Studies Of Comprehensive Compensation For Traction Substation In Electrified Railway

With the development of electrified railway, electric traction loads increase quickly. As a large power single phase rectified load, the electric traction load has many disadvantages such as heavy distortion, acute fluctuation and severe asymmetry. The safe and economic operation of power systems and of other users in points of common coupling is badly influenced. Therefore, the research on harmonic elimination scheme for electric traction load is becoming a hot subject in recent years.To compensate the harmonic current and reactive power of the traction substations, according to the specific property of traction supply system a novel structure of hybrid power filter is proposed. The hybrid power filter is composed of passive power filter, active power filter and switchable reactive power compensation device.The working principle of the switchable reactive power compensation device is analyzed, the detecting method for harmonic current and reactive current is proposed and the control strategy of the hybrid power filter is given.The harmonic current detection of APF decides its compensation performance. The detection method based on the instantaneous reactive power theory is popularly applied in APF device .In this paper, the detection method based on the instantaneous reactive power theory is researched, and its current detection error is analyzed deeply, including influences of the frequency and phase errors of Phase-Locked Loop (PLL), time delay of sampling and calculating on current detection error, and the Low-pass Filer (LPF) on current detection error. Some proper ways to reduce the error is proposed and improved by MATLAB.A novel hunt hybrid active power filter is introduced in this paper, according to the universal electric model, this paper analysis the filter system based on three kinds of basic control strategies. Further more, a comparison research, which focuses on the influence of shunt hybrid active power filter operating performance, produced by different control strategies, is put forward when power network parameters change. The conclusion may help to the optimized choice of the basic control strategy under the complex operating mode .