Sustainable Energy, Grids and Networks | 2021
Security constrained OPF for AC/DC systems with power rescheduling by power plants and VSC stations
Abstract
Abstract This paper describes a novel modelling framework for security constrained optimal power flows (SCOPF) aimed at multi-terminal VSC-based AC/DC systems, where power rescheduling by power plants and converters is considered by means of voltage/power droop controls. The optimisation method is based on a linear programming model where generation cost curves and AC/DC power losses are included by piecewise linear functions. The formulation accommodates arbitrary network models with numerous VSC-connected AC grids. This leads to a suitable modelling flexibility for corrective SCOPF analysis of practical AC/DC grids formed by VSC-based transmission grids. The proposed SCOPF formulation enables efficient contingency analysis involving the disconnection of AC branches, DC lines, power plants, and VSC units. This is confirmed using an AC/DC grid with four VSC-connected AC systems. Simulation results show that this new method presents average errors inferior to 5% whereas computing times are reduced by more than 90% with respect to a nonlinear SCOPF method based on sequential quadratic programming. The practicality of the proposed method is also proven by studying an AC/DC system comprising seven VSC-coupled AC grids totalling seventy dispatchable generators.