Border control-based three-active full-bridge converter circuit switching method and system

Abstract

The application discloses a kind of based on boundary control's three active full bridge converter circuit switching method and system, according to the topological structure of TAB converter, the dynamic characteristics of converter are expressed using state space modeling method, and the standardized natural trajectory is obtained;According to the working characteristics of TAB conversion device, define multiple switching surfaces, each switching surface corresponds to the operation boundary of a state mode conversion, guide the operating point of the system to switch between these switching surfaces;When the state variable reaches the switching boundary, trigger the switching operation, go to the next switching surface, so that the operating point of the converter is kept near the target output voltage.By introducing natural switching surface (NSS) theory and boundary control strategy, the problems of slow dynamic response, overshoot voltage and other problems faced by traditional control methods during load variation and fast start-up process are solved.The method can significantly improve the response speed and system stability of TAB converter during load switching process.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of multi-port converter, and relates to a three-active full-bridge converter circuit switching method and system based on boundary control. BACKGROUND

[0002] With the rapid development of renewable energy technology, smart grid and electric vehicles, multi-port converter (MPC) has become a research hotspot in the field of energy conversion. As a kind of multi-port power conversion system, three-active full-bridge (TAB) converter is widely used in electric vehicle charging, micro-grid, energy storage system and power electronic interface equipment, such as Figure 1 TAB converter has the characteristics of bidirectional power flow and high efficient power conversion, but in the process of high dynamic load variation and rapid start-up, the traditional PI control method has certain limitations, especially in the case of severe load change or large voltage fluctuation, the dynamic response speed of the control system is insufficient, resulting in overshoot voltage, overload phenomenon and poor system stability.

[0003] Therefore, how to improve the dynamic response speed of TAB converter in the process of load change under the premise of ensuring system stability, and avoid current overload and voltage fluctuation, is an important direction of current research. SUMMARY

[0004] The purpose of the application is to provide a three-active full-bridge converter circuit switching method and system based on boundary control, which uses natural switching surface (NSS) theory to optimize the dynamic performance of TAB converter through boundary control strategy. This method can significantly improve the starting speed of the system, shorten the response time when the load changes, and ensure the stability of the system, avoiding overshoot voltage and overload phenomenon.

[0005] The technical solution for achieving the purpose of the application is:

[0006] A three-active full-bridge converter circuit switching method based on boundary control, comprising the following steps:

[0007] S01: According to the topology structure of TAB converter, the state space modeling method is used to represent the dynamic characteristics of the converter, and the standardized natural trajectory is obtained;

[0008] S02: According to the working characteristics of TAB converter, define multiple switching surfaces, each switching surface corresponds to an operation boundary of state mode conversion, and guide the operation point of the system to switch between these switching surfaces;

[0009] S03: When the state variable reaches the switching boundary, trigger the switching operation, and go to the next switching surface, so that the operation point of the converter is kept near the target output voltage.

[0010] In the preferred technical solution, the dynamic characteristic expression of the TAB converter in step S01 is:

[0011] ;

[0012] in, For output voltage, , , These represent the voltage polarities at both ends of the transformer. For output power, For inductor current, Where C is time and C is the output capacitor value. This is the inductance value. This is the input voltage.

[0013] In the preferred technical solution, the method for obtaining the natural trajectory in step S01 includes:

[0014] Using inductor current and output voltage as state variables, the behavior of the TAB converter is obtained based on multiple operating modes. The dynamic behavior of the converter is simplified into a set of circular trajectories represented in the phase plane. The radius of the trajectory is related to the initial conditions. By normalizing the state variables, a standardized natural trajectory is obtained.

[0015] In the preferred technical solution, under the varying natural switching surface, the inductor current... and output voltage The transient behavior is characterized by differential equations:

[0016] ;

[0017] in, C is the output capacitor value. This is the inductance value;

[0018] Based on the above derivation, the general solution can be represented as a circle by the following equation:

[0019] ;

[0020] in, To normalize the output voltage, To normalize the output power, For normalized inductor current, For normalized input voltage, The voltage ratio at the three ports of transformers k1, k2, and k3 is given by the normalized input current. Let be the general solution representing the radius of the circle.

[0021] In the preferred technical solution, the voltage polarity across the transformer is set , , and the corresponding switch state combination results in 6 operating modes λ 1- λ 6.

