Multi-terminal DC 시스템의 초전도 LC 공진 DC 차단기에 관한 연구

Abstract

A study on the Superconducting LC Resonant DC Circuit Breaker in Multi-terminal DC Systems Kim Jihye Advisor: Prof. Choi Hyo-Sang, Ph.D. Department of Electrical Engineering, Graduate School of Chosun University As the deployment of renewable energy increases due to international environmental policies, there is a growing challenge of distance between power generation sources and demand centers. To address this issue, the necessity of High Voltage Direct Current (HVDC) systems is emphasized. However, the HVDC system faces the problem of rapid increase in fault currents due to its low inductance. Additionally, existing research on protective modules is not easily applicable to HVDC systems, and there is a lack of relevant standards. This paper introduce the application of superconducting fault current limiting (SFCL) module and LC resonant DC circuit module to effectively reduce fault currents. Determining the optimal LC resonant frequency for the superconducting LC resonant DC circuit breaker is very important. Through an investigation of the operating mechanism of the superconducting LC resonant DC circuit breaker, this paper aims to propose a novel approach for its stable application. We analyzed experimental data on the operational characteristics of the superconducting LC resonant DC circuit breaker using FFT analysis, comparing the relationship between the LC resonant frequency of the circuit and its operating conditions. Furthermore, we examined the applicability of the superconducting LC resonant DC circuit breaker in a Voltage Source Converter-HVDC (VSC-HVDC) based Multi-Terminal DC (MTDC) system by performing FFT analysis on fault currents in the system. Through experiments and simulations, we presented a method for determining the resonant frequency of the superconducting LC resonant DC circuit breaker and verified its stable operation. We proposed a method to effectively interrupt fault currents by aligning the FFT of the system with the resonant frequency of the superconducting LC resonant DC circuit breaker. Analyzing the frequency domain enables the efficient design of the superconducting LC resonant DC circuit breaker. The main factor affecting FFT was variation in fault current, while circuit complexity didn't have a big impact. Through frequency domain analysis, efficient design became feasible. Moreover, the use of superconducting current modules enhanced the stability of resonant frequencies, necessitating their application to the LC resonant DC breaker module.