The Analysis Of Ground Automatic Convert Scheme And Its Overvoltage And The Research Of Its Suppression Methods

To decrease negative sequence current and harmonics, electrified railways adopted changing phase scheme. It brings some problems such as speed lose and electromagnetic transient process. Before the comprehensive development of co-phase power supply technology, excessive phase system problem is still worth working on.This paper introduced the detailed analysis of the three automatic excessive phase schemes which had been most widely used, compared technical index of these schemes. Based on these comparisons, the author studied the scheme of the self-checking switch scheme which changes over the excessive phases automatically and its improvement scheme. In this paper, the author analyzed the principle of the process about the self-checking automatic switch changes over the excessive phase, built a general model of ground automatic convert scheme. By using the general model,the author analyzed the electromagnetic transient process of the scheme, and calculated the parameter of the intercepting overvoltage and the closing overvoltage in this process, then analyzed the inrush current which produced by the locomotive main transformer residual magnetism at the time of the switch closing. With the using of MATLAB/Simulink platform, the author built a simulation model of electric locomotive and a system of self-checking switch scheme which changes over phases automatically, and simulation these two combinational models. Verifed the model that the theoretical analysis of this scheme of electromagnetic transient phenomenon, and compared with analysis of the theory, the author verified the general circuit model and factors of the over-voltages. Acroding to the theorical analysis and simulation, this paper put forward the inhibited scheme about the overvoltage causing by the automatic convert scheme:using high-pass filtering RC circuit and resistance suppressor for overvoltage. With simply anglicizing two inhibited measures and calculating the parameters, the author built the simulation model in the MATLAB/Simulink platform, verified the inhibitory effect of these measures.The final results showed that this scheme provides a simple structure and help reduce the lose of speed. Though the analysis of the electromagnetic transient process of the scheme using general model of ground automatic convert scheme, this paper verified the scheme of self-check switch scheme could meet the requirement that the train could keep charging when pass phase separation. The intercepting overvoltage is effected by the phase angle of current while the closing overvoltage and the inrush current are related to the phase angle of voltage and the amplitude of neutral section voltage. And it can adapt to both high-pass filtering RC circuit and resistance suppressor for overvoltage device to inhibit the overvoltage. So, this scheme might be suitable for the railway electrification which might be widely used in our railways.