Lifetime-Oriented Droop Control Strategy for AC Islanded Microgrids

This paper presents a lifetime-oriented droop control approach for AC islanded microgrids, which is able to perform equal thermal stress distribution among paralleled inverters. An electro-thermal model and temperature estimation model is first established to observe the thermal stress of inverters, and then the temperature-power droop characteristic are built according to the electro-thermal model. Finally, the lifetime-oriented droop controller is proposed. Simulation results show that the proposed droop control strategy is able to perform automatically thermal stress sharing by regulating output powers of paralleled inverters, which thus mitigates the effect of unequal thermal-mechanical stresses on long term lifetime of paralleled inverters. The proposed droop control approach preserves the advantages of conventional droop control methods, and also implements the active thermal control for islanded microgrids. It thus increases the average lifetime and enhances long-time reliability of microgrids.