A dual active full bridge converter and a control method thereof
Patent Information
- Application Number
- CN202311605460.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-28
- Publication Date
- 2026-11-03
- Estimated Expiration
- 2043-11-28
AI Technical Summary
Existing control methods for dual active full-bridge DC-DC converters are not very stable and have low robustness, making it difficult to meet the requirements of high-performance control systems in fields such as new energy power generation and electric vehicles.
Virtual damping is injected in parallel into the secondary full-bridge converter of the dual active full-bridge converter, and the energy is reconstructed using the Brayton-Moser control strategy to obtain a control signal to control the switching transistors.
It achieves fast response, no overshoot, high anti-interference, and small output voltage fluctuation, thus improving control reliability and robustness.
Smart Images
Figure CN117728689B_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of power technology, and in particular to a dual active full-bridge converter and its control method. Background Technology
[0002] Dual active full-bridge DC-DC converters offer advantages such as bidirectional energy flow, high transmission efficiency, electrical isolation, and low reactive power demand, leading to their widespread application in new energy power generation, electric vehicles, and energy storage. However, because power electronic converters are strongly coupled nonlinear systems and are affected by factors such as circuit parameter perturbations, load and input voltage variations, and unmodeled dynamics, existing control methods for dual active full-bridge DC-DC converters suffer from low stability and robustness. Summary of the Invention
[0003] Therefore, the purpose of this disclosure is to propose a dual active full-bridge converter and its control method.
[0004] Based on the above objectives, in a first aspect, this disclosure provides a control method for a dual active full-bridge converter, the dual active full-bridge converter including a primary-side full-bridge converter and a secondary-side full-bridge converter, wherein the output capacitor of the secondary-side full-bridge converter is connected to the load; The method includes: The measured value V1 of the primary DC side voltage of the primary full-bridge converter and the measured value V2 of the output capacitor are collected. The expected voltage trajectory V based on the output capacitor 2d The measured value V1 of the primary side DC-side voltage, the measured value V2 of the secondary side DC-side voltage, and the parallel injection impedance G of the secondary side full-bridge converter. i The parallel injection damping G of the primary-side full-bridge converter and the secondary-side full-bridge converter are used to obtain the duty cycle d of the primary-side full-bridge converter and the secondary-side full-bridge converter; The switching control signal is obtained by modulation processing based on the duty cycle d; The switching control signal controls the switching transistors in the primary-side full-bridge converter and the secondary-side full-bridge converter.
[0005] In some embodiments, the voltage expected trajectory V based on the output capacitor 2d The measured value V1 of the primary side DC-side voltage, the measured value V2 of the secondary side DC-side voltage, and the parallel injection impedance G of the secondary side full-bridge converter. i The parallel injection damping G of the primary-side full-bridge converter and the secondary-side full-bridge converter are used to obtain the duty cycle d of the primary-side full-bridge converter and the secondary-side full-bridge converter, including: The expected voltage trajectory V based on the output capacitor 2dThe error trajectory of the secondary DC-side voltage is obtained by combining the measured value V2 of the secondary DC-side voltage. ; Based on the parallel injection impedance G of the output capacitor i The error trajectory of the secondary DC side voltage The duty cycle d of the primary-side DC-side voltage V1 and the parallel injection damping G of the secondary-side full-bridge converter are obtained by using the measured value V1 of the primary-side DC-side voltage and the parallel injection damping G of the secondary-side full-bridge converter.
[0006] In some embodiments, the dual active full-bridge converter further includes a transformer connected between the primary-side full-bridge converter and the secondary-side full-bridge converter, wherein the input inductor in the primary-side full-bridge converter is connected to the transformer; Based on the parallel injection impedance G of the secondary full-bridge converter i The error trajectory of the secondary DC side voltage The measured value V1 of the primary-side DC-side voltage and parameter G are used to obtain the duty cycle d of the primary-side full-bridge converter and the secondary-side full-bridge converter, including: Where fs is the operating frequency of the dual active full-bridge converter, L is the inductance value of the input inductor, n is the turns ratio of the transformer coil, and C2 is the capacitance value of the output capacitor.
