Design of Comprehensive Compensation System for Railway Power Distribution System

The railway distribution system is the only power supply for non-traction load along the railway. Aiming at the power factor reduction caused by cable capacitance effect and the harmonic problem caused by nonlinear load in railway distribution system, this paper designs a comprehensive compensation system which adopts the mode of centralized and scattered compensation. In order to solve the power quality problem of railway distribution system, the integrated compensation device is taken as the centralized compensation part. This system combines the traditional design scheme of fixed reactive power compensation and realizes the compensation of reactive power and harmonic current at the same time. It has the advantages of fast dynamic response and high reliability. In order to realize the dynamic compensation of reactive current, the integrated compensation device adopts the double closed-loop control strategy based on DQ decoupling. Based on reactive power compensation, ip-iq algorithm is used to detect harmonic current, and predictive current control is designed as a harmonic compensation control strategy. Finally, the compensation effect of the integrated compensation system is verified by simulation. The simulation results show that the system can compensate the reactive and harmonic currents and effectively solve the power quality problems in railway distribution system. After compensation, the voltage and current at the grid side are in the same phase, and THD is 1.48%.This system can be used as a reference for engineering applications.