that is, the phase shift angle value at the start time of the boost and buck mode switching, i.e., t = 0. τ represents the time constant, and t represents the time variable, which starts timing from the start time of the mode switching; Monitor the phase shift angle change value, and dynamically adjust the dead time based on the phase shift angle change value through the dynamic dead time model. Specifically, the dynamic dead time model is as follows: Wherein, represents the dead time at time t, represents the preset basic dead time, represents the reference value preset under room temperature conditions, represents the temperature of the semiconductor junction inside the switching device, represents the room temperature, represents the maximum allowable temperature of the semiconductor junction inside the switching device, represents the instantaneous change rate of the leakage inductance current of the transformer, represents the rated current passing through the dual-active bridge, and β represents the action weight coefficient of the phase shift angle dynamic term on the dead time, represents the change amount of the phase shift angle at time t relative to the previous moment, represents the maximum allowable phase shift angle, represents the attenuation weight coefficient.

[0014] A continuously variable voltage regulating device with a bidirectional voltage regulating function proposed by the present invention, the device includes: A power transmission control module, which is used to realize continuously variable voltage regulation of the output voltage by constructing the relationship between the input voltage at the input end of the first full-bridge circuit and the output voltage at the output end of the second full-bridge circuit through the turns ratio of the isolation transformer and the duty cycle of the full-bridge switching tubes, and then realizes power transmission control through the combination of phase shift control and dynamic duty cycle modulation; A bidirectional control module, which is used to further precisely control the output voltage at the output end of the second full-bridge circuit after establishing a bidirectional voltage regulation mathematical model; An adjustment control parameter module, which is used to detect the output voltage at the output end of the second full-bridge circuit in real time, compare it with the target voltage to generate an error signal, and adjust the control parameters according to the error signal through a parameter adjustment law; A control dead time module, which is used to adopt a transition strategy to achieve smooth transition of the phase shift angle to avoid voltage jump when switching between the boost and buck modes, and dynamically adjust the dead time based on the change value during the smooth transition of the phase shift angle.

[0015] Further, the power transmission control module includes: A control input-output voltage relationship module, which is used to control the amplitude of the output voltage at the output end of the second full-bridge circuit through an input-output voltage relationship model. Specifically, the input-output voltage relationship model is as follows:

[0016] Wherein, Vout represents the output voltage at the output terminal of the second full-bridge circuit, n represents the turns ratio of the isolation transformer, D represents the duty cycle of the switching transistor in the first full-bridge circuit, Vin represents the input voltage at the input terminal of the first full-bridge circuit; The power regulation module is configured to then control the power transfer by adjusting the phase difference between the first full-bridge circuit and the second full-bridge circuit and the output voltage at the output terminal of the second full-bridge circuit based on the power transfer model. Specifically, the power transfer model is:

[0017] where P represents the magnitude of the active power between the first full-bridge circuit and the second full-bridge circuit in the dual-active-bridge circuit, f represents the switching frequency, L represents the leakage inductance of the isolation transformer, δ represents the phase difference between the first full-bridge circuit and the second full-bridge circuit.

[0018] Further, the bidirectional control module includes: When the preset boost mode is set, energy is transferred from the input side of the first full-bridge circuit to the output side of the second full-bridge circuit. When in the buck mode, energy is transferred from the output side of the second full-bridge circuit to the input side of the first full-bridge circuit; The bidirectional voltage regulation module is configured to then control the output voltage at the output terminal of the second full-bridge circuit through a bidirectional voltage regulation mathematical model after implementing the power transfer control. Specifically, the bidirectional voltage regulation mathematical model is:

[0019] where R represents the equivalent resistance value presented by the load connected to the output terminal of the second full-bridge circuit in the dual-active-bridge circuit.

[0020] Further, the adjustment control parameter module includes: The error signal acquisition module is configured to detect the output voltage at the output terminal of the second full-bridge circuit in real time and generate an error signal by comparing it with the target output voltage: where e represents the error signal, Vref represents the target output voltage of the second full-bridge circuit, Vout represents the actually detected output voltage at the output terminal of the second full-bridge circuit; The duty cycle and phase shift angle adjustment module is configured to adjust the duty cycle and phase shift angle of the switching transistors of the full-bridge circuit based on the error signal through a parameter adjustment law. Specifically, the parameter adjustment law is: where, D(k) represents the duty cycle of the switching transistors of the full-bridge circuit at the k-th time step, It represents the duty cycle of the switching tubes in the full-bridge circuit at the (k + 1)-th time step. It represents the proportionality coefficient. It represents the integral coefficient. It represents the discrete control period. It represents the error signal at the i-th time step. Among them, It represents the phase shift angle between the driving signals of the switching tubes in the first full-bridge circuit and the second full-bridge circuit in the dual-active-bridge circuit at the (k + 1)-th time step. It represents the phase shift angle between the driving signals of the switching tubes at the input end of the first full-bridge circuit and the output end of the second full-bridge circuit in the dual-active-bridge circuit at the k-th time step. It represents the sign function, which is used to judge the positive and negative of the error signal e.

[0021] Furthermore, the control dead-time module includes: The smooth transition module is used to achieve the smooth transition of the phase shift angle by adopting a transition strategy when switching between the boost mode and the buck mode. Specifically, the transition strategy is: Among them, It represents the phase shift angle between the driving signals of the switching tubes in the input-side and output-side full-bridge circuits in the dual-active-bridge circuit at time t. It represents the initial value of the phase shift angle, that is, the magnitude of the phase shift angle at the start time of the switching between the boost mode and the buck mode, i.e., t = 0. τ represents the time constant, and t represents the time variable, which starts timing from the start time of the mode switching. The dynamic dead-time adjustment module is used to monitor the change value of the phase shift angle and dynamically adjust the dead time based on the change value of the phase shift angle through the dynamic dead-time model. Specifically, the dynamic dead-time model is: Among them, It represents the dead time at time t. It represents the preset basic dead time. It represents the reference value preset under room temperature conditions. It represents the temperature of the semiconductor junction inside the switching device. It represents the room temperature. It represents the maximum temperature allowed for the semiconductor junction inside the switching device. It represents the instantaneous change rate of the leakage inductance current of the transformer. It represents the rated current passing through the dual-active bridge. β represents the action weight coefficient of the phase shift angle dynamic term on the dead time. It represents the change amount of the phase shift angle at time t relative to the previous moment. represents the maximum allowable phase shift angle, represents the attenuation weight coefficient.

