Research On Fault-tolerant Strategies For Full Bidirectional Switches Two Stage Matrix Converter

With the rapid development of power electronic technology,AC-AC converter is widely used in various industrial fields as the energy transfer and conversion mechanism in AC adjustable speed drive,AC power source and variable speed constant frequency system.Considering the harsh working environment in some applications and high reliability requirements of the system,the AC-AC converter's fault tolerant research has become the focus of domestic and foreign scholars.Compared to the traditional back to back converter,matrix converter has the advantages of small size,light weight and high power density.Thus,it has important theoretical significance and practical value to use matrix converter in above AC system.Full bidirectional switches two stage matrix converter(FBS-TSMC)is a transitional topology between direct matrix converter(DMC)and TSMC.Compared with DMC and TSMC,FBS-TSMC has 6 more switches,which result in less attention in this topology from academic in past decades.However,the special structure of FBS-TSMC makes it not only has the advantages of TSMC but also has fault tolerant capability.Thus,it is suitable for the system which has high requirements on reliability.The research is directed by theoretical analysis,and is carried on via both computer simulation and hardware experiments.The correctness of theoretical derivation results and validity of the proposed fault tolerant strategies are all verified in this thesis.The topology and characteristics of FBS-TSMC are introduced in this paper.It is pointed out that its highly symmetrical structure,redundant switch and bidirectional dc bus voltage polarity provide FBS-TSMC fault tolerant capability.The double space vector modulation(DSVM)is introduced in this paper.Resulting from FBS-TSMC's bidirectional structure,there are three driving signal distribution modes in inverter stage whose characteristics are compared in this paper.And the driving signals in normal working state are obtained.Various failures may occur in FBS-TSMC.Six fault tolerant strategies aiming at one bidirectional switch open-circuit failure in rectifier stage,two different side bidirectional switches open-circuit failure in rectifier stage,one bidirectional switch open-circuit failure in inverter stage,one bidirectional switch short-circuit failure in inverter stage,one unbidirectional switch open-circuit failure in inverter stage and one unbidirectional switch short-circuit failure in inverter stage are proposed in this paper,which can ensure system's stable operation and unchanged performance.Two mode changing strategies,which are suitable for rectifier and inverter fault tolerant strategies respectively,are also proposed to ensure the secure and effective implementation of the fault tolerant strategies.The model of FBS-TSMC is built in Matlab/Simulink.The simulation results are in line with the theoretical analysis and the feasibility of the fault tolerant strategy is verified.Finally,a prototype of FBS-TSMC is built and the implementation method of the hardware and software of the system is introduced in detail.The feasibility and effectiveness of the proposed method in this paper is validated by extensive experimental results.