A stepless voltage regulation method and device with bidirectional voltage regulation function

Abstract

The present invention proposes a stepless voltage regulation method and device with bidirectional voltage regulation. The method includes: establishing a relationship between the input voltage at the input end of a first full-bridge circuit and the output voltage at the output end of a second full-bridge circuit by using the turns ratio of an isolation transformer and the duty cycle of full-bridge switches to achieve stepless output voltage regulation; then combining phase shift control with dynamic duty cycle modulation to achieve power transmission control; establishing a mathematical model for bidirectional voltage regulation to further precisely control the output voltage at the output end of the second full-bridge circuit; detecting the output voltage at the output end of the second full-bridge circuit in real time, comparing it with a target voltage to generate an error signal, and adjusting control parameters based on the error signal using a parameter adjustment law; and, when switching between boost and buck modes, employing a transition strategy to achieve a smooth transition of the phase shift angle to avoid voltage jumps, and dynamically adjusting the dead time based on the change in the phase shift angle during the smooth transition. This method and corresponding device can improve the energy conversion efficiency of the circuit.

Description

Technical Field

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

[0002] Traditional voltage regulation schemes typically use a fixed dead time to prevent simultaneous conduction of the upper and lower switches in the same voltage regulator arm, thereby preventing short-circuit failures. However, this fixed dead time cannot adapt to varying operating conditions and circuit parameter variations. In some cases, a long fixed dead time can increase switching losses and reduce system efficiency. In other cases, a short fixed dead time may not guarantee safe operation of the switches, posing the risk of a voltage shoot-through. Traditional voltage regulation schemes are prone to voltage jumps when switching between boost and buck modes. This is because the conduction state of the switches and circuit parameters suddenly change during the mode transition, causing the output voltage to momentarily deviate from the target value. This voltage jump can damage the load, especially devices sensitive to voltage fluctuations. Traditional voltage regulation schemes are also prone to output voltage fluctuations when the load changes. Due to changes in circuit parameters and varying load characteristics, the output voltage may deviate from the set value when the load current increases or decreases, affecting system stability and reliability. Traditional voltage regulation methods struggle to accurately and in real time compensate for the effects of load changes on voltage. 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:

[0004] The present invention proposes a stepless voltage regulation method with a bidirectional voltage regulation function. The stepless voltage regulation method with a bidirectional voltage regulation function is based on a symmetrical topology structure of a dual active bridge. The symmetrical topology structure of the dual active bridge includes two sets of full-bridge circuits and an isolation transformer, supporting bidirectional energy flow. The specific steps include:

[0005] 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. Then, power transmission control is achieved by combining phase shift control with dynamic duty cycle modulation.

[0006] After establishing a bidirectional voltage regulation mathematical model, the output voltage at the output end of the second full-bridge circuit is further precisely controlled;

[0007] 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 the control parameters through a parameter adjustment law according to the error signal;

[0008] 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, and the dead time is dynamically adjusted based on the change in the phase shift angle during the smooth transition.

[0009] 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 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. Then, power transmission control is achieved by combining phase shift control with dynamic duty cycle modulation, including:

[0010] The output voltage amplitude of the output end of the second full-bridge circuit is controlled by an input-output voltage relationship model. Specifically, the input-output voltage relationship model is:

[0011]

[0012] in, represents the output voltage of the output end of the second full-bridge circuit, n represents the turns ratio of the isolation transformer, and 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;

[0013] 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 of the output end of the second full-bridge circuit. Specifically, the power transmission model is:

[0014]

[0015] 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.

[0016] Furthermore, a bidirectional voltage regulation mathematical model is established to further accurately control the output voltage at the output end of the second full-bridge circuit, including:

[0017] 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 and second full-bridge circuits to the input side of the first full-bridge circuit;

[0018] After power transmission control is achieved, the output voltage of the output end of the second full-bridge circuit is controlled by a bidirectional voltage regulation mathematical model. Specifically, the bidirectional voltage regulation mathematical model is:

[0019]

[0020] 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.

