Research On Three-phase AC/DC/AC Converter Topology And Control Strategy

Three-phase AC converter is widely used in power conversion,This makes the three-phase AC converter get more application and development.Based on the above,In this paper,the topology and the control algorithm of AC/DC/AC converter are studied,and the theoretical analysis is given and verified by the simulation results.The traditional three-phase AC/DC/AC back-to-back circuit uses seven or five segment SVPWM control strategy,The semiconductors devices in the topology have high switching frequency and more switching losses,which causes low converter efficiency.Several three-phase AC/DC/AC converter topologies are studied in this paper,and their PWM control strategies are discussed.Because of hard-switching characteristic of above mentioned topologies,the switching losses are hard to decrease largely,and the converter efficiency of converter become lower when switching frequency is higher.This paper proposes a three-phase AC/DC/AC ZVS soft-switching converter.Comparing to traditional back-to-back topology,proposed topology adds a DC resonant circuit including only one switch.The proposed topology ensure ZVS switching on and ZVS switching off for all switches and anti-parallel diodes,under any operational conditions.For the proposed topology,this paper proposes a combined PWM control method,which uses three segment SVPWM in rectifier side converter,and uses virtual zero vector SVPWM in inverter side,the SVPWM of rectifier side and inverter side is synchronized also.This combined PWM method can realize ZVS switching for all switches and diode,under the condition which angle between inverter voltage and current is unlimited.The simulation results verify the feasibility of proposed topology and control method.