A new algorithm 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. In this paper the traction system load is characterized and an algorithm for compensating simultaneously the both harmonics and load unbalances is presented. It is based on the use of hybrid active filter. 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. The algorithm 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.