Controlled islanding for a hybrid AC/DC grid with VSC-HVDC using semi-supervised spectral clustering
For power system operators, this work addresses the problem of preventing blackouts in hybrid AC/DC grids by leveraging VSC-HVDC links for power exchange between islands, though it is an incremental extension of spectral clustering to a specific grid topology.
The paper proposes a controlled islanding model for hybrid AC/VSC-HVDC grids that minimizes composite power-flow disruption by placing DC terminals of a VSC-HVDC link in different islands, and solves it with a semi-supervised spectral clustering approach. Simulations on IEEE 39-bus and a real-world system show the approach effectively reduces generation-load imbalance in real time.
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 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 our work 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.