Balance Coordination Control Of The Two Phase Traction Power Supply System In Electrified Railway

The negative sequence, the harmonic and the reactive problems in electrifiedrailway have been the major issues which research workers in all countries analyzingand trying to solve. It takes adverse effects to both electrified railway and public powergrid. Therefore, it is very important to eliminate the negative sequence, the harmonicand the reactive problems. How to eliminate these three problems at a time is a veryworthful research.This paper proposes a kind of balance coordination control scheme used inelectrified railway of two phase traction power supply. Based on BT traction powersupply mode，through analyze the current and voltage relationships between the firstand the second side of four different connecting forms traction transformer, this paperget the expressions of ideal current which the traction transformer should output toeach traction power supply arm of it’s second side when the negative sequence andreactive current have been eliminate completely. At the same time, using the idealcurrent expression, it also works out the equation between the effective value of theideal current and the base wave active component of the load current of each tractionpower supply arm.Through analyze the existing reactive and harmonic current detection method, andbased on single-phase circuit structure of the electrified railway, I choose single-phaseinstantaneous current assay method based on phase discrimination principle to be thecurrent detection method of the two phase balance coordinate device. According to thecurrent detection method and the ideal current expression of the traction transformer. Iplot out the current detection diagram of the60°and90°wiring traction transformer.Through the understanding of FACTS devices, and the analysis of its controlmethod, I build out the two phase balance coordination control device which caneliminate the problems of electrified railway. It based on the voltage type converter,using two back-to-back connecting single-phase twin bridge arm STATCOM, withparallel a large capacitance on its DC side to buffer energy. Through analysis I choosedouble hysteresis current compare state optimization control method to be the controlmethod of the two phase balance coordination control device.I emulate the two phase balance coordination control device using Matlab/Simlinksoftware. Through simulation, I make seriatim detection to validation its ability to balance the active power on two sides of the power supply arm, to regulate the reactivepower distribution and to regulate the current angle of two power supply arm. At thesame time, I also take some test on its ability to detect and eliminate harmonic current.The results indicate that the two phase balance coordinate device can play a good rolein eliminating the negative sequence current, improving power factor, and restraintharmonic current of the three-phase power grid side of the traction transformer.