Voltage robust stability in microgrid power management

Voltage stability is of essential importance for power grids. The emergence of distributed energy generators, controllable loads, and local-area energy storage capabilities will introduce new scenarios for distribution networks in which classical frameworks for voltage stability may be inadequate. This paper introduces a control-theoretic framework for studying voltage stability and its robustness, as well as optimal power management in distribution systems composed of networked microgrids. The framework involves descriptions of the loads and generators by nonlinear state space models and the network connections by a set of topology-based algebraic equations. The combined system leads to a general nonlinear state space model for the microgrid systems. Four stability margins are introduced to capture different scenarios in microgrid power management capabilities and load disturbances. LMI (linear matrix inequality) methods are employed for computing stability margins. Illustrative examples are used to demonstrate the methods.