Droop-free team-oriented control for AC distribution systems

Abstract

Droop control is conventionally used for load sharing in AC distribution systems. Despite decentralized nature of the droop technique, it requires centralized secondary control to provide voltage and frequency regulation across the system. Distributed control, as an alternative to the centralized controller, offers improved reliability and scalability. Accordingly, a droopfree distributed framework is proposed that fine-tunes the voltage and frequency at each source to handle 1) Voltage regulation, 2) Reactive power sharing, 3) Frequency synchronization, and 4) Active power sharing. The controller includes three modules, namely, voltage regulator, reactive power regulator, and active power regulator. The voltage regulator boosts the voltage across the distribution system to satisfy the global voltage regulation. Proportional load sharing is adopted, where the total load is shared among sources in proportion to their rated powers. The active power regulator addresses frequency synchronization without using any frequency feedback/measurement, which improves the system dynamic. Simulation results are provided to verify the performance of the proposed control methodology.