Realizing Unified Microgrid Voltage Profile and Loss Minimization: A Cooperative Distributed Optimization and Control Approach

Cooperative distributed optimization is proposed in this paper to optimally dispatch the reactive power of the distributed generators (DGs). The overall objective is to minimize the cost function that is the sum of all quadratic voltage errors of the DG nodes and other critical nodes in the system. It is assumed that each DG is only aware of its own cost function defined as the quadratic voltage error of its respective node. In the proposed method, every DG performs optimization with respect to its own objective function while considering the information received locally from the neighboring nodes in the microgrid, and the critical nodes without DG also contribute to optimization. The proposed distributed optimization and control scheme enables the microgrid to have a unified voltage profile, and incorporating the subgradient method facilitates its application even when the microgrid information is unknown. Microgrid active power loss is also investigated, and it is shown that the unified voltage profile naturally leads to the overall active power loss minimization as well. Stability analysis and criteria are provided. Simulation results of a typical microgrid illustrate superior performance of the proposed technique.