[0021] Detecting the output voltage of the output terminal of the second full-bridge circuit in real time, comparing it with the target voltage to generate an error signal, and adjusting the control parameters according to the error signal through a parameter adjustment law, including:

[0022] The output voltage of the second full-bridge circuit output terminal 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 actual detected output voltage at the output end of the second full-bridge circuit;

[0023] The duty cycle and phase shift angle of the full-bridge circuit switch are adjusted based on the error signal through a parameter adjustment law. Specifically, the parameter adjustment law is:

[0024]

[0025] 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 period, represents the error signal at the i-th time step;

[0026]

[0027] in, It represents the phase shift angle between the driving 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 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.

[0028] Furthermore, 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 the smooth transition, including:

[0029] When switching between the boost and buck modes, a transition strategy is used to achieve a smooth transition of the phase shift angle. Specifically, the transition strategy is:

[0030]

[0031] in, It represents the phase shift angle between the input side and output side full bridge circuit switch 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 boost and buck mode switching, i.e., t = 0. τ represents the time constant, and t represents the time variable, which is measured from the start of the mode switching.

[0032] Monitor the phase shift angle change value, and dynamically adjust the dead time based on the phase shift angle change value through a dynamic dead time model. Specifically, the dynamic dead time model is:

[0033]

[0034] in, represents the dead time at time t, Indicates the preset basic dead time. Indicates the preset reference value at room temperature. 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 rate of change 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, Indicates the phase shift angle change at time t relative to the previous moment, represents the maximum allowable phase shift angle, Represents the attenuation weight coefficient.

[0035] The present invention proposes a stepless voltage regulating device with a bidirectional voltage regulating function, the device comprising:

[0036] A power transmission control module is used to establish 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 by using 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 realize power transmission control by combining phase shift control with dynamic duty cycle modulation;

[0037] A bidirectional control module is used to establish a bidirectional voltage regulation mathematical model and further accurately control the output voltage of the output end of the second full-bridge circuit;

[0038] a control parameter adjustment module, configured to detect the output voltage of the output terminal of the second full-bridge circuit in real time, compare the output voltage with the target voltage to generate an error signal, and adjust the control parameter according to the error signal through a parameter adjustment law;

[0039] The dead time control module is used to achieve a smooth transition of the phase shift angle to avoid voltage jumps when switching between boost and buck modes, and dynamically adjust the dead time based on the change value of the phase shift angle during the smooth transition.

[0040] Furthermore, the power transmission control module includes:

[0041] 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:

[0042]

[0043] in, represents the output voltage of the output end of the second full-bridge circuit, n represents the turns ratio of the isolation transformer, and 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;

[0044] The power adjustment module is used to control 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:

[0045]

[0046] 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.

[0047] Furthermore, the bidirectional control module includes:

[0048] 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 and second full-bridge circuits to the input side of the first full-bridge circuit;

[0049] 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:

[0050]

[0051] 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.

[0052] Furthermore, the control parameter adjustment module includes:

[0053] The error signal acquisition module is used to detect the output voltage of the second full-bridge circuit output terminal 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 actual detected output voltage at the output end of the second full-bridge circuit;

[0054] 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 a parameter adjustment rate based on the error signal. Specifically, the parameter adjustment law is:

[0055]

[0056] 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 period, represents the error signal at the i-th time step;

[0057]

[0058] in, It represents the phase shift angle between the driving 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 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.

[0059] Furthermore, the dead time control module includes:

[0060] The smooth transition module is used to implement a smooth transition of the phase shift angle using a transition strategy when switching between the boost and buck modes. Specifically, the transition strategy is:

[0061]

[0062] in, It represents the phase shift angle between the input side and output side full bridge circuit switch 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 boost and buck mode switching, i.e., t = 0. τ represents the time constant, and t represents the time variable, which is measured from the start of the mode switching.

[0063] The dynamic dead time adjustment module is used to monitor the phase shift angle change value and dynamically adjust the dead time based on the phase shift angle change value through a dynamic dead time model. Specifically, the dynamic dead time model is:

[0064]

[0065] in, represents the dead time at time t, Indicates the preset basic dead time. Indicates the preset reference value at room temperature. 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 rate of change 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, Indicates the phase shift angle change at time t relative to the previous moment, represents the maximum allowable phase shift angle, Represents the attenuation weight coefficient.

