Effect Of Energy Storage System (ESS) in Low Inertia Power System with High Renewable Energy Sources

Intermittence and variability of renewable resources is often a barrier to their huge penetration in power systems. Another barrier is the lack of synchronous generators providing rotational inertia. The replacement of conventional synchronous generation with converter connected renewable energy sources reduces system inertia and impacts primary frequency response of the system. In order to keep frequency in permissible limits in systems with low rotational inertia, certain requirements from inertia must be met in order to avoid system instability. By adding such new requirements, the traditional unit commitment problem may be modified as more synchronous generators may be dispatched for the only purpose of bringing inertia which is not really benefits for power system operators. Energy storage systems (ESS) combined with renewable energy resources (RES) are an efficient and serviceable solution to bring inertia to the system. In such way, this paper discusses the effect of energy storage systems (ESS) on system having low inertia by modeling a block diagram of frequency response of a low-inertia system including energy storage system. Then effect of ESS on the frequency response is shown. Further the energy storage system is sized and evaluation of its impact on the unit commitment based on a study case system with high wind energy penetration is performed by using Matpower Optimal Scheduling Tool (MOST).