Calculation And Analysis For Negative Sequence Current In Traction System

When the electric locomotive moves in the power system, it will produce a negative sequence current. The negative sequence current will threat the electrization railway and the power system security operation. In order to offer the theory basis for the attemper department and the power department to reduce the negative sequence current, this paper discusses the methods of calculation, detect and compensation primarily.First of all, the paper adopts the symmetrical component method to calculate the negative sequence current, which is immited into the power system from the tractiontransformer substation. Secondly, the paper optimizes the negative sequence impedance matrix arithmetic, and adopts the negative sequence current distribution coefficient method to calculate the negative sequence current value of each surveillance spur track. Thirdly, the paper introduces one kind of the new negative sequence current detection method without phase-locked loop, according to the three-phase circuit instantaneous reactive power, and analyses the calculation method of the negative sequence current compensation. Finally, the paper analyses the advantages and disadvantages of the common methods that is used to reduce the negative sequence current from the electrified railway and power supply systems aspects.This paper adopts the Matlab6.5 software to simulate analysis the relationship between the current asymmetry value and traction current under different traction transformer, and find the best running way of electric locomotive. This paper adopts Matlab6.5 software to simulate analysis the new negative sequence current detection method and the accuracy of etection method is proved. The high efficiency of negative sequence impedance matrix Optimization Algorithm is proved by one actual example. The correctness of negative sequence current calculation method is proved by the comparative analysis of negative sequence current measured data and calculated valuescorrect. This paper also analyses the feasibility and the limitations of the common methods that is used to reduce the negative sequence current.