An interior-angle analysis of power for fault detection in VSC-based HVDC-grids

The VSC-based HVDC networks have become a reliable candidate for integrating renewable energy resources over long distances. However, the development of these networks faces protection challenges against DC shortcircuit faults, where fault detection in these networks is at top of the issues. This paper proposes a fast fault identification strategy based on the Interior-Angle analysis between the powers of the DC-link capacitor and the protected DC-line. In the proposed scheme, first, the time-domain mathematical expression of the power signals is extracted, and second, the angle analysis of the power signals through the normalized interior-product approach is carried out. Accordingly, a fast fault identification index is introduced that detects the fault conditions in about 1.0 msec. The presented strategy only relies on conventional voltage/current measurements and does not require any extra sensor. Moreover, it can discriminate the faulted branch from the healthy ones with a considerable safety margin. To validate the performance of the proposed method, a complete set of fault scenarios are investigated on a bipolar meshed multi-terminal VSC-HVDC network. It is shown that the proposed method appropriately detects the pole-to-ground and pole-to-pole DC faults at different locations with zero and high resistance faults.