This paper proposes a flexible control scheme (FCS) of a photovoltaic (PV) power plant to support the voltage stability and provide fast recovery after the grid faults in a power system with high penetration renewable energy sources (RES). To achieve these goals, the proposed FCS includes two control loops: a reactive current (IQ) injection loop and a frequency-damping control (FDC) loop. The IQ injection loop injects IQ in proportion to the terminal voltage of the PV during a fault. After the fault clearance, the FDC loop provides active and/or reactive power modulation to stabilize system frequency; then, the FDC loop puts the system recovery forward by damping out the remaining synchronous machines' frequency oscillations. The FDC loop comprises active power damping function without PV power curtailment and reactive power damping function. We verified the proposed FDC's performance in a two-area system for various penetration levels of inverter-based resources (IBRs) using PSCAD simulator. We investigated the control schemes' effectiveness by comparing the efficiency and the response in mitigating the post-fault oscillations and restoring the voltage regulation.

This paper proposes a coordinated control scheme of a utility-scale photovoltaic (PV) power plant and a wind power plant (WPP) to support voltage stability and provide fast recovery after the grid faults in a power system with high penetration renewable energy sources (RES). The operation of PV and wind plants are time-shifted by approximately twelve hours. PV generates during the daytime, and wind plants usually produce peak power at night. Seasonally, the PV plants generate peak power on summer days, and wind plants produce maximum power during winter nights. These characteristics present an opportunity to use both types of renewables to complement each other in producing power and transforming energy, and also in providing active damping to safeguard the power system. To achieve these goals, two separate power oscillation damping (POD) control loops have been included for active and reactive power modulation in both PV and WPP. In both PV and WPP, an active power damping function without any power curtailment and a reactive power damping function modulating the reactive current (I_Q) on the voltage control loop have been included. This paper uses the nearest synchronous generator's local bus angle and speed as feedback for each of these loops. The performance of the proposed coordinated scheme based on the time of the day has been verified in a two-area system using the PSCAD simulator. The effectiveness of the control schemes has been investigated during the different timings of the day by observing the efficiency and the response time of the post-fault oscillations mitigation and the voltage restoration.