Dynamic Stability Enhancement of a DC-Segmented AC Power System Via HVDC Operating-Point Adjustment

Hopf bifurcation phenomenon of a power system results in oscillatory dynamics which can lead to instabilities in the system. Therefore, it is desirable to operate the system such that a sufficient margin to Hopf bifurcation is ensured. This paper presents a methodology based on the adjustment of the setpoint values of the HVDC link controllers, to prevent instability or increase the stability margin of the system subject to Hopf bifurcation. In this paper, the first-order sensitivities of the Hopf stability margin to the setpoint values of the HVDC links are presented. These sensitivities identify the optimum direction to change the HVDC setpoints to steer the system away from instability, increase the stability margin, and improve the damping of oscillatory modes. The proposed method is evaluated on various system configurations subject to Hopf bifurcation phenomena caused by a variety of events, such as load and line impedance variations. Simulation results show that at the optimum operating point, for a variety of Hopf bifurcations, the stability margin and damping of the oscillatory modes improve.