Research On Comprehensive Active Compensation Of Electrified Railway Traction Power Supply System

With the development of electrified railway,traction load have caused some power quality problems such as harmonic,reactive power and negative sequence,this have become an important factor which is affecting security and stable operation of power system and power supply system.Negative sequence problem in high speed electrified railway is more prominent than that in normal speed electrified railway.Using active compensation to compensate power quality of traction substation in electrified railway,is an important means to ensure safety and effective operation of electrified railway.It has the theoretical significance and practical value to study the active compensation to electrified railway power quality improvement.The effects of electrified railway on power quality of power system are analyzed,the compensation methods of power system harmonic,reactive power and negative sequence are summarized,the classification and existing problems of electrified railway active compensation are concluded. Various types of negative sequence current of traction transformer and unbalanced degree are analyzed.This works provide the theoretical basis for proper selection of traction transformer main connection wiring to inhibit negative sequence current.The formulas for electrified railway active compensation are deduced on compensation system of electrified railway single-arm load. The formulas for identifying the basic topological quantity of electrified railway active compensation are formulated, identification methods of topology is presented,structure characteristics and scope of all sorts of different topologies are analyzed and compared. Four new hybrid active compensation topologies are presented based on the analysis of electrified railway active compensation topologies.This four topologies can reduce capacity and voltage level of active component.Combining the topological structure are proposed solution, electrified railway power quality integrated solution active compensation scheme is gived. Operating principle electrified railway comprehensive active compensation is analyzed. The expressions of current control on various compensation conditions are presented. The primary voltage and current and the secondary voltage and current expressions of tration transformer and comprehensive active compensation currents are also presented.It has the guiding significance for the actual compensation current calculation.Output filter design of electrified railway active compensation is studied. LC output filter is improved based on the analysis of the common four types output filters characteristics. Output filter parameters are designed by fuzzy optimization.The improved output filter has good filtering effect in compensation frequency range, and can better meet the requirement system synthetical compensation.It is verified that this method can realize the compensation for harmonic, reactive power and negative sequence and improve the tration power quality.