3L-DAB converter primary side and secondary side fusion full-power optimization modulation method
By optimizing the shift ratio of the 3L-DAB converter to the combination of D1 and D2, current stress suppression and soft switching are achieved across the entire power range, solving the problem of high switching losses and improving system efficiency and reliability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEFEI INSTITUTE OF PHYSICAL SCIENCE CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2026-03-31
- Publication Date
- 2026-05-12
AI Technical Summary
Traditional three-level dual active bridge (3L-DAB) converters suffer from high current stress and high switching losses across the entire power range, affecting system efficiency and reliability.
By establishing a mathematical model and optimizing the shift ratio of D1 and D2, and using KKT conditions and boundary analysis, current stress is suppressed across the entire power range, enabling soft switching of the primary and secondary switching transistors and generating drive signals to control the switching transistors' on and off states.
Significantly reduces switching losses and improves system efficiency. It is suitable for 3L-DAB converters of various voltage and power levels, and its control logic is clear and easy to implement.
Smart Images
Figure CN122026730A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of power electronic control technology and relates to a full-power optimization modulation method for primary and secondary sides of a 3L-DAB (Three-Level Dual Active Bridge) converter. Background Technology
[0002] With the transformation of energy structure and the rapid development of distributed renewable energy, DC-DC conversion technology that is efficient, high-power-density, electrically isolated, and supports bidirectional power flow is receiving increasing attention. Dual Active Bridge (DAB) converters, due to their advantages such as high-frequency electrical isolation, ease of soft-switching implementation, and flexible bidirectional power flow control, have become one of the core topologies of medium- and high-power isolated DC-DC conversion systems, and are widely used in photovoltaic power generation, energy storage systems, electric vehicle charging, and other fields.
[0003] However, with the increase in system voltage levels and power capacity, traditional two-level DAB converters face problems such as high voltage stress on switching devices and low modulation freedom. Although the withstand voltage can be improved by connecting modules in series, this introduces complex voltage equalization control, increasing system cost and control difficulty. To address this, the three-level dual active bridge (3L-DAB) converter has emerged. Its primary and secondary structure is symmetrical, which can reduce the voltage stress on the switching devices to half that of the two-level topology, making it suitable for medium and high voltage DC power distribution systems such as rail transit and ship power supply.
[0004] However, the 3L-DAB converter contains up to 16 switches. If a traditional modulation strategy is used, it can easily lead to large circulating current and switching current stress, increasing conduction and switching losses, and even causing hard switching, affecting system efficiency and reliability. Therefore, a new modulation strategy is urgently needed to effectively suppress current stress across the entire power range and maximize zero-voltage turn-on of the switches, thereby improving the overall performance of the converter. Summary of the Invention
[0005] The technical solution of this invention is used to solve the problem of how to effectively suppress the current stress of the 3L-DAB converter by optimizing the shift ratio.
[0006] The present invention solves the above-mentioned technical problems through the following technical solutions:
[0007] This invention provides a method for primary-secondary side fusion full-power optimized modulation of a 3L-DAB converter, comprising the following steps: Step 1: Establish the voltage conversion ratio of the 3L-DAB converter Maximum current stress Mathematical models for primary-side soft-switching conditions and secondary-side soft-switching conditions, wherein, ; Step 2: Based on the given input voltage of the 3L-DAB converter Output voltage and transformer turns ratio Calculate transmission power ; Maximum current stress With transmission power Per-unit processing is performed to obtain the per-unit current stress. and per-unit transmission power Establish the objective function for current stress of the 3L-DAB converter; The formula for the objective function of current stress of the 3L-DAB converter is as follows:
[0008] in, Let current stress be the objective function. For Lagrange operators, Compared to inward movement, Compared to moving outwards; Step 3: Within the applicable power range of the secondary and primary sides respectively, find the combination of shift ratios D1 and D2 that minimizes the current stress; The method for finding the shift ratio combination D1 and D2 that minimizes current stress is as follows: in the high-power range, the internal solution of the KKT condition is used to optimize the current stress and soft switching of the single-sided switch; in the low-power range, the boundary analysis method is used to achieve critical soft switching and expand the shift ratio applicable to the single-sided soft switching to the full power range. Step 4: The shift ratio with the least current stress is fed into the pulse generator in combination with D1 and D2 to generate a drive signal, which drives the primary and secondary side switches of the 3L-DAB converter to turn on and off.