[0007] In some embodiments, the voltage expected trajectory V based on the output capacitor 2d The error trajectory of the secondary DC-side voltage is obtained by combining the measured value V2 of the secondary DC-side voltage. ,include: Based on the measured value V2 of the secondary DC side voltage and the expected trajectory V 2d The difference is used to obtain the error trajectory of the secondary DC-side voltage. .
[0008] In some embodiments, based on the parallel injection impedance G of the output capacitor i The error trajectory of the secondary DC side voltage The measured value V1 of the primary-side DC-side voltage and the parallel injection damping G of the secondary-side full-bridge converter are used to obtain the duty cycle d of the primary-side full-bridge converter and the secondary-side full-bridge converter, including: Determine the average state equation of the dual active full-bridge converter based on the BM model with respect to the state variables, including the current measurement value i of the input inductor. L and the measured voltage V2 of the output capacitor; The expected current trajectory of the input inductor and the expected voltage trajectory of the output capacitor are determined based on the average state equation. The error dynamics equation of the dual active full-bridge converter is determined based on the expected current trajectory and the expected voltage trajectory. Based on the error dynamics equation and the parallel injection damping connected in parallel with the output capacitor, the closed-loop dynamics equation based on the BM model is obtained. The duty cycle d of the primary-side full-bridge converter and the secondary-side full-bridge converter is obtained based on the closed-loop dynamic equation.
[0009] In some embodiments, the average state equation of the dual active full-bridge converter with respect to state variables includes: Where P is the power of the dual active full-bridge converter.
[0010] In some embodiments, the desired current trajectory of the input inductor and the desired voltage trajectory of the output capacitor include: , The desired trajectory of the input inductor, The desired trajectory of the average output voltage; Based on the expected trajectories of the input inductor and the output capacitor, the error dynamics equation of the dual active full-bridge converter is determined, including: .
[0011] In some embodiments, based on the error dynamics equation and the parallel injected damping connected in parallel with the output capacitor, a closed-loop dynamics equation based on the BM model is obtained, including: , , , To inject damping into the parallel connection.
[0012] In some embodiments, the duty cycle d of the primary-side full-bridge converter and the secondary-side full-bridge converter is obtained based on the closed-loop dynamic equation, including: Based on the expected current trajectory of the input inductor and the expected voltage trajectory of the output capacitor, and the closed-loop dynamic equation, the control law of the dual active full-bridge converter based on the BM model is obtained, including: ; The duty cycle d is determined based on the control law.
[0013] On the other hand, this disclosure provides a dual active full-bridge converter controlled by the method described in the first aspect.
[0014] As can be seen from the above, the dual active full-bridge converter and its control method provided in this disclosure inject virtual damping in parallel into the secondary-side full-bridge converter of the dual active full-bridge converter, and reconstruct the energy in the BM control strategy to obtain a control signal to control the switching transistors of the dual active full-bridge converter. This enables the dual active full-bridge converter to achieve a fast response speed during control, eliminates overshoot, and exhibits small or even no output voltage fluctuations when the load changes abruptly, demonstrating high anti-interference capability and improving the control reliability and robustness of the dual active full-bridge converter. Attached Figure Description
[0015] To more clearly illustrate the technical solutions in this disclosure or related technologies, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0016] Figure 1 This is a schematic main circuit diagram of a dual active full-bridge converter according to an embodiment of the present disclosure.
[0017] Figure 2 This is a schematic diagram of the secondary-side output voltage of a dual active full-bridge converter according to an embodiment of the present disclosure during the startup phase.
[0018] Figure 3 This is a schematic diagram of the secondary-side output voltage of a dual active full-bridge converter under load sudden change according to an embodiment of this disclosure.
[0019] Figure 4 This is a schematic diagram of the secondary-side output voltage of a dual active full-bridge converter during a desired voltage change, according to an embodiment of this disclosure. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.
[0021] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this disclosure should have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "first," "second," and similar terms used in the embodiments of this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.
