A Distributed Secondary-Tertiary Coordinated Control Framework for Islanded Microgrids

In this paper, a fully distributed secondary-tertiary coordinated control framework for islanded ac microgrids has been proposed. First, the distributed secondary control for frequency restoration, voltage regulation and power sharing has been proposed. Therefore, the system frequency and bus voltages can be maintained at set points. Each DG can follow the tertiary control signals, while the rest load-generation mismatch is proportionally shared among DGs. Then in the tertiary control, optimal power flow of islanded ac microgrids is formulated as an optimization problem and solved by alternating direction method of multipliers. The entire control framework is achieved in a distributed way with sparse communication networks among each agent. A cyber-physical microgrid platform has been built to validate the proposed controller design in a real-time and hardware-in-the-loop condition. A six-bus three-DG microgrid is developed on the platform and the experimental results validate the effectiveness of the proposed method.