[0009] Furthermore, the specific shift ratio with minimum current stress within the applicable power range of the secondary side, corresponding to the combination of D1 and D2, is as follows: Within the applicable power range Within this range, the formula for calculating the shift ratio corresponding to the minimum current stress of the combination of D1 and D2 is: ; Within the applicable power range Within the range, the formula for calculating the shift ratio corresponding to the minimum current stress of the combination of D1 and D2 is as follows: .
[0010] Furthermore, the specific combination of D1 and D2 that minimizes the current stress within the primary side's applicable power range is as follows: Within the applicable power range Within the range, the formula for calculating the shift ratio corresponding to the minimum current stress of the combination of D1 and D2 is as follows: ; Within the applicable power range Within the range, the formula for calculating the shift ratio corresponding to the minimum current stress of the combination of D1 and D2 is as follows: .
[0011] Furthermore, the mathematical model is as follows: The voltage transformation ratio expression is:
[0012] Maximum current stress The expression is:
[0013] The primary-side soft switching condition is:
[0014] The secondary soft-switching condition is:
[0015] in, This is the input voltage of the 3L-DAB converter. This refers to the output voltage of the 3L-DAB converter. For transformer turns ratio, for The current is constantly transmitted through the inductor. For the switching frequency, To transmit inductance, Compared to inward movement, For the outward shift comparison, the range that the shift comparison must satisfy is: .
[0016] Furthermore, the transmission power The formula is: .
[0017] Furthermore, the per-unit current stress The formula is: .
[0018] Furthermore, the per-unit transmission power The formula is: .
[0019] The present invention also provides a 3L-DAB converter, wherein the 3L-DAB converter uses the above-mentioned 3L-DAB converter primary and secondary side fusion full power optimization modulation method to drive the primary and secondary side switching transistors to turn on and off.
[0020] The present invention also provides an electronic device, including a memory and a processor, wherein the memory is used to store a program that supports the processor in executing the above-described 3L-DAB converter primary-secondary side fusion full-power optimized modulation method, and the processor is configured to execute the program stored in the memory.
[0021] The present invention also provides a storage medium storing a computer program, which, when executed by a processor, performs the steps of the above-described 3L-DAB converter primary-secondary side fusion full-power optimization modulation method.
[0022] The beneficial effects of this invention are as follows: This invention optimizes the phase shift combination across the entire power range (especially in buck or high-power modes with K≥1), significantly suppressing current stress; by satisfying the soft-switching conditions of the primary and secondary sides, it maximizes zero-voltage turn-on and reduces switching losses; experimental verification shows that the optimized switching losses are significantly reduced and the overall system efficiency is significantly improved; it is applicable to 3L-DAB converters of various voltage and power levels, and has good versatility and engineering promotion value; based on mathematical modeling and objective function optimization, the control logic is clear and easy to implement in embedded systems. Attached Figure Description
[0023] Figure 1 This is a circuit structure diagram of the 3L-DAB converter according to an embodiment of the present invention; Figure 2 This is a control waveform diagram of the 3L-DAB converter according to an embodiment of the present invention; Figure 3 This is a flowchart of the steps of the full-power optimization modulation method for primary and secondary side fusion of the 3L-DAB converter according to an embodiment of the present invention; Figure 4 These are the experimental waveforms of the optimized secondary-side switching transistors of the 3L-DAB converter in this embodiment of the invention. Figure 5 The waveforms are experimental waveforms of the primary-side switching transistors of the 3L-DAB converter in this embodiment of the invention after optimization. Detailed Implementation
[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0025] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments: Example 1 like Figure 1 The diagram shown is a circuit structure diagram of the 3L-DAB converter in this embodiment, including 16 switching transistors (S). 11 ~S 18 S 21 ~S 28 ), 8 diodes (D C1 ~D C8 ), 4 flying capacitors (C SS1 ~C SS4 ), 4 supporting capacitors (C) 11 C 12 C 21 C 22 ), 1 inductor (L r ) and 1 transformer (T r );like Figure 2 The figure shows the control waveform diagram of the 3L-DAB converter. In the figure, t0 to t6 represent the start time of the working mode at different stages.
