Research On Co-phase Traction Power Supply System Based On V Type Connection Traction Transformer

27.5k V/50 Hz single-phase AC power supply system has been widely used in China’s electrified railway.However,because of single-phase independence and asymmetry of existing traction power supply system,the neutral section and power quality problems have become two key constraints which affecting development of high-speed and heavy-haul railways.With implementation of China’s "Medium & Long-term Railway Network Planing" and "14th Five-Year Plan",the volume of railway passengers and freight have increased year by year.At the same time,the organization density and speed of train are also constantly refreshed records,which lead power quality problems dominated by negative sequence have become more prominent.As an effective technical means to comprehensively solve the problems of neutral section and power quality,Co-phase traction power supply system has lead the technological revolution for next generation of traction power supply system.Therefore,the novel comprehensive compensation schemes for Co-phase traction power supply which constructed by V type connection traction transformer and SVG active reactive power compensation technology were proposed in this paper.In order to improve power quality while avoiding the series of adverse effects caused by electric locomotives passing through neutral section,so as to ensure the safe,stable and efficient operation of electrified railways.In this paper,the main components and technical points of two comprehensive compensation schemes were introduced in detail.Combined with actual operation characteristics of different traction loads,three typical compensation modes of comprehensive compensation device were proposed.On this basis,the negative sequence and reactive power treatment principles of compensation schemes with relationship of electrical quantities between each traction compensation ports were analyzed.In addition,the comprehensive compensation mathematical models were established,and theoretical calculation formulas of capacity configuration for compensation device were deduced.At the same time,the system control strategy suitable for negative sequence and reactive power comprehensive compensation was established.The calculation strategy of expected compensation current was constructed by single-phase load current detection algorithm and SVG direct current control method.Therefore,the command current calculation and control driving functions of SVG compensation device can be realized.Furthermore,take national power quality standard as constraints,the switching strategy of system working mode and calculation method for compensation device capacity while under condition of satisfactory compensation were given.Based on measured load data,the load process analysis was carried out for two comprehensive compensation schemes.Moreover,the simulation models were built with MATLAB/Simulink to verified system operation characteristics and compensation effect under different load conditions.The results show that all kinds of compensation schemes can effectively achieved expected objectives,and comprehensive treatment effect is good,which proved effectiveness of proposed scheme and control strategy.Finally,in order to test engineering feasibility of proposed schemes and real-time performance of control strategy,the low-power experimental platforms for two compensation schemes were built with d SPACE real-time simulation system.The compensation principles and actual compensation effects were fully verified by experimental tests,which provided technical experience support for development of larger-scale experimental platforms and practical engineering applications.