Exponential-function-based droop control for islanded microgrids

An exponential-function-based droop control strategy for the distributed energy resources (DERs) is proposed to reduce the reactive power-sharing deviation, limit the minimum value of frequency/voltage, whilst improving the utilization rate of renewable energy. Both DERs and loads are interconnected to achieve a power exchange by converters, where the power management system should accurately share the active/reactive power demand. However, the proportional reactive power sharing often deteriorates due to its dependence on the line impedances. Thus, an exponential-function-based droop control is proposed to ① prevent voltage and frequency from falling to the lower restraint, ② achieve accurate reactive power sharing, ③ eliminate communication and improve the usage ratio of renewable energy. Furthermore, its stability is analyzed, and the application in islanded AC/DC hybrid microgrids is investigated to achieve the bidirectional power flow. The simulation and experimental results show that the reactive power sharing deviation can be reduced, and the utilization rate of renewable energy is improved by using the proposed method. Moreover, the simulation results illustrate that the system can maintain stable operation when the microgrid is switched from one supplied energy operation condition to another absorbed one.