[0066] The beneficial effects of the present invention are: achieving stepless voltage regulation, and by continuously changing the duty cycle and phase shift angle of the full-bridge switch tube, being able to continuously adjust the output voltage within a wider range to meet the diverse voltage requirements of different loads, and having higher flexibility and adaptability than the traditional hierarchical voltage regulation method; precise power transmission control, the combination of phase shift control and dynamic duty cycle modulation enables the system to accurately control the direction and size of power transmission according to actual needs, and can achieve efficient and stable power conversion in both boost and buck modes, thereby 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 reduce the error between the output voltage and the target voltage, improve the accuracy and stability of the output voltage, and provide a more stable and reliable supply for the load. Power supply; enhance 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 system. At the same time, dynamic dead time adjustment optimizes the dead time in real time according to the system operating status to prevent the switch tube from being directly connected, thereby improving the reliability and stability of the system; dynamic duty cycle modulation and phase shift control can adjust the system's working state in real time according to load changes and reduce unnecessary energy loss; dynamic dead time adjustment shortens the dead time and reduces switching loss while ensuring safety, thereby improving the energy conversion efficiency of the entire system; bidirectional stepless voltage regulation and power transmission control capabilities make it suitable for a variety of application scenarios, such as new 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 This is a schematic diagram of a stepless voltage regulation method with a bidirectional voltage regulation function according to the present invention. DETAILED DESCRIPTION

[0068] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein may be combined with each other.

[0069] The following description sets forth numerous specific details to facilitate a thorough understanding of the present invention. The embodiments described are merely a portion of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0070] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0071] One embodiment of the present invention provides a stepless voltage regulation method with a bidirectional voltage regulation function. The stepless voltage regulation method with a bidirectional voltage regulation function is based on a symmetrical topology structure of a dual active bridge. The symmetrical topology structure of the dual active bridge includes two sets of full-bridge circuits and an isolation transformer, supporting bidirectional energy flow. The specific steps include:

[0072] 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. Then, power transmission control is achieved by combining phase shift control with dynamic duty cycle modulation.

[0073] After establishing a bidirectional voltage regulation mathematical model, the output voltage at the output end of the second full-bridge circuit is further precisely controlled;

[0074] 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 the control parameters through a parameter adjustment law according to the error signal;

[0075] 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, and the dead time is dynamically adjusted based on the change in the phase shift angle during the smooth transition.

[0076] The working principle and effect of the above technical solution are as follows: bidirectional stepless voltage regulation and power transmission control are realized around the dual active bridge (DAB) circuit. The core is to comprehensively use multiple control means to accurately adjust the output voltage. 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 through the turns ratio of the isolation transformer and the duty cycle of the full-bridge switch tube. By continuously changing the duty cycle, the output voltage can be continuously adjusted, thereby realizing stepless voltage regulation of the output voltage; a method combining phase shift control and dynamic duty cycle modulation is adopted. The phase shift control controls the direction and size of energy transmission by adjusting the phase shift angle between the drive signals of the switch tubes of the first full-bridge circuit and the second full-bridge circuit. The dynamic duty cycle modulation adjusts the conduction time of the switch tube in real time according to system requirements and works in conjunction with the phase shift control to achieve precise control of power transmission; a mathematical model for bidirectional voltage regulation is established, which can accurately calculate the output voltage according to the input and operating status of the system. The control parameters required to achieve the desired output voltage are calculated, thereby achieving 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; based on the error signal, the control parameters (duty cycle and phase shift angle) are adjusted through a parameter adjustment law to form a closed-loop control so that the output voltage continuously approaches the target voltage; when switching between the boost and buck modes, a transition strategy is adopted to achieve a smooth transition of the phase shift angle to avoid output voltage jumps caused by sudden changes in the phase shift angle; at the same time, based on the change value of the phase shift angle during the smooth transition, the dead time is dynamically adjusted through a dynamic dead time adjustment formula to ensure safe and reliable operation of the switch tube and reduce switching losses.It realizes stepless voltage regulation. By continuously changing the duty cycle and phase shift angle of the full-bridge switch tube, it can continuously adjust the output voltage within a wide range to meet the diverse voltage requirements of different loads. Compared with the traditional hierarchical voltage regulation method, it has higher flexibility and adaptability; precise power transmission control, the combination of phase shift control and dynamic duty cycle modulation enables the system to accurately control the direction and size of power transmission according to actual needs. Whether in boost or buck mode, it can achieve efficient and stable power conversion and improve 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 reduce the error between the output voltage and the target voltage, improve the accuracy and stability of the output voltage, and provide a more stable and reliable power supply for the load; increase Strong 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 system. At the same time, the dynamic dead time adjustment optimizes the dead time in real time according to the system operating status to prevent the switch tube from being directly connected, thereby improving the reliability and stability of the system; dynamic duty cycle modulation and phase shift control can adjust the system's working state in real time according to load changes to reduce unnecessary energy loss; dynamic dead time adjustment shortens the dead time and reduces switching loss while ensuring safety, thereby improving the energy conversion efficiency of the entire system; bidirectional stepless voltage regulation and power transmission control capabilities make it suitable for a variety of application scenarios, such as new 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.

