Reactive power control for improving primary frequency response in power systems

The present paper proposes a method to counteract active power imbalance through voltage channel. The purpose is to develop a supplementary method for damping very low frequency oscillation by reactive power modulation. In this aim, a two-band power system stabilizer is presented, tuned for very low-frequency common swing mode, to adaptively adjust reference voltage of a Synchronous Condenser (SC) and to modulate its reactive power. Several simulations have been performed on four well-known benchmarks to demonstrate the general applicability of this concept. The results show that VAR modulation by SC has considerable control effect on primary frequency oscillations, even more than so-called load modulation schemes in some cases, a phenomenon which has not been reported yet by researchers. In addition, it is shown that proposed controlling method can improve the damping of very low frequency common modes of all test systems.