Review of Fault Ride Through Support Schemes and a New Strategy for Low-Inertia Power Systems

A massive deployment of renewable energy sources (RESs) is required to enable the decarbonization of the energy infrastructure. The replacement of conventional generators with inverter-based RESs reduces the rotational inertia and can threaten the frequency stability of the system. This work is motivated by analyzing an actual cascading event in a low-inertia system where a voltage sag event that was cleared within few milliseconds triggers a severe frequency disturbance. During a low voltage sag event, the reactive power is prioritized for voltage support purposes according to the existing low voltage fault ride through (LVFRT) grid regulations, which lead to a significant reduction of active power by RESs that triggers the cascading phenomenon. This event indicates that the existing LVFRT regulations require re-evaluation, especially in low-inertia power systems with increased penetration of RESs. Therefore, the existing grid regulations are thoroughly analyzed with a particular emphasis  on the coupling phenomena where a voltage support can threat the frequency stability. Moreover, a new LVFRT strategy is proposed where active power prioritization is introduced for enabling an intense voltage support without causing a significant reduction on active power. The existing and proposed LVFRT schemes are benchmarked considering theoretical and simulation-based analysis indicating that the proposed scheme provides improved support and is adequate for low-inertia power systems with intense RESs penetration.