Enhancing the resilience of inverter-dominated power networks via novel distributed secondary integral control

In this paper, a novel distributed integral control algorithm is proposed that enhances the resilience of power systems consisting of inverter-interfaced Distributed Energy Resources (DERs). Utilising the structure of the bounded integral controller, the proposed solution achieves frequency restoration, voltage regulation and accurate active and reactive power sharing among the inverters, while inherently satisfying a given apparent power constraint for each inverter via its unique dynamic structure. The boundedness property of the controller is analytically proven using invariance set theory. Furthermore, in the case where one or more inverters reach their apparent power limit as a result of a disturbance (e.g. change in load demand, cyber-attack etc.), the non-compromised inverters restore the grid frequency to its nominal value and continue to share the active and reactive power among them, while the compromised units are automatically excluded from the power sharing procedure, hence enhancing the system resilience. The effectiveness of the proposed controller in achieving the desired control tasks, even in presence of cyber attacks, is validated using a 4-node microgrid with 4 inverter-interfaced DERs created in the Typhoon HIL real time digital simulator.