On the Impact of Non-Synchronous Devices over the Critical Clearing Time of Low-Inertia Systems

This paper discusses the impact of the inertia of conventional power plants as well as of the frequency control of non-synchronous devices on the Critical Clearing Time (CCT) following a three-phase fault in a benchmark power system model. The nonsynchronous devices studied in this paper are wind power plants, energy storage devices, and an average model of thermostatically controlled loads. The case study consists in a parametric analysis where the total inertia of the system is varied and the dynamic response of the system is evaluated by considering different scenarios and control strategies. Simulation results lead to the non-intuitive conclusion that, for any given level of inertia, non-synchronous devices always lead to an increase in the CCT of the system.