[0022] In recent years, to meet the continuously growing energy demand, DC-DC converters have been widely used in DC microgrids and electric vehicle charging. Among them, the dual active bridge (DAB) DC-DC converter has advantages such as bidirectional energy flow, high transmission efficiency, electrical isolation, and low reactive power demand, and has been widely used in new energy power generation, electric vehicles, and energy storage. However, with the increasing proportion of power electronic converters in the power conversion field and the rising demand for high performance, higher requirements are being placed on the robustness and dynamic performance of power electronic converters. Because power electronic converters are strongly coupled nonlinear systems and are affected by circuit parameter perturbations, load and input voltage changes, and unmodeled dynamics, traditional linear control methods can no longer meet the requirements of high-performance control systems in practical applications. Existing control methods for dual active bridge DC-DC converters suffer from low stability and robustness. Therefore, improving the control stability and robustness of dual active bridge converters is an urgent technical problem to be solved.
[0023] Therefore, this disclosure provides a dual active full-bridge converter and its control method. By injecting virtual damping in parallel into the secondary-side full-bridge converter of the dual active full-bridge converter, and reconstructing the energy in the BM control strategy, a control signal is obtained to control the switching transistors of the dual active full-bridge converter. This enables the dual active full-bridge converter to achieve a fast response speed during control, eliminates overshoot, and exhibits small or even no output voltage fluctuations when the load changes abruptly, demonstrating high anti-interference capability and improving the control reliability and robustness of the dual active full-bridge converter.
[0024] See Figure 1 , Figure 1 A schematic main circuit diagram of a dual active full-bridge converter according to an embodiment of the present disclosure is shown. Figure 1The dual active full-bridge converter 100 may include a primary-side full-bridge converter 110, a transformer 120, and a secondary-side full-bridge converter 130 connected in sequence. Specifically, the AC side of the primary-side full-bridge converter 110 is connected to one side of the transformer 120, and the AC side of the secondary-side full-bridge converter 130 is connected to the other side of the transformer 120. The dual active full-bridge converter 100 can achieve DC-AC voltage conversion through the primary-side full-bridge converter 110 and AC-DC voltage conversion through the secondary-side full-bridge converter 130. The transformer can achieve voltage matching, electrical isolation, and temporary energy storage between the primary and secondary sides.
[0025] In some embodiments, the primary-side full-bridge converter 110 may include: The primary-side filter capacitor C1 has its first and second terminals connected to the first DC power supply. The primary-side first switching unit, primary-side second switching unit, primary-side third switching unit, and primary-side fourth switching unit; wherein, the primary-side first switching unit includes a primary-side first switching transistor S1 and a first diode D1 connected in parallel with the primary-side first switching transistor S1, the primary-side second switching unit includes a primary-side second switching transistor S2 and a second diode D2 connected in parallel with the primary-side second switching transistor S2, the primary-side third switching unit includes a primary-side third switching transistor S3 and a third diode D3 connected in parallel with the primary-side third switching transistor S3, and the primary-side fourth switching unit includes a primary-side fourth switching transistor S4 and a fourth diode D4 connected in parallel with the primary-side fourth switching transistor S4. The primary-side first switch S1 and the primary-side second switch S2 are connected in series across the filter capacitor C1 to form the primary-side first bridge arm; the primary-side third switch S3 and the primary-side fourth switch S4 are connected in series across the filter capacitor C1 to form the primary-side second bridge arm; the first terminal of the primary-side first switch S1, the primary-side third switch S3, and the filter capacitor C1 are all connected to the positive terminal of the first DC power supply to the first connection point a; The input inductor L has its first end connected to the connection point of the first primary switch S1 and the second primary switch S2. The second end of the input inductor L is connected to the first end of the primary winding of the transformer 120. The second end of the primary winding of the transformer 120 is connected to the connection point of the third primary switch S3 and the fourth primary switch S4.
[0026] In some embodiments, transformer 120 may be a high-frequency transformer (HFT). The turns ratio of the transformer coil may be n:1. For example, the AC side of the primary-side full-bridge converter 110 may be connected to the primary winding, and the secondary-side full-bridge converter 130 may be connected to the secondary winding of the transformer.
