Finite Control Set MPC for Voltage and Frequency Stabilization in Islanded AC Microgrids with Line Impedance Consideration and Enhanced Power Sharing Control

Abstract

This paper presents a hierarchical wireless control scheme for parallel distributed generation (DG) units in islanded AC microgrids. The proposed control scheme is divided into primary and secondary control layers. The primary control layer includes an improved finite set-model predictive control (FS-MPC) with a dualobjective cost function based on the proposed droop approach. The benefit of the proposed droop approach is the ability to generate the reference voltage without any amplitude deviation, unlike the conventional droop technique, which may cause deviations. Furthermore, double virtual impedances are proposed, with the first one being used to reduce the effects of feeders' mismatched impedance, while the second one is used to increase the output impedance resistance, leading to enhanced accuracy of active and reactive power sharing among DG units. The secondary control layer helps to establish global controllability by keeping the frequency and amplitude voltage of the AC bus at their nominal values. The simulation results show that the proposed control is capable of ensuring appropriate power sharing among parallel DG units and achieving voltage quality at the AC bus under different load conditions.

Improved Droop Controller for Distributed Generation Inverters in Islanded AC Microgrids

“…The virtual output impedance selection can be accomplished using the summation approach [25,26], which ensures balanced reactive power sharing by maintaining a consistent voltage drop from each inverter to the AC bus as follows:…”