Operation of a 12-pulse converter in closed loop for controlled P-Q operation

In this paper, a new four quadrant active-reactive power controller is presented. The proposed system consists of a 12-pulse converter operating under asymmetrical firing angle operation, integrated to a combination of tuned passive filters. The study shows that by suitable choice of firing angles of the constituent 6-pulse converters, the active and reactive power exchanged by the 12-pulse converter can be independently controlled. The 12-pulse converter always absorbs reactive power from the supply while it can either absorb from or supply active power to the supply. On the other hand, under fundamental frequency of operation, the passive filters act as a source of reactive power. The combined system of 12-pulse converter and passive filter thus acts as a four quadrant P-Q controller connected at the point of common coupling between the supply and the load. Simulated results followed by experimental verifications show that such a system can always make the supply operate at unity power factor besides maintaining system voltage and frequency constant.