[0027] In some embodiments, the secondary-side full-bridge converter 130 may include: The secondary side includes a first secondary side switching unit, a second secondary side switching unit, a third secondary side switching unit, and a fourth secondary side switching unit. The first secondary side switching unit includes a first secondary side switching transistor Q1 and a fifth diode D5 connected in parallel with the first secondary side switching transistor Q1. The second secondary side switching unit includes a second secondary side switching transistor Q2 and a sixth diode D6 connected in parallel with the second secondary side switching transistor Q2. The third secondary side switching unit includes a third secondary side switching transistor Q3 and a seventh diode D7 connected in parallel with the third secondary side switching transistor Q3. The fourth secondary side switching unit includes a fourth secondary side switching transistor Q4 and an eighth diode D8 connected in parallel with the fourth secondary side switching transistor Q4. The first secondary switch Q1 and the second secondary switch Q2 are connected in series to form the first secondary bridge arm; the third secondary switch Q3 and the fourth secondary switch Q4 are connected in series to form the second secondary bridge arm; the connection point of the first secondary switch Q1 and the second secondary switch Q2 is connected to the first end of the secondary coil of transformer 120, and the connection point of the third secondary switch Q3 and the fourth secondary switch Q4 is connected to the second end of the secondary coil of transformer 120. Output capacitor C2, with its first and second ends connected to the two ends of the first and second bridge arms of the secondary side, respectively; the first and third switches of the secondary side, Q1 and Q3, and the first end of output capacitor C2 are all connected to the second connection point b.
[0028] Specifically, such as Figure 1 As shown, the DC side of the secondary-side full-bridge converter 130 can also be connected to the load R and a second DC power supply. Single-phase-shift (SPS) modulation can be used, with the primary-side first switch S1 and the primary-side fourth switch S4 of the primary-side full-bridge converter 110 conducting complementaryly, and the primary-side second switch S2 and the primary-side third switch S3 conducting simultaneously, generating a square wave voltage V with a 50% duty cycle on the primary side of the transformer T. H1 Similarly, in the secondary-side full-bridge converter 130, the first secondary-side switch Q1 and the fourth secondary-side switch Q4 are complementaryly turned on, while the second secondary-side switch Q2 and the third secondary-side switch Q3 are simultaneously turned on, generating a square wave voltage V with a duty cycle of 50% on the secondary side of the transformer T. H2 .
[0029] Neglecting converter losses, the power of the dual active full-bridge converter 100 can be: (1) Where n is the turns ratio of transformer 120, V1 is the primary DC side voltage of primary full-bridge converter 110, V2 is the secondary DC side voltage of secondary full-bridge converter 130, d is the duty cycle of primary full-bridge converter 110 and secondary full-bridge converter 130, L1 is the input inductance of primary full-bridge converter 110, and fs is the operating frequency of dual active full-bridge converter 100.
[0030] The KCL equations for the second connection point b in the secondary-side full-bridge converter 130 can include: (2) Where C2 is the output capacitor of the secondary-side full-bridge converter 130, and R is the load of the secondary-side full-bridge converter 130.
[0031] The 110 KVL equations for the original side-side full-bridge converter can include: (3) Solving the two equations (1) and (2) above simultaneously can include: (4) The new state variable (i) derived from the Brayton-Moser formula L The equivalent state equation of the dual active full-bridge converter 100 (V2) can be: (5) Dual active full-bridge converters are widely used in DC microgrids and electric vehicle charging, offering advantages such as high power density, easy soft-switching, and bidirectional power transfer capability. Traditional linear controllers struggle to meet the increasingly demanding requirements for speed and robustness. According to the control method of this disclosure, a passive control strategy based on Brayton-Moser can improve the performance of dual active full-bridge DC-DC converters.
