Research On SVPWM Method For New Modular Multilevel Rectifier

In voltage source high voltage dc transmission system and in the field of highspeed,a new type of modular multilevel converter (MMC) has a broad applicationprospect, compared with the traditional multilevel converter, it has a smaller switchloss, lower switching frequency (equal to the fundamental frequency), larger outputcapacity, the demand for power electronics device is lower, have better scalability,and has the advantages of better steady state and transient performance.On the basis of reading many Foreign related books and literatures,in this paper,the topological structure and its working principle modulation methods and controlstrategies of a new type of modular five-level of the rectifier are studied and analyzed,And through the simulation verified the validity of research results in this paper.At first,the article introduce the background and significance of MMC-HVDCare introduced,then describes the MMC-HVDC research status and application athome and abroad, the basic working principle and the modulation method、the maincircuit topology structure of MMC has been carried on a brief introduction, at thesame time,this paper describes the present situation and tendency of MMC and theproblem we have faced. the second,the article describes the topology structure ofMMC，the basic working principle,the operation characteristics and mathematicalmode,the method of design the capacitance parameters bridge of arm module aregiven. The third chapter expounds the several kinds of SVPWM algorithm ofmultilevel voltage source converter, With new modular multilevel of the rectifier asan example, a kind of space vector pulse width modulation (SVPWM) algorithmwhich are applicable to MMC is studied.In this algorithm, reference voltage positionis located by nine judging rules, and in order to avoid the abrupt change of outputvoltage vectors during the process of desired vector changing from one section toanother, used the method that made the out put vector changes of the two adjacenttriangle in the opposite direction.and then according to the mathematical modelmentioned in the second chapter,the application of control strategy in the newmodular multilevel of the rectifier is given in this article, namely, inner ring currentvoltage control strategy,outer ring dc voltage control strategy,and put forward a kindof startup control method to applicable to MMC-HVDC.Finally, MATLAB/Simulinktoolbox is used to simulate the proposed control strategy and modulation algorithm,and then the paper analysis the simulation results. The results and analysis of simulation show that research on SVPWM method for new modular five-level rectifieris reasonable.