Advanced control to damp power oscillations with VSC‐HVDC links inserted in meshed AC grids

Abstract

In this article, we consider the particular situation of a HVDC link inserted in a meshed AC grid, which has interarea modes at upper frequencies than the usual ones. In this case, the standard IEEE (lead-lag plus gain) controllers may not be efficient. As a matter of fact, in this grid situation, the control is challenged by unstable zeros and system uncertainties, systematically put into evidence. Two original robust strategies based on matching a reference model using LMI optimization approach are designed to provide coordinated active and reactive power modulation for the HVDC link. They are based on a reduced order control model of the HVDC and the neighboring AC zone, which integrates the dynamics of interest. Besides increased damping and diminished impact of the unstable zeros, this new control achieves robustness against grid variations. Investigations with both linearized and nonlinear model of the system are carried out to settle and validate the approach. The efficiency and robustness of the proposed controllers are tested and compared with the ones of several standard controllers on a realistic benchmark of 19 generators interconnected by a meshed AC grid.