[0032] The average state-space equation of the dual active full-bridge converter 100 can be written in BM form as follows: (6) The expected trajectory of the average state variable is as follows: (7) Among them, i Ld V represents the desired trajectory of the average inductor current of the input inductor L of the primary-side full-bridge converter 110. 2d The desired trajectory of the average output voltage of the output capacitor C2 of the secondary-side full-bridge converter 130. According to equations (6) and (7), the error trajectory of the state variables can be determined as follows: (8) The error dynamics equation can be described as follows: (9) By adding series and parallel damping dissipation factors to the above error dynamics equation, we can obtain: (10) in, , R is the damping dissipation factor. i and G i These are the injection impedances of the input inductor L connected in series with the primary-side full-bridge converter 110 and the injection impedances of the output capacitor C2 connected in parallel with the secondary-side full-bridge converter 130, respectively.
[0033] In the BM control strategy, the energy of the control system, including the dual active full-bridge converter 100, is reconfigured to obtain the control function. Energy reconfiguration can be achieved by injecting virtual damping into the system. The virtual damping factor can be inserted in series with the input inductor or in parallel with the output capacitor.
[0034] Specifically, select an output capacitor to be inserted in parallel, and let P... Ri =0, then the closed-loop dynamic equation is: (11) The closed-loop dynamic equation of equation (11) for the expected trajectory of the average state variable can be obtained by subtracting equation (11): (12) Therefore, the closed-loop dynamic equation of the dual active full-bridge converter 100 based on the BM model can be derived: (13) The control law for the dual active full-bridge converter 100 based on the BM model is: (14) Therefore, the duty cycle of the parallel damper can be obtained: (15) The control method for a dual active full-bridge converter according to embodiments of this disclosure may include: Step S1: Collect the measured value V1 of the primary DC side voltage of the primary full-bridge converter and the measured value V2 of the voltage of the output capacitor; Step S2: Based on the desired voltage trajectory V of the output capacitor 2d The measured value V1 of the primary side DC-side voltage, the measured value V2 of the secondary side DC-side voltage, and the parallel injection impedance G of the secondary side full-bridge converter. i The parallel injection damping G of the primary-side full-bridge converter and the secondary-side full-bridge converter are used to obtain the duty cycle d of the primary-side full-bridge converter and the secondary-side full-bridge converter; Step S3: Modulate the signal based on the duty cycle d to obtain the switch control signal; Step S4: Control the switching transistors in the primary-side full-bridge converter and the secondary-side full-bridge converter based on the switching control signal.
[0035] In some embodiments, the voltage expected trajectory V based on the output capacitor 2d The measured value V1 of the primary side DC-side voltage, the measured value V2 of the secondary side DC-side voltage, and the parallel injection impedance G of the secondary side full-bridge converter. i The parallel injection damping G of the primary-side full-bridge converter and the secondary-side full-bridge converter are used to obtain the duty cycle d of the primary-side full-bridge converter and the secondary-side full-bridge converter, including: The expected voltage trajectory V based on the output capacitor 2d The error trajectory of the secondary DC-side voltage is obtained by combining the measured value V2 of the secondary DC-side voltage. ; Based on the parallel injection impedance G of the output capacitor i The error trajectory of the secondary DC side voltage The duty cycle d of the primary-side DC-side voltage V1 and the parallel injection damping G of the secondary-side full-bridge converter are obtained by using the measured value V1 of the primary-side DC-side voltage and the parallel injection damping G of the secondary-side full-bridge converter.
[0036] In some embodiments, the dual active full-bridge converter further includes a transformer connected between the primary-side full-bridge converter and the secondary-side full-bridge converter, wherein the input inductor in the primary-side full-bridge converter is connected to the transformer; Based on the parallel injection impedance G of the secondary full-bridge converter i The error of the secondary DC side voltage The measured value V1 of the primary-side DC-side voltage and the parallel injection damping G of the secondary-side full-bridge converter are used to obtain the duty cycle d of the primary-side full-bridge converter and the secondary-side full-bridge converter, including: Where fs is the operating frequency of the dual active full-bridge converter, L is the inductance value of the input inductor, n is the turns ratio of the transformer coil, and C2 is the capacitance value of the output capacitor.
