Controlled Islanding for a Hybrid AC/DC Grid With VSC-HVDC Using Semi-Supervised Spectral Clustering

As the last resort of emergency control, controlled islanding is an effective means of preventing fault propagation and a system-wide blackout. However, conventional ac transmission lines are unavailable to be employed for power exchange between these islands. To make full use of the dc power modulation capability of voltage source converter-based high-voltage direct current (VSC-HVdc) links, a new controlled islanding model is put forward for an ac/VSC-HVdc hybrid grid to minimize the composite power-flow disruption, in which the dc-terminals belonging to a VSC-HVdc link are placed in different islands. To solve this model, a semi-supervised spectral clustering-based approach is proposed by transforming the problem into a weighted undirected graph segmentation problem. The novelty of this paper is to find an optimal islanding solution in real time such that the power exchanges between islands are implemented via a VSC-HVdc link to reduce the generation-load imbalance. The simulation results on the IEEE 39-bus system and a real-world system verify the effectiveness and superiority of the proposed approach.