DESIGNING AND MODELLING OF REACTIVE POWER COMPENSATION AND HARMONIC MITIGATION FOR AC RAILWAY BY SVC AND SAPF

Abstract

In Ethiopia's single phase 25kV AC electrified railway system, the power quality issues based on high reactive power consumption and harmonic distortion should be the main focus of attention. The locomotives' non-linear and shifting load characteristics result in large reactive power consumption and strong harmonic currents, which negatively impacts the overall power factor. The quantity of power supplied to the locomotive may be limited as a result of these power quality issues in the AC railway system, which could also negatively impact the public grid. Hence, it was imperative to conduct a comprehensive examination of reactive power and harmonic distortion reduction in the railway substations. The research work focuses on the Ethio-Djibouti railway line as a prime example to explore the compensatory consumption of reactive power and the mitigation of harmonics in a 25 kV AC railway system. The ability of SVC and Active Power Filter combinations to reduce harmonics and reactive power problems has drawn a lot of attention to them due to their fast control response, less harmonic generation than mechanically switched devices and controller flexibility. The control theory used to create the SVC and active filter's control algorithm determines how well the combination of SVC and active power filter performs. The controller of the SVC and active filter is the primary component that significantly influences the filter's performance. Therefore, the main focus is on designing SVC and shunt active filters using Synchronous (d-q) reference frame theory to reduce harmonics and reactive power issues with controllers. For the thesis, MATLAB/Simulink is the simulation tool. The simulation result of THD load current shows that when the Static Var Compensation (SVC) and Shunt Active power factor (SAPF) are connected to the system, the THD of load current decreases from 19.575% to 0.26%, which is below the IEEE 519 standard's harmonic limit of 5%. The power factor is increased from 0.85 to 0.99, the traction system voltage is increased, and the reactive power requirement is almost zero. As a result, after the suggested system was put into practice, modeling results demonstrated that the combined system successfully mitigated harmonics and compensated reactive power.