An Extended State Observer Based Adaptive Backstepping Controller for Microgrid

This paper proposes development of a robust distributed secondary control scheme for a photovoltaic (PV) source integrated and inverter-interfaced islanded AC microgrid (MG). The control objective is to regulate the voltage, frequency, and achieve the desired active and reactive power sharing among the distributed generations (DGs) while supporting plug and play operation (PnP) and handling abnormal situations. The above objectives are to be achieved in face of uncertainties in inverter switching pulses, intermittent nature of PV source, dynamic load changes, and disturbances. A backstepping (BS) controller is designed to track the nominal voltage and frequency, whilst an extended state observer (ESO) is designed to estimate the disturbance. The stability of the MG with ESO-BS controller is proved by using Lyapunov stability theory, and graph theory. To verify the effectiveness of the proposed controller, both numerical simulation in MATLAB, and experimentation on OPAL-RT at different operating conditions are pursued. The proposed controller is compared with the distributed averaging based secondary control (Simpson-Porco et al., 2015), secondary controller based on MG centralized controller (MGCC) (Shafiee et al., 2014). It is observed that the proposed controller outperforms in terms of enhanced robustness and steady-state performance.