[0022] Advantages of the present invention: Stepless voltage regulation is achieved. By continuously changing the duty cycle and phase shift angle of the full-bridge switching tubes, the output voltage can be continuously adjusted within a wide range to meet the diverse voltage requirements of different loads. Compared with the traditional stepwise voltage regulation method, it has higher flexibility and adaptability; Precise power transfer control. The combination of phase shift control and dynamic duty cycle modulation enables the system to accurately control the direction and magnitude of power transfer according to actual needs. Whether in the boost or buck mode, efficient and stable power conversion can be achieved, improving energy utilization efficiency; The establishment of a two-way voltage regulation mathematical model and the introduction of an error feedback control mechanism can monitor and adjust the output voltage in real time, effectively reducing the error between the output voltage and the target voltage, improving the accuracy and stability of the output voltage, and providing a more stable and reliable power supply for the load; Enhanced system stability. When switching between the boost and buck modes, the smooth transition strategy of the phase shift angle avoids voltage jumps and reduces the impact on the load and the system. At the same time, the dynamic dead time adjustment optimizes the dead time in real time according to the system operating state to prevent the switching tubes from experiencing shoot-through phenomena, improving the reliability and stability of the system; The dynamic duty cycle modulation and phase shift control can adjust the working state of the system in real time according to load changes, reducing unnecessary energy losses; The dynamic dead time adjustment shortens the dead time while ensuring safety, reducing switching losses, thereby improving the energy conversion efficiency of the entire system; The two-way stepless voltage regulation and power transfer control capabilities make it applicable to a variety of application scenarios, such as new energy energy storage systems, electric vehicle charging and discharging, uninterruptible power supplies, etc., and can meet the high-performance requirements of power supply systems in different fields. Description of the Drawings

[0023] Figure 1 is a schematic diagram of a stepless voltage regulation method with a two-way voltage regulation function according to the present invention. Detailed Embodiments

[0024] In order to more clearly understand the above objects, features, and advantages of the present invention, the present invention will be described in detail below with reference to the drawings and specific embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0025] Many specific details are set forth in the following description in order to fully understand the present invention. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the description of the present invention herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention.

[0027] An embodiment of the present invention is a stepless voltage regulation method with bidirectional voltage regulation function. The stepless voltage regulation method with bidirectional voltage regulation function is based on a symmetrical topology of a dual active bridge. The symmetrical topology of the dual active bridge includes two full-bridge circuits and an isolation transformer, and supports bidirectional energy flow. The specific steps include: The relationship between the input voltage at the input end of the first full-bridge circuit and the output voltage at the output end of the second full-bridge circuit is constructed through the turns ratio of the isolation transformer and the duty cycle of the full-bridge switching tubes to achieve stepless voltage regulation of the output voltage. Then, power transmission control is achieved through the combination of phase-shift control and dynamic duty-cycle modulation; After establishing a mathematical model for bidirectional voltage regulation, precise control of the output voltage at the output end of the second full-bridge circuit is further achieved; The output voltage at the output end of the second full-bridge circuit is detected in real time, compared with the target voltage to generate an error signal, and the control parameters are adjusted according to the error signal through a parameter adjustment law; When switching between the boost and buck modes, a transition strategy is adopted to achieve smooth transition of the phase-shift angle to avoid voltage jumps, and the dead time is dynamically adjusted based on the change value during the smooth transition of the phase-shift angle.

[0028] The working principle and effects of the above technical solution are as follows: It realizes bidirectional stepless voltage regulation and power transmission control around the dual active bridge (DAB) circuit. The core is to comprehensively use various control means to accurately regulate the output voltage. By establishing the relationship between the input voltage at the input end of the first full-bridge circuit and the output voltage at the output end of the second full-bridge circuit through the turns ratio of the isolation transformer and the duty cycle of the full-bridge switching tubes, the magnitude of the output voltage can be continuously adjusted by continuously changing the duty cycle, thus realizing stepless voltage regulation of the output voltage. A method combining phase-shift control and dynamic duty-cycle modulation is adopted. Phase-shift control controls the direction and magnitude of energy transmission by adjusting the phase-shift angle between the drive signals of the switching tubes in the first full-bridge circuit and the second full-bridge circuit. Dynamic duty-cycle modulation works in coordination with phase-shift control by adjusting the on-time of the switching tubes in real time according to system requirements to achieve precise control of power transmission. A bidirectional voltage-regulation mathematical model is established, which can accurately calculate the control parameters required to achieve the desired output voltage according to the input and operating states of the system, so as to achieve precise control of the output voltage at the output end of the second full-bridge circuit. The output voltage at the output end of the second full-bridge circuit is detected in real time and compared with the target voltage to generate an error signal. According to the error signal, the control parameters (duty cycle and phase-shift angle) are adjusted through the parameter adjustment law to form a closed-loop control, making the output voltage continuously approach the target voltage. When switching between the boost and buck modes, a transition strategy is adopted to achieve smooth transition of the phase-shift angle, avoiding output voltage jumps caused by sudden changes in the phase-shift angle. At the same time, based on the change value during the smooth transition of the phase-shift angle, the dead time is dynamically adjusted through the dynamic dead-time adjustment formula to ensure the safe and reliable operation of the switching tubes and reduce switching losses.Stepless voltage regulation is achieved. By continuously changing the duty cycle and phase-shift angle of the full-bridge switching transistors, the output voltage can be continuously adjusted within a wide range, meeting the diverse voltage requirements of different loads. Compared with traditional stepwise voltage regulation methods, it has higher flexibility and adaptability; precise power transfer control. The combination of phase-shift control and dynamic duty-cycle modulation enables the system to accurately control the direction and magnitude of power transfer according to actual needs. Whether in boost or buck mode, efficient and stable power conversion can be achieved, improving energy utilization efficiency; the establishment of a bidirectional voltage regulation mathematical model and the introduction of an error feedback control mechanism can monitor and adjust the output voltage in real time, effectively reducing the error between the output voltage and the target voltage, improving the accuracy and stability of the output voltage, and providing a more stable and reliable power supply for the load; enhancing system stability. When switching between boost and buck modes, the smooth transition strategy of the phase-shift angle avoids voltage jumps and reduces the impact on the load and the system. At the same time, the dynamic dead-time adjustment optimizes the dead time in real time according to the system operating state, preventing the switching transistors from experiencing shoot-through phenomena, and improving the reliability and stability of the system; dynamic duty-cycle modulation and phase-shift control can adjust the working state of the system in real time according to load changes, reducing unnecessary energy losses; the dynamic dead-time adjustment shortens the dead time while ensuring safety, reducing switching losses, thereby improving the energy conversion efficiency of the entire system; the bidirectional stepless voltage regulation and power transfer control capabilities make it suitable for a variety of application scenarios, such as new energy energy storage systems, electric vehicle charging and discharging, uninterruptible power supplies, etc., and can meet the high-performance requirements of power supply systems in different fields.

