Recent Iberian Peninsula blackout indicates the stability concerns of interarea oscillations, which happened a few minutes before the blackout event. Power system stabilizers (PSS) have been conventionally providing oscillation damping services to power systems by modulating the field voltage of a synchronous generator (SG) through normal automatic voltage regulator (AVR) control. It utilizes the machine’s power couplings to damp low frequency oscillation in multi-area power systems; hence, the proper turning of PSS requires complicated state-space modal analysis which involves high-order of SG models.

Power system low frequency oscillations have been proven as a small-signal stability property. Modulating system active power flow can be very efficient in damping such oscillations. Previous PHIL (Power-hardware-in-the-loop) demonstration by NREL showed a 10MW battery inverter that can effectively stabilize a GW-scale interarea system by injecting active power compensation off-phase to system frequency oscillations. This gives the opportunities for SG-based power plants to perform more efficient PSS functions using active power modulation given sufficient control bandwidth of SG’s governor.

This paper presents the PHIL demonstration of how a SG-based power plant (Synchronous Wind power plant) can provide low frequency oscillation damping, using active power and reactive power modulations. A synchronous wind turbine is a variable-speed wind turbine interfacing with the grid through a fixed-speed SG using a hydraulic torque converter. Therefore, their operation and consequent grid impacts are similar to conventional machine-based power plants. The PHIL show a SG-based plant can provide efficient damping for interarea oscillations, without using curtailment (for wind power plant); however, it triggers machine natural oscillation mode when the reference of damping torque reaches its upper or lower limit. The results can bring further insights to how a group of small SGs with fast power control bandwidth can contribute to interarea oscillation damping and enhance power system small-signal stability.