[0077] In one embodiment of the present invention, 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 using the turns ratio of the isolation transformer and the duty cycle of the full-bridge switch tube to achieve stepless output voltage regulation. Then, power transmission control is achieved by combining phase shift control with dynamic duty cycle modulation, including:

[0078] The output voltage amplitude of the output end of the second full-bridge circuit is controlled by an input-output voltage relationship model. Specifically, the input-output voltage relationship model is:

[0079]

[0080] in, represents the output voltage of the output end of the second full-bridge circuit, n represents the turns ratio of the isolation transformer, and 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;

[0081] 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 of the output end of the second full-bridge circuit. Specifically, the power transmission model is:

[0082]

[0083] 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.

[0084] The working principle and effect of the above technical solution are as follows: The input-output voltage relationship model establishes the relationship between the input voltage of the first full-bridge circuit, the turns ratio of the isolation transformer, the duty cycle of the first full-bridge circuit's switches, and the output voltage of the second full-bridge circuit. By changing the duty cycle, the output voltage amplitude can be directly controlled. For example, when the output voltage needs to be increased, the duty cycle can be increased; if the input voltage fluctuates, the duty cycle can also be adjusted to maintain the output voltage stability. The power transmission model describes the relationship between the active power and input and output voltages, switching frequency, isolation transformer leakage inductance, and phase difference between the first and second full-bridge circuits in the dual active bridge circuit. By adjusting the phase difference and the already controlled output voltage, power transmission can be controlled. When increased power transmission is needed, the phase difference can be appropriately increased; conversely, the phase difference can be decreased. Flexible voltage regulation allows the output voltage amplitude to be easily adjusted according to load requirements. Both step-up and step-down can be achieved by varying the duty cycle, adapting to the diverse voltage requirements of different loads. High voltage stability allows timely adjustment of the duty cycle when the input voltage fluctuates, maintaining a relatively stable output voltage and providing a reliable power supply for the load. Precise power regulation allows precise control of the active power transfer between the two bridges in the dual-active bridge circuit by adjusting the phase difference and output voltage. This allows for precise control of the active power transfer between the two bridges in the dual-active bridge circuit, meeting power transmission requirements under various operating conditions and improving energy efficiency. The system supports bidirectional power transfer, transferring energy from the first full-bridge circuit to the second (e.g., in step-up mode) and in the reverse direction (e.g., in step-down mode), making it suitable for applications requiring bidirectional energy flow, such as charging and discharging of energy storage systems.

[0085] In one embodiment of the present invention, a bidirectional voltage regulation mathematical model is established to further accurately control the output voltage at the output end of the second full-bridge circuit, including:

[0086] 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 and second full-bridge circuits to the input side of the first full-bridge circuit;

[0087] After power transmission control is achieved, the output voltage of the output end of the second full-bridge circuit is controlled by a bidirectional voltage regulation mathematical model. Specifically, the bidirectional voltage regulation mathematical model is:

[0088]

[0089] 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.

