Participation of battery energy storage system for frequency control in wind dominated power systems: An analytical approach

Abstract

The frequency performance of a power grid is effectively maintained through the utilization of inertia and power reserve provided by synchronous generators. The growing concerns surrounding global warming and the greenhouse effect have led to a significant increase in the integration of wind energy into the grid. But the system may face frequency instability following a contingency due to lack of sufficient inertia and headroom of wind generators. Therefore, the grid operator may require shedding some loads to prevent the system from severe frequency excursion. In this paper, we have estimated proper amount of load shedding through the formulation of analytical expression that will keep a highly wind penetrated & Battery Energy Storage System (BESS) integrated system stable. For this purpose, the maximum amount of wind power penetration level (WPPL) is first calculated using a fast analytical approach which utilizes two frequency response performance metrics, frequency nadir and Rate of Change of Frequency (ROCOF). In scenarios where the wind penetration level exceeds the calculated allowable threshold, it becomes necessary to implement load shedding measures following a contingency event. After installation of BESS, grid frequency response is much enhanced, hence, the required load shedding amount is also different. Therefore, we have derived an analytical expression for a quick measurement of frequency response enhancement attained by BESS. Finally, a frequency nadir-based load shedding scheme, being the goal of this paper, is proposed for a heavily wind penetrated grid with BESS, using the previously derived expression, to retain the grid at its nominal operating condition following a severe contingency. Our proposed scheme incorporates an analytical method to prevent over load shed. We have used DIgSILENT PowerFactory to validate our proposed analytical approaches through dynamic simulation. Results obtained from the proposed approaches nearly resemble the simulated one. Hence, this paper can help generating simplified yet effective models to conduct analysis on a wind integrated grid. This paper can also be regarded as a guide to ensure a wind penetrated resilient grid in view of frequency stability.

Keywords

• Wind energy
• Renewable energy integration
• Analytical modeling
• Contingency
• Frequency nadir
• ROCOF