Coordination of multiple adjustable speed drives for power quality improvement

The proliferation of semiconductor-based non-linear devices in power systems has caused serious concern over power quality problems. This paper proposes a control strategy to coordinate multiple adjustable speed drives (ASDs) so that harmonic currents as well as reactive power generated by non-linear loads can be compensated. Under the proposed control strategy, the power quality improvement task is distributed to multiple adjustable speed drives and their contribution to the task is determined proportionally to their instantaneous power margins. The proposed control strategy can be a fairly flexible and economical solution for power quality improvement especially for the places where multiple machine drives are already-installed or required, for example, manufacturing factories or shipboard or aircraft power systems, because the adjustable speed drives can be fully utilized to improve power quality without additional compensators as well as conditioning end-use machines. Detailed simulation results using switching-level converter models verify the performance of the proposed coordination strategy.