[0022] In the preferred technical solution, step S03 further comprises setting a maximum current, and before the state variable reaches the switching boundary, determining whether the current reaches the maximum current.

[0023] In the preferred technical solution, the method for determining whether the state variable reaches the switching boundary in step S03 comprises:

[0024] Write each natural trajectory λi as a symbolic function;

[0025] When λi≥ 0, trigger the switching operation.

[0026] In the preferred technical solution, step S03 is further followed by, after each switching, optimizing the dynamic response of the system by adjusting the switch state, so that the fixed frequency operation is maintained during the switching process.

[0027] The application also discloses a three-active full-bridge converter circuit switching system based on boundary control, comprising:

[0028] A TAB converter dynamic modeling module, which adopts state space modeling method to represent the dynamic characteristics of the converter according to the topology structure of the TAB converter, and obtains standardized natural trajectories;

[0029] A boundary control module, which defines multiple switching surfaces according to the operating characteristics of the TAB converter, each switching surface corresponding to an operating boundary of state mode conversion, and guiding the operating point of the system to switch between the switching surfaces;

[0030] A switching adjustment module, which triggers the switching operation when the state variable reaches the switching boundary, and goes to the next switching surface, so that the operating point of the converter is kept near the target output voltage.

[0031] The application further discloses a computer storage medium, which stores a computer program, and the computer program is executed to realize the three-active full-bridge converter circuit switching method based on boundary control.

[0032] Compared with the prior art, the application has the following advantages:

[0033] By introducing a boundary control strategy, combined with the natural switching surface (NSS) method, the operating boundaries of the TAB converter in different operating modes are accurately selected. This method optimizes the switching timing during the startup phase and load switching phase of the converter, achieving fast response and stable transition.

[0034] The present application not only optimizes the dynamic response, but also avoids the phenomenon of transformer magnetic saturation by controlling the switching frequency. This is because fixed frequency operation can stabilize the operating state of the converter without generating excessive high frequency harmonics, thereby ensuring that the system can maintain a stable operating state under different load and voltage conditions.

[0035] The maximum current boundaries (such as ±Ipeak) of the TAB converter are strictly controlled by the method of the present application. The current and voltage of the system are always maintained within these safe boundaries, avoiding current exceeding the design limit, thereby reducing the risk of system overload. This boundary control method optimizes the switching action and current distribution of the converter, ensuring effective operation under various operating conditions.

[0036] In traditional control methods, the system often needs to be adjusted and corrected several times before it stabilizes. Through the system of the present application, the system can quickly respond when starting, load changes, and reference voltage changes, and effectively control the system state. This fast dynamic response greatly shortens the recovery time of the system, while ensuring accurate control of the output voltage in a stable state, avoiding excessive fluctuations or oscillations. It has wide application prospects, especially suitable for electric vehicle charging, microgrid, energy storage systems and other fields. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 is the topology of the TAB converter of the present embodiment;

[0038] Figure 2 is the flow chart of the circuit switching method of the three active full-bridge converter based on boundary control of the present embodiment;

[0039] Figure 3 is the flow chart of the boundary control;

[0040] Figure 4 is the equivalent circuit of the TAB converter;

[0041] Figure 5 is the phase diagram of the trajectory of the λ1 state;

[0042] Figure 6 is the phase diagram of the trajectory of the λ2 state;

[0043] Figure 7 is the phase diagram of the trajectory of the λ3 state;

[0044] Figure 8is the phase plot of the trajectory of the λ4 state;

[0045] Figure 9 is the phase plot of the trajectory of the λ5 state;

[0046] Figure 10 is the phase plot of the trajectory of the λ6 state;

[0047] Figure 11a is i L and v o is a typical steady-state waveform plot of

[0048] Figure 11b is the phase plane;

[0049] Figure 12a is a typical waveform of the TAB converter start-up process without maximum current limit control;

[0050] Figure 12b is a typical waveform of the TAB converter start-up process with maximum current limit control;

[0051] Figure 13a is a start-up process time-domain simulation waveform of the TAB converter with current limit boundary control;

[0052] Figure 13b is a start-up process trajectory phase plane simulation waveform of the TAB converter with current limit boundary control;

[0053] Figure 14a is a start-up process time-domain simulation waveform of the TAB converter with current limit boundary control;

[0054] Figure 14b is a start-up process trajectory phase plane simulation waveform of the TAB converter with current limit boundary control;

[0055] Figure 15a is a start-up process time-domain waveform of the output power switching of the TAB converter;

[0056] Figure 15b is a start-up process trajectory phase plane of the output power switching of the TAB converter. DETAILED DESCRIPTION

[0057] The principle of the present application is: using the natural switching surface (NSS) theory, the dynamic performance of the TAB converter is optimized through the boundary control strategy. This method can significantly improve the start-up speed of the system, shorten the response time when the load changes, and at the same time ensure the stability of the system, avoid the occurrence of overshoot voltage and overload phenomenon.

