Fault Detection and AC-DC System Dynamics Analysis of a Modular Multi-level Converter Based HVDC Network Under DC Faults

The interconnection of HVDC (High Voltage Direct Current) transmission has proved its strength in being competent with the HVAC transmission for the bulk amount of power transfer over a large distance. With the adaption of interconnected hybrid systems, there arises the need to develop or modify the existing protection techniques, to protect the interconnected AC-DC system. If a fault occurs on either side in an interconnected VSC-HVDC network, the disturbance may travel to another part of the hybrid network. The transient current has fatal effects on the power electronics devices of the converters of the VSC-HVDC configuration. This may cause failure of switches like diodes, IGBTs, and submodules which are the building blocks of the converter unit. The consecutive result may be the failure of the DC link. This article provides an analysis of the network under DC faults. This study may be helpful in knowing the system behavior so, the protection scheme can be designed accordingly. In this article, the Teager Kaiser Energy Operator (TKEO) is used to perform the task. This energy spectrum provides a robust and efficient performance to detect the fault with adequate accuracy and faster speed. The current signal signature is noted for the different fault cases. The novelty is established in terms of accurate and efficient fault detection with the proposed technique. For the DC fault transients, the proposed technique proves its potency with the detection speed and accuracy. The proposed network is simulated using the PSCAD/EMTDC and MATLAB platform. The technique proves its efficiency in various tested fault scenarios.