Exploring the Utilization of Energy Storage Systems for Frequency Response Adequacy of a Low Inertia Power Grid

The utilization of Energy Storage Systems (ESS) for improving the frequency response of a low inertia power system is investigated in this article. Substantial wind power penetration is causing the replacement of conventional synchronous generators in several power systems. Variable speed wind machines traditionally do not contribute to frequency regulation without additional control strategy. As a result, a wind dominated power grid may have inadequate inertia and governor responsive reserve. In such situation, a large contingency may yield undesirable Rate of Change of Frequency (ROCOF) and frequency deviation. To overcome this problem, deployment of ESS, namely, Superconducting Magnetic Energy Storage (SMES) and Battery Energy Storage System (BESS) can be a worthwhile solution. Since these devices are costly, their appropriate sizing and operational approach are crucial. Therefore, in this paper, analytical expressions are derived to find the minimum ratings of SMES and BESS. To this end, system frequency deviation, ROCOF, inertial response and governor response are taken into account. Also, a coordinated operational strategy is proposed to retain frequency response adequacy and minimize under-frequency load shedding where SMES is triggered when system ROCOF supersedes a certain limit and BESS is activated due to system frequency surpassing a preset threshold. The performance of the proposed strategy is explored in a low inertia network under substantial wind penetration considering several different wind penetration levels. Also, the results are validated against two existing approaches. Simulation results reveal that the proposed methodology considerably enhances the frequency response in various operating conditions.