Distributed Optimal Consensus-Based Secondary Frequency and Voltage Control of Isolated AC Microgrids

Abstract

Diverse consensus-based distributed secondary control mechanisms of isolated AC micro-grids (MG) have been proposed for achieving the autonomous steady-state power sharing and frequency synchronizations. However, their transient responses are not specified. To tackle out this issue, a fully distributed optimal control strategy is studied in this paper in which their transient responses are characterized in the objective function. A two cascaded loops control strategy for each distributed generator (DG) is proposed to achieve this control objective. In the local inner loop, auxiliary inputs are designed for adjusting local frequency and voltage. In the outer control loop, the distributed optimization problem is proposed under both agent dynamics and consensus constraints. By defining the augmented Lagrangian, a fully distributed optimization algorithm can be developed by integrating the method of alternating direction method of multipliers (ADMM) and Lyapunov function approach. To demonstrate the applicability of the proposed method, real-time simulation studies of IEEE 34-node MG are performed. Comparison studies between the proposed approach and the distributed PI-based consensus control also indicate the effectiveness of the proposed method.