[0029] In one embodiment of the present invention, stepless voltage regulation of the output voltage is achieved by constructing the relationship between the input voltage at the input end of the first full-bridge circuit and the output voltage at the output end of the second full-bridge circuit through the turns ratio of the isolation transformer and the duty cycle of the full-bridge switching transistors. Then, power transfer control is achieved through the combination of phase-shift control and dynamic duty-cycle modulation, including: Controlling the amplitude of the output voltage at the output end of the second full-bridge circuit through the input-output voltage relationship model. Specifically, the input-output voltage relationship model is:

[0030] Wherein, represents the output voltage at the output end of the second full-bridge circuit, n represents the turns ratio of the isolation transformer, D represents the duty cycle of the switching transistors in the first full-bridge circuit, represents the input voltage at the input end of the first full-bridge circuit; Then, based on the power transfer model, the control of power transfer is achieved by adjusting the phase difference between the first full-bridge circuit and the second full-bridge circuit and the output voltage at the output end of the second full-bridge circuit. Specifically, the power transfer model is:

[0031] where \(P\) represents the magnitude of the active power between the first full-bridge circuit and the second full-bridge circuit in the dual-active-bridge circuit, \(f\) represents the switching frequency, \(L\) represents the leakage inductance of the isolation transformer, and \(\varphi\) represents the phase difference between the first full-bridge circuit and the second full-bridge circuit.

[0032] The working principle and effects of the above technical solution are as follows: The input-output voltage relationship model establishes the relationship between the voltage at the input end of the first full-bridge circuit, the turns ratio of the isolation transformer, the duty cycle of the switching tubes in the first full-bridge circuit, and the voltage at the output end of the second full-bridge circuit. By changing the duty cycle, the amplitude of the output voltage can be directly controlled. For example, when it is necessary to increase the output voltage, the duty cycle can be increased; if the input voltage fluctuates, the output voltage can also be maintained stable by adjusting the duty cycle. The power transfer model describes the relationship between the active power between the first full-bridge circuit and the second full-bridge circuit in the dual-active-bridge circuit and the input-output voltage, switching frequency, leakage inductance of the isolation transformer, and the phase difference between the two bridge circuits. By adjusting the phase difference and the already controlled output voltage, the control of power transfer can be achieved. When it is necessary to increase power transfer, the phase difference can be appropriately increased; conversely, it is decreased. The voltage regulation is flexible, and the amplitude of the output voltage can be conveniently adjusted according to the requirements of the load. Whether it is step-up or step-down, it can be achieved by changing the duty cycle, adapting to the diverse voltage requirements of different loads. The voltage stability is high. When the input voltage fluctuates, the duty cycle can be adjusted in a timely manner to keep the output voltage relatively stable, providing a reliable power supply for the load. The power regulation is precise. By adjusting the phase difference and the output voltage, the active power transfer between the two bridges in the dual-active-bridge circuit can be precisely controlled, meeting the power transfer requirements under different working conditions, improving the energy utilization efficiency, supporting bidirectional power transfer, that is, energy can be transferred from the input side of the first full-bridge circuit to the output side of the second full-bridge circuit (such as in the step-up mode), or it can be transferred in the reverse direction (such as in the step-down mode), suitable for application scenarios where energy bidirectional flow is required, such as the charge and discharge of energy storage systems.

[0033] In one embodiment of the present invention, a bidirectional voltage regulation mathematical model is established to further precisely control the output voltage at the output end of the second full-bridge circuit, including: When the preset step-up mode is , energy is transferred from the input side of the first full-bridge circuit to the output side of the second full-bridge circuit. When in the step-down mode, , energy is transferred from the output side of the second full-bridge circuit to the input side of the first full-bridge circuit; After realizing the power transfer control, then the output voltage at the output end of the second full-bridge circuit is controlled through the bidirectional voltage regulation mathematical model. Specifically, the bidirectional voltage regulation mathematical model is:

[0034] Among them, R represents the equivalent resistance value presented by the load connected to the output terminal of the second full-bridge circuit in the dual-active-bridge circuit.

