A Fast Protection of Multi-terminal HVDC System Based on Transient Signal Detection

HVDC technologies are widely acknowledged as one of solutions for the interconnection of renewable energy resources with the main electric power grid. The application of the latest modular multi-level converter (MMC) makes power conversion much more efficient. Due to the relatively low impedance in a DC system, DC fault currents may rise to an extremely high level in a short period of time, which can be very dangerous for HVDC converters. To improve the sustainability and security of electricity transmission, protection solutions for HVDC systems are being developed. Nevertheless, they have various drawbacks on fault signal detection and timely clearance. This paper proposes a protection method that provides a fast and reliable solution addressing those drawbacks. A protection algorithm based on travelling wave simulation and analysis is proposed to detect abrupt transient signals. The algorithm shows high efficiency, reliability, selectivity and has low sampling frequency requirements. The proposed protection method has been validated through a cyber-physical simulation platform, developed using a real-time digital simulator (RTDS) and IEC 61850 communication links. The obtained results show that the proposed method has good potential for practical applications.