Optimal Distributed ADMM-Based Control for Frequency Synchronization in Isolated AC Microgrids

Abstract

To restrict transient dynamics of each distributed generator (DG) in isolated AC micro-grids (MGs), an optimal distributed alternating direction method of multiplier (ADMM)-based control scheme, will be explored for achieving frequency synchronization within a given finite horizon. By introducing the consensus variable, we re-phrase the frequency synchronization problem as a linear quadratic tracking problem under the framework of multi-agent systems. The objective function of each individual DG is defined as the accumulation of quadratic frequency errors and quadratic inputs. Since the consensus variable is also part of the decision variable, more flexibility can be gained in developing the optimal distributed ADMM-based algorithm within a finite horizon. Since the direct extension of ADMM for static optimization can not be fully distributed, a fully distributed ADMM-based control is developed by exploring the optimal distributed control theory in each DG. To validate the performance of the proposed method, real-time simulations on OPAL-RT are conducted to validate the effectiveness of the proposed optimal distributed ADMM-based control strategy even under large load variations and plug-and-play operations of DGs.