Research On Modulation Strategy Of Current Source Converter In Microgrid

Due to the feature of simple topology,high quality of input/output current waveform,easy current fault management and four-quadrant operation,current source converters(CSCs)can be effectively utilized in microgrids.This paper researches issues exposed in microgrids with CSCs.Unbalanced DC current sharing,common-mode voltage(CMV)and modulation of a novel topology for CSCs are keys of this paper.The research work and novel ideals are organized as following:Under the background of interlinking microgrids,a multiport CSC is proposed.The impacts of electronic switches on CMV are analyzed in detail.To solve the problem of serious motor damage,electromagnetic interference in microgrid cluster,an enhanced comprehensive space vector modulation(SVM)is proposed to suppress the spike of CMV.Besides,corresponding analysis of characteristics of different methods are also obtained.In allusion to unbalancing power sharing and large CMV in parallel CSCs,the impacts of unsymmetrical factors on DC current balancing is studied.In addition,the mechanism of CMV induced by the parallel system is carried out in this paper.A novel two layer selection strategy is proposed based on conventional SVM.Through properly selecting redundant switching statuses of medium and small vectors,DC current balancing and CMV reduction can be realized at the same time.For back to back CSCs,too many switches may amplify the financial burden and reduce capacity density.A nine-switch topology is proposed where rectify and inverter share same switches in middle side.The relationship between Ampere-Second balancing principle and SVM is studied and a new modulation method for the new topology is proposed.Finally,the description of experimental platform is conducted.The code of DC current balancing and CMV reduction is complied for the parallel system and results show the correctness of the proposed strategy.