[0090] The working principle and effect of the above technical solution are as follows: In the dual active bridge (DAB) circuit, the phase shift angle is the key parameter for controlling the direction and magnitude of power transmission. When the boost mode is preset, the setting At this time, there is a positive phase difference between the switch tube driving signals of the first full-bridge circuit and the second full-bridge circuit. This phase difference causes the first full-bridge circuit to input electrical energy to the isolation transformer. After the transformer's voltage transformation, the energy is transferred 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 the load with electrical energy higher than the input voltage. In the buck mode, the setting , the phase difference of the switch tube driving signal between the two bridge circuits is negative. This changes the direction of energy transmission, so that the energy is transmitted in reverse from the output side of the second full-bridge circuit to the input side of the first full-bridge circuit, achieving the purpose of voltage reduction. The electric energy at the load end can be fed back to the power supply side or subjected to voltage reduction processing. After completing the control of the direction and size of power transmission, it is necessary to accurately control the output voltage at the output end of the second full-bridge circuit. The bidirectional voltage regulation mathematical model takes into account the influence of multiple key factors on the output voltage, transformer turns ratio and duty cycle: the transformer turns ratio determines the basic conversion ratio of the voltage, and the duty cycle of the full-bridge switch tube controls the effective action time of the input voltage in one switching cycle. The two jointly affect the size of the output voltage; the phase shift angle affects the output voltage through a sine function; in the process of boosting or bucking, changing the phase shift angle can adjust the energy transfer between the two bridges, thereby affecting the output voltage;

[0091] The switching frequency, transformer leakage inductance and load equivalent resistance together constitute the denominator The term reflects the impact of circuit characteristics and load conditions on the output voltage. The load equivalent resistance R reflects the load's impedance characteristics. Different loads will cause the output voltage to vary. This model allows control parameters to be adjusted based on the load conditions to stabilize the output voltage. It achieves bidirectional power transmission and voltage regulation, and offers flexible operating modes. By controlling the positive and negative phase shift angle, it can easily switch between boost and buck operating modes, meeting the voltage fluctuation requirements of different application scenarios. For example, in a new energy storage system, during charging, the buck mode can be used to step down grid power and store it in the battery; during discharge, the boost mode is used to boost battery power and feed it back into the grid. The mathematical model for bidirectional voltage regulation accurately controls the output voltage by considering the impact of multiple factors. Based on the actual circuit parameters and load conditions, it can precisely control the output voltage at the output of the second full-bridge circuit by adjusting control parameters such as the duty cycle and phase shift angle, stabilizing the output voltage at the desired value. The model also improves the system's adaptability and stability, allowing it to adapt to different loads. The inclusion of the load equivalent resistance allows the system to automatically adjust the output voltage based on changes in the load. When the load changes, the control parameters are adjusted to ensure the output voltage remains constant. Stability is improved, and the system's adaptability to different loads is improved; Enhance system stability: Through precise control of power transmission and output voltage, voltage fluctuations and power shocks are reduced, and the stability of the entire system is improved. During the mode switching process, a smooth transition can be achieved by reasonably adjusting the phase shift angle and duty cycle to avoid damage to the load and system caused by voltage jumps; Improve energy utilization efficiency and optimize energy transmission. In different working modes, power transmission and output voltage can be precisely controlled according to actual needs, reducing energy loss during transmission and conversion, and improving energy utilization efficiency. For example, in the bidirectional charging and discharging process, reasonable voltage and power control can reduce battery charging and discharging losses and extend battery life.

[0092] In one embodiment of the present invention, 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 by a parameter adjustment law, including:

[0093] The output voltage of the second full-bridge circuit output terminal 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 actual detected output voltage at the output end of the second full-bridge circuit;

[0094] The duty cycle and phase shift angle of the full-bridge circuit switch are adjusted based on the error signal through a parameter adjustment law. Specifically, the parameter adjustment law is:

[0095]

[0096] 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 period, represents the error signal at the i-th time step;

[0097]

[0098] in, It represents the phase shift angle between the driving 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 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.

