Analysis And Control Of The Harmonics Caused By Electrified Railway In Inner Mongolia Hohhot-Baotou

At present harmonic is the most prevalent phenomenon in the power system. It is the most main power quality indicator. In recent years, with the accelerating of electrified railway construction, electric locomotive is gradually becoming one of the main sources of the harmonic in power system. It has brought great harm to the safe operation of the electrified railway and power grid.In order to reduce the harm of harmonic caused by electrified railway to power system, the currently using method is to install passive or active filter at the junction of electrified railway systems and power grid to restraint harmonic, making sure it meets the national standard for harmonic. The traditional passive compensation device is the LC filters. Its structure and principle is simple, maintenance is also convenient, and its operation is reliable and costs low. Its main drawback is that compensation characteristic is easily influenced by system impedance and the operation state of grid. It easily occurs parallel resonant with power system, and the compensation effect is also inferior. Active filter can realize dynamic compensation of harmonic and reactive power. It overcomes the shortcomings that traditional LC filters compensation effect is poor. Active filter can realize dynamic and real-time compensation of harmonic that varies in size and frequency and changing reactive power. Active filter has a fast compensation response, and it's not easily influenced by power system parameters and it's not easily to cause system resonance. But active filter costs so much that it's not widely used now.SVC is a new type of passive reactive power compensation and harmonic control device. Its investment cost is low, control simply. And it can better realize the dynamic compensation of reactive power. Considering the electrified railway system is single-phase load, and system power factor is low. While SVC can be very good for reactive compensation and improving power factor. So using SVC for electric locomotive reactive power compensation and harmonic control is a very good choice.Firstly this paper expatiates the basic concept of harmonic, and analyzes the principle of electrified railway harmonics. The harmonic analysis method that based on fast Fourier transform is emphatically elaborated. Electric locomotive load harmonic source model is built in the platform of Matlab/Simulink. Then do the harmonic analysis on the current at system junction. Analysis results indicate that the electrified railway infuse great harmonic to the grid, so corresponding control measures must be taken. Then the paper gives two kinds of harmonic control scheme based on SVC. Through comparing the two solutions this paper selected the one that has better feasibility. Then this paper verified the feasibility of the solution connecting with traction substation of Hudong. Finally this paper analyzed the sampling data of junction and other nodes of the system furnishing with SVC. The results show that the SVC harmonic control scheme is effective.