Probabilistic Sizing of Virtual Energy Storage Devices for Transient Stability Enhancement

The penetration level of renewable energy sources and distributed generators (DGs) has been rapidly increasing, which severely impacts power system dynamic performance. Such sources usually have very small or no rotating inertia, thus resulting in a significant reduction in the overall system inertia. Low inertia can lead to loss of synchronism even for small disturbances, cascading failures, and blackouts. Virtual Synchronous Generators (VSG) have the potential to compensate for the reduced inertia due to the high penetration of renewable energy sources and DGs. However, determining the minimum sizes of VSG to maintain power system stability is a challenging task. In this paper, a probabilistic approach is proposed to determine the sizes of VSG to enhance the dynamic performance of power systems under various loading and failure conditions. In the proposed approach, Monte Carlo simulations are performed to emulate the variability of system loads and uncertainties of fault clearing times. The time domain simulation approach for multi-machine systems is performed to determine the required sizes of VSG. The proposed method is demonstrated on the reduced Western Electricity Coordinating Council 9-bus transmission system. The results show that the determined sizes of VSG are sufficient to maintain the stability of low-inertia power systems.