[0058] Example 1:

[0059] As Figure 2 shown, a boundary control based three active full bridge converter circuit switching method, comprising the following steps:

[0060] S01: According to the topology of TAB converter, the state space modeling method is used to express the dynamic characteristics of the converter, and the normalized natural trajectory is obtained;

[0061] S02: According to the working characteristics of TAB converter, a plurality of switching surfaces are defined, each switching surface corresponds to an operating boundary of state mode conversion, and the operating point of the system is switched between these switching surfaces;

[0062] S03: When the state variable reaches the switching boundary, trigger the switching operation, and go to the next switching surface, so that the operating point of the converter is kept near the target output voltage.

[0063] In a preferred embodiment, the expression of the dynamic characteristics of the TAB converter in step S01 is:

[0064] ;

[0065] Wherein, is the output voltage, , , is the voltage polarity of the transformer, is the output power, is the inductance current, is the time, C is the output capacitance value, is the inductance value, is the input voltage.

[0066] In a preferred embodiment, the method for obtaining the natural trajectory in step S01 comprises:

[0067] The inductance current and the output voltage are taken as state variables, the behavior of the TAB converter is obtained based on multiple operating modes, the dynamic behavior of the converter is simplified into a group of circular trajectories represented in the phase plane, the radius of the trajectory and the initial condition are related, the state variable is normalized, and the normalized natural trajectory is obtained.

[0068] In a preferred embodiment, under the varying natural switching surface, the transient behavior of the inductance current and the output voltage is characterized by the differential equation:

[0069] ;

[0070] Wherein, C is the output capacitance value, L is the inductance value;

[0071] According to the above derivation, the general solution is expressed as a circle by the following equation:

[0072] ;

[0073] where, Vout is the normalized output voltage, Pout is the normalized output power, IL is the normalized inductance current, Vin is the normalized input voltage, Iin is the normalized input current, k1, k2, k3 are the voltage ratios of the transformer three-port, R is the radius of the circle expressed by the general solution.

[0074] In a preferred embodiment, the voltage polarity of the transformer two ends is , , and the corresponding switch state combination obtains 6 operation modes λ 1- λ 6.

[0075] In a preferred embodiment, step S03 further includes setting a maximum current, and before the state variable reaches the switching boundary, determining whether the current reaches the maximum current.

[0076] In a preferred embodiment, the method for determining whether the state variable reaches the switching boundary in step S03 includes:

[0077] Write each natural trajectory λi as a sign function;

[0078] When λi≥ 0, trigger the switching operation.

[0079] In a preferred embodiment, step S03 further includes, after each switching, optimizing the dynamic response of the system by adjusting the switch state, so that the fixed frequency operation is maintained during the switching process.

[0080] Another embodiment is a computer storage medium having stored thereon a computer program, which, when executed, implements the above-mentioned switching method of the three-active full-bridge converter circuit based on boundary control. The specific implementation adopts the above-mentioned switching method of the circuit, which will not be described here.

[0081] Another embodiment is a switching system of a three-active full-bridge converter circuit based on boundary control, which includes:

[0082] The TAB converter dynamic modeling module uses the state space modeling method to represent the dynamic characteristics of the converter according to the topology of the TAB converter, and obtains the standardized natural trajectory.

[0083] A boundary control module defines multiple switching surfaces, each corresponding to an operating boundary for a state mode transition, based on the operating characteristics of the TAB converter, guiding the system's operating point to switch between these switching surfaces;

[0084] A switching adjustment module triggers a switching operation when the state variable reaches the switching boundary, moving to the next switching surface, so that the operating point of the converter remains near the target output voltage.

