A hierarchical control strategy of microgrids toward reliability enhancement

Reliability and operation efficiency are important concerns in microgrids. Existing hierarchical control strategies have paid limited attentions on these topics. This paper presents a reliability-oriented hierarchical control strategy to enhance operation efficiency and long-term reliability of microgrids. The proposed hierarchical control strategy is composed of three levels. (1) In primary control level, lifetime-oriented droop control strategy is proposed to perform equal thermal sharing among paralleled inverters. (2) In secondary control level, efficiency optimization control and active thermal management are developed to improve operation efficiency of microgrids under different load profiles and long-term reliability. (3) Tertiary control is presented to mitigate harmonic resonance of microgrid by impedance optimization in weak grid. Simulation and experimental results show that the proposed hierarchical control structure is able to perform equal thermal sharing, and improve operation efficiency under different load profiles, and mitigate harmonic resonance in weak grid. Therefore, the proposed hierarchical control is able to enhance operation performance of microgrids.