Adaptive resonant based multi-loop control strategy for parallel distributed generation units in standalone microgrid application

- Both frequency and gain adaptation are incorporated on the resonant based current and voltage controllers.
- An islanded microgrid of a single and multiple distributed generation units is considered.
- A modified droop controller is adopted along with a virtual output impedance control loop.
- Experimental evaluating of an islanded microgrid under large operating point variations.

This paper proposes a novel control strategy to deal efficiently with the recurrent frequency and amplitude adjustments that occur in standalone microgrid application. These frequent variations are commonly introduced by the droop based controllers in order to accurately regulate the power sharing among the parallel connected distributed generators. In this way, a double current and voltage control structure based on adaptive proportional plus multi resonant controllers is designed to address the aforementioned challenges. The proposed adaptive control technique allows maintaining high performance voltage reference tracking with a reduced rate of harmonic distortion in spite of load transients and under significant operating frequency deviation. The designed control structure is then expanded to parallel-distributed generation units through a modified droop based power-sharing controller. Experimental results are presented to show the feasibility of the proposed adaptive control scheme and its effectiveness to cope with large frequency variations.