A topology of Hybrid Active Power Filter for simultaneously compensating harmonics and load unbalance in single phase traction systems

Electrified Traction systems cause power quality problems in their power supply system. This is mainly due to the power electronic converters of traction system drives and their single phase operation. The created harmonics and unbalance currents are propagated in the upstream electrical network. Also, the created harmonics put the power quality of the traction system in danger. In this paper the traction system load is characterized, an algorithm for compensating simultaneously the both harmonics and load unbalances, and a topology of Hybrid Active Power Filter (HAFP) for improving of power quality in upstream network and the traction system is presented. The proposed algorithm can be adapted to any traction transformer connections / configurations. Besides, the load side compensation is used which reduces the cost of installations. And the proposed topology caused reducing the size of the Active Power Filter (APF). The topology is successfully tested under normal operation and load change conditions. The simulation results show the good performance of the algorithm under non-stiff supply network as well.