[0035] The working principle and effects of the above technical solution are as follows: In a dual-active-bridge (DAB) circuit, the phase-shift angle is a key parameter for controlling the power transmission direction and magnitude. When the preset boost mode is set, , at this time, there is a positive phase difference between the switching tube drive signals of the first full-bridge circuit and the second full-bridge circuit. This phase difference enables the first full-bridge circuit to input electrical energy to the isolation transformer. After the voltage transformation of the transformer, the energy is transmitted from the input side of the first full-bridge circuit to the output side of the second full-bridge circuit, realizing the boost function and providing electrical energy higher than the input voltage for the load; in the buck mode, set , and the phase difference between the switching tube drive signals of the two bridge circuits is negative. This changes the energy transmission direction, enabling the energy to be reversely transmitted from the output side of the second full-bridge circuit to the input side of the first full-bridge circuit, achieving the purpose of bucking, and the electrical energy at the load end can be fed back to the power supply side or bucked. After completing the control of the power transmission direction and magnitude, it is necessary to precisely control the output voltage at the output terminal of the second full-bridge circuit. The bidirectional voltage regulation mathematical model considers the influence of multiple key factors on the output voltage, including the transformer turns ratio and the duty cycle: the transformer turns ratio determines the basic voltage transformation ratio, and the duty cycle of the full-bridge switching tube controls the effective action time of the input voltage within a switching cycle. The two jointly affect the magnitude of the output voltage; the phase-shift angle affects the output voltage through a sine function; during the boost or buck process, changing the phase-shift angle can adjust the energy transmission between the two bridges, thereby affecting the output voltage; The switching frequency, transformer leakage inductance, and load equivalent resistance together constitute the This item reflects the influence of the circuit characteristics and load conditions on the output voltage. The load equivalent resistance R reflects the impedance characteristics of the load. Different loads will cause changes in the output voltage. Through this model, the control parameters can be adjusted according to the load conditions to stabilize the output voltage. Realize bidirectional power transmission and voltage regulation, with flexible working modes. By controlling the positive and negative of the phase shift angle, it is convenient to switch between the step-up and step-down working modes, meeting the requirements for voltage rise and fall in different application scenarios. For example, in a new energy energy storage system, the buck mode can be adopted during charging to step down the grid power and store it in the battery; during discharging, the boost mode is used to step up the battery power and feed it into the grid. Precise voltage control. The bidirectional voltage regulation mathematical model takes into account the influence of various factors on the output voltage. It can accurately control the output voltage at the output end of the second full-bridge circuit by adjusting control parameters such as the duty cycle and phase shift angle according to the actual circuit parameters and load conditions, so that the output voltage is stabilized at the desired value. Improve the adaptability and stability of the system, adapt to different loads. The load equivalent resistance is included in the model, enabling the system to automatically adjust the output voltage according to the load changes. When the load changes, by adjusting the control parameters, the stability of the output voltage is ensured, improving the adaptability of the system to different loads. Enhance system stability: Through precise control of power transmission and output voltage, voltage fluctuations and power surges are reduced, improving the stability of the entire system. During the mode switching process, smooth transition can also be achieved by reasonably adjusting the phase shift angle and duty cycle, avoiding voltage jumps from damaging the load and the system. Improve energy utilization efficiency and optimize energy transmission. In different working modes, it can accurately control power transmission and output voltage according to actual needs, reducing energy losses during transmission and conversion, and improving energy utilization efficiency. For example, during bidirectional charging and discharging, reasonable voltage and power control can reduce the charging and discharging losses of the battery and extend the battery life.

[0036] In one embodiment of the present invention, the output voltage at the output end of the second full-bridge circuit is detected in real time, compared with the target voltage to generate an error signal, and the control parameters are adjusted according to the error signal through a parameter adjustment law, including: Detect the output voltage at the output end of the second full-bridge circuit in real time, and compare it with the target output voltage to generate an error signal: , where e represents the error signal, represents the target output voltage of the second full-bridge circuit, represents the actually detected output voltage at the output end of the second full-bridge circuit; Based on the error signal, adjust the duty cycle and phase shift angle of the switching tubes of the full-bridge circuit through a parameter adjustment rate. Specifically, the parameter adjustment law is:

[0037] Where, denotes the duty cycle of the switching transistors in the full-bridge circuit at the k-th time step, denotes the duty cycle of the switching transistors in the full-bridge circuit at the (k + 1)-th time step, denotes the proportionality coefficient, denotes the integral coefficient, denotes the discrete control period, denotes the error signal at the i-th time step;

[0038] wherein, denotes the phase shift angle between the driving signals of the switching transistors in the first full-bridge circuit and the second full-bridge circuit in the dual-active-bridge (DAB) circuit at the (k + 1)-th time step, denotes the phase shift angle between the driving signals of the switching transistors at the input terminal of the first full-bridge circuit and the output terminal of the second full-bridge circuit in the dual-active-bridge circuit at the k-th time step, denotes the sign function, which is used to judge the positive and negative of the error signal e.

[0039] The working principle and effect of the above technical solution are as follows: Error signal generation. In the dual-active-bridge (DAB) circuit, in order to accurately control the voltage at the output terminal of the second full-bridge circuit, it is necessary to monitor its actual output voltage in real time, compare it with the preset target output voltage, and obtain the error signal through subtraction operation. This error signal reflects the deviation between the actual output voltage and the target value. If e is greater than 0, it means that the actual output voltage is lower than the target value; if e < 0, it indicates that the actual output voltage is higher than the target value; if e is equal to 0, it means that the actual output voltage is exactly equal to the target value. Duty cycle adjustment adopts the proportional-integral (PI) control algorithm. The proportional control part of the parameter adjustment law multiplies the proportionality coefficient by the current error signal. Its function is to immediately generate a change in the control quantity according to the magnitude of the current error. If the error is large, the proportional term will cause a large adjustment of the duty cycle to quickly reduce the error. For example, when the actual output voltage is much lower than the target value, the proportional term will cause the duty cycle to increase rapidly, thereby increasing the output voltage. The integral control part multiplies the integral coefficient by the sum of the error signals of all past time steps. The integral action is mainly used to eliminate the steady-state error of the system. Even if the error signal is very small, with the accumulation of time, the integral term will continue to increase or decrease, continuously adjusting the duty cycle until the error is eliminated. The sign function is used to judge the positive and negative of the error signal, which determines the direction of the phase shift angle adjustment. If the actual output voltage is lower than the target value, the phase shift angle will be adjusted in the increasing direction; if the actual output voltage is higher than the target value, the phase shift angle will be adjusted in the decreasing direction; The coefficient is used to adjust the amplitude of the phase shift angle adjustment, making the adjustment amount proportional to the square root of the error. Such a design allows for a larger adjustment amplitude when the error is large, quickly approaching the target value; when the error is small, the adjustment amplitude is correspondingly reduced to avoid over-adjustment. Precise voltage control, fast response, proportional control, and phase shift angle adjustment based on the square root of the error can quickly adjust the duty cycle and phase shift angle according to the current error, causing the output voltage to rapidly approach the target value. When the system is disturbed or the load changes, causing the output voltage to deviate from the target value, the controller can respond within a short time to reduce the error; to eliminate the steady-state error, the integral control part continuously accumulates the error signal and continuously adjusts the duty cycle, ultimately eliminating the steady-state error of the system and stabilizing the actual output voltage near the target value, improving the accuracy of voltage control; the control algorithm can adaptively adjust the duty cycle and phase shift angle according to the magnitude and sign of the error, avoiding problems of over-adjustment or under-adjustment. During the operation of the system, whether it is a small disturbance or a large load change, the output voltage can be kept stable through reasonable adjustment. During the adjustment process, the changes in the duty cycle and phase shift angle are continuous, avoiding voltage mutations, enabling the system to achieve smooth transitions under different operating conditions, reducing the impact on the load and circuit components, and improving the reliability of the system; this control scheme does not rely on an accurate system model and has strong robustness to system parameter changes and external disturbances. For example, when parameters such as transformer parameters and load resistance change, the controller can still ensure the stability of the output voltage by adjusting the duty cycle and phase shift angle in real time.

