Research On The Reactive Power Compensation In Traction Substation Of Montanic Region Railway

Power quality is a big problem in public Power network at home and abroad, and its indexes include : voltage offset ,harmonics, unbalance, voltage fluctuation , flicker and so on.Random fluctuation and nonlinear of traction load reduce the power quality of electric railway . Therefore, before operation of each electric railway, many power quality problems are focused, such as power factor, harmonics, unbalance and so on.One of the effective ways to enhance power quality of electric railway is to increase power factor of traction substation in order to improve system voltage quality and reduce loss. Electrical railway substation supplies power to locomotive which adopts single-phase AC-DC Transmission System. However, random fluctuation and nolinear of traction load would lead to low power factor and much harmonics.Huge divergence of geographical features determines that electrical railway system in mountain region will different from each other. Thus, research on reactive power compensation of substation in mountain regions is important.In this paper, fundamental of reactive compensation and reactive current detection is analyzed. The paper provides two schemes which are apt to reactive compensation of substation in mountain regions, based on researching existing technologies.The first one is SVC of TCR+FC. The paper takes "Yichang-Wanzhou" line as an example and aims to solve some issues as no-load reverse reactive, one train compensation in a section, instantaneous reactive surge and improving mean power factor. On the bases of comparative analysis of four schemes-fixed compensation, controlled saturation reactor compensation, thyristor controlled capacitance and fixed fliter-thyristor controlled reactor, the paper points out that SVC with TCR+FC is practical for "Yi-Wan" line. The scheme can manage voltage fluctuation and flicker, and filter out set harmonic waves effectively owing to its adaptability of large reactive impact and load variance. The paper has yet designed this scheme preliminary.The second one is intelligent zero-crossing-switching shunt capacitor compensation system. It compensates reactive power and filters harmonic dynamically by monitoring reactive power of traction network. The compensate mode is automatic tracking switching that is to divide total compensation capacitance into many groups and put in necessary ones according to the load variation.Finally, the second scheme is applied in Zhangjiajie and Xiangbizi substations of "Shimen-Huaihua" railway line. After compensation, the daily mean power factors of two substations are above, that means the method realizes reactive power compensation.