[0037] In some embodiments, the voltage expected trajectory V based on the output capacitor 2d The error trajectory of the secondary DC-side voltage is obtained by combining the measured value V2 of the secondary DC-side voltage. ,include: Based on the measured value V2 of the secondary DC side voltage and the expected trajectory V 2d The difference is used to obtain the error trajectory of the secondary DC-side voltage. .
[0038] In some embodiments, based on the parallel injection impedance G of the output capacitor i The error trajectory of the secondary DC side voltage The measured value V1 of the primary-side DC-side voltage and the parallel injection damping G of the secondary-side full-bridge converter are used to obtain the duty cycle d of the primary-side full-bridge converter and the secondary-side full-bridge converter, including: Determine the average state equation of the dual active full-bridge converter based on the BM model with respect to the state variables, including the current measurement value i of the input inductor. L and the measured voltage V2 of the output capacitor; The expected current trajectory of the input inductor and the expected voltage trajectory of the output capacitor are determined based on the average state equation. The error dynamics equation of the dual active full-bridge converter is determined based on the expected current trajectory and the expected voltage trajectory. Based on the error dynamics equation and the parallel injection damping connected in parallel with the output capacitor, the closed-loop dynamics equation based on the BM model is obtained. The duty cycle d of the primary-side full-bridge converter and the secondary-side full-bridge converter is obtained based on the closed-loop dynamic equation.
[0039] In some embodiments, the average state equation of the dual active full-bridge converter with respect to state variables includes: Where P is the power of the dual active full-bridge converter.
[0040] In some embodiments, the desired current trajectory of the input inductor and the desired voltage trajectory of the output capacitor include: , The desired trajectory of the input inductor, The desired trajectory of the average output voltage; Based on the expected trajectories of the input inductor and the output capacitor, the error dynamics equation of the dual active full-bridge converter is determined, including: .
[0041] In some embodiments, based on the error dynamics equation and the parallel injected damping connected in parallel with the output capacitor, a closed-loop dynamics equation based on the BM model is obtained, including: , , , To inject damping into the parallel connection.
[0042] In some embodiments, the duty cycle d of the primary-side full-bridge converter and the secondary-side full-bridge converter is obtained based on the closed-loop dynamic equation, including: Based on the expected current trajectory of the input inductor and the expected voltage trajectory of the output capacitor, and the closed-loop dynamic equation, the control law of the dual active full-bridge converter based on the BM model is obtained, including: ; The duty cycle d is determined based on the control law.
[0043] Specifically, the measured value V1 of the primary-side DC-side voltage of the primary-side full-bridge converter 110 and the measured value V2 of the secondary-side DC-side voltage of the secondary-side full-bridge converter 130 can be acquired. The expected trajectory i of the average inductor current of the primary-side full-bridge converter 110 is then calculated. Ld The expected trajectory V of the average output voltage of the secondary-side full-bridge converter 130 2d The error trajectory of the average inductor current of the primary-side full-bridge converter 110 can be obtained. Error trajectory of the average output voltage of the secondary DC side voltage Based on the series-parallel damping dissipation factor and the error trajectory of the average inductor current and the average output voltage, the error dynamic equation of the dual active full-bridge converter can be obtained, for example, equation (10). Further, based on the parallel insertion of the output capacitor C2 of the secondary-side full-bridge converter 130, the power P injected by the series damping inductor on the primary-side full-bridge is... Ri =0, then the closed-loop dynamic equation can be obtained, for example, equation (11). Based on this closed-loop dynamic equation, and the expected trajectory of the average state variables (average inductor current iL of the primary-side full-bridge converter 110, average output voltage V2 of the secondary-side full-bridge converter 130), for example, equation (7), the closed-loop dynamic equation of the dual active full-bridge converter based on the BM model can be obtained, for example, equation (13). Thus, the control law of the dual active full-bridge converter based on the BM model can be obtained, for example, equation (14). According to this control law, the duty cycle d of the dual active full-bridge converter based on the BM model can be obtained, for example, equation (15). Based on this duty cycle d, PWM modulation (e.g., phase-shifted PWM) is performed to obtain the switching control signal of the dual active full-bridge converter based on the BM model, so as to control the switching transistors S1-S4 and Q1-Q4 of the dual active full-bridge converter.
