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 short-circuit 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.