[0085] The following is a detailed description of a preferred embodiment, which includes the following steps:

[0086] 1. Determine the natural trajectory of the system

[0087] Using geometric modeling methods, analyze the behavior of the TAB converter based on inductor current and output voltage as state variables. 1-

[0088] Normalize these state variables to obtain the standardized natural trajectory. The natural trajectory represents the natural evolution path of the TAB converter without external control.

[0089] 2. Define the switching surfaces

[0090] Based on the operating characteristics of the TAB converter (such as voltage, current and power limits), define multiple switching surfaces (such as λ 1- λ 6), each corresponding to a boundary for a state mode transition.

[0091] These switching surfaces are defined by the relationship between state variables (such as output voltage and inductor current ), the purpose is to ensure that the converter can operate stably and efficiently in different operating states.

[0092] 3. Set boundary conditions (such as current limits)

[0093] Set maximum current boundaries (such as Ipeak) and voltage boundaries to avoid the system entering an overload or saturation state.

[0094] Use these boundary conditions to limit the operating state of the system, ensuring that the operating point of the system always remains within a safe operating interval. In the maximum current mode, the NSS will ensure that when the current limit is reached, it will automatically switch to the appropriate operating structure to avoid overload.

[0095] 4. Precise selection of switching timing

[0096] Real-time monitoring of the system's output voltage and inductor current State variables.

[0097] When the operating point of the system approaches a certain switching surface (such as λ1 or λ2), the switching timing needs to be considered. At this time, the control system needs to accurately determine whether to continue moving along the current trajectory or switch to the next state.

[0098] When the state variable (such as or ) reaches the switching boundary, the control system will immediately trigger the switching operation and switch to the next switching surface. For example, when λ2 becomes positive, the system switches from λ 1 to λ 2. As shown in Figure 3 , the switching boundary is shown in Figure 11b , and each circle represents a trajectory, and the intersection of the circles is the switching point where each λ enters the next λ, so it is called the switching boundary.

[0099] In the design of boundary control, each natural switching curve λi (i = 1…6) is written as a symbolic function - when the operating point is located on the "inside" of the curve λi < 0, on the curve λi = 0, and crosses the curve into the next region λi > 0.

[0100] Therefore, when λi ≥ 0, the switching operation is triggered.

[0101] In the selection of switching timing, special attention should be paid to avoid excessive oscillation, especially when the load suddenly changes or the voltage reference changes. The NSS ensures that the system returns to the stable state along the optimal path.

[0102] 5. Optimization adjustment after switching

[0103] After each switching, the NSS control law optimizes the dynamic response of the system by adjusting the switching state (such as changes in u1, u2 and u3).

[0104] Ensure that the system maintains fixed frequency operation during switching and avoids transformer magnetic saturation and current overload by adjusting the sequence of switching surfaces.

[0105] By selecting appropriate natural trajectories (such as λ2, λ3, λ4), ensure that the system quickly reaches the target steady state and avoids large output voltage fluctuations or current abnormalities.

[0106] 6. Real-time monitoring and feedback

[0107] Real-time monitoring of output voltage and inductor current, depending on the current system state, to determine whether the control strategy needs to be adjusted.

[0108] Adjust the switching surface and switching timing according to the feedback results to ensure that the system remains stable under various loads and voltage conditions.

[0109] Specifically, the dynamic modeling and operation mode of the TAB converter:

[0110] Based on the topology of the TAB converter, the dynamic characteristics of the converter are represented using state-space modeling. Different switching states (such as λ1, λ2, λ3, etc.) correspond to different operating modes, and the changes in inductor current and output voltage under each mode can be obtained through mathematical equations.

[0111] The equivalent circuit of a TAB converter, such as Figure 4 As shown, it is used for state-space modeling.

[0112] Topology: The circuit consists of three full-bridge converters (H1, H2, H3). Each full-bridge converter consists of four transistors and one capacitor, used to control the voltage applied to the inductor and the load.

[0113] Inductors and capacitors: Each full-bridge circuit has capacitors C1 and C2 on the input side and a third capacitor C3 on the output side to smooth the output voltage. Inductors are located in the middle of the circuit to smooth current flow and improve power conversion efficiency.

[0114] Switching control: The transistors in H1, H2, and H3 regulate the power flow to the input and output by controlling their switching states. In this way, the circuit can achieve efficient energy conversion.

[0115] According to Kirchhoff's laws, the dynamic characteristics of the TAB converter can be derived as follows:

[0116] (1)

[0117] in, For output voltage, , , These represent the voltage polarities at both ends of the transformer. For output power, For inductor current, Where C is time and C is the output capacitor value. This is the inductance value. This is the input voltage.

