Estimation of Minimum Inertia and Fast Frequency Support for Renewable Energy Dominated Power Systems

Abstract

Displacement of conventional generations with the rapid adoption of renewable energy (RE) sources has led to diminishing system inertia and active power reserves. Consequently, power systems with high shares of RE sources have become more susceptible to frequency stability issues, often experiencing higher rates of change of frequency (RoCoF) and frequency deviations. Accurate estimation of essential system services required to maintain a stable and economic operation has become crucial. This article proposes a new method for the accurate estimation of minimum synchronous inertia and frequency containment reserve (FCR) response to ensure compliance with system-specified RoCoF and frequency deviation limits. First, the minimum synchronous inertia requirement for a specified RoCoF limit is calculated, which also considers the instantaneous response from demand, Type-I and Type-II wind generators, which are generally difficult to monitor. The overall FCR requirement is then estimated to maintain the frequency deviation within the predefined limits. Dynamic FCR response includes fast frequency response (FFR) from inverter-based resources (IBRs) and responses from load and governors from conventional generations. Finally, the share of FFR contribution coming from IBRs, representing the system service requirement, is segregated from the overall FCR and estimated accurately. With the proposed method, system operators can be best informed of the exact minimum inertia (MI) and FFR requirement to ensure frequency stability. The proposed methodology is tested and validated in a modified IEEE 39-bus system and an actual grid model of the Gujarat State in India.