Particle-Swarm Optimization Control of Active-Power Filter for Harmonic Mitigation of Hybrid Electric-Unbalanced Traction-System

Using of un-symmetrical solid-state control loads leads to huge amount of harmonics fed to the balanced three-phase systems. Dependently, the harmonics cause many problems with un-balanced and distorted supply waveforms. In this paper, three-phase 3-wire balanced source energizes a hybrid electric-unbalanced traction system that fed from two independent rectified single-phase supplies. Both trains are fed from a balanced three-phase 3-wire supply via V/V transformer. A proposed shunt active power filter (SAPF) is introduced to mitigate most of the harmonics and rebalance the supply. Intelligent PI-controller is used with self-tuning to regulate the voltage of the DC-link for the proposed filter. This smart controller and its parameters is tuned and optimized by using intelligent technique with the particle swarm optimization (PSO). PSO is one of the most prevailing methods to solve the non-linear optimization problems. Also, the system includes a hysteresis current regulator for generating the IGBT-triggering pulses of the inverter. The proposed system is designed, simulated and implemented with the help of the Matlab/Simulink software package. The test results are obtained and compared with and without optimization technique. With optimized algorithm, the total harmonic distortion (THD) is minimized; restoring the balance of the system, and the power factor of the supply is improved to unity. However, those results demonstrate that the proposed system is robust to non-linearity and more suitable for harmonic mitigation in electric traction.