Efficiency-Prioritized Droop Control Strategy of AC Microgrid

Operation efficiency is one of important concerns for power conversion system. Efficiency issue of microgrids with multiple paralleled inverters has been paid slightly concerns. Therefore, this paper presents an efficiency analysis method of microgrid in system level and an efficiency-prioritized droop control strategy to improve operation efficiency of microgrids under different load profiles. Efficiency model of microgrid is first established to reveal time-varying efficiency characteristic under different load profiles. Then, optimum solution of efficiency model is derived by Lagrange Multiplier Method, and optimum conditions to capture maximum efficiency are obtained. Furthermore, an efficiency-prioritized droop control strategy is proposed to improve operation efficiency according to the established efficiency model. In addition, stability analysis of the proposed droop controller is performed, from which the guideline for controller design is given. Simulation and experimental results are provided to validate the proposed efficiency-prioritized droop control strategy. The proposed droop control strategy is able to improve overall efficiency of microgrid under different load profiles, which also preserves advantages of conventional droop control strategy.