Comparative Study Of Three Soft-switching Topologies Based On SiC&Si Hybrid ANPC Inverter

Active neutral point clamp(ANPC)inverters have been widely used due to their low switching loss and uniform loss distribution.The use of SiC devices can further improve efficiency.Increasing the switching frequency can increase the power density of SiC inverters,but when the switching frequency increases to several hundred kilohertz(kHz),the switching loss increases significantly,which limits the further increase of power density.Therefore,it is very meaningful to use soft switching technology to reduce the switching loss of high-frequency ANPC inverters.Firstly,the commutation principle of hard-switching inverter is analyzed.The design and selection basis of main circuit components are given.The loss model is established.According to the loss results,in the high switching frequency,medium and large output power occasions,the necessity of using soft switching technology in the inverter is analyzed.Aiming at the problem of the large number of auxiliary tubes in ANPC softswitching topology 1,ANPC soft-switching topology 2 is proposed.The single-phase auxiliary circuit contains only one switching tube.The working principle of soft switching topology 2 is analyzed in detail.Based on the precharge strategy and the non-precharge strategy,the basic guidelines and design process of resonance parameter design are given respectively.Two solutions to the problem of auxiliary circuit current reversal are discussed.The loss model of the soft-switching inverter is established,and the theoretical efficiency of soft-switching inverter and hard-switching inverter are compared.Aiming at the problem that the ANPC soft switching topology 1 can’t achieve soft switching when the load current is small,the ANPC soft switching topology 3 is proposed.The main circuit switch tube can also achieve ZVS turn-on when the load current is small.The commutation principle and resonance parameter design of soft switching topology 3are introduced.Three kinds of soft switching topologies are comprehensively compared,including auxiliary circuit current reverse problem,resonance parameter design,soft switching realization situation and auxiliary circuit loss,etc.The influence of the damage of auxiliary circuit components on the circuit is analyzed.Finally,PSIM simulations are built to verify the accuracy of the theoretical analysis of the three soft-switching topologies,and an experimental platform is built to measure the experimental waveforms and efficiency of the hard-switching inverter and the softswitching inverter,and compare them.