Research On Reliability Of Single-phase Combined Co-phase Power Supply Device

At present,Chinese electrified railways have entered a stage of high speed and heavy load,and the traditional traction power supply system will gradually fail to meet its needs.The emerging co-phase power supply system simultaneously solves the problems of electrical phase separation and power quality,which can adapt to the development of electrified railways and has become a hot research project in recent years.The single-phase combined co-phase power supply system is particularly concerned for its advantages such as high capacity utilization and small floor space.The most important thing for electrified railways is to be able to operate safely and stably.Therefore,the study of its reliability is extremely important significance.This thesis takes single-phase combined CPD as the research object.Aiming at the traditional single-phase combined co-phase compensation device(CPD)and a single-phase combined co-phase compensation device based on modular multilevel converter(MMC),completing its reliability assessment.And the redundancy configuration majorization of MMC-CPD.The main research contents of this thesis are as follows:(1)This thesis first briefly describes the combined in-phase power supply system and analyzes its traditional cascading topology and MMC-based topology and expounds the operating principle of MMC.This paper compares the structural reliability analysis methods of CPD and selects the reliability model suitable for this thesis.Furthermore,the reliability analysis methods of CPD main devices are introduced and the CPD reliability evaluation process is explained.(2)This thesis combines the physical failure mechanism of Insulated Gate Bipolar Transistor(IGBT)module and the finite element analysis method to complete the construction of the electric-thermal-mechanical coupling model,determine its weak links and use thermal fatigue cycle simulation to obtain number of failure cycles.Then this thesis uses the linear fatigue cumulative damage model to analyze its reliability data.Reliability data analysis of capacitors,reactors,controllers and other major devices in single-phase combined CPD is conducted through the Electronic Equipment Reliability Prediction Manual.(3)This thesis uses the k/n(G)system reliability model to complete the construction of the reliability model of the cascaded CPD,and evaluates its reliability without standby.Then,the reliability modeling of the four-arm MMC-CPD sub-module and the bridge arm is carried out,the reliability of the non-standby condition is evaluated,and the reliability of the MMC-CPD and the cascaded CPD is compared and analyzed under the non-standby condition.(4)In this thesis,the redundancy design of MMC-CPD and the reliability model in the case of redundancy are built.The impact of backup strategy,submodule redundancy and subsystem redundancy on its reliability is analyzed,and the reliability of MMC-CPD is completed.This thesis takes the cascaded CPD already used in the project as a reference,comparatively analyzes the redundancy configuration of MMC-CPD,and provides a reference for the use of MMC-CPD in the actual project.