Reseach On The Comprehensive Compensation Program Of Daqin Railway

Daqin railway is a modernized dedicated transportation line for coal, which is the first heavy haul electrified and the most important railway in China. The electrical railway is a special user of power system; the load has many disadvantages like acute fluctuation, nonlinear and asymmetry. It produces serial power quality problems such as reactive power excessive, negative exceeding, containing high harmonic. These problems influence not only the operating of electrical railway safely and efficiency but also the power quality of power system, thus influence other users. Therefore, to solve power quality problems of Daqin railway is a very significant research topic, which would not only reduce operational costs of the Daqin railway, but also prevent the electrical pollution injected to the power system.In this paper, based on the detected data of a transformer substation of Daqin railway, the power quality of this transformer is analyzed, and the purpose of comprehensive compensation is determined. Aiming to the wiring mode of Scott balance transformer, the analysis methods of reactive, negative and harmonic are introduced. In terms of analysis of principle above, a dual-phase SVG program is proposed since compare with other compensation program. Then the principle of this SVG is elaborated, the structure is analyzed, the balance principle and the equal models in railway power supply are also analyzed. For the simple-phase feature of traction grid and the active power circulating between the two arms, an improved method of simple-phase compensating current detecting is used. And then the control strategy is formulated, the tracking control of instruction current is realized. On the basis of the work above the compensation current needed is produced by the dual-phase SVG.On the analysis and computation, the parameter of main circuit and the capacity is to be reached. The simulation model of the SVG is build up by using Matlab/Simulink, and the load model is constructed according to the data of detecting. The results show that the effects of reactive power compensation, negative balance and harmonic inhibition are all satisfactory. Finally the conclusion is that the dual-phase SVG program is effective.