Study On Harmonic Characteristic And Reactive Power Compensation Method Of Electrified Railway

In recent years,with the rapid development of electrified railway in our country,the electric locomotives are becoming one of the main harmonic sources of regional power network and public network.The type of electric locomotives operated in the traction power supply network of the electrified railway concludes both conventional AC-DC electric locomotives and AC-DC-AC electric locomotives with obvious advantages.However,at present,the influence of the variation of harmonic distribution in mixed operation of different locomotive types under the same traction and harmonic mechanism of various types of locomotives in different operation scheduling modes is less studied,and this phenomenon is prevalent in the actual railway operation and dispatching in our country.Therefore,in view of the current situation of electrified railway in China,it is very important to analyze the harmonic characteristics of the mixed operation condition of AC-DC and AC-DC-AC locomotives and to study the influence and compensation method of the power supply network.In the locomotive dispatching,AC-DC locomotive and AC-DC-AC locomotive running separately or two types of locomotives running in the same traction,these complex conditions have serious influence on network current.This paper focuses on the whole modeling of the AC-DC electric locomotive(SS4)and the AC-DC-AC electric locomotive(HXD3)in the traction power supply system of the electrified railway.The principle of the rectifier circuit of the SS4 electric locomotive is analyzed.Through the main circuit and control method,the harmonic generation mechanism is studied theoretically,and the simulation model of the locomotive traction rectifier is built on the MATLAB platform.The harmonic current distribution of SS4 locomotive are quantitatively studied by simulation experiment.The main circuit principle andPWM control mode of the HXD3 with two-level four-quadrant rectifier are studied.Based on the analysis of the mechanism of the harmonic generation of the locomotive,the main circuit of three-phase voltage inverter of the HXD3 locomotive,the space vector pulse width modulation(SVPWM)and the traction motor vector control principle are studied.The simulation model of HXD3 electric locomotive is established,and the characteristics of harmonic characteristics of different typical working conditions are analyzed by simulation analysis of traction condition and regenerative braking condition.The theory of harmonic harmonic superposition of electric locomotive traction load is introduced.Based on the actual working conditions in the locomotive dispatching,the mixed operation model of the two types of locomotives with the same traction variable is set up.The model of the mixed operation of the two types of locomotives is analyzed.Three typical working conditions models were set up in the same traction substation.Two AC-DC locomotives were running at the same time.Two AC-DC-AC locomotives were running at the same time.The AC-DC and AC-DC-AC locomotives were running at the same time.The harmonics and the total current distortion were analyzed under different typical operating conditions.The harmonic characteristics of the traction power supply system under different typical operating conditions were obtained.It provide effective basic data support for analyzing the propagation law of harmonics in traction power supply system under various complicated conditions and electrified railway power quality control.As the electrified railway traction load non-linearity,frequent fluctuations and other characteristics,resulting in access to local area network voltage fluctuations,the impact of safe operation of the grid can not be ignored.The dynamic reactive power optimization of the power system for electric iron access can effectively improve the voltage quality of the power grid system and ensure the stability of the system.Power system reactive power optimization has many characteristics,such as multiply targets,multiply constraints,multi-variable controls,continuous variables and discrete variables mixing.The conventional algorithm is often limited when dealing with the problem.The dynamic reactive power optimization,which takes into account the change of the electric load,will provide the theoretical support for the electric power production operation of the electrified railway after considering the load variation of the tractionpower supply system and the constraint of the number of times of the discrete adjustment equipment.In this paper,based on the sub-time treatment of the electric load of the traction power supply system,the hybrid optimization strategy combining the interior point method and the immune-chaos algorithm algorithm is used to solve the dynamic reactive power optimization.The example shows that the method can make the optimization results of the two mutually beneficial and mutually beneficial,and ensure the overall optimization efficiency of the hybrid optimization strategy.Considering the influence of load change and the access of electric iron,the dynamic reactive power optimization of power grid after electrified railway access is effectively solved.