The Power Quality Optimization Methods For Traction And Electric Propulsion Systems Based On New Transformers

To improve the typical power qualities,such as harmonics,negative sequence components,reactive power,voltage fluctuation in traction and electric propulsion systems,and solve the problems of core equipment,such as large volume,high cost and low service life in engineering application,with the support of the International Science and Technology Cooperation Program of China under Grant2018YFE0125300,the National Natural Science Foundation of China under Grant51822702,etc.,referring to the engineering data,the traction and electric propulsion systems based on new transformers have been porposed in this paper,for optimizing the power supply performance and engineering application potential.some key technology issues,including system topology and structure,equipment selection and parameter allocation,power quality optimization methods,comprehensive performance analysis and evaluation,model simulation and experiment,and so on are analyzed and studied broadly.Specifically,the following aspects are emphasized:(1)To solve the power quality problems in electrified railway,an ACBTT-based Railway Traction Power Supply System(RTPSS-AT)is proposed,whilst the topology and structure have been introduced.the Asymmetrical Connection Balance Transformer(ACBT)characterized with a much higher material utilization,is selected as the traction transformer.The Inductively Filtered Rectifier Transformer(IFRT),with Filter Tuned Branches(FTBs)is used for filtering harmonics and compensating reactive power,and can be also used as a coupling stage of Railway Power Conditioning,which can greatly reduce the investment and the improve power quality.Based on the characteristics of ACBTT,the concrete methods for improving power quality in ACBTT-AT is explained,and the compensation control method and controller parameters are also given and analyzed.(2)Based on the actual data of railway traction substation,a cost-function optimization has been proposed to minimize the system investment.By optimizing the installed capacity of compensation devices in ACBTT-AT,the capacity allocation strategy can enable a satisfactory compensation performance with relatively attractive costs.Under the precondition of power factor in grid and feeders,the cost-function optimization designs the capacity of FTBs and RPC,respectively,and the minim um value is available for the cost of compensation system.Meanwhile,numerous simulation and experiment work has been carried out for the validation of the system device selection,circuit topology,parameter design and cost-function optimization,and all the results demonstrate the effect of the proposed ACBTT-AT.(3)A magnetic-integrated multi-pulse rectifier transformer(MI-MPRT)is proposed,with the advantages of small size,low cost and better short-circuit impedance balance,has been proposed for traction and electric propulsion system.The structure configuration of MI-MPRT is introduced,and cooperated with staggered winding-arrangement,a tight impedance equalizing strategy is proposed to optimize the winding thickness and insulation distance comprehensively,and MI-MPRT would be designed in a minimum axial dimension,with equalizing short-circuit impedance.Rated at 500 k VA,the MI-MPRT prototype has been manufactured,and by the standard test on the prototype,the reliability and effectiveness of MI-MPRT are confirmed.(4)Taking the shipboard electric propulsion system as typical application scenario,based on the MI-MPRT,a DC Multi-Pulse Integrated Shipboard Power Supply System(DC-MISPSS)is proposed.In addition,to explore some certain standards and references for engineering application,the typical power quality indexes of DC-MISPSS are calculated quantitatively.And especially,considering the MI-MPRT non-integer turns ratio deviation in practice,the actual system performances are also analyzed.Further,based on the engineering prototype,the simulation and experimental platform are established,and the satisfying performances and theoretical analysis of the proposed system are validated sufficiently.(5)To optimize the evaluation methods and analyze the application potential of multi-pulse integrated metro traction power supply system(MI-MTPSS)under bilateral-ring structure,a multi-attribute and multi-dimensional based comprehensive evaluation method(MAMD-CEM)is proposed.With comprehensive evaluation indexes,the proper evaluation methods are used for evaluating power quality,application economy and operational reliability respectively.And the most optimal metro traction power supply system combination under specific application scenarios can be found,and correspondingly,the optimal condition of every MTPSS combination can also be obtained.With the practical data of metro traction substation and equipment,the rational,scientific and effective of MAMD-CEM can be verified.