Lagrange Multiplier-Based Optimization Control for Distribution Power Loss Minimization of Islanded Three-Phase AC Microgrids

In this paper, the distribution power loss of islanded three-phase AC microgrids comprising both line loss and power converter loss is modelled as a quadratic function of current allocation coefficients, which is a convex function with constraints. On basis of convex optimization theory, the optimal current allocation coefficients of distributed energy resources (DERs) for distribution loss minimization are on-line calculated by Lagrange multiplier method. By adopting the average reactive power sharing scheme, the proposed control strategy is can obtain the optimal power allocation coefficients for minimizing the distribution power loss of AC microgrids in real time. Then, an improved adaptive droop control strategy is proposed to allocate output active power and reactive power of DERs for achieving the given current-sharing rate. In this way, the real-time efficiency optimization control of AC microgrid can be realized, regardless of line resistance and load variations. The effectiveness of the proposed control strategy is validated by simulation-based case studies.