Influence Of High-speed Railway Traction Load On Power Quality Of Power Grid And Comprehensive Evaluation

With the increasingly vigorous development of China’s high-speed railway,a large number of EMUs have been put into use,resulting in the continuous increase of the number,traffic density and power of EMUs.As a special load of traction power supply system,EMU has the characteristics of complex operating conditions,a large number of nonlinear components and high power.At the same time,a large number of negative sequence current and harmonic current are injected into the power grid through the traction power supply system,causing power quality problems to the power grid.Therefore,this dissertation makes a simulation study on the impact of high-speed railway traction load on power quality of power grid,and uses the comprehensive evaluation method to comprehensively evaluate the impact of traction load on power quality of power grid,which provides a theoretical basis for power quality management of high-speed railway and enables staff to grasp the actual situation of power quality of power grid.(1)According to the actual parameters of each part of high-speed railway traction power supply system,the simulation model of traction power supply system is built.Taking CR300 EMU as the research object,the EMU simulation model is built according to the structure and actual parameters of EMU transmission system.The EMU operates at different power under traction condition and regenerative braking condition.The simulation results show that the current harmonic characteristics at the networking side of the EMU are consistent with the theoretical analysis results,which verifies the correctness of the EMU simulation model.(2)The joint simulation model of EMU traction power supply system is built.Through the analysis of traction network voltage level,it is verified that the voltage of traction network can meet the requirements of EMU.Through the generalized Nyquist stability criterion,the influence of the number of multiple units on the stability of vehicle network system is analyzed.The influence of CR300 multiple units in different numbers,positions and operating conditions on the power quality of 220 k V power grid is simulated and analyzed,and the resonance at the low-voltage side of traction substation is investigated.The simulation results show that the more the number of EMUs,the more unstable the train network system is;The farther the EMU is from the traction substation,the more serious the impact on the power quality of the power grid;The EMU has a more serious impact on the power quality of the power grid under braking condition than under traction condition;The parallel resonance point at the low-voltage side of the traction substation will not change with the number,position and operating conditions.(3)According to the traction load characteristics of high-speed railway,the power quality evaluation index system of high-speed railway is established.The analytic hierarchy process and coefficient of variation method are selected to determine the subjective and objective weight,and the game theory method is used to determine the comprehensive weight.Based on the variable fuzzy set,the set pair analysis theory is introduced to determine the comprehensive evaluation results of each group of data.Five groups of data evaluation results of traction substation are combined based on eigenvalue weighting method,and the power quality evaluation grade of traction substation is obtained.The feasibility of this method is verified by comparing with the results of other comprehensive evaluation methods.