Research on control and protection technology of flexible low-frequency AC transmission project

Abstract

With the development of offshore wind power development to deep and far sea, offshore flexible low-frequency AC (LFAC) transmission technology has attracted more and more attention from academia and industry in recent years. The control and protection system is the brain of flexible LFAC transmission, which is directly related to the performance, safety and benefit of LFAC transmission. In order to improve its operation reliability and limit the impact caused by any control link fault, in this paper, the control system is divided into system level control strategy, converter station level control strategy and valve level control strategy, which is from high level to low level according to the stratification principle. For the protection system, a specific zoning protection scheme is proposed. Finally, a two-terminal flexible LFAC transmission system is built in PSCAD/EMTDC. The simulation results prove the validity and correctness of the proposed control and protection strategy.

Keywords

• Low-frequency AC (LFAC)
• System level control
• Converter station level control
• Valve level control
• Protection