Power system stability enhancement by WAMS-based supplementary control of multi-terminal HVDC networks

This paper deals with supplementary control of a MTDC network designed for the stability enhancement of a AC power system. The proposed control is a WAMS-based control modulating the real and reactive power at the terminals of the DC network. Relevant control formulas have been derived for a linear multi-machine system model with the application of the direct Lyapunov method. Validity and robustness of the proposed control has been verified by computer simulation for a multi-machine test system using a nonlinear model and detailed modeling of power system components. The proposed control is robust and insensitive to changes in the network configuration and loading conditions in the AC power system. In the case, when more of the MTDC networks and/or the HVDC links are used in one interconnected power system the proposed stabilizing control produces additive damping i.e. each controlled network element contributes to the positive damping. Some practical aspects have also been discussed. The proposed WAMS-based stabilizing control of the MTDC network is innovative by both its main concept and the derivation of control formulas using the direct Lyapunov method.

► MTDC networks can be used to enhance transient stability of AC power systems.
► The proposed control is insensitive to changes in the network configuration.
► The proposed control is insensitive to changes in the loading conditions.
► Each device controlled by proposed method contributes with positive damping.
► The proposed control can be realized as the WAMS-based supplementary control.