Enhancement of Stabilizing Performance of a Microgrid Using Energy Storage System with Under Frequency Relay

Abstract

This paper presents a method to enhance the stabilizing performance of a microgrid using an energy storage system (ESS) with under frequency (UF) relay. A microgrid is considered as a small-scale power grid that involves generation, distribution and energy storage systems operating independently from the main grid. Typically, a microgrid uses renewable energy to produce electricity as a main source. Due to the uncertain generation of power from renewable supply in a microgrid, the controlling of power balance between supply and demand of a microgrid is difficult in the islanded operation mode. When a microgrid is subjected to a large disturbance, the frequency of a microgrid may change rapidly due to the low inertia present in a microgrid. It is essential to maintain the frequency of a microgrid within acceptable ranges, particularly in islanded mode. Therefore, utilizing an ESS with UF relay gives benefits in maintaining and stabilizing the frequency effectively. In this paper, a system identification technique is applied to a microgrid to formulate a mathematical model systematically. Then, with the obtained identified model, the robust controller of an ESS can be designed by using H-infinity loop shaping procedure (HLSP). The application of such ESS with the appropriate load shedding by UF relay is also proposed. The proposed study system is implemented on DIgSILENT PowerFactory and MATLAB software. The obtained simulation results demonstrate that the stabilizing performance of frequency in a microgrid is more effective in terms of smaller frequency deviations, faster responses and minimum load shedding when collaborative ESS control and appropriate load shedding with UF relay are used.
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