Aggregation Optimization-Based Secondary Control for DC Microgrids

To achieve control objectives of voltage regulation and current sharing and realize economic operation such as minimizing generation costs and line losses, in this paper, an aggregate optimization framework is established for DC microgrids and an objective function is constructed consisting of voltage error, current sharing error, generation cost and line loss, with flexible weights assigned to each items. A distributed secondary controller involving two auxiliary variables is proposed. The two auxiliary variables are designed to track two global signals within a fixed settling time by interacting with neighbors and evolving in a distributed manner. Theoretical analysis is provided to show that the optimal decision variables can be achieved and the global objective function can be minimized. At the optimal point, the controller not only guarantees voltage regulation and current sharing, but also ensures minimum generation costs and line losses. Numerical simulations and experimental tests are conducted to verify the effectiveness of the proposed controller and its advantage in global optimization.