Decentralized Voltage Control of AC Microgrids With Constant Power Loads Using Control Barrier Functions

This paper proposes a novel nonlinear decentralized voltage controller for constrained regulation of meshed AC Microgrid networks with high penetration of time-varying constant power loads. Modelling the load demand as a constantly evolving unknown disturbance, the network model is reformulated in a cascaded structure composed of a nominal,i.e.uncertainty-free, and an error subsystem. By adopting a suitable control barrier function, we formulate a continuous-time control law and derive analytic conditions on the tuning parameters, such that the distance between the true and the nominal state trajectories is bounded at all times. Under sufficient conditions, we prove asymptotic stability of the cascaded dynamics with respect to an equilibrium set and also provide an estimate of the region of attraction. In addition, it is rigorously shown that the proposed nonlinear control law enforces constrained regulation around a rated voltage value, without the need of saturation devices. The operation of the closed-loop system is illustrated both via simulation and real-time HIL scenarios, demonstrating bounded operation and convergence to a neighbourhood of the desired reference vector.