Control Strategy Improvement of Active Power Filters for Harmonic Elimination in Heavy Rail Systems With Installed PV Arrays

Electric train transportation requires a substantial amount of electrical energy to power trains’ propulsion systems. Consequently, photovoltaic (PV) arrays are considered for installation at traction substations in heavy rail systems to supply this energy. However, nonlinear loads in heavy rail systems cause power quality issues that affect the grid distribution system. To mitigate these issues, an active power filter (APF) is employed to eliminate harmonics and improve the power factor. This paper introduces an APF control strategy for heavy rail systems integrated with installed PV arrays. The proposed harmonic detection method for calculating the APF reference current has been improved to achieve fast computation and more accurate reference current value. In addition, the injection of compensating current by the APF is controlled using a model predictive current control strategy, which incorporates a current injection model through a transformer for high voltage system. The MPC controller effectively compensates for digital delays and minimizes the ripple in the compensating current. Real-time simulations conducted on OPAL RT-LAB hardware was used to verify the performance of the proposed control strategy. The experimental results confirm that the proposed APF control strategy effectively eliminates harmonics and complies with IEEE 519-2022 and MEA standards for power factor correction in heavy rail systems.