Robust high-voltage direct current stabilising control using wide-area measurement and taking transmission time delay into consideration

This study presents a robust wide-area stabilising control approach to enhance the stability of large power systems, including high-voltage direct current (HVDC) transmission. It can utilise both the wide-area measurement data and the HVDC supplementary modulation function and select suitable feedback signals for implementing a quick and robust wide-area stabilising control (WASC) against potential power oscillations. The linearised model is established taking the unavoidable transmission time delay of the wide-area measurement signals into consideration. In order to prevent the negative impact of transmission delay on HVDC-WASC, the linearised model is formulated as the standard control problem of delay-dependent feedback control, based on the robust control theory and the improved linear matrix inequalities (LMI) approach. The controller parameters are optimised by the proposed LMI-iterated solution algorithm. In addition, a state observer is designed with the pole-placement method for the feedback-input state variables of the HVDC-WASC. Finally, non-linear simulations on two typical test systems installed with HVDC devices are performed to evaluate the control performance of the designed robust HVDC-WASC.