Reactive Power Compensation with Hybrid Compensator Combining a Synchronous Motor and Switched Capacitors

Abstract

Switched capacitors are the most common tools used for reactive power compensation. For this purpose, inverter-based static compensators, thyristor-based static compensators and synchronous machines can also be used. Although switched capacitors are cost-effective, it is almost impossible to achieve full reactive power compensation with them. Other tools that their reactive power outputs are fully controllable are expensive so-lutions. Therefore, by taking into account the balance between cost and performance, a new hybrid system is developed and introduced in this paper. The hybrid compensation system provides to reach unity power factor through the coordinated control of a synchronous motor and switched capacitors. In the proposed structure, switched capacitors produce the main part of reactive power demand, while the power requirement between the stages is met by a synchronous motor. With the help of adjustable coils connected in series to each phase of three-phase synchronous motor, it has been possible to obtain different amounts of reactive powers from the phases. The hybrid system has been tested by experimental works. Test results have shown the proposed hybrid reactive power compensation method has better performance than conventional systems with switched capacitor and ensure to reach almost unity power factor even under unbalanced load conditions.