Resilient Distributed Control for Power Systems With Multiple Synchronous Generators and DERs Satisfying Capability Curve Requirements

In this paper, a novel distributed integral controller is proposed for a power system with multiple synchronous generators (SGs) and inverter-interfaced distributed energy resources (DERs) that ensures grid frequency restoration, voltage regulation and accurate power sharing while satisfying technical/operational constraints for the real and reactive power imposed by the capability curve of each unit. By taking into account the generic nonlinear dynamic model of the entire power system and considering only neighbour-to-neighbour communication among SGs and DERs, the proposed controller is suitably designed to inherently guarantee the capability curve constraints using invariant set theory (Nagumo's theorem), without introducing saturation units that may lead to instability, as commonly used in the existing literature. Furthermore, closed-loop system stability is also investigated to prove convergence to the desired equilibrium point for different values of the controller gains. Finally, it is analytically shown that in the case where one or more SG or DER units are forced to reach their capability curve limits, due to abnormal conditions caused by sudden load changes, cyber attacks, measurement faults, etc., the remaining non-compromised units will automatically continue to accomplish the control tasks (frequency regulation, power sharing); thus enhancing the resilience of the entire power system. The effectiveness of the proposed controller is verified under 3 extreme scenarios (load change, setpoint attack, measurement fault) on an experimental setup using the Typhoon HIL real-time system for a 10-bus and a 14-bus power network, both with 4 SGs and 2 inverter-interfaced DERs and is directly compared to a conventional distributed integral controller.