Optimization-Based Distributed Controller for Multi-Agents System in Microgrid Secondary Control

Abstract

Micro-grids function to connect to power system power produced by the renewable energy resources. In islanded micro-grids, grid-forming units collaborate to maintain the micro-grids voltage and frequency by utilizing droop control technique that includes primary, secondary and tertiary levels. Secondary control intervenes to improve power sharing and restore voltage and frequency to their nominal levels. However, the conventional droop control applied to a grid with mismatched line parameters experiences a trade-off between reactive power sharing and voltage regulations. This paper applies real-time trajectory tracking convex optimization to ensure by communicating power sharing between units in a consensus topology. The optimization function is designed with local frequency and voltage constraints to maintain the frequency at its nominal value and ensure the voltage remains within a 5% tolerance range.. The proposed controller maintains power sharing among all units at the global consensus average value with constraints to within the limits. When the voltage limit is reached, the reactive power automatically deviates from the agreed global average in an optimal manner. The performance of the controller is shown using MATLAB/SIMULINK for different control parameters. The performance is compared to centralized-based topology. Finally, the controller is tested for grids with different line-parameters mismatches. The results show the reactive power sharing in an optimized manner.