Research On Accelerated Life Test Method Of MMC Sub Module

China’s power grid has stepped into the era of UHV and large-scale interconnected power grids.Facing the economic,technological and environmental challenges,The power industry needs to adopt a more economical,environmentally-friendly and flexible power transmission.Voltage Source Converter HVDC(VSC-HVDC),also known as Flexible High Voltage DC transmition or Light High Voltage DC transmition,was first proposed by Canadian scholar Boon-Teck Ooi.for supplying power to urban power grids,renewable energy sources Network,passive network power supply,asynchronous AC power grid interconnection and other fields VSC-HVDC have played an important role,and made considerable progress in recent years,the reliability of the VSC-HVDC converter valve has also become a research hot spot.VSC-HVDC converter valve topology has two-level topology,three-level topology and Modular Multi-level Converter(MMC)topology,this paper focuses on the reliability of the MMC converter valve.In this paper,we firstly study the accelerated life test method of MMC submodules.The topology and operating principle of MMC-HVDC converter valve are introduced,and the failure mechanism of MMC sub-module is analyzed.To reproduce the most serious conditions during the operation of sub-module is principle of MMC sub-module accelerated life test method design.Then the test circuit of MMC submodule is designed,and the test current and test voltage are calculated according to the actual project.The simulation model of test circuit is built in PSCAD/EMTDC simulation software to prove the correctness and equivalence of test circuit.And the temperature measurement system of on-line monitoring IGBT module junction temperature was designed.The junction temperature of IGBT module is closely related to the reliability of DC transmission system in engineering.The monitoring of IGBT junction temperature can realize the dynamic control of VSC.Therefore,according to the requirement of actual project,the paper puts forward an engineering on-line monitoring IGBT module junction Method of temperature and calculate measurement error of this method.The temperature measurement method can directly and quickly obtain the junction temperature of the IGBT module,avoiding the error caused by the indirect measurement,and improve the accuracy of the junction temperature measurement.