CAJ | 학술논문

直流输电线路具有相对于交流线路更强的固有频率信号。结合电压源换流器型直流输电（VSC—HVDC）的系统结构，可得固有频率值与线路长度具有明确的函数关系。区外故障时，两侧固有频率主频与线路全长相关，频率差理论上为零；区内故障时，固有频率主频与故障点位置相关，非中点故障时频率差为一很大的值。据此，提出了通过Prony算法对电流进行频谱分析，计算两端的固有频率主频差，进而实现直流输电线路纵联频率保护的原理和保护主判据。针对中点处死区问题，提出了辅助判据。同时在PSCAD上搭建的VSC—HVDC系统上进行了仿真。仿真结果表明，该保护原理只利用两端电流信息，频率的传输无需严格同步，原理上不受过渡电阻的影响。
직류수전선로구유상대우교류선로경강적고유빈솔신호。결합전압원환류기형직류수전（VSC—HVDC）적계통결구，가득고유빈솔치여선로장도구유명학적함수관계。구외고장시，량측고유빈솔주빈여선로전장상관，빈솔차이론상위령；구내고장시，고유빈솔주빈여고장점위치상관，비중점고장시빈솔차위일흔대적치。거차，제출료통과Prony산법대전류진행빈보분석，계산량단적고유빈솔주빈차，진이실현직류수전선로종련빈솔보호적원리화보호주판거。침대중점처사구문제，제출료보조판거。동시재PSCAD상탑건적VSC—HVDC계통상진행료방진。방진결과표명，해보호원리지이용량단전류신식，빈솔적전수무수엄격동보，원리상불수과도전조적영향。
The natural frequency signal of DC lines is more obvious than that of AC lines. Combining the system structure, it is found that the natural frequency of VSC-HVDC is related with line length. Theoretically, the natural frequency differential is zero for external fault and it is a huge value for the internal fault. Accordingly, a new pilot protection principle and its primary criterion for HVDC transmission line are proposed based on current spectrum a- nalysis at both ends. For the dead zone at the midpoint of the line, a secondary criterion is proposed. At the same time, the system of VSC-HVDC is built in PSCAD and various faults are simulated. In the protection principle,only current information of both converters are used and synchronization is not needed for the transmission of natural fre- quency. The simulation results show that the protection principle can identify the faults reliably and rapidly in differ- ent conditions, and is not affected by the fault resistance.