Research And Design Of Three-Phase Single-Stage Resonant Isolated PFC Converter

Three-phase isolated PFC converter is widely used in electric vehicle charging,data center power supply and other fields.With the increasing number of electric vehicles in the world and the power consumption of data centers,the market of threephase isolated PFC converter is expanding rapidly.Existing three-phase isolated PFC converters generally adopt two-stage topology,and the power has been transformed twice,so the control is complex and the efficiency is low.The three-phase isolated PFC converter with single-stage topology can simplify control,improve efficiency,save energy and reduce emission because the power is transformed only once.Therefore,the research of three-phase PFC isolation converter is of great significance.Compared with phase shifte full bridge converter,LLC resonant converter can better improve the efficiency of the converter because of its superior soft switching characteristics.Therefore,based on LLC resonant converter,a single-phase singlestage isolated PFC converter is proposed,and the parameter design method of the converter is introduced.Then the converter is combined as a module,and a three-phase single-stage resonant isolated PFC converter is proposed to improve the power level of the converter.Compared with the existing technical scheme,the converter proposed in this paper realizes soft switching in the full load range,complete decoupling between modules,simple design,and more convenient later debugging and replacement.Then the three-phase single-stage resonant isolated PFC converter with line voltage input and parallel output is determined as the main research object of this paper,and the basic control strategy and improved control strategy are given.The feasibility of the proposed converter is verified by PSIM simulation.Aiming at the common working condition of three-phase power grid voltage imbalance,this paper analyzes the influence of power grid voltage imbalance on the proposed converter.The imbalance of grid voltage will make the output voltage of the converter have obvious double frequency ripple.Due to the existence of double frequency ripple,the total harmonic distortion rate(THD)of the input current will also be increased.In order to solve this problem,an output ripple suppression strategy based on instantaneous power equalization is proposed in this paper.The ripple suppression coefficient is introduced into the control strategy.By controlling the input current of each module,the input power of the converter is instantaneously equal to the output average power,and the double frequency ripple of the output voltage is suppressed from the root.The effectiveness of ripple suppression strategy is verified by PSIM simulation.Finally,an experimental prototype with 380 V AC input and 200V/3.3k W DC output is built.The feasibility of the proposed converter and its control strategy are verified through experiments.