Analysis of the DC Overvoltage Caused by the Blocking of MMC Inverter Station

摘要

In this paper, the mechanism of DC overvoltage is discussed, which caused by block fault in the converter station connected with the active network, and the dynamic process of DC voltage is analyzed in detail according to the equivalent circuit and the operating state of sub-module. Moreover, the DC overvoltage caused by the blocking of converter station is studied with the consideration of different blocking time. It is found that the development process of DC overvoltage is independent of fault time, and the virtual overvoltage is generated in steady state mainly contributed by the defect of simulation software that the disconnection of circuit breakers could not be truly reflected in the simulation software. The study of DC overvoltage can provide recommendation for the safety and stability of practical project and the design of insulation grade and protection. Finally a two-terminal MMC-HVDC simulation model built on PSCAD/EMTDC shows the effectiveness of the proposed analysis method.