Study On Analysis And Harnessing Of Electrified Railway Power Quality

In recent decades,China’s railway developed rapidly,and has become an indispensable way of transportation for people.Especially the development of electrified railway has brought great convenience to people’s life.However,as the main type of electrified railways,the AC-DC and the AC-DC-AC electric locomotives mainly bring power quality problems to the power grid,which seriously affects the safe and stable operation of the power grid.At the same time,because of the different working principles and control modes of the two models,the power quality characteristics of them are different,which makes it difficult to analyze the characteristics of electrified railway power quality.Therefore,starting from the establishment of different locomotive models,this paper analyzes the power quality characteristics of different locomotives,and puts forward a comprehensive control plan to solve the power quality problems caused by electrified railways.The main work of this paper are as follows:1)Taking the SS9 electric locomotive and CRH2 EMU as research object.For SS9 locomotive simulation,this paper analyzes the different level of power quality characteristics;for CRH2 EMU,a simulation model of the EMU system was established by using the three-level PWM rectifier,neutral-point-clamped(NPC)three-level inverter and three-phase asynchronous motor.In this paper,control factor f is adopted to solve the problem of unbalanced DC side voltage in NPC.The power quality characteristics of CRH2 EMU operating under traction and inverter conditions are simulated and analyzed,and the influence of the midpoint voltage balance control on the power quality of the traction net is also studied.2)A single-phase detection method based on active power separation and instantaneous reactive power theory is selected,and a comparative simulation analysis is carried out.Meanwhile,aiming at the problem of voltage interference in phase-locked loop based on instantaneous reactive power single-phase detection,an instantaneous reactive single phase detection method without phase-locked loop is adopted,and the effectiveness of the method is verified by simulation.3)Based on the modeling of SS9 electric locomotive and CRH2 EMU,the MATLAB/Simulink simulation models of the above two kinds of locomotive running mixed were established,and the power quality characteristics under different operation conditions were simulated and analyzed.In view of the power quality characteristics of mixed running mode,two comprehensive compensation schemes of HAPF+MCR and HAPF+SVG are proposed,and the compensation effect is compared by simulation.A cooperative optimization control strategy is proposed in the case of the unreasonable capacity allocation of the comprehensive compensation device,and the effectiveness of the method is verified by simulation.