Sliding Droop Control For Distributed Generation In Microgrids

Abstract

This paper proposes a fully autonomous controller that slides the droop curves of a Static Synchronous Generator, avoiding the need of hierarchical controllers to perform power sharing and frequency and voltage regulation. The aim of this controller is to enhance the primary controller in order to perform additional functionalities in a similar way as those performed in a secondary control level hierarchy, avoiding the need of a communication- system and without mischaracterizing the primary behavior as a virtual synchronous machine. The proposed seamless controller is still compatible with conventional communication-systems, and can receive inputs from hierarchical controllers. In grid-connected microgrids, distributed generation (DG) units perform active-power supply and adequate voltage regulation, whereas the system frequency is imposed by the grid. Contrarily, in islanded microgrids, DG units have to perform active-power sharing between all units, reactive-power sharing, as well as to ensure adequate frequency control and voltage regulation. When static droop curves are employed, power dispatch planning along with coordinated set of DG units is required to achieve accurate active-power sharing. This drawback is mitigated with the proposed fully autonomous controller. Simulation results were obtained in a microgrid scenario to demonstrate the effective approach for power sharing. Experimental results are also presented.