A Novel Strategy for Optimal Battery Sizing Based on MG Frequency Security Criterion

In this paper, a two-stage frequency control consisting of primary and secondary frequency control is proposed. Lithium type battery with the overloading capability to fast charge and discharge, is used for primary frequency control. The modified overloading characteristics is presented for optimal battery sizing and also to avoid damaging the battery during fast charge/discharge. By amplification the frequency controller of battery energy storage system, it can inject/absorb more power at a higher rate which results in less frequency deviation. In this paper, this technique is used with the proposed frequency control to inject/absorb as much power as required to maintain frequency deviation within safe limits that on this basis, the optimal size of battery is determined. In this regard, two case studies with the most shortage and surplus of power generation as the result of the unplanned islanding are considered. The slow micro-sources like diesel generator are used for secondary frequency control to restore frequency to its nominal value. In order to validate the performance of the proposed strategy, simulation studies are carried out on the modified CIGRE low voltage benchmark system by simulation in MATLAB/Simulink software that the simulation results show the effectiveness of the proposed approach.