[0040] In one embodiment of the present invention, when switching between the boost and buck modes, a transition strategy is adopted to achieve smooth transition of the phase shift angle to avoid voltage jumps, and the dead time is dynamically adjusted based on the change value during the smooth transition of the phase shift angle, including: When switching between the boost and buck modes, a transition strategy is adopted to achieve smooth transition of the phase shift angle. Specifically, the transition strategy is:

[0041] Wherein, represents the phase shift angle between the drive signals of the full-bridge circuit switch tubes on the input side and the output side in the dual-active-bridge circuit at time t, represents the initial value of the phase shift angle, that is, the magnitude of the phase shift angle at the start time of the boost and buck mode switching, i.e., t = 0. τ represents the time constant, and t represents the time variable, starting from the start time of the mode switching for timing; Monitor the change value of the phase shift angle, and dynamically adjust the dead time based on the change value of the phase shift angle through the dynamic dead time model. Specifically, the dynamic dead time model is: Wherein, represents the dead time at time t, Indicates the preset basic dead time. Indicates the preset reference value under room temperature conditions. Indicates the temperature of the semiconductor junction inside the switching device. Indicates room temperature, Indicates the maximum temperature allowed by the semiconductor junction inside the switching device. Indicates the instantaneous change rate of transformer leakage inductance current, represents the rated current through the dual active bridge, β represents the weight coefficient of the phase shift angle dynamic term on the dead time, It represents the change of phase shift angle at time t relative to the previous time. represents the maximum permissible phase shift angle, Represents the decay weight coefficient.

[0042] The working principle and effect of the above technical solution are as follows: During the switching process between the boost and buck modes of the dual active bridge (DAB) circuit, the sudden change of the phase shift angle may cause problems such as output voltage jump, power impact and electromagnetic interference. Therefore, a transition strategy is adopted to achieve a smooth transition of the phase shift angle based on the characteristics of the exponential function. When the mode switching starts, , that is, the phase shift angle changes from the initial value, as time increases, The value of gradually decreases, and the phase shift angle gradually approaches the target value. The time constant determines the speed of change of the phase shift angle. The larger the time constant, the slower the phase shift angle changes; the smaller the time constant, the faster the phase shift angle changes. By reasonably selecting the value of the time constant, the phase shift angle can smoothly transition from the initial value to the target value during the mode switching process, avoiding sudden changes in the phase shift angle; the dead time is a time interval set to prevent the upper and lower switches on the same bridge arm from being turned on at the same time. During the mode switching process, changes in the phase shift angle will cause changes in current and voltage, thereby affecting the working state of the switch tube; in order to ensure the safe and reliable operation of the switch tube, it is necessary to dynamically adjust the dead time according to the change in the phase shift angle. The influence of the junction temperature of the switching device is considered in part. As the junction temperature increases, the performance of the switching device will change. Through this part of the adjustment coefficient, the dead time can adapt to the temperature change and ensure the safe operation of the switch tube at different temperatures. It reflects the rate of change of the transformer leakage inductance current. When the current slope is large, the switching process of the switch tube may be more complicated, and the dead time needs to be appropriately increased to avoid the bridge arm from being directly connected. The change in the phase shift angle is taken into consideration. The greater the change in the phase shift angle, the more drastic the change in the working state of the switch tube, and the dead time needs to be adjusted accordingly. The error between the actual output voltage and the target output voltage is considered. When the voltage error is large, the system may be in an unstable state, and appropriately increasing the dead time can improve the safety of the system; when the voltage error is small, reducing the dead time can reduce the switching loss; the smooth transition of the phase-shifting angle reduces the voltage jump. The smooth transition of the phase-shifting angle avoids the output voltage jump caused by the sudden change of the phase-shifting angle, enabling the output voltage to smoothly transition from one stable value to another. This is crucial for loads with high requirements for voltage stability (such as precision electronic equipment), and can reduce the damage to the load caused by voltage fluctuations; reduce the power impact. During the mode switching process, the smooth change of the phase-shifting angle reduces the sudden change of power, reducing the power impact on the power supply and the load. This helps to improve the reliability and stability of the system and extend the service life of the equipment; reduce electromagnetic interference. The smooth transition of the phase-shifting angle reduces the sudden changes of voltage and current, thereby reducing the generation of electromagnetic interference. This is of great significance for application scenarios with high requirements for electromagnetic compatibility (such as communication equipment, medical equipment, etc.), and can reduce the interference to surrounding electronic equipment; dynamic dead time adjustment improves the safety of the switching tube. Dynamic dead time adjustment can adjust the dead time in real time according to the actual working state of the switching tube (such as temperature, current slope, phase-shifting angle change, etc.), avoiding the occurrence of the through phenomenon of the bridge arm and improving the safety and reliability of the switching tube; reduce the switching loss. When the system is operating stably and the voltage error is small, the switching loss can be reduced by reducing the dead time, improving the energy conversion efficiency of the system. For example, during steady-state operation, appropriately shortening the dead time can reduce the on and off time of the switching tube and reduce the energy loss during the switching process; enhance the system adaptability. This model comprehensively considers the influence of various factors on the dead time, enabling the dead time to adapt to different working conditions and environmental conditions. Whether it is under temperature changes, load fluctuations or mode switching, etc., it can ensure the stable operation of the system, enhancing the adaptability and robustness of the system.

