A Hybrid FACTS Topology for Reactive Power Support in High Voltage Transmission Systems

This paper proposes a hybrid FACTS topology for constant reactive current support, within a reasonable range of power system voltage, in high voltage (HV) and extra high voltage (EHV) transmission systems. The configuration is an economical solution to the high cost involved in providing voltage support in HV systems. It consists of a Static VAr compensator (SVC) in series with a static synchronous compensator (STATCOM) with significantly lower rating. The hybrid configuration is put in shunt to the point of common coupling (PCC). A vector control based control strategy is proposed, such that the STATCOM is rated for just 15% of the total compensation and the SVC is rated for the rest of the 85%, thus providing a lower cost solution for applications in HV and EHV systems. The control of the hybrid topology enables it to provide a constant reactive current support. Also a control strategy is proposed for balancing the isolated dc-link voltages of the parallel connected inverters.