[0026] like Figure 3 As shown in the figure, this embodiment provides a full-power optimization modulation method for primary and secondary side fusion of a 3L-DAB converter, which specifically includes the following steps: Step 1: Establish the voltage conversion ratio of the 3L-DAB converter ( Maximum current stress Mathematical models for primary-side soft-switching conditions and secondary-side soft-switching conditions.
[0027] The voltage transformation ratio is expressed as follows:
[0028] The maximum current stress The expression is:
[0029] The primary-side soft switching condition is:
[0030] The secondary soft-switching condition is as follows:
[0031] in, This is the input voltage of the 3L-DAB converter. This refers to the output voltage of the 3L-DAB converter. For transformer turns ratio, for The current is constantly transmitted through the inductor. For the switching frequency, To transmit inductance, Compared to inward movement, For the outward shift comparison, the range that the shift comparison must satisfy is: .
[0032] Step 2: Based on the given input voltage of the 3L-DAB converter Output voltage and transformer turns ratio Calculate transmission power ; Maximum current stress With transmission power Per-unit processing is performed to obtain the per-unit current stress. and per-unit transmission power We establish the objective function for current stress in the 3L-DAB converter, transforming the current stress and soft-switching problem into a problem related to the shift ratio. , The mathematical optimization problem.
[0033] The transmission power The calculation formula is as follows:
[0034] The per-unit current stress The calculation formula is as follows:
[0035] The standardized transmission power The calculation formula is as follows:
[0036] The formula for the objective function of current stress of the 3L-DAB converter is as follows:
[0037] in, Let current stress be the objective function. For Lagrange operators.
[0038] Step 3: Within the applicable power range of the secondary and primary sides respectively, find the shift ratio combination of D1 and D2 that minimizes the current stress, thereby changing the phase between the drive pulses and controlling the modulation waveform of the primary and secondary switching transistors of the 3L-DAB converter.
[0039] The method for finding the combination of shift ratios D1 and D2 that minimizes current stress described in this embodiment is as follows: In the high-power range, the internal solution of the KKT (Karush-Kuhn-Tucker conditions) is used to optimize the current stress and soft switching of the single-sided switching transistor. In the low-power range, the boundary analysis method is used to achieve critical soft switching and expand the shift ratio applicable to the single-sided soft switching to the full power range.
[0040] The minimum current stress ratios for the secondary and primary sides within their respective power ranges are shown in Tables 1 and 2.
[0041] Table 1. Minimum Current Stress for D1 and D2 Combinations within the Applicable Power Range of the Secondary Side
[0042] Table 2. Minimum Current Stress for Shift Ratios D1 and D2 Combinations within the Applicable Power Range of the Primary Side
[0043] Step 4: The shift ratio with the minimum current stress corresponding to Table 1 and Table 2 is combined with D1 and D2 and sent to the pulse generator to generate a drive signal to drive the primary and secondary side switches of the 3L-DAB converter to turn on and off.
[0044] Experimental results Taking the buck 3L-DAB converter as an example, such as Figure 4 and Figure 5 The optimized experimental waveforms of the secondary and primary side switches are shown in the figure. Figure 4 The stepped square wave line represents the voltage experimental waveform on the secondary side, and the curve represents the current experimental waveform on the secondary side. Figure 5 The stepped square wave line represents the voltage experimental waveform of the primary side, and the curve represents the current experimental waveform of the primary side. As can be seen from the figure, by changing the shift ratio of the DPS control, the magnitude of the current stress is reduced, enabling soft switching of the eight switches on both the secondary and primary sides. This solves the problem of excessive switching losses in the 3L-DAB converter during operation, significantly reduces the switching losses of the 3L-DAB converter, reduces the current stress of the 3L-DAB converter in actual operation, and improves the system efficiency.
[0045] Example 2 An electronic device includes a memory and a processor, the memory being used to store a program that supports the processor in executing the full-power optimized modulation method for primary and secondary side fusion of the 3L-DAB converter as described in Embodiment 1, the processor being configured to execute the program stored in the memory.
[0046] Example 3 A storage medium storing a computer program, which, when executed by a processor, performs the steps of the full-power optimization modulation method for primary and secondary side fusion of the 3L-DAB converter in Embodiment 1.
