Research On RB-IGBT Based T-type Three-level Inverter And Its Soft-Switching Technology

With the development of social economy and the requirementt of energy conservation and emission reduction,the industry put forward higher requirements on the inverter output voltage and current waveform quality.With its advantages of low harmonic content and low electromagnetic loss,three-level inverters are studyed widely in the railway industry,photovoltaic field,uninterruptible power supply and other aspects of application.Compared with the traditional neutral clamped inverter,the T-type three-level inverter has fewer devices,less conduction loss,which has some advantages.The traditional clamped bridge of T-type three-level inverter consists of two common IGBT series reversely,with RB-IGBT devices available,RB-IGBT can be applyed to replace the ordinary IGBT,and RB-IGBT conduction loss is smaller,which can improve the efficiency of inverter.Based on this,this paper will give a comprehensive comparison between RB-IGBT based T-type three-level inverter and traditional two-level inverter in output characteristics and efficiency,furthermore,The T-type three-level inverter and its soft switching technology are deeply studied.The related simulation models and experimental platforms are built to verify the feasibility of the T-type three-level inverter.This paper will study the following aspects:This paper first analyzes the working principle of RB-IGBT based T-type three-level inverter,establishes three-level inverter simulation model,and then tests the characteristics of T-type three-level inverter.After that,the paper uses the traditional two-level inverter as the object,a comprehensive study of T-type three-level inverter is carried out from two aspects of output characteristics and efficiency.For output characteristics,it verifys that the T-type three-level inverter is better than the traditional two-level inverter from the two aspects of simulation and experiment,showing lower output voltage harmonics,lower ripple current of filter inductance and higher voltage utilization.For efficiency analysis,the formula of DC side capacitance loss and total loss of switching devices of RB-IGBT based T-type three-level inverter and traditional two-level inverter are derived.The calculation results show that the capacitance losses of DC side of two inverter is the same.Meanwhile,the conduction loss of T-type three-level inverter is lower than that of the two-level inverter.With the increase of power level,the conduction loss advantage is more obvious,but the switching loss of T-type three-level inverter is higher than that of two-level inverter.In summary,the RB-IGBT based T-type three-level inverter is suitable for use in low frequency and high power situations.Finally,in order to reduce the voltage stress and electromagnetic interference of switches in T-type three-level inverter and reduce the switching loss at the same time,the soft-switching technology with RB-IGBT based T-type three-level inverter is studied.Firstly,the working principle of the RB-IGBT based T-type three-level soft-switching inverter is analyzed,and the conditions of the inverter to realize the soft switching technology are derived and the parameters are designed.Then both of the soft-switching inverter models under the ideal experimental condition and under the parasitic parameters are established,and the scheme is proposed to solve the shock problem caused by parasitic parameters.Finally,the experimental platform is designed and built to further verify the feasibility of RB-IGBT based T-type three-level soft switching inverter.