Power Quality Compensation and Power Flow Control in AC Railway Traction Power Systems

Rail transport is one of the transportation methods on earth that is very frugal in energy consumption. Electric railway technology has many advantages and disadvantages as well. The most important disadvantage of this technology is the creation power quality problems in the upstream power system. In other words, electric railway traction systems due to continuous load variations, Reactive power demand, asymmetry and harmonic Pollution can be challenged for the upstream power system. In this paper, after introducing the structure of the AC electric railway network and its related power quality issues, the railway power quality compensator (RPQC) is introduced. Also, in order to active power transfer between the various lines of electric railway, a railway interline power flow controller (RIPFC) has been introduced. The proposed structure RIPFC is in parallel, unlike the conventional one which is installed in series with the lines. RPQC and RIPFC contains two Separate single phase converters that are connected back to back (B2B) by sharing the same dc link. Extraction of compensating currents for RPQC and RIPFC is based on current measurement and its separation into active, reactive and harmonic components. Moreover, a controller is proposed to maintain the dc-link voltage. The simulation results using PSCAD/EMTDC are provided to demonstrate that the proposed strategies is very effective.