Reliability Research Of Power Electronic Converter Based On The Advanced Traction Substation

The operational safety and reliability of the Advanced Cophase Traction Power Supply System(ACTPSS)are the key factors affecting its promotion and application.As the most important device in ACTPSS,the reliability research of power electronic converter is very important.Due to the fault-tolerant characteristics of power electronic converter,the reliability evaluation of the converter cannot use traditional reliability models.Various working states of the converter must be considered,including normal working and fault tolerant working.Therefore,it is necessary to establish a proper reliability model and research reliability evaluation methods of power electronic converters used in ACTPSS.This thesis firstly introduces the composition and structure of ACTPSS.Taking Cascaded H-Bridge Converter(CHBC)and Three-Level Neutral Point Clamped Cascaded Converter(3LNPC-CC)as research objects,the control method and modulation strategy of the objects are analyzed.Fault-tolerant operation of the converter is also researched based on the application background.The scheme and the algorithm of the maximum allowable fault modules of the converter are analyzed,which is verified the correctness and effectiveness combining with the simulation.Secondly,from three aspects of “device-level,module-level,system-level”,this thesis conducts modeling of the converter considering the “normal,alive and failed”operating states.The failure rate models of IGBT,diode,capacitor and inductor are studied at the device level.The operating losses of the power switching device used in H-bridge and 3LNPC converters under the SPWM modulation method are analyzed respectively.And the device junction temperature prediction model is built.At the module level,considering the reliability composition and operating characteristics of the converter,the reliability model of the submodule of the converter is established based on the Fault Tree Analysis(FTA).At the system level,based on Markov’s theory,the reliability model of the system is established.In the meantime,the calculation method of the state transition probability between states is researched.To meet the high reliability design requirements for engineering applications of ACTPSS,the reliability optimization method of the converter is further studied.To be more specific,the reliability optimization model is established from the device level and the module level.Finally,based on the above research,a reliability evaluation method for cascaded converter is proposed in this thesis.The reliability of CHBC and 3LNPC-CC are evaluated respectively.On this basis,the reliability of the two topology converters is compared and optimized.Considering the requirements of system reliability,space utilization and controller adaptation,the topology selection of power electronic converters in the advanced traction substation is suggested when the capacity is designed as 20 MVA.