[0099] 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 end of the second full-bridge circuit, it is necessary to monitor its actual output voltage in real time and compare it with the preset target output voltage. The error signal is obtained by performing a difference 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 means 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. The duty cycle is adjusted using the proportional-integral (PI) control algorithm. The proportional coefficient of the proportional control part of the parameter adjustment law is multiplied by the current error signal. Its function is to immediately generate a duty cycle according to the size of the current error. If a control quantity changes, if the error is large, the proportional term will make a large adjustment to the duty cycle to quickly reduce the error. For example, when the actual output voltage is far lower than the target value, the proportional term will rapidly increase the duty cycle, 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 effect is mainly used to eliminate the steady-state error of the system. Even if the error signal is very small, the integral term will continue to increase or decrease as time accumulates, and the duty cycle will be continuously adjusted until the error is eliminated. The sign function is used to judge the positive or negative nature 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 direction of increase; if the actual output voltage is higher than the target value, the phase shift angle will be adjusted in the direction of decrease. The role of The coefficient adjusts the phase-shift angle adjustment so that the adjustment is proportional to the square root of the error. This design allows for larger adjustments when the error is large, quickly approaching the target value; when the error is small, the adjustment is reduced to avoid over-adjustment. Precise voltage control, fast response, proportional control, and square-root-error-based phase-shift angle adjustment enable rapid adjustments to the duty cycle and phase-shift angle based on the current error, bringing the output voltage quickly toward the target value. When system disturbances or load changes cause the output voltage to deviate from the target value, the controller responds quickly to reduce the error. To eliminate steady-state error, the integral control component continuously accumulates the error signal and adjusts the duty cycle, ultimately eliminating the system's steady-state error and stabilizing the actual output voltage near the target value, improving voltage control accuracy. The control algorithm adaptively adjusts the duty cycle and phase-shift angle based on the magnitude and sign of the error, avoiding over- or under-adjustment. During system operation, the output voltage can be kept stable through reasonable adjustments, regardless of whether it's a minor disturbance or a major load change. During this adjustment process, the duty cycle and phase-shift angle change continuously, avoiding sudden voltage fluctuations. This allows the system to achieve smooth transitions under different operating conditions, reduces impacts on loads and circuit components, and improves system reliability. This control scheme does not rely on a precise system model and is highly robust to changes in system parameters and external interference. For example, when transformer parameters or load resistance change, the controller can still maintain output voltage stability by adjusting the duty cycle and phase-shift angle in real time.

[0100] In one embodiment of the present invention, when switching between boost and buck modes, a transition strategy is adopted 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 in the phase shift angle during the smooth transition, including:

[0101] When switching between the boost and buck modes, a transition strategy is used to achieve a smooth transition of the phase shift angle. Specifically, the transition strategy is:

[0102]

[0103] in, It represents the phase shift angle between the input side and output side full bridge circuit switch 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 boost and buck mode switching, i.e., t = 0. τ represents the time constant, and t represents the time variable, which is measured from the start of the mode switching.

[0104] Monitor the phase shift angle change value, and dynamically adjust the dead time based on the phase shift angle change value through a dynamic dead time model. Specifically, the dynamic dead time model is:

[0105]

[0106] in, represents the dead time at time t, Indicates the preset basic dead time. Indicates the preset reference value at room temperature. 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 rate of change 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, Indicates the phase shift angle change at time t relative to the previous moment, represents the maximum allowable phase shift angle, Represents the attenuation weight coefficient.

