Abstract：With the increasing demand for flexible control of DC transmission, a large number of flexible HVDC transmission projects with MMC (modular multilevel converter) topology converter are put into construction and operation. Such as the national "863" project of China Southern Power Grid Nan'ao flexible HVDC project, and Yunnan Luxi back-to-back flexible HVDC project, the converter equipment are based on the topological structure of MMC is more advanced at present. And pre-charging of the converter has been widely studied, charging resistance of the uncontrolled charging method has been a large number of flexible engineering favor. In this paper, the basic structure and working principle of the modular multilevel converter DC transmission are introduced. The principle of MMC-HVDC is introduced, and the pre charging process of MMC converter is introduced. Finally, by PSCAD simulation, combined with the design parameters of a foreign flexible project. The selection of starting resistance is obtained by the simulation results the guiding significance of the selection of the charging starting resistor for the flexible HVDC project is described.
2018, Vol. 19 
