Integration of distributed energy systems in micro-grid architecture for making a virtual power plant

This paper presents a novel concept for increasing the penetration level of distributed renewable energy systems into the main electricity grid. When increasing the renewable energy penetration, it is important to implement the frequency based power delivery in distributed generators and work as traditional synchronous generators. This can be achieved by improving the power processing unit of each renewable generation units to work as active generators. But in existing grid architecture, the gridfrequency is controlled as one common variable over the electricity grid. With such a method, it is difficult to use frequency based power sharing in small distributed generators and participate in gridfrequency control activities.

In this proposed grid connected micro-grid architecture, the micro-grid is connected to the main-grid via back-to-back converter, which gives the facility to use distributed local frequency droop settings within the micro-grids and isolate the two AC grids via intermediate DC link. Frequency Droop control has been implemented in the micro-grid side of back to back converter. With this method, the small renewable generations in micro-grid can adjust their power level in response to the local frequency variations and sharing loads effectively while reducing the large power variations from the main-grid.