电工技术学报2024，Vol.39Issue(14)：4480-4494,15.DOI:10.19595/j.cnki.1000-6753.tces.230861
双有源桥串联欠谐振变换器的最小回流电流控制
Minimum Backflow Current Control of Under-Resonant-Dual-Bridge-Series-Resonant Converter
摘要
Abstract
With bi-directional power transmission capability and high conversion efficiency,a dual-bridge-series-resonant converter(DBSRC)has attracted wide attention in battery charging and DC distribution systems.Since the soft-switching implementation of DBSRC is challenging when the voltage gain and load vary over a wide range,improvements in hardware and modulation schemes have been proposed to extend the soft-switching regions of the DBSRC.Nevertheless,it is still worth investigating to make the circuit simultaneously achieve full-load zero-voltage-switching(ZVS)operation and low circulating losses within a narrow switching frequency range without resorting to additional hardware components.This paper proposes an improved under-resonant control strategy,combining variable-frequency control and phase-shift control to minimize backflow current and optimize the root-mean-square(RMS)current. Firstly,inductor current expressions and ZVS conditions for different switches are explored through time-domain analysis.Compared with the optional range of Dϕ under ZVS conditions,the soft-switching conditions of the circuit are simplified.When the voltage gain is less(more)than 1,implementing soft-switching on the V1(V2)side enables full ZVS operation.Secondly,this paper adopts the KKT condition to derive the closed-form solutions of control variables to optimize backflow current while achieving full-load-range ZVS operation.According to the optimization results,the inner-phase-shift ratio is fixed at 1,and the outer-phase-shift ratio(Dϕ)is expressed as a function of the frequency ratio and voltage gain.According to the r obtained from the output of the PI controller and the voltage gain of the circuit,a look-up table is established to quickly determine the value of Dϕ,enhancing computational efficiency and dynamic performance. A 2 kW DBSRC prototype with an output voltage variation of 250 V～360 V was designed to estimate the effect of different control strategies.When the over-resonant variable-frequency phase-shift(VFM+PSM)control is adopted,a switching frequency range of 350 kHz to 660 kHz is required to ensure the circuit operates at full-range ZVS under different load conditions.The extended-pulse-width modulation(EPWM)control can hardly prevent the circuit from experiencing hard-switching at light-to-medium load conditions.In contrast,when the proposed minimum backflow current control is applied,a switching frequency range of 350 kHz to 450 kHz demonstrates the ability to achieve full-range ZVS operation even when the voltage gain is equal to or deviates from 1.It improves the ZVS performance and reduces the switching frequency range.Additionally,the proposed control strategy effectively reduces the backflow current and inductor RMS current,and a 2 A inductor RMS current reduction can be achieved under most load conditions. According to the experimental results,the effects of the proposed control strategy are summarized as follows.(1)The proposed minimum backflow current control provides full-range ZVS operation for the circuit without additional hardware components.(2)Compared with conventional strategies,the proposed control strategy can effectively extend the ZVS range while reducing the required switching frequency range.(3)In under-resonant operating mode,minimum backflow current control provides lower backflow current and inductor RMS current to reduce the circulating,conduction,and copper losses,improving transmission efficiency.关键词
双有源桥串联欠谐振变换器/软开关/最小回流电流控制/变频控制Key words
Under-resonant-dual-bridge-series-resonant converter/zero-voltage-switching/minimum back-flow current control/variable-frequency control分类
信息技术与安全科学引用本文复制引用
高祎韩,周子航,张欣,马皓..双有源桥串联欠谐振变换器的最小回流电流控制[J].电工技术学报,2024,39(14):4480-4494,15.基金项目
国家自然科学基金资助项目(62227802). （62227802）
