Robust μ-synthesis control of a four-wire autonomous electronically-interfaced distributed generation unit for mitigation of harmonic voltage disturbance

This paper proposes a robust performance H_∞ controller for autonomous (stand-alone) operation of a four-wire distributed generation (DG) unit. The controller is designed to provide robustness against system and load parametric uncertainties as well as a worst-case performance guarantee for voltage disturbance rejection. The proposed control strategy employs: 1) an internal oscillator to maintain the frequency of the island; and 2) a feedback control system to regulate the voltage of the island. A robust performance μ-synthesized controller is designed using the D-K iteration technique. The performance of the proposed robust controller is compared to a standard PID controller and a “PI-type-3” controller under varying system and load conditions. The superiority of the proposed control strategy is demonstrated using time-domain simulations carried out on a single-DG test system in MATLAB/Simulinkr environment.