Inter-Area Oscillation Damping via Hybrid LQR State Feedback Control of Large-Scale Battery

The increasing penetration of renewable energy sources in power grids highlights the role of battery energy storage systems (BESSs) in enhancing the stability and quality of electricity. One of the significant applications of BESSs is to control and damp the frequency deviations in power grids. In this paper, we consider a two-area four-machine power grid system with large-scale battery integration. We model the battery energy storage with two dynamic models in d-q axis for charging and discharging modes and augment the battery model with the rest of the power grid system. For each of these modes, we design an optimum controller using linear quadratic regulator (LQR) techniques to damp the frequency deviations of all generators in the case study. Unlike the majority of existing studies merely focus on the active power of BESSs, we consider both active and reactive powers of BESSs. Next, we design a hybrid controller with a switching policy to select the battery's operating mode based on the cost functions of optimal controllers (LQRs). The hybrid controller selects the minimum cost function for each time interval and updates all states of the power system accordingly. The simulation results of the proposed methodology are provided in SIMULINK/MATLAB to illustrate this approach's effectiveness.