Research On A Comprehensive Control Method For Electric Power Quality Of Electrified Railway Based On YN/VD Balanced Transformer

As the big artery of economic and social development,electrified railway has the advantages of heavy load,high speed,low pollution and so on.Modern electric locomotive consists of two types,AC-DC and AC-DC-AC.AC-DC train with disadvantages of asymmetric,nonlinear and fluctuation,and owing to the complex power supply system as well as the changing operating conditions,which all result in main power quality problems like reactive power,negative sequence,harmonics and voltage fluctuation of the main electric traction network in operation that have a serious threat to the safety and stability of electric traction.In order to solve the power quality problems in electrified railway,this thesis is supported by Project 51520105011 funded by the National Natural Science Foundation and major science and technology projects 2015GK1002 in Hunan,it is relied on the data measured in laboratory YN/VD balanced transformer and then have a comprehensive comparison with traditional pure passive compensation system,at last but the main point of the thesis is that it put forward a comprehensive control method for power quality problems in electrified railway based on YN/VD balanced transformer.The main research work and innovation of this thesis are as follows:First,it summarizes the current research status of the solution to electrified railway power quality at home and abroad,and then analyzes the advantages and disadvantages of the existing governance principles.So a new method of harmonic suppression and reactive power compensation is proposed,which is a comprehensive control method for electric power quality of electrified railway based on YN/VD balanced transformer.To reveal its harmonic suppressing mechanism,the mathematical model and transforming relationship in harmonic frequency were presented as well.Based on that,the harmonics filtering characteristics and the resonance damping performance of this system were quantificationally analyzed,which shows its good performance.Second,it elaborates the suppression principle of negative current and compensation principles reactive power in high-speed railway power supply system with YN/VD balanced transformer;the reactive power and harmonic detection method,and the signals of voltage and current detection method is proposed,at the same time,the control strategy of the voltage and current in NCCS which belong to the power supply system of high speed railway is posed.Finally,the simulation and experiment of mathematical modeling are carried out.According to different operation conditions,it proposed compensation capacity of hybrid compensation system.Mathematical deduction and simulation show that under the same compensation current,the compensation capacity of the active part of the system is much lower than that of the pure passive compensation system,which greatly reduces the installation difficulty,occupying space and overall cost of the electrified railway compensation system,and achieves superior compensation effect.To further assure the correctness of the system,the small power model is based on a YN/VD balanced transformer and other experimental equipment in laboratory.The experimental results verify the validity and feasibility of system theory,so this system has very important theoretical value and broad prospects for industrial applications.