[0118] ( , , (This is used as an indicator of the different operating modes of the TAB converter.) , , ), for example (1, 1, 1), (-1, 1, 1), (-1, -1, 1), (-1, -1, -1), (1, -1, -1) and (1, 1, -1), six unique modes of operation can be depicted. , , ) and the corresponding switching states (on / off) are shown in Table 1:

[0119] Table 1 Complete state and switching sequence

[0120]

[0121] λ 1- λ 6are different states, i.e. different modes of operation.

[0122] When the switch is in the λ1 state, Figure 1 The dynamic behavior of the TAB converter is determined by the following equation:

[0123] (2)

[0124] At the same time, when the switch is in the λ2-λ6 state, the dynamic behavior of the TAB converter can be determined as:

[0125] (3)

[0126] (4)

[0127] (5)

[0128] (6)

[0129] (7)

[0130] Figure 5 The stability behavior of the λ1 state can be investigated, which is obtained by simulating the system shown in Figure 1 . The TAB converter has the following parameters: vin = 20 V, Pout = 25 W, L = 45 μH, C = 47 μF. The corresponding phase diagram of the converter dynamic behavior between λ2-λ6 is shown in Figures 6-10 .

[0131] The operating trajectory of the TAB converter in various modes is shown in Figures 5-10The numbers not only provide a clear visual representation of the trajectories but also clearly indicate where these trajectories eventually converge. On this basis, the present study can construct a framework in the normalized geometric domain. By deriving and modeling the state-space equations of the TAB converter, it is possible to determine the state trajectories and switching points based on the natural switching surfaces.

[0132] The NSS determines the natural trajectories of the TAB converter through geometric analysis, which are designed based on the intrinsic behavior of the converter, such as inductor current and output voltage, as Figures 5-10 By simplifying the dynamic behavior of the converter into a set of circular trajectories that can be represented in the phase plane. The radius of the trajectories and the initial conditions are related, and the converter can be guided from the initial state to the target state quickly by the natural trajectories.

[0133] In these natural trajectories, the converter operates along predetermined paths in different operating states. The NSS control law ensures that the system always progresses along these natural trajectories without easily deviating from the expected trajectory, thereby avoiding excessive dynamic fluctuations or unstable behavior.

[0134] Design of switching surfaces

[0135] In NSS control, a set of switching surfaces ( λ 1- λ 6) are defined, each representing the operating boundary of the system in different states. The control strategy guides the operating point of the system to switch between these switching surfaces, ensuring a smooth transition from the initial state to the target steady state. Each switching surface corresponds to a transition of operating mode, effectively preventing the system's operating boundary from being breached and thus preventing unstable situations.

[0136] Fixed-frequency operation and magnetic saturation avoidance

[0137] An important feature of the NSS design is fixed-frequency operation. In this way, the NSS not only optimizes the dynamic response but also avoids transformer magnetic saturation by controlling the switching frequency. This is because fixed-frequency operation can stabilize the converter's operating state without generating excessive high-frequency harmonics, ensuring that the system can maintain a stable operating state under different load and voltage conditions.

[0138] According to equation (1), the transient behavior of the inductor current ( ) and output voltage ( ) under varying natural switching surfaces can be characterized by subsequent differential equations

[0139] (8)

[0140] Here ;

[0141] From the above derivations, the general solution can be expressed as a circle using the following equation:

[0142] (9)

[0143] where, is the normalized output voltage, is the normalized output power, is the normalized inductor current, is the normalized input voltage, is the normalized input current, k1, k2, k3 are the voltage ratios of the transformer three-port, is the radius of the circle represented by the general solution.

[0144] Figures 11a-11b Typical steady-state waveforms and phase planes for and are shown.

[0145] Maximum current limiting mechanism:

[0146] During the fast switching process, the control strategy takes into account the inductor current limit, when the current reaches a set maximum value, by changing the operating mode (switching different switching states from λ 1- λ 6, the size of the current and voltage) to avoid excessive current, to prevent the system from overloading. This strategy effectively avoids the possible damage to semiconductor elements and saturation of magnetic elements during the fast switching process.