[0047] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for full-power optimized modulation of primary and secondary sides of a 3L-DAB converter, characterized in that, Includes the following steps: Step 1: Establish the voltage conversion ratio of the 3L-DAB converter Maximum current stress Mathematical models for primary-side soft-switching conditions and secondary-side soft-switching conditions, wherein, ; Step 2: Based on the given input voltage of the 3L-DAB converter Output voltage and transformer turns ratio Calculate transmission power ; Maximum current stress With transmission power Per-unit processing is performed to obtain the per-unit current stress. and per-unit transmission power Establish the objective function for current stress of the 3L-DAB converter; The formula for the objective function of current stress of the 3L-DAB converter is as follows: in, Let current stress be the objective function. For Lagrange operators, Compared to inward movement, Compared to moving outwards; Step 3: Within the applicable power range of the secondary and primary sides respectively, find the combination of shift ratios D1 and D2 that minimizes the current stress; The method for finding the shift ratio combination D1 and D2 that minimizes current stress is as follows: in the high-power range, the internal solution of the KKT condition is used to optimize the current stress and soft switching of the single-sided switch; in the low-power range, the boundary analysis method is used to achieve critical soft switching and expand the shift ratio applicable to the single-sided soft switching to the full power range. Step 4: The shift ratio with the least current stress is fed into the pulse generator in combination with D1 and D2 to generate a drive signal, which drives the primary and secondary side switches of the 3L-DAB converter to turn on and off.
2. The full-power optimized modulation method for primary and secondary sides of the 3L-DAB converter according to claim 1, characterized in that, The specific shift ratio with minimum current stress within the applicable power range of the secondary side, corresponding to the combination of D1 and D2, is as follows: Within the applicable power range Within this range, the formula for calculating the shift ratio corresponding to the minimum current stress of the combination of D1 and D2 is: ; Within the applicable power range Within the range, the formula for calculating the shift ratio corresponding to the minimum current stress of the combination of D1 and D2 is as follows: .
3. The full-power optimized modulation method for primary and secondary sides of the 3L-DAB converter according to claim 1, characterized in that, The specific shift ratio with minimum current stress within the applicable power range of the primary side, corresponding to the combination of D1 and D2, is as follows: Within the applicable power range Within the range, the formula for calculating the shift ratio corresponding to the minimum current stress of the combination of D1 and D2 is as follows: ; Within the applicable power range Within the range, the formula for calculating the shift ratio corresponding to the minimum current stress of the combination of D1 and D2 is as follows: .
4. The full-power optimized modulation method for primary and secondary sides of the 3L-DAB converter according to claim 1, characterized in that, The specific mathematical model is as follows: The voltage transformation ratio expression is: Maximum current stress The expression is: The primary-side soft switching condition is: The secondary soft-switching condition is: in, This is the input voltage of the 3L-DAB converter. This refers to the output voltage of the 3L-DAB converter. For transformer turns ratio, for The current is constantly transmitted through the inductor. For the switching frequency, To transmit inductance, Compared to inward movement, For the outward shift comparison, the range that the shift comparison must satisfy is: .
5. The full-power optimization modulation method for primary and secondary sides of the 3L-DAB converter according to claim 4, characterized in that, The transmission power The formula is: .
6. The full-power optimized modulation method for primary and secondary sides of the 3L-DAB converter according to claim 4, characterized in that, The per-unit current stress The formula is: .
7. The full-power optimized modulation method for primary and secondary sides of the 3L-DAB converter according to claim 4, characterized in that, The standardized transmission power The formula is: .
8. A 3L-DAB converter, characterized in that, The primary and secondary side switching transistors of the 3L-DAB converter are driven to turn on and off using the full-power optimized modulation method of primary-secondary side fusion as described in any one of claims 1 to 7.
9. An electronic device, comprising a memory and a processor, characterized in that, The memory is used to store a program that supports the processor in executing the full-power optimized modulation method for primary and secondary side fusion of the 3L-DAB converter according to any one of claims 1 to 7, and the processor is configured to execute the program stored in the memory.
10. A storage medium storing a computer program, characterized in that, When a computer program is run by a processor, it executes the steps of the full-power optimization modulation method for primary and secondary side fusion of the 3L-DAB converter as described in any one of claims 1 to 7.