Research On Control Method Of Modular Multilevel Rectifier With N Single-phase AC Inputs

Under the situation of global shortage of fossil energy,high efficiency energy saving and new energy has become the two theme of the development of electric power industry.These years,a large number of multilevel converter topologies have been proposed,but the existing topology are generally single input and output and they can't meet the needs of multi input and multi output occasions.Multi-input/output multilevel converter is a kind of new multilevel converter with multiple AC ports.It achieves multiple AC voltage input / output which can reduce the number of switch components and converter cost.It has broad application prospects in the industrial fields such as smart grid,multiterminal HVDC,multiterminal AC transmission,multi motor high voltage variable frequency drive,PET,power quality compensation device and so on.But multilevel converters with multi AC input or output are still confined to the concept of topology research stage because of the limitation of the control method.Therefor,this paper puts forward a kind of switch group control method on depth analysis of the topological characteristics and working mechanism of MMC rectifier with N single-phase AC inputs.The main work of this paper is summarized as follows:(1)Reviewed the research status of multilevel converter and summarized the existing circuit topologies and control methods.(2)Analyzed the operating principle of MMC rectifier with N single-phase AC inputs in detail,pointed out the advantages of rectifier and the deficiency of the existing control method through simulation.(3)Derived switch group control method by the arms' electrical symmetry and node voltage method,which decoupled the modulation signals of switching groups on the same bridge,and make each switch group has independent modulation signal.(4)Designed capacitor voltage balancing control according to the capacitor voltage balance of each power module,and capacitor voltage averaging control according on the analysis of unbalanced voltage drop in each switch group.(5)Experimental platform is built to verify the feasibility of the proposed control method.