Research And Experiment On The Balancer Of Cophase Traction Power Supply System

The traction load is a protean single-phase AC load, which causes the imbalance in three phase current of the traction power supply system, and there are reactive power and harmonic current. Traction transformers with phase conversion connection are set to reduce influence of unbalanced three phases, which causes the different phase voltages of each power feed section, so the neutral section insulator is necessary. But it also leads to lose traction and speed that would seriously restrict the development of high speed and heavy haul railways. Therefore, in order to solve these problems, it is necessary to apply the cophase traction power supply system which bases on V,v connection and balancer. Through the detecting system integrally compensates the harmonic, reactive power and negative sequence currents, the cophase traction power supply system would basically eliminate the imbalance of three phase voltages, and radically resolve the main contradiction between the railway department and the electric power utility. Removing split phase conform to the trend of high speed and heavy haul.This paper researches and analyses the balancer. First, the paper set up a mathematical model design the main parameters on the balancer using three-phase converter and a two single-phase converter. By using two different structures balancer of cophase traction power supply system with a comparative analysis, the paper obtain a conclusion that using a two single-phase converter more advantage than using a three-phase converter in the cophase traction power supply system. Secondly, this paper takes the balancer using two single-phase converter structures as the research object; systematically analyzes the method of reference compensatory current generation, the method of triangular carrier control and the method of DC voltage stable control and so on. Digital PWM control technology has been used to design the control circuit. Based on a TMS320LF2812 DSP, reference compensatory current detection algorithm, current carrier control and DC voltage stable control have been implemented.In the end, simulation and experimental analysis of 14kVA cophase traction power supply system prototype are given in the paper. The simulation and experimental tests verify the effectiveness of the detection and control algorithm.