| With the development of electric vehicle industry and the increasingly prominent energy problem,it is of great significance to develop the Vehicle-Grid(V2G)system,which can effectively cut peak and valley of power grid energy,regulate power quality and grid frequency.In this paper,the two-way charging system of electric vehicle used in V2 G system is taken as the research object,and its key technologies are studied.The existing topology of DC/DC converter is analyzed.An improved three-level LLC DC/DC topology is proposed,which improves the voltage gain and soft switching range.The working mode and state of the proposed topology are analyzed.The switching control methods in forward high gain,low gain,reverse intermittent mode and continuous mode are given,and the corresponding equivalent circuits in each stage are given.The voltage gain and soft switching characteristics of the bidirectional three-level LLC DC/DC converter are analyzed and the corresponding switching mode of the converter is given.In addition,the loss of duty cycle of driving waveform of primary side switch tube of transformer is analyzed,and the corresponding solutions are given.The causes of voltage oscillation of secondary side switch tube are analyzed,and the solution using RCD absorption circuit is proposed.The mathematical model of three-phase T-type three-level converter is established,the control system parameters are designed,the control strategy is given and the neutral point potential is controlled by the balance factor method.In addition,the SVPWM algorithm based on reference voltage decomposition is studied.Finally,an experimental prototype of bidirectional charging converter for V2 G system is designed,and the prototype is tested according to the relevant design indicators.The results prove the correctness and effectiveness of the method studied in this paper. |
PDF Full Text Request