Research On CLLC Resonant Converter Based On V2G And Its Control Strategy

As countries around the world vigorously promote the reform of energy structure,the electric vehicle industry has ushered in a vigorous development.V2G(vehicle-to-grid)technology has attracted wide attention as an important support technology for the bidirectional flow of energy between electric vehicles and power grid.Bidirectional DC-DC converter is the core component of V2 G technology,which has high requirements on output power quality and energy conversion efficiency.In this paper,the symmetric CLLC resonant converter is taken as the research object,and its resonant network parameter optimization design and closed-loop control strategy in the V2 G scenario are studied.The main research contents of this paper are as follows:(1)The effects of resonant network parameters on voltage gain characteristics and boundary switching conditions are studied.Based on the analysis of the working requirements of CLLC resonant converter used in V2 G scenario,the requirements to be met in the design of resonant network parameters and control strategy are proposed,and then the working principle and characteristics of each section of the converter are analyzed.The voltage gain formula and boundary switching conditions of CLLC resonant converter in the process of voltage boost and voltage drop are derived by using the time-domain approximation method,and the influence of resonant network parameters on voltage gain characteristics and boundary switching conditions is studied,which lays a theoretical foundation for the design of resonant network parameters.(2)An optimal parameter selection method is proposed to realize soft switching and high efficiency energy transmission in the full load range.Based on the requirements of voltage gain range,soft switch realization and high efficiency energy transmission,the restriction conditions of resonant network parameters selection are given,and according to the mathematical relationship between resonant network parameters and the influence on voltage gain and soft switch realization,an optimal parameter selection method is proposed which can realize the soft switch and high efficiency energy transmission in the full load range.According to the design requirements,the resonant network parameters are calculated and the key components are selected.A simulation model is established to verify the proposed design method of resonant network parameters.(3)An active disturbance rejection control strategy based on particle swarm optimization algorithm is proposed.In order to solve the problems of insufficient dynamic performance of traditional PID(proportion-integral-derivative)voltage closed-loop control strategy,which leads to large disturbance caused by input voltage change and load switching,and the difficulty of parameter setting of active disturbance rejection controller in the design process,an active disturbance rejection control strategy based on particle swarm optimization algorithm was proposed.Particle swarm optimization algorithm was used to obtain the optimal parameters of the automatic disturbance rejection controller,and the improved integral error(ITAE)was used as the performance index.A simulation model was built to compare and analyze the two control strategies.The results show that the dynamic performance of the active disturbance rejection controller optimized by particle swarm optimization algorithm is obviously improved.(4)The experimental prototype was built for experimental verification.According to the research requirements,a 3k W experimental prototype was built to carry out bidirectional operation experiments on the designed CLLC resonant converter in different working intervals.The results show that the design of CLLC resonant converter is reasonable.It can satisfy the voltage gain range and the realization of soft switch in the forward and reverse operation process,and the designed converter can meet the working requirements in the V2 G scenario.