Research On Efficiency Optimization Strategy Of Dual Active Half-Bridge DC Converter

In the context of the rapid increase in installed capacity of green renewable energy sources such as solar and wind power generation,the use of bidirectional multi-port DC converters has attracted more attention.The dual active bridge DC converter as a typical topology has many advantages.In addition to achieving bidirectional power transmission,it also includes the lower difficulty in soft switching,the converter can achieve higher power density,fewer switching devices and smaller size,gradually become a popular research direction.It is used in power electronic transformers and new energy vehicles and other working scenarios.In this paper,the research is carried out under the support of Sichuan Provincial Outstanding Young Scientific and Technological Talent Project(2020JDJQ0037).The research object is selected as the symmetrical half-bridge topology in the dual-active bridge DC converter suitable for applications in the small power range—dual active-half-bridge DC converter(DAHB),but DAHB under the traditional phase shift control in the process of energy transmission large loss and narrow range of zero voltage switch(ZVS)has become a constraint on the development of the converter great resistance.Focusing on the problems of the above DC converter in the process of energy transmission,this paper describes the key characteristics and principles of DAHB working under phase-shifting control strategy from the perspective of the dual active-half-bridge DC converter,and analyzes the source of loss and low efficiency in the process of operation.In order to make full use of the performance of the DAHB,two efficiency Optimization strategies were proposed to improve the dual active-half-bridge DC converter by combining with particle swarm optimization algorithm(PSO)and Q-learning algorithm.The specific research work completed is as follows:Firstly,the principle of DAHB under phase-shifting control is described,the traditional single-phase-shifting control strategy(SPS)is analyzed,and the corresponding dual-phase-shifting control strategy(DPS)is obtained by adding a control degree of freedom according to the proposed topology.The characteristics of DAHB under phase-shifting control are analyzed,and the various operation modes and switching states of the converter are studied.The effective values of inductance current,loss characteristics and power transmission characteristics of the converter under phase-shifting control are obtained,and the range of zero voltage switching operation under different modes is given.Secondly,it introduces the basic principles and main methods of swarm intelligence algorithm,describes the main model of PSO algorithm,and combines it with the traditional dual active half-bridge phase shift control strategy,and proposes a dual active half-bridge based on PSO algorithm.The efficiency optimization scheme PDPS of the bridge DC converter realizes the ZVS operation of the converter in the full range.Later,the basic ideas and main algorithms of reinforcement learning are introduced,and the mathematical model of reinforcement learning algorithms is described.And on this basis,it focuses on the analysis of the classic reinforcement learning algorithm Q-learning algorithm,and then combines it with the traditional dual-active half-bridge phase-shifting control strategy.By setting the Q-learning algorithm environment and training parameters,completing the training process,a dual-active half-bridge DC converter efficiency optimization scheme QDPS based on the reinforcement learning algorithm is obtained.Finally,the simulation verification of the proposed dual-active half-bridge DC converter efficiency optimization scheme based on swarm intelligence algorithm and reinforcement learning algorithm is carried out.The operating conditions of dual active half-bridge DC converters under SPS,DPS,PDPS and QDPS control strategies are compared and simulated under different voltage transfer ratios and different active power outputs.The efficiency characteristics of the converter under the four control strategies are also analyzed.This paper compares the performance of dual-active half-bridge DC converters with traditional phase-shifting control strategies,and confirms that the efficiency optimization scheme proposed in this paper effectively improves the energy transmission efficiency of dual active half-bridge DC converter.