Reactive power assisted frequency regulation scheme for large-scale solar-PV plants

Due to reduction in power system inertia and frequency regulation reserve with high penetration of power-electronic converter (PEC) interfaced renewable sources, advanced control strategies must be developed to exploit the full potential of solar-photovoltaic (PV) systems to improve the frequency stability. In this paper, a new frequency regulation approach is proposed based on reactive-power control (i.e., frequency regulation via reactive-power control (FRQC) scheme) for solar-PV systems, which manipulates the active power demand as a function of the system frequency deviation by varying network voltages via reactive power control. The feasibility of the proposed control scheme is investigated using both theoretical analysis and simulation studies following a loss of a major generation source. Frequency and voltage deadbands, and time delays are added to the FRQC scheme to activate and deactivate the control scheme, and hence it maximises the frequency support without affecting the voltage stability. The reliability and voltage stability (RVS) test system is used to demonstrate the effectiveness of the proposed FRQC scheme under different gains of the controller, PV loading levels, and different PV penetration levels. The comparative results show that the proposed FRQC scheme improves the post-fault frequency trajectory, and hence the system frequency stability.