Robust H∞ Decentralized Control Design for HVDC Link Embedded in a Large-scale AC Grid

This paper proposes a static decentralized controller design method for an HVDC link embedded in a large-scale AC grid based on the Linear Matrix Inequalities (LMIs) technique. The considered studied system is treated as composed by two overlapping subsystems. The interconnection between the two subsystems is nonlinear and is treated by increasing disturbance rejection and robustness against norm-bounded parametric uncertainties of the closed-loop. Indeed, the overall robustness and tracking ability of the entire closed-loop is significantly improved with the proposed controller. This is both analytically ensured in the synthesis of the gains of the regulators and, next proven by validation simulations. The overall robustness and tracking ability of the entire closed loop system can be significantly improved. It is shown that this control can deal with HVDC link with different lengths, including the short ones for each the coupling between the two converters is strong.Another advantage of the proposed decoupling control is the resilience: as no communication is used between the two stations, in case of failure of one converter or loss of measures as control, the control of the other converter is not affected. Moreover, it guarantees the stability of the overall system. Finally, the efficiency and robustness of the proposed controllers are tested and compared with each others, to illustrate the control synthesis and its effectiveness.