Overvoltage Analysis Of Converter Station In MMC-HVDC System Considering Wideband Characteristic

According to operation experience of the traditional HVDC power transmission project,the operating over-voltage caused by fault or operating and the lightning over-voltage seriously threat the safety of the equipments in converter station.Along with the construction of VSC-HVDC based on MMC(modular multilevel converter),the overvoltage characteristics of the converter station will directly affect the design of insulation coordination and system stability.Therefore,studying on overvoltage characteristics of the converter station has a great value.In this thesis,overvoltage characteristics of the luxi back-to-back converter station of asynchronous interconnection for Yunnan power and China southern power grid considering wideband characteristics is studied.The overvoltage simulation model of MMC-HVDC system has been built under the PSCAD/EMTDC simulation environment.The control and protection system of MMC-HVDC has been considered minutely which can take control of converter station under steady state and fault state.The frequency dependent model of key equipment in converter station has been built which can be applied to the analysis of lightning overvoltage.The fault characteristics of key equipments in MMC-HVDC converter station have been analyzed in theory under typical faults.On the basis of the overvoltage simulation model of MMC-HVDC system,the overvoltage characteristics caused by typical faults have been simulated in detail.