Research On Topology Of Three-Phase Soft-Switching Converter

With the rapid development of three-phase DC/AC inverters,they are developing towards higher switching frequency,greater transmission power and better performance.The switching loss problem caused by the increase of switching frequency becomes very prominent.The soft switch technology is proposed and applied in three-phase inverter.When the main circuit IGBT is switched off in a typical dc link resonant soft switch inverter,the the main circuit IGBT is ZVS turn-off by parallel buffer capacitance.The typical ac link resonant ZCT soft switch inverter main circuit IGBT opening process can achieve ZCS turn-on,but still has a certain turn-on loss.This paper presents a new topology of ZVS turn-on and ZCS turn-off soft-switch inverter.The topological inverter can completely eliminate the turn-on loss and turn-off loss of the main circuit IGBT.Combined with the improved PWM control strategy proposed in this paper,the overall loss of the inverter system can be further reduced.Finally,the effectiveness of the proposed topology and control strategy is verified by simulation.In this paper,the above soft switch and hard switch inverters are simulated loss calculation and comparison.According to the calculation results,the new type of soft-switch inverter proposed in this paper has the minimum loss under the comparison of various load currents and the switching frequency of the main circuit.And with the increase of switching frequency,the new type of ZVS turn-on ZCS turn-off soft-switch inverter proposed in this paper has a more prominent ability to reduce loss.In this paper,an experimental prototype is built for the proposed ZVS open ZCS shutdown soft-switching inverter.It is proved by experiments that the soft-switching inverter can greatly reduce the turn-on and turn-off losses of the main circuit IGBT,and realize the soft switching of the auxiliary switch.The characteristics of the action verify the correctness of the proposed topology and control strategy.