Stability of a Cyber-physical Smart Grid System Using Cooperating Invariants

Cyber-Physical Systems (CPS) consist of computational components interconnected by computer networks that monitor and control switched physical entities interconnected by physical infrastructures. A fundamental challenge in the design and analysis of CPS is the lack of common semantics across the components. We address this challenge by employing a novel approach that composes the correctness of various components instead of their functionality using a conjunction of non-interfering logical invariants. We present a distributed algorithm that uses this approach to adaptively schedule power transfers between nodes in a smart power grid in such a way that the stability of both the computer network and the physical system are maintained. Simulation results demonstrate the necessity and usefulness of our approach in maintaining overall system stability in the presence of uncertainties in the computer network and with limited information about the global state of the system.