On the coordinated control of multiple HVDC links using input-output exact linearization in large power systems

Stability of power systems may limit the amount of transfer capacity between areas as the systems tend to be more utilized. The controllability brought by the high voltage direct current (HVDC) links is a possible access to increase the stability and thereby the power transfer. The main contribution of this article is a coordinated control strategy for multiple HVDC links to improve both transient and small signal stability. The input-output exact feedback linearization is used to map the nonlinear system model to a linear model seen from the input to the output. Linear control design can now be used, such as the linear quadratic regulator (LQR). This linearization is not the commonly used Taylor linearization, the input-output exact feedback linearization cancels the nonlinearities by a pre-feedback loop. An extension of the internal node representation by including the dynamics of the HVDC links in the nonlinear differential swing equations is also developed, which is needed for the feedback control design. (C) 2012 Elsevier Ltd. All rights reserved.