[0043] An embodiment of the present invention, a stepless voltage regulating device with bidirectional voltage regulating function, the device includes: A power transmission control module, used to realize stepless voltage regulation of the output voltage by constructing the relationship between the input voltage at the input end of the first full-bridge circuit and the output voltage at the output end of the second full-bridge circuit through the turns ratio of the isolation transformer and the duty cycle of the full-bridge switching tubes, and then realize power transmission control through the combination of phase-shift control and dynamic duty cycle modulation; A bidirectional control module, used to further precisely control the output voltage at the output end of the second full-bridge circuit after establishing a bidirectional voltage regulation mathematical model; An adjustment control parameter module, used to detect the output voltage at the output end of the second full-bridge circuit in real time, compare it with the target voltage to generate an error signal, and adjust the control parameters according to the error signal through a parameter adjustment law; A control dead-time module is used to adopt a transition strategy to achieve smooth transition of the phase-shift angle to avoid voltage jumps when switching between the boost and buck modes, and dynamically adjust the dead time based on the change value during the smooth transition of the phase-shift angle.

[0044] In one embodiment of the present invention, the power transmission control module includes: A control input-output voltage relationship module is used to control the output voltage amplitude at the output end of the second full-bridge circuit through an input-output voltage relationship model. Specifically, the input-output voltage relationship model is:

[0045] Wherein, represents the output voltage at the output end of the second full-bridge circuit, n represents the turn ratio of the isolation transformer, D represents the duty cycle of the switching tube in the first full-bridge circuit, represents the input voltage at the input end of the first full-bridge circuit; An adjustment power module is used to then control the power transmission by adjusting the phase difference between the first full-bridge circuit and the second full-bridge circuit and the output voltage at the output end of the second full-bridge circuit based on a power transmission model. Specifically, the power transmission model is:

[0046] Wherein, P represents the magnitude of the active power between the first full-bridge circuit and the second full-bridge circuit in the dual-active-bridge circuit, f represents the switching frequency, L represents the leakage inductance of the isolation transformer, represents the phase difference between the first full-bridge circuit and the second full-bridge circuit.

[0047] In one embodiment of the present invention, the bidirectional control module includes: When the preset boost mode is set, , energy is transmitted from the input side of the first full-bridge circuit to the output side of the second full-bridge circuit. When in the buck mode, , energy is transmitted from the output side of the second full-bridge circuit to the input side of the first full-bridge circuit; A bidirectional voltage regulation module is used to then control the output voltage at the output end of the second full-bridge circuit through a bidirectional voltage regulation mathematical model after achieving power transmission control. Specifically, the bidirectional voltage regulation mathematical model is:

[0048] Wherein, R represents the equivalent resistance value presented by the load connected to the output end of the second full-bridge circuit in the dual-active-bridge circuit.

[0049] In one embodiment of the present invention, the adjustment control parameter module includes: An error signal acquisition module, which is used to detect the output voltage at the output end of the second full-bridge circuit in real time, compare it with the target output voltage, and generate an error signal: , where e represents the error signal, represents the target output voltage of the second full-bridge circuit, represents the actual detected output voltage at the output end of the second full-bridge circuit; A duty cycle and phase shift angle adjustment module, which is used to adjust the duty cycle and phase shift angle of the switching tubes of the full-bridge circuit based on the error signal through a parameter adjustment rate. Specifically, the parameter adjustment law is:

[0050] where, represents the duty cycle of the switching tubes of the full-bridge circuit at the k-th time step, represents the duty cycle of the switching tubes of the full-bridge circuit at the (k + 1)-th time step, represents the proportionality coefficient, represents the integral coefficient, represents the discrete control period, represents the error signal at the i-th time step;

[0051] where, represents the phase shift angle between the driving signals of the switching tubes of the first full-bridge circuit and the second full-bridge circuit in the dual-active-bridge circuit at the (k + 1)-th time step, represents the phase shift angle between the driving signals of the switching tubes at the input end of the first full-bridge circuit and the output end of the second full-bridge circuit in the dual-active-bridge circuit at the k-th time step, represents the sign function, which is used to judge the positive and negative of the error signal e.

[0052] In an embodiment of the present invention, the control dead time module includes: A smooth transition module, which is used to achieve a smooth transition of the phase shift angle by adopting a transition strategy when switching between the boost and buck modes. Specifically, the transition strategy is:

[0053] where, represents the phase shift angle between the driving signals of the switching tubes of the full-bridge circuits on the input side and the output side in the dual-active-bridge circuit at time t, represents the initial value of the phase shift angle, that is, the phase shift angle at the start time of the boost and buck mode switching, i.e., t = 0. τ represents the time constant, and t represents the time variable, which starts timing from the start time of the mode switching; The dynamic dead-time adjustment module is used to monitor the change value of the phase-shift angle and dynamically adjust the dead time based on the change value of the phase-shift angle through a dynamic dead-time model. Specifically, the dynamic dead-time model is as follows: Wherein, represents the dead time at time t, represents the preset basic dead time, represents the reference value preset under room temperature conditions, represents the temperature of the semiconductor junction inside the switching device, represents the room temperature, represents the maximum allowable temperature of the semiconductor junction inside the switching device, represents the instantaneous change rate of the transformer leakage inductance current, represents the rated current passing through the dual-active bridge, and β represents the action weight coefficient of the phase-shift angle dynamic term on the dead time, represents the change amount of the phase-shift angle at time t relative to the previous moment, represents the maximum allowable phase-shift angle, represents the attenuation weight coefficient.