[0147] The start-up process of the TAB converter is shown in Figure 12a Initially, at point A, the TAB converter is set to the initial conditions of vo = 0 and iL = 0. To guide the operating point (switching point) from A to B, the intersection of the natural trajectories λ1 and λ2, the boundary control uses the operating trajectory (state is trajectory, each state corresponds to a trajectory, one-to-one) λ1 (u1 = 1, u2 = -1, u3 = -1). After that, the trajectory λ3 (u1 = 1, u2 = 1, u3 = 1) is executed until point D is reached. Subsequently, the TAB converter is guided to the steady-state point using trajectories λ4 and λ5. It is clear that by switching the natural trajectories, the boundary control significantly shortens the duration of the start-up phase, enabling the entire process to be completed.

[0148] However, during the start-up process, the inductor current The size of the inductor current during the transient period is significantly larger than that during the steady state, which can cause damage to the semiconductor devices and saturation of the magnetic components. To ensure the safe operation of the TAB converter, the upper limit of the inductor current must be limited by the boundary control law. Figure 12b The operation of the TAB converter during the start-up phase is shown, with the maximum inductor current limit of "±Ipeak". When the inductor current reaches Ipeak, the operating trajectory of the TAB converter is observed to move from λ3 to λ4 at point D. Once point E is reached, λ6 is used until the inductor current equals the negative current limit "-Ipeak". Thus, the inductor current oscillates periodically within the inductor current limit ±Ipeak, while the output voltage Vo steadily increases until the reference voltage Vref is reached and the steady state operation is transitioned to. Although implementing the maximum inductor current limit results in more switching actions and longer transient time to reach the steady state operation, it effectively prevents potential overcurrent faults in the semiconductor devices.

[0149] Simulation and experimental verification:

[0150] A closed-loop simulation model is constructed using simulation tools such as MATLAB / Simulink to verify the effectiveness of the boundary control strategy. Under the conditions of start-up process and load mutation, the simulation results show that the proposed method can stabilize the system in a short time, and the output voltage reaches the target value in an instant without problems such as excessive current or voltage overshoot.

[0151] When the converter is not working, the output voltage is zero. Therefore, during the start-up phase, the output voltage must be raised to the predetermined level through a series of switching actions.

[0152] The transient phenomenon generated during the start-up process is shown in Figure 13a During this transient process, the control law specifies the process from time zero to 0.06 ms to reach the steady state. Therefore, only one switching action is needed to achieve the steady state. Figure 13b The trajectory of the state plane during the above start-up process is shown.

[0153] When the boundary control with current limit is utilized, the input and output voltage values of the TAB converter are established as 20V and 40V, respectively. In Figures 14a-14bIn the simulations, the results show that the current limit boundary control effectively guarantees the stability of the system, and the start-up, shut-down and off-state characteristics of the TAB converter with and without current limit boundary control are compared. The rising process and the trajectory phase plane show significant differences. Specifically, the simulation results for the TAB converter without current limit show a current exceeding 7 A, while the corresponding maximum current with current limit is 6 A. Moreover, the trajectory phase planes of these converters also show significant differences. Therefore, when the maximum current limit mode is activated, the control law requires more switching actions to reach the desired target. By implementing the control law with current boundary limit, the potential saturation of the transformer can be avoided while maintaining voltage balance.

[0154] Figures 15a-15b The voltage variation when the output power is suddenly changed from 30 W to 70 W is shown. It is clear that the boundary control is able to change to the new operating state in as little as 0.15 ms. It is worth noting that this transition occurs without any DC bias current, oscillations. The results show that the boundary control is able to effectively perform the step response under load conditions within a single cycle, a performance level that is superior to the conventional PI controller, highlighting the effectiveness of the boundary control.

[0155] The above embodiments are preferred embodiments of the present application, but the embodiments of the present application are not limited to the above embodiments, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application should be equivalent replacement methods, and are included in the protection scope of the present application.