[0044] The control method based on the BM model of the present disclosure can be used to perform parallel injection damping simulation verification on the dual active full-bridge converter. The simulation parameters are shown in Table 1.
[0045] Table 1
[0046] See Figure 2 , Figure 2 A schematic diagram of the secondary-side output voltage of a dual active full-bridge converter according to an embodiment of the present disclosure during the startup phase is shown. Figure 2 According to the control method of this embodiment, the secondary-side output voltage curve of the dual active full-bridge converter during the startup phase is 210, the output voltage V2 is 750V, the injected damping G is 0.01515Ω, and Gi is 0.0088Ω. In the conventional method, the PI controller uses control parameters Kp=0.0008 and Ki=0.05, and the secondary-side output voltage curve of the conventional control method is 220. It can be seen that, according to the BM model-based control method of this embodiment, the output voltage V2 reaches the desired value at t1=0.033s and gradually stabilizes, while with the PI control in the conventional method, the output voltage reaches the desired value at t2=0.085s and there is overshoot, with an overshoot of approximately 20.6%. Therefore, compared with the conventional PI control, the BM model-based control method of this embodiment has a faster response speed for the dual active full-bridge converter system and no overshoot, effectively resolving the contradiction between the speed and overshoot of the conventional PI control.
[0047] See Figure 3 , Figure 3 A schematic diagram of the secondary-side output voltage of a dual active full-bridge converter under load abrupt change is shown according to an embodiment of the present disclosure. Figure 3 In this embodiment, a 448Ω resistor can be connected in parallel on the secondary side at 0.25s to simulate a sudden load change. The input voltage remains at 450V, and the output voltage is 750V. According to the control method of this disclosure, when a sudden load change occurs on the secondary side, the output voltage remains at the desired value of 750V without significant voltage fluctuation, as shown in curve 310. With conventional PI control, a more significant voltage fluctuation occurs during a sudden load change, with a fluctuation of approximately 3.53%, followed by a return to steady state of 750V at 0.315s, as shown in curve 320. Therefore, compared to conventional PI control, the control method of this disclosure exhibits no significant output voltage fluctuation during a sudden load change.
[0048] See Figure 4 , Figure 4 A schematic diagram of the secondary-side output voltage of a dual active full-bridge converter during a desired voltage change is shown according to an embodiment of the present disclosure. Figure 4In the example, at 0.2s, the input voltage abruptly changes from 750V to 680V. According to the BM-based control method of this embodiment, after a disturbance is introduced into the system, it recovers to a steady state at t3=0.2032s, with the voltage stabilizing at 680V and showing no significant fluctuations, as shown in curve 410. When using traditional PI control, it recovers to a steady state at t4=0.237s, and exhibits more significant fluctuations compared to the control method of this embodiment, with a fluctuation amount of approximately 1.62%, as shown in curve 420. It can be seen that compared to traditional PI control, the BM control according to this embodiment has a certain degree of speed and no significant fluctuations after a disturbance.
[0049] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of this disclosure (including the claims) is limited to these examples; within the framework of this disclosure, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the embodiments of this disclosure as described above, which are not provided in detail for the sake of brevity.
[0050] Additionally, to simplify the description and discussion, and to avoid obscuring the embodiments of this disclosure, the provided drawings may or may not show well-known power / ground connections to integrated circuit (IC) chips and other components. Furthermore, the apparatus may be shown in block diagram form to avoid obscuring the embodiments of this disclosure, and this also takes into account the fact that the details of implementation of these block diagram apparatuses are highly dependent on the platform on which the embodiments of this disclosure will be implemented (i.e., these details should be fully understood by those skilled in the art). While specific details (e.g., circuits) have been set forth to describe exemplary embodiments of this disclosure, it will be apparent to those skilled in the art that the embodiments of this disclosure can be implemented without these specific details or with variations thereof. Therefore, these descriptions should be considered illustrative rather than restrictive.
