Time-Varying Optimization-Based Consensus Control For Microgrid's Secondary Control

Abstract

In this paper, a time-varying convex optimization-based consensus controller is utilized for the secondary control of Microgrid in islanded mode. During this mode, grid-forming units are responsible for controlling the frequency and voltage of the microgid. Hierarchical control structure based on droop control is utilized to provide these functionalities. In primary control level, the system stability is maintained through supplying required active and reactive power leaving a deviation in the frequency and voltage magnitudes. The secondary control level is introduced to restore the frequency and voltage to their nominal values. However, droop-based hierarchal control suffers from poor reactive power sharing due to voltage drop in the lines. The proposed controller aims to restore the frequency to its nominal value and voltage within a predefined limit while keeping the active and reactive power sharing difference between units to the minimum. The proposed controller employs consensus-based distributed communication where each unit only communicates with its neighbor. This paper provides optimality and consensus analysis of time-varying optimization-based consensus control as well as a design procedure of the controller. The proposed controller is validated through SIMULINK/ MATLAB simulation. The real-time convex optimization solver is provided by CVXGEN.