Research Of Isolated DC-DC Converter Based On MMC

With the rapid development of world science and technology and economy, high power converter of success, for the high voltage direct current transmission (for direct current HVDC) to break the technical barriers, DC transmission technology receives people’s attention. All over the world have been gradually built and put into operation of a large number of HVDC projects, experts and scholars of various countries for HVDC research is more and more extensive, can imagine in the future in the transmission network using DC transmission technology for power transmission proportion will be more and more big.Modular multilevel converter (modular multilevel converter, MMC) the modular structure of extremely easy extension, can through changes in access for flow is the number of sub modules to meet the requirements of different power and voltage level, easy to achieve integration, shorten the project cycle, cost savings, and the AC output terminal voltage to realize four quadrant operation, so that the energy can flow in both directions.MMC is applied to the DC-DC converter, through the transformer isolation, to build a MMC-IDC converter, in the two MMC to join the 1 AC transformer, through the transformer to complete the power conversion. MMC-IDC converter realized the two-way flow of energy, photoelectric isolation, passive device volume small and short circuit fault with the advantages of self protection, through an appropriate increase in the frequency of the alternating current transformer loss and the volume can be reduced, which can satisfy the requirements of high voltage, high power, high efficiency and reduce the design cost, construction of smart grid is of great significance for solving the problems existing in the DC transmission technology and.Firstly the basic topological structure of a conventional MMC system and sub module are analyzed, in HBSM basis for MMC-IDC proposed a DC fault crossing capacity of the sub topology module, through the basic theory of MMC of MMC-IDC topological structure, working principle and commonly used modulation method and control strategy. Then, the MMC-IDC control system simulation experiment platform is designed, and the related controller hardware part is explained in detail. Finally, the sub module controller simulation experiment are carried out.