Research on Fault Analysis and Relay Protection for Flexible DC Grid Lines Considering Distributed and Frequency-Dependent Parameters

Speaker:       Zhiquan Liu

Time:            14:00, Sep. 19th

Location:      SIST 1C-101

Host:             Prof. Yu Liu  Prof. Haoyu Wang

Abstract:

With the rapid growth of renewable energy, high-voltage direct current (HVDC) technology is emerging as a key solution for long-distance, large-scale power transmission. Among the different HVDC approaches, systems based on Modular Multilevel Converters (MMCs) are especially favored due to their outstanding controllability, high modularity, and relatively low switching losses. These features make MMC-HVDC systems highly competitive for integrating variable renewable energy sources into traditional AC networks. However, compared with conventional transmission lines, MMC-HVDC systems exhibit more complex and severe transient fault dynamics, posing significant challenges for existing fault analysis methods, protection schemes, and fault location techniques. Addressing these challenges is crucial to ensuring the secure, reliable, and efficient operation of next-generation HVDC grids.

This seminar will present new developments in three key areas: fault analysis, line protection, and fault location. For fault analysis, analytical expressions have been derived to characterize fault-induced voltage and current traveling waves at line terminals, incorporating both frequency-dependent and distributed line parameters. For line protection, a differential protection scheme based on partial differential equations and a compact frequency-dependent line model has been proposed, delivering higher accuracy with improved computational efficiency. For fault location, a novel velocity-free, single-ended method based on traveling wave characteristics has been introduced, enabling reliable and precise fault identification without the need for wave velocity estimation.

Bio:

Mr. Zhiquan Liu joined PSPAL in September 2023. He is currently a master student in PSPAL (starting from September 2023). He received the B.S. degree of hydraulic and hydro-power engineering from Huazhong University of Science and Technology, Wuhan, China, in summer 2023. His research interests include transmission line modeling, protection and fault location.