[0107] 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 surge 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 phase shift angle change. 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 be smoothly transitioned 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 partially considered. As the junction temperature rises, the performance of the switching device will change. By adjusting the coefficient in this part, the dead time can adapt to the temperature change and ensure the safe operation of the switching 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 shoot-through. Taking into account the change in phase shift angle, the greater the change in 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 and target output voltages is taken into account. When the voltage error is large, the system may become unstable. Appropriately increasing the dead time can improve system safety. When the voltage error is small, reducing the dead time can reduce switching losses. A smooth phase-shift angle transition reduces voltage jumps. This smooth transition avoids output voltage jumps caused by sudden changes in the phase-shift angle, allowing the output voltage to smoothly transition from one stable value to another. This is crucial for loads with high voltage stability requirements, such as precision electronic equipment, as it reduces damage to the load caused by voltage fluctuations. It also reduces power surges. During mode switching, the smooth change in the phase-shift angle reduces sudden power surges, minimizing power surges to the power supply and load. This helps improve system reliability and stability, extending equipment life. It also reduces electromagnetic interference. The smooth transition of the phase-shift angle reduces sudden voltage and current fluctuations, thereby reducing electromagnetic interference. This is of great significance for application scenarios with high electromagnetic compatibility requirements (such as communications equipment and medical equipment), as it can reduce interference with surrounding electronic equipment. Dynamic dead time adjustment improves the safety of the switch tube. Dynamic dead time adjustment can adjust the dead time in real time according to the actual operating state of the switch tube (such as temperature, current slope, phase shift angle change, etc.), avoiding the occurrence of bridge arm shoot-through and improving the safety and reliability of the switch tube. It reduces switching losses. When the system is operating stably and the voltage error is small, reducing the dead time can reduce switching losses and improve the system's energy conversion efficiency. For example, in steady-state operation, appropriately shortening the dead time can reduce the on and off time of the switch tube and reduce energy loss during the switching process. It also enhances system adaptability. The model comprehensively considers the impact of multiple factors on the dead time, allowing the dead time to adapt to different operating conditions and environmental conditions. Whether in the case of temperature changes, load fluctuations, or mode switching, it can ensure stable operation of the system, enhancing the system's adaptability and robustness.

[0108] One embodiment of the present invention provides a stepless voltage regulating device with a bidirectional voltage regulating function, the device comprising:

[0109] A power transmission control module is used to establish 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 by using 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 realize power transmission control by combining phase shift control with dynamic duty cycle modulation;

[0110] A bidirectional control module is used to establish a bidirectional voltage regulation mathematical model and further accurately control the output voltage of the output end of the second full-bridge circuit;

[0111] a control parameter adjustment module, configured to detect the output voltage of the output terminal of the second full-bridge circuit in real time, compare the output voltage with the target voltage to generate an error signal, and adjust the control parameter according to the error signal through a parameter adjustment law;

[0112] The dead time control module is used to achieve a smooth transition of the phase shift angle to avoid voltage jumps when switching between boost and buck modes, and dynamically adjust the dead time based on the change value of the phase shift angle during the smooth transition.

[0113] In one embodiment of the present invention, the power transmission control module includes:

[0114] 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:

[0115]

[0116] in, represents the output voltage of the output end of the second full-bridge circuit, n represents the turns ratio of the isolation transformer, and 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;

[0117] The power adjustment module is used to control 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:

[0118]

[0119] 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.

[0120] In one embodiment of the present invention, the bidirectional control module includes:

[0121] 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 and second full-bridge circuits to the input side of the first full-bridge circuit;

[0122] 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:

[0123]

[0124] 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.

[0125] In one embodiment of the present invention, the control parameter adjustment module includes:

[0126] The error signal acquisition module is used to detect the output voltage of the second full-bridge circuit output terminal 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 actual detected output voltage at the output end of the second full-bridge circuit;

[0127] 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 a parameter adjustment rate based on the error signal. Specifically, the parameter adjustment law is:

[0128]

[0129] 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 period, represents the error signal at the i-th time step;

[0130]

[0131] in, It represents the phase shift angle between the driving 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 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.

[0132] In one embodiment of the present invention, the dead time control module includes:

[0133] The smooth transition module is used to implement a smooth transition of the phase shift angle using a transition strategy when switching between the boost and buck modes. Specifically, the transition strategy is:

[0134]

[0135] in, It represents the phase shift angle between the input side and output side full bridge circuit switch 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 boost and buck mode switching, i.e., t = 0. τ represents the time constant, and t represents the time variable, which is measured from the start of the mode switching.

[0136] The dynamic dead time adjustment module is used to monitor the phase shift angle change value and dynamically adjust the dead time based on the phase shift angle change value through a dynamic dead time model. Specifically, the dynamic dead time model is:

[0137]

[0138] in, represents the dead time at time t, Indicates the preset basic dead time. Indicates the preset reference value at room temperature. 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 rate of change 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, Indicates the phase shift angle change at time t relative to the previous moment, represents the maximum allowable phase shift angle, Represents the attenuation weight coefficient.

