Modeling and Stability of Microgrids with Smart Loads

Abstract

A demand-side technology called “electric springs” was recently proposed to stabilize the future smart grid subject to large penetration of renewable energy sources. Based on power flow and basic circuit theory, this paper establishes a comprehensive microgrid model that consists of energy sources interfaced via inverters and smart loads for which electric springs are installed. Modeling it as a controlled voltage source, we can design the high-level control for the electric spring such that the load bus dynamics can be shaped to have desired frequency and voltage dynamics. We conduct the small-disturbance stability analysis on the established microgrid model where both generation and load buses implement frequency and voltage droop control. Finally, a graph-theoretic like stability condition is obtained.