Claims

1. A switching method for a three-active full-bridge converter circuit based on boundary control, characterized in that, Includes the following steps: S01: Based on the topology of the TAB converter, the dynamic characteristics of the converter are represented by the state-space modeling method to obtain the standardized natural trajectory; Using inductor current and output voltage as state variables, the behavior of the TAB converter is obtained based on multiple operating modes. The dynamic behavior of the converter is simplified into a set of circular trajectories represented in the phase plane. The radius of the trajectory is related to the initial conditions. The state variables are normalized to obtain the standardized natural trajectory. S02: Obtained via analog TAB converter λ 1- λ The stability characteristics under 6 different operating modes were obtained. λ 1- λ The phase diagram of the 6-state trajectory is obtained. λ 1- λ The final convergence position of the 6 trajectories is determined by constructing a framework in the normalized geometric domain. Through the derivation and modeling of the state space equation of the TAB converter, the state trajectory and switching point based on the natural switching surface are determined. According to the working characteristics of the TAB converter, multiple switching surfaces are defined, each corresponding to an operational boundary of a state mode transition, guiding the system's operational point to switch between these switching surfaces. S03: Output voltage of the real-time monitoring system v 0 and inductor current i L State variables; when the state variables reach the switching boundary, a switching operation is triggered, moving to the next switching surface, so that the operating point of the converter remains near the target output voltage; Methods for determining whether a switching boundary has been reached include: Write each natural trajectory λi as a sign function; A switching operation is triggered when λi ≥ 0.

2. The method for switching a three-active full-bridge converter circuit based on boundary control according to claim 1, characterized in that, The dynamic characteristic expression of the TAB converter in step S01 is: in, v o For output voltage, u 1 , u 2 , u 3 These represent the voltage polarities at both ends of the transformer. P out For output power, i L For inductor current, t Where C is time and C is the output capacitor value. L This is the inductance value. v in This is the input voltage.

3. The method for switching a three-active full-bridge converter circuit based on boundary control according to claim 1, characterized in that, Under the changing natural switching surface, the inductor current i L and output voltage v o The transient behavior is characterized by differential equations: in, C is the output capacitor value. L This is the inductance value; Based on the above derivation, the general solution can be represented as a circle by the following equation: in, v on To normalize the output voltage, P on To normalize the output power, i Ln For normalized inductor current, v inn For normalized input voltage, The voltage ratio at the three ports of transformers k1, k2, and k3 is given by the normalized input current. r n Let be the general solution representing the radius of the circle.

4. The method for switching three active full-bridge converter circuits based on boundary control according to claim 1, characterized in that, The voltage polarity at both ends of the transformer u 1, u 2, u 3. Combining with the corresponding switch states yields 6 operating modes. λ 1- λ 6.

5. The method for switching three active full-bridge converter circuits based on boundary control according to claim 1, characterized in that, Step S03 also includes setting the maximum current and determining whether the current has reached the maximum current before the state variable reaches the switching boundary.

6. The method for switching three active full-bridge converter circuits based on boundary control according to claim 1, characterized in that, Step S03 is followed by optimizing the dynamic response of the system by adjusting the switch state after each switch, so as to maintain a fixed frequency of operation during the switch process.

7. A three-active full-bridge converter circuit switching system based on boundary control, characterized in that, include: The TAB converter dynamic modeling module uses state-space modeling to represent the dynamic characteristics of the converter based on its topology, and obtains a standardized natural trajectory. Using inductor current and output voltage as state variables, the behavior of the TAB converter is obtained based on multiple operating modes. The dynamic behavior of the converter is simplified into a set of circular trajectories represented in the phase plane. The radius of the trajectory is related to the initial conditions. The state variables are normalized to obtain the standardized natural trajectory. The boundary control module obtains this through an analog TAB converter. λ 1- λ The stability characteristics under 6 different operating modes were obtained. λ 1- λ The phase diagram of the 6-state trajectory is obtained. λ 1- λ The final convergence position of the 6 trajectories is determined by constructing a framework in the normalized geometric domain. Through the derivation and modeling of the state space equation of the TAB converter, the state trajectory and switching point based on the natural switching surface are determined. According to the working characteristics of the TAB converter, multiple switching surfaces are defined, each corresponding to an operational boundary of a state mode transition, guiding the system's operational point to switch between these switching surfaces. Switch the adjustment module to monitor the system's output voltage in real time. v 0 and inductor current i L State variables; when the state variables reach the switching boundary, a switching operation is triggered, moving to the next switching surface, so that the operating point of the converter remains near the target output voltage; Methods for determining whether a switching boundary has been reached include: Write each natural trajectory λi as a sign function; A switching operation is triggered when λi ≥ 0.

8. A computer storage medium having a computer program stored thereon, characterized in that, When the computer executes the computer program, it implements the three-active full-bridge converter circuit switching method based on boundary control as described in any one of claims 1-6.

Images