[0054] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A stepless voltage regulation method with bidirectional voltage regulation function, characterized in that: The stepless voltage regulation method with bidirectional voltage regulation function is based on a symmetrical topological structure of a dual active bridge, wherein the symmetrical topological structure of the dual active bridge includes two sets of full bridge circuits and an isolation transformer, supports bidirectional energy flow, and the specific steps include: The relationship between the input voltage at the input end of the first full-bridge circuit and the output voltage at the output end of the second full-bridge circuit is established by the turns ratio of the isolation transformer and the duty cycle of the full-bridge switch tube to achieve stepless output voltage regulation, and then power transmission control is achieved by combining phase shift control with dynamic duty cycle modulation. After establishing the bidirectional voltage regulation mathematical model, the output voltage at the output end of the second full-bridge circuit is further precisely controlled; detecting the output voltage of the output end of the second full-bridge circuit in real time, comparing it with the target voltage to generate an error signal, and adjusting the control parameter through a parameter adjustment law according to the error signal; When switching between the boost and buck modes, a transition strategy is used to achieve a smooth transition of the phase shift angle to avoid voltage jumps, and the dead time is dynamically adjusted based on the change value of the phase shift angle during the smooth transition.

2. According to claim 1, a stepless voltage regulation method with bidirectional voltage regulation function is characterized in that: The relationship between the input voltage at the input end of the first full-bridge circuit and the output voltage at the output end of the second full-bridge circuit is established by the turns ratio of the isolation transformer and the duty cycle of the full-bridge switch tube to realize stepless voltage regulation of the output voltage, and then the power transmission control is realized by combining phase shift control with dynamic duty cycle modulation, including: The output voltage amplitude of the output end of the second full-bridge circuit is controlled by the input-output voltage relationship model. Specifically, the input-output voltage relationship model is: in, represents the output voltage of the output end of the second full-bridge circuit, n represents the turns ratio of the isolation transformer, D represents the duty cycle of the switch tube in the first full-bridge circuit, represents the input voltage at the input end of the first full-bridge circuit; Then, based on the power transmission model, the power transmission is controlled by adjusting the phase difference between the first full-bridge circuit and the second full-bridge circuit and the output voltage at the output end of the second full-bridge circuit. Specifically, the power transmission model is: Wherein, P represents the active power between the first full-bridge circuit and the second full-bridge circuit in the dual active bridge circuit, f represents the switching frequency, and L represents the leakage inductance of the isolation transformer. represents the phase difference between the first full-bridge circuit and the second full-bridge circuit.

3. The stepless voltage regulation method with bidirectional voltage regulation function according to claim 1, characterized in that: A bidirectional voltage regulation mathematical model is established to further achieve precise control of the output voltage at the output end of the second full-bridge circuit, including: When the boost mode is preset, , energy is transferred from the input side of the first full-bridge circuit to the output side of the second full-bridge circuit. In buck mode, , energy is transferred from the output side of the second full-bridge circuit to the input side of the first full-bridge circuit; After the power transmission control is realized, the output voltage at the output end of the second full-bridge circuit is then controlled by a bidirectional voltage regulation mathematical model. Specifically, the bidirectional voltage regulation mathematical model is: Wherein, R represents the equivalent resistance value presented by the load connected to the output end of the second full-bridge circuit in the dual active bridge circuit.

4. The stepless voltage regulation method with bidirectional voltage regulation function according to claim 1, characterized in that: The output voltage of the output terminal of the second full-bridge circuit is detected in real time, the output voltage is compared with the target voltage to generate an error signal, and the control parameter is adjusted according to the error signal through the parameter adjustment law, including: The output voltage at the output end of the second full-bridge circuit is detected in real time, and compared with the target output voltage to generate an error signal: , where e represents the error signal, represents the target output voltage of the second full-bridge circuit, represents the output voltage of the output terminal of the second full-bridge circuit actually detected; The duty cycle and phase shift angle of the full-bridge circuit switch are adjusted by a parameter adjustment rate based on the error signal. Specifically, the parameter adjustment law is: in, represents the duty cycle of the full-bridge circuit switch at the kth time step, represents the duty cycle of the full-bridge circuit switch at the k+1th time step, represents the proportionality coefficient, represents the integral coefficient, represents the discrete control cycle, represents the error signal at the i-th time step; in, represents the phase shift angle between the switch drive signals of the first full-bridge circuit and the second full-bridge circuit in the dual active bridge circuit at the k+1th time step, It represents the phase shift angle between the switch tube drive signals at the input end of the first full-bridge circuit and the output end of the second full-bridge circuit in the dual active bridge circuit at the kth time step, Represents the sign function, which is used to determine the positive or negative nature of the error signal e.

5. The stepless voltage regulation method with bidirectional voltage regulation function according to claim 1, characterized in that: When switching between boost and buck modes, a transition strategy is used to achieve a smooth transition of the phase shift angle to avoid voltage jumps. The dead time is dynamically adjusted based on the change in the phase shift angle during smooth transition, including: When switching between the boost mode and the buck mode, a transition strategy is used to achieve a smooth transition of the phase shift angle. Specifically, the transition strategy is: in, It represents the phase shift angle between the input side and output side full bridge circuit switch tube drive signals in the dual active bridge circuit at time t, represents the initial value of the phase shift angle, that is, the phase shift angle at the start of the step-up and step-down mode switching, i.e., t=0, τ represents the time constant, t represents the time variable, and the timing is started from the start of the mode switching; Monitor the phase shift angle change value, and dynamically adjust the dead time through a dynamic dead time model based on the phase shift angle change value. Specifically, the dynamic dead time model is: in, represents the dead time at time t, Indicates the preset basic dead time. Indicates the preset reference value under room temperature conditions. Indicates the temperature of the semiconductor junction inside the switching device. Indicates room temperature, Indicates the maximum temperature allowed by the semiconductor junction inside the switching device. Indicates the instantaneous change rate of transformer leakage inductance current, represents the rated current through the dual active bridge, β represents the weight coefficient of the phase shift angle dynamic term on the dead time, It represents the change of phase shift angle at time t relative to the previous time. represents the maximum permissible phase shift angle, Represents the decay weight coefficient.

