On the coordinated control of multiple HVDC links

In this paper, coordinated control of multiple HVDC links in a small AC/DC power system is investigated. A coordinated control strategy is proposed to increase the transient stability and the damping in the AC/DC system. The system power loading is set by the well-known N - 1 criteria, i.e. that the system should remain intact (in the sense of both transient and small-signal stability) despite the loss of any important component. Since both transient stability and damping are increased by coordination of the control of the HVDC links, the allowed transmission capacity can be increased. The control strategy proposed in this paper posses the ability of damping power oscillations and improving the transient stability in the test system, it can also be used in a large scale power system. In the test system, the HVDC links are not operating in parallel with the AC lines, therefore coordination of the HVDC links is necessary to achieve significant better damping and transient stability.