Hybrid droop and current control for seamless transition mode of microgrids

This paper proposes a smooth transition control strategy for voltage source inverters between standalone (SA) and grid connected (GC) modes of operation. During transition both current control and droop control will participate in formulating the inverter output voltage but with different weights or coefficients. In transition mode the controller varies the output coefficients of the current and droop control depending on the frequency variation to regulate the real power flow. In the proposed controller, no additional unit, like central controller, is needed to flow the required power in the transition period and no explicit communication between the inverters is required. In the transition mode, the proposed controller takes the responsibility and ensures the continuous power delivery to the load. The performance of the proposed control technique has been verified with simulation and experimental studies.