Showing papers by "Qobad Shafiee published in 2013"

Stability, power sharing, & distributed secondary control in droop-controlled microgrids

Abstract: Motivated by the recent and growing interest in microgrids, we study the operation of droop-controlled DC/AC inverters in an islanded inductive microgrid. We present a necessary and sufficient condition for the existence of a synchronized steady state that is unique and locally exponentially stable. We discuss a selection of controller gains which leads to a sharing of power among the generators, and show that this proportional selection enforces actuation constraints for the inverters. Moreover, we propose a distributed integral controller based on averaging algorithms which dynamically regulates the system frequency in the presence of a time-varying load. Remarkably, this distributed-averaging integral controller has the additional property that it maintains the power sharing properties of the primary droop controller. Finally, we present experimental results validating our controller design, along with simulations of extended scenarios. Our results hold without assumptions on uniform line admittances, inverter power ratings, or voltage magnitudes.

A novel robust communication algorithm for distributed secondary control of islanded MicroGrids

Abstract: Distributed secondary control (DSC) is a new approach for MicroGrids (MGs) such that frequency, voltage and power regulation is made in each unit locally to avoid using a central controller. Due to the constrained traffic pattern required by the secondary control, it is viable to implement dedicated local area communication functionality among the local controllers. This paper presents a new, wireless-based robust communication algorithm for DSC of MGs designed to avoid communication bottlenecks and enable the plug-and-play capability of new DGs. Real-time simulation and experimental results are presented to evaluate the feasibility and robustness endowed by the proposed algorithm.