Wide-area time-delay damping control to prevent power oscillations in HVDC/AC interconnected power systems

In this paper, a robust high voltage direct-current (HVDC) wide-area time-delay damping control strategy is proposed to prevent the potential low-frequency power oscillation and enhance the power stability of HVDC/AC interconnected power systems. Firstly, the basic design concept and the related design flow are presented. Then, the general wide-area power system model with the time-delay characteristic is described by the linearization modeling method. The practical reduced-order algorithm is introduced to further obtain the reduced system state-space model that maintains the low-frequency oscillation mode. Furthermore, considering the inevitable time delay in the wide-area feedback control signals transmitted by the wide-area measurement system (WAMS), the improved linear matrix inequality (LMI) method is applied to design the robust supplementary damping controller associated to the HVDC converter pole-control. Such controller can efficiently suppress the negative effect of time delay of the wide-area control signals on the oscillation damping performance. In addition, the iterative algorithm is proposed to search the optimal overall gain matrix for the state feedback control, and the state observer is also designed based on the classic pole-placement method to realize the observability on the state variables of the reduced system. Finally, a case study on a benchmark system of small signal stability study is performed to validate the proposed HVDC wide-area time-delay damping control strategy.