6. A stepless voltage regulating device with bidirectional voltage regulating function, characterized in that: The device comprises: A power transmission control module is used to construct a relationship between an input voltage at an input end of a first full-bridge circuit and an output voltage at an output end of a second full-bridge circuit by using the turns ratio of an isolation transformer and a duty cycle of a full-bridge switch tube to achieve stepless output voltage regulation, and then achieve power transmission control by combining phase shift control with dynamic duty cycle modulation; A bidirectional control module, used to establish a bidirectional voltage regulation mathematical model and further achieve precise control of the output voltage at the output end of the second full-bridge circuit; A control parameter adjustment module is used to detect the output voltage of the output end of the second full-bridge circuit in real time, compare it with the target voltage to generate an error signal, and adjust the control parameter through a parameter adjustment law according to the error signal; The dead time control module is used to adopt a transition strategy to achieve a smooth transition of the phase shift angle to avoid voltage jump when switching between the boost and buck modes, and dynamically adjust the dead time based on the change value of the phase shift angle during the smooth transition.

7. A stepless voltage regulating device with bidirectional voltage regulating function according to claim 6, characterized in that: The power transmission control module comprises: The input-output voltage relationship control module is used to control the output voltage amplitude of the output end of the second full-bridge circuit through the input-output voltage relationship model. Specifically, the input-output voltage relationship model is: in, represents the output voltage of the output end of the second full-bridge circuit, n represents the turns ratio of the isolation transformer, D represents the duty cycle of the switch tube in the first full-bridge circuit, represents the input voltage at the input end of the first full-bridge circuit; The power adjustment module is used to control the power transmission by adjusting the phase difference between the first full-bridge circuit and the second full-bridge circuit and the output voltage of the output end of the second full-bridge circuit based on the power transmission model. Specifically, the power transmission model is: Wherein, P represents the active power between the first full-bridge circuit and the second full-bridge circuit in the dual active bridge circuit, f represents the switching frequency, and L represents the leakage inductance of the isolation transformer. represents the phase difference between the first full-bridge circuit and the second full-bridge circuit.

8. The stepless voltage regulating device with bidirectional voltage regulating function according to claim 6, characterized in that: The bidirectional control module comprises: The preset module is used to preset the boost mode. , energy is transferred from the input side of the first full-bridge circuit to the output side of the second full-bridge circuit. In buck mode, , energy is transferred from the output side of the second full-bridge circuit to the input side of the first full-bridge circuit; The bidirectional voltage regulation module is used to control the output voltage of the output end of the second full-bridge circuit through a bidirectional voltage regulation mathematical model after realizing power transmission control. Specifically, the bidirectional voltage regulation mathematical model is: Wherein, R represents the equivalent resistance value presented by the load connected to the output end of the second full-bridge circuit in the dual active bridge circuit.

9. A stepless voltage regulating device with bidirectional voltage regulating function according to claim 6, characterized in that: The control parameter adjustment module comprises: The error signal acquisition module is used to detect the output voltage of the output end of the second full-bridge circuit in real time, and compare it with the target output voltage to generate an error signal: , where e represents the error signal, represents the target output voltage of the second full-bridge circuit, represents the output voltage of the output terminal of the second full-bridge circuit actually detected; The duty cycle and phase shift angle adjustment module is used to adjust the duty cycle and phase shift angle of the full-bridge circuit switch tube through the parameter adjustment rate based on the error signal. Specifically, the parameter adjustment law is: in, represents the duty cycle of the full-bridge circuit switch at the kth time step, represents the duty cycle of the full-bridge circuit switch at the k+1th time step, represents the proportionality coefficient, represents the integral coefficient, represents the discrete control cycle, represents the error signal at the i-th time step; in, represents the phase shift angle between the switch drive signals of the first full-bridge circuit and the second full-bridge circuit in the dual active bridge circuit at the k+1th time step, It represents the phase shift angle between the switch tube drive signals at the input end of the first full-bridge circuit and the output end of the second full-bridge circuit in the dual active bridge circuit at the kth time step, Represents the sign function, which is used to determine the positive or negative nature of the error signal e.

10. The stepless voltage regulating device with bidirectional voltage regulating function according to claim 6, characterized in that: The dead time control module comprises: The smooth transition module is used to adopt a transition strategy to achieve a smooth transition of the phase shift angle when switching between the boost mode and the buck mode. Specifically, the transition strategy is: in, It represents the phase shift angle between the input side and output side full bridge circuit switch tube drive signals in the dual active bridge circuit at time t, represents the initial value of the phase shift angle, that is, the phase shift angle at the start of the step-up and step-down mode switching, i.e., t=0, τ represents the time constant, t represents the time variable, and the timing is started from the start of the mode switching; The module for dynamically adjusting the dead time is used to monitor the change value of the phase shift angle, and dynamically adjust the dead time through a dynamic dead time model based on the change value of the phase shift angle. Specifically, the dynamic dead time model is: in, represents the dead time at time t, Indicates the preset basic dead time. Indicates the preset reference value under room temperature conditions. Indicates the temperature of the semiconductor junction inside the switching device. Indicates room temperature, Indicates the maximum temperature allowed by the semiconductor junction inside the switching device. Indicates the instantaneous change rate of transformer leakage inductance current, represents the rated current through the dual active bridge, β represents the weight coefficient of the phase shift angle dynamic term on the dead time, It represents the change of phase shift angle at time t relative to the previous time. represents the maximum permissible phase shift angle, Represents the decay weight coefficient.

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