Failure-Tolerant Fully-Distributed OPF Algorithm for System-Level Control of Multi-Terminal DC Grids

Abstract

In the future multi-terminal DC (MTDC) distribution grids, with high penetration of converter-interfaced distributed energy resources (DER), the system-level control is expected to be realised through a fully-distributed optimal power flow (OPF) algorithm that determines the voltage and power set-points for the converters. The OPF problem is divided to nodal OPF sub-problems, which are solved by distributed control units (DCUs) operating as a networked control system (NCS). This paper presents a fully-distributed OPF algorithm with an incorporated strategy, to survive failures in the NCS, such as permanent changes in the NCS topology due to the crash of a DCU or the loss of a communication link. By changing the constraints of the OPF sub-problems of the affected DCUs upon the detection of the failure in the NCS, the fully-distributed algorithm becomes tolerant to permanent changes in the NCS topology and converge to a feasible OPF solution. Simulation results in different IEEE networks and failure scenarios demonstrate the fast convergence, irrespective of the number and location of the failures in the NCS or the failure time-point during the execution of the algorithm.