Robust Traveling Wave-based Protection Scheme For Multiterminal DC Grids

Abstract

The DC transmission line protection
technology is crucial for the development of multi-terminal Voltage Source
Converter (VSC)-based HVDC systems. This article proposes a robust non-unit
traveling wave protection (TWP), which deals with the DC fault area
identification and fault type discrimination for high impedance fault
conditions. The authors applied the traveling wave (TW) reflection and
refraction method for the line-mode network. The distinctive features of
high-frequency components contained in the line-mode and pole-mode voltage TWs
at different relay units are used for the algorithm modeling. Discrete Wavelet
Transform (DWT) is selected as the time-frequency analysis tool. The performed
simulations are conducted for a four-terminal VSC-HVDC system, and validate the
protection feasibility and robustness. More precisely, the proposed protection
scheme identifies the internal and external DC faults within 2 ms, and provides
correct operation during high-impedance faults (HIF) with a 25 dB level noise interference.
This protection scheme makes use of a VSC-assisted resonant current (VARC)
direct current circuit breaker (DCCB), that successfully interrupts the fault
currents in less than 10 ms after the fault inception. The authors also
comprehensively compared the proposed scheme with the existing methods. The
obtained results show that the proposed protection scheme is superior in terms
of sensitivity and selectivity performance.