Simulation Research Of Power Quality Improvement Effect On Yunnan Electric Railway

Low power factor, abundant harmonics and negative sequence are the three main characters of electrical railway traction load. The harmful effects brought by reactive power,harmonics and negative sequence usually be evaluated on some sensitive power system nodes and be comprehensive solved in the traction power system.The research of the power quality is based on the mode of electic component, so first of all,the paper improve the three phase model of each component in the power grid and traction system and worked out a three phase power flow calculation program, which can be used for the calculation of negative phase sequence generated from traction load and the distribution of harmonic within grid.At present, the fixed parallel capacitor compensation devices have been widely adopped in Yunnan traction power system, but as the policy of "reactive power returning back as positive value" employed, it is difficult to conform to the limit standard of the traction load power factor set up by the power supply departments. This paper discusses the effectiveness of this mode of capacitor compensation and introduces simple and useful assessment methods for evaluation programs.The reactive power and negative sequence current appear at the same time following traction load. It is insignificant to compensate one of them, so, we have to study the comprehensive compensation for reactive power and negative sequence.The paper analyzes the rule of negative sequence and try to find a type of optimizatonal capability allocating schemes, the destination is to decrease the negative sequence current to the min and increase the power factor at the same time.The electrical traction harmonics have some unique features such as large amplitude range,phase dispersion and severe deviation of the maximum. According to the actual working conditions,the paper researches the best distribution scheme combined with the comprehensive compensation for reactive power and negative sequence.On the basis of studying the distribution of traction load, the statistical method is used to predict the power quality caused by electrified railways in the paper at last.