The Research On Theory And Application Of The High Cost-Effective Power Quality Control System For Electrical Railway Power System

Facing the power quality problems—negative sequence components(NSCs),reactive power,harmonics,feeder voltage fluctuation and so on—in electrical railway power system(ERPS),this dissertation develops a series of theoretical and application studies on how to integrate the power electronics system with traction supply system to enhance the power quality in ERPS with high cost-efficiency.The researches of this paper have significant value in both theory and industrial applications.The research of this dissertation is supported by National Natural Science Foundation of China under Grant 51477046 and 51077044,the Key Project of Hunan Provincial Natural Science Foundation under Grant 12JJ2034,the Hunan Province Innovation Foundation for Postgraduate under Grant CX2014B131,and the Science and Technology Program of China State Grid Corp.under Grant 5216A014002.The main research work of this paper includes the following aspects.(1)The manifestations and original reasones of Chinese ERPS's power quality problems are discussed.A comprehensive exposition are also focused on the winding connection principle and characteristics of the traction transformer common used in China.Additinally,The operating principle,characteristics,and application occasions of the power quality control system with practical application value and market prospect in ERPS are systematically analyzed.(2)Based on the amount of measured data,this paper gives the property of the power quality problems in ERPS.Besides,combining the practical example,the main power quality indexes'evaluating methods and some practical measuring method in ERPS are analyzed in detail.(3)Taking the multi-purpose balance transformer(MPBT)as the research object,the“winding compensating idea(WCI)”is first proposed in this paper.Based on WCI,the compensating principle,voltage perturbation phenomeno n,mathematic model,resonance characteristic,and control system of the“pure”and“hybrid”MPBT-based electrical railway power quality control system are deeply and systematically analyzed,the unique operating mechanism and the items should be emphasize d in the designing process are also discussed.Besides,the analyzing method used in this dissertation is universal;similar method can also be used in the traction transformer with three-phase output port in the secondary winding,such as Y-?balance transformer,Y/>/?balance transformer,YN/?/~-V balance transformer,and so on.WCI fully explores the potentials of MPBT,successfully integrate the active system with the main transformer without other expensive low frequency auxiliary transformer,enhan ces the integration of the whole compensating system,the installing difficulty,covering space,and initial investment are also decreased significantly(if balance transformer is adopted).Hence,it can be concluded that WCI-based compensating system opens up a new way and an alternative scheme with high-cost efficiency for ERPS.(4)Focus on the Co-phase supply system which industrial application value is on the horizon,this paper first presented a hybrid railway power conditioning system to deal with the power quality problems.The L branches of the conventional railway static power conditioner(RPC)are substituted by two well-designed LC-coupling branches in this new system.The output voltage,dc-link voltage,and designing power rating of the active system can be decreased 30%~40%caused by this small change.The operating efficiency,reliability,and cost-efficiency are enhanced significantly as well.How to design a good LC-branches and adoption of an appropriate dc-link voltage value in the condition of load changes(include the load current and power factor)is the greatest contribution of this paper.The studying found that the proposed system has the advantage in the heavy loaded freight lines with concentrated load condition(where has many AC-DC locomotive).(5)The mathematic model,analysis method and designing essential of the control system,and the converter's core main-circuit parameters'design principle of the MW-level RPC are first deeply and systematically discussed in this paper.All the proposed methods are repeatedly verified by the practical RPC system,which has significant value in both theoretical study and industrial applications.(6)Successfully developed a V/v transformer-based RPC experimental system at the rank of 2×5k W,the related parameters and control(or debugging)essentials are also given in this paper in detial.A mount of experiences are developed based on this system,which verifies the correctness of the control system and feasibility of the RPC used in V/v transformer based traction substation.(7)A MW-level industrial designing scheme of V/v transformer based railway power quality control system(domestic initiative)is proposed in this paper.Based on the data measured of the MW-level RPC in a long period of time,the manifestations of the NSC,reactive power,harmonics,feeder voltage fluctuation,and economic benefits before and after RPC starts operation are systematically analyzed.Besides,this paper also gives the method of how to make RPC avoiding the dc-component generated by traction load.The measured results demonstrate that RPC can not only effectively suppressed the power quality problems in primary side of V/v transformer,but also has obvious benefit on decrease the fluctuation of the feeder voltage.So,application of RPC in the traction supply system can not only satisfy the power quality indexes limited by the grid,but also has big advantage in the optimal and economic operation of the traction supply system,so it has significant promotional value.The high cost-effective electrical railway power quality control system fully explores the potentials of the traction transformer,passive equipment,and the power electronic system.In the premise of getting good compensating effect,it significantly decreases the initial investment of the whole compensating system.Th is set of compensating system not only adapted the strict power quality requirements of the utility,but also catering to the mentality of freedom from receiving penalty and recovering the cost in a short time so as to get profits of the railway operator.So,it has important theoretical value and wider industrial application prospect.