Distributed Transient Safety Verification via Robust Control Invariant Sets: A Microgrid Application

Modern safety-critical energy infrastructures are operated in a hierarchical and modular control framework allowing only limited data exchange between modules. In this context, to assure system-wide safety each module must synthesize and communicate constraints on the values of exchanged data. To ensure transient safety in inverter-based microgrids, we develop a set invariance-based distributed safety verification algorithm for each inverter module. Applying Nagumo's invariance condition, we construct a robust polynomial optimization problem to jointly search for safety-admissible set of control set-points and design parameters, under allowable disturbances from neighbors. We solve the verification problem with sum-of-squares programming and we perform numerical simulations using grid-forming inverters to illustrate our method.