[0051] This disclosure is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure.
Claims
1. A control method for a dual active full-bridge converter, characterized in that, The dual active full-bridge converter includes a primary-side full-bridge converter and a secondary-side full-bridge converter, wherein the output capacitor of the secondary-side full-bridge converter is connected to the load; the dual active full-bridge converter also includes a transformer connected between the primary-side full-bridge converter and the secondary-side full-bridge converter, wherein the input inductor of the primary-side full-bridge converter is connected to the transformer; The method includes: The measured value V1 of the primary DC side voltage of the primary full-bridge converter and the measured value V2 of the voltage of the output capacitor are collected. The expected voltage trajectory V based on the output capacitor 2d The measured values of the primary DC-side voltage V1, the secondary DC-side voltage V2, and the parallel injection impedance G of the secondary full-bridge converter. i The parallel injection damping G of the primary-side full-bridge converter and the secondary-side full-bridge converter are used to obtain the duty cycle d of the primary-side full-bridge converter and the secondary-side full-bridge converter, including: The expected voltage trajectory V based on the output capacitor 2d The error trajectory of the secondary DC-side voltage is obtained by combining the measured value V2 of the secondary DC-side voltage. ; Based on the parallel injection impedance G of the output capacitor i Error trajectory of the secondary DC side voltage The measured value V1 of the primary-side DC-side voltage and parameter G are used to obtain the duty cycle d of the primary-side full-bridge converter and the secondary-side full-bridge converter, including: Determine the average state equation of the dual active full-bridge converter based on the BM model with respect to the state variables, including the current measurement value i of the input inductor. L and the measured voltage V2 of the output capacitor; The expected current trajectory of the input inductor and the expected voltage trajectory of the output capacitor are determined based on the average state equation. The error dynamics equation of the dual active full-bridge converter is determined based on the expected current trajectory and the expected voltage trajectory. Based on the error dynamics equation and the parallel injection impedance connected in parallel with the output capacitor, the closed-loop dynamics equation based on the BM model is obtained. Based on the closed-loop dynamic equation, the duty cycle d of the primary-side full-bridge converter and the secondary-side full-bridge converter is obtained: Where fs is the operating frequency of the dual active full-bridge converter, L is the inductance value of the input inductor, n is the turns ratio of the transformer coil, and C2 is the capacitance value of the output capacitor. The switching control signal is obtained by modulation processing based on the duty cycle d; The switching control signal controls the switching transistors in the primary-side full-bridge converter and the secondary-side full-bridge converter.
2. The method according to claim 1, characterized in that, The expected voltage trajectory V based on the output capacitor 2d The error trajectory of the secondary DC-side voltage is obtained by combining the measured value V2 of the secondary DC-side voltage. ,include: Based on the measured value V2 of the secondary DC side voltage and the expected trajectory V 2d The difference is used to obtain the error trajectory of the secondary DC-side voltage. .
3. The method according to claim 1, characterized in that, The average state equation of the dual active full-bridge converter with respect to the state variables includes: Where P is the power of the dual active full-bridge converter.
4. The method according to claim 3, characterized in that, The desired current trajectory of the input inductor and the desired voltage trajectory of the output capacitor include: , The desired trajectory of the input inductor, The desired trajectory of the average output voltage; Based on the expected trajectories of the input inductor and the output capacitor, the error dynamics equation of the dual active full-bridge converter is determined, including: 。 5. The method according to claim 4, characterized in that, Based on the aforementioned error dynamics equation and the parallel injection impedance connected in parallel with the output capacitor, the closed-loop dynamics equation based on the BM model is obtained, including: This is the parallel injection impedance.
6. The method according to claim 5, characterized in that, The duty cycle d of the primary-side full-bridge converter and the secondary-side full-bridge converter is obtained based on the closed-loop dynamic equation, including: Based on the expected current trajectory of the input inductor and the expected voltage trajectory of the output capacitor, and the closed-loop dynamic equation, the control law of the dual active full-bridge converter based on the BM model is obtained, including: ； The duty cycle d is determined based on the control law.