[0139] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A stepless voltage regulation method with a bidirectional voltage regulation function, characterized in that: The stepless voltage regulation method with bidirectional voltage regulation function is based on a symmetrical topology structure of a dual active bridge. The symmetrical topology structure of the dual active bridge includes two sets of full-bridge circuits and an isolation transformer, supporting 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 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. Then, power transmission control is achieved by combining phase shift control with dynamic duty cycle modulation. After establishing a 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 the output voltage with the target voltage to generate an error signal, and adjusting the control parameters through a parameter adjustment law according to the error signal; 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, and the dead time is dynamically adjusted based on the change in the phase shift angle during the smooth transition. Detecting the output voltage of the output terminal of the second full-bridge circuit in real time, comparing it with the target voltage to generate an error signal, and adjusting the control parameters according to the error signal through a parameter adjustment law, including: The output voltage of the second full-bridge circuit output terminal 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 actual detected output voltage at the output end of the second full-bridge circuit; The duty cycle and phase shift angle of the full-bridge circuit switch are adjusted based on the error signal through a parameter adjustment law. 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 period, represents the error signal at the i-th time step; in, It 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 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.

2. A stepless voltage regulation method with bidirectional voltage regulation function according to claim 1, 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 achieve stepless output voltage regulation. Then, power transmission control is achieved 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 an 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, and 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 of 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 and second full-bridge circuits to the input side of the first full-bridge circuit; After power transmission control is achieved, the output voltage of the output end of the second full-bridge circuit is 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: 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 the smooth transition, including: When switching between the boost and buck modes, 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 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 boost and buck mode switching, i.e., t = 0. τ represents the time constant, and t represents the time variable, which is measured from the start 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 a dynamic dead time model. 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 at room temperature. 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 rate of change 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, Indicates the phase shift angle change at time t relative to the previous moment, represents the maximum allowable phase shift angle, Represents the attenuation weight coefficient.

5. A stepless voltage regulating device with bidirectional voltage regulating function, characterized in that: The device comprises: A power transmission control module is used to establish 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 by using 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 realize power transmission control by combining phase shift control with dynamic duty cycle modulation; A bidirectional control module is used to establish a bidirectional voltage regulation mathematical model and further accurately control the output voltage of the output end of the second full-bridge circuit; a control parameter adjustment module, configured to detect the output voltage of the output terminal of the second full-bridge circuit in real time, compare the output voltage with the target voltage to generate an error signal, and adjust the control parameter according to the error signal through a parameter adjustment law; The dead time control module is used to implement a transition strategy to achieve a smooth transition of the phase shift angle to avoid voltage jumps when switching between boost and buck modes, and dynamically adjust the dead time based on the change in the phase shift angle during the smooth transition; The control parameter adjustment module includes: The error signal acquisition module is used to detect the output voltage of the second full-bridge circuit output terminal 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 actual detected output voltage at the output end of the second full-bridge circuit; 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 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 period, represents the error signal at the i-th time step; in, It 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 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.

6. A stepless voltage regulating device with bidirectional voltage regulating function according to claim 5, characterized in that: The power transmission control module includes: 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, and 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 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.

7. The stepless voltage regulating device with bidirectional voltage regulating function according to claim 5, characterized in that: The bidirectional control module includes: 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 first and second full-bridge circuits 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.

8. The stepless voltage regulating device with bidirectional voltage regulating function according to claim 5, characterized in that: The dead time control module includes: The smooth transition module is used to implement a smooth transition of the phase shift angle using a transition strategy when switching between the boost and buck modes. Specifically, the transition strategy is: in, It represents the phase shift angle between the input side and output side full bridge circuit switch 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 boost and buck mode switching, i.e., t = 0. τ represents the time constant, and t represents the time variable, which is measured from the start of the mode switching. The dynamic dead time adjustment module is used to monitor the phase shift angle change value and dynamically adjust the dead time based on the phase shift angle change value through a dynamic dead time model. 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 at room temperature. 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 rate of change 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, Indicates the phase shift angle change at time t relative to the previous moment, represents the maximum allowable phase shift angle, Represents the attenuation weight coefficient.

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