CAJ | 학술논문

在考虑直流控制系统影响的情况下，详细分析了 HVDC输电线路区内、区外的故障特征以及直流控制系统的动作特性和控制状态。引入并分析了基于开关函数的交直流系统二次谐波计算等值模型。通过分析故障期间换流器触发角和直流侧二次谐波量的变化特征，提出了一种新的以换流器触发角为保护动作量，利用二次谐波分量闭锁的直流线路后备保护方案，给出了保护整定的理论计算方法。与直流线路纵联差动保护相比，该保护不因直流电流波动影响而被闭锁，保护动作时间较快；与微分欠压保护相比，具有更高的抗过渡电阻能力。通过PSCAD/EMTDC大量仿真计算，验证了该保护能可靠区分直流线路区内、区外故障，与直流线路纵联差动保护和微分欠压保护相比具有明显的优越性。
재고필직류공제계통영향적정황하，상세분석료 HVDC수전선로구내、구외적고장특정이급직류공제계통적동작특성화공제상태。인입병분석료기우개관함수적교직류계통이차해파계산등치모형。통과분석고장기간환류기촉발각화직류측이차해파량적변화특정，제출료일충신적이환류기촉발각위보호동작량，이용이차해파분량폐쇄적직류선로후비보호방안，급출료보호정정적이론계산방법。여직류선로종련차동보호상비，해보호불인직류전류파동영향이피폐쇄，보호동작시간교쾌；여미분흠압보호상비，구유경고적항과도전조능력。통과PSCAD/EMTDC대량방진계산，험증료해보호능가고구분직류선로구내、구외고장，여직류선로종련차동보호화미분흠압보호상비구유명현적우월성。
The fault characteristic and the states of DC control system during HVDC transmission line inner and external fault are analyzed in detail considering the influence of DC control system. An equivalent circuit of second-order harmonic based on switch function theory is introduced and analyzed. A new backup protection scheme for DC transmission line is proposed by analyzing the feature of converter firing angle and second-order harmonic in failure period. Converter firing angle is used as operating value and second-order harmonic is used as blocking signal for the backup protection. In addition, theoretical calculation method for the protection settings is provided. Compared with DC line differential protection, the proposed protection can operate with higher speed and will be independent of DC current fluctuations. Compared with derivative under-voltage protection, it can operate well during much higher resistance ground fault. Comprehensive simulation using PSCAD/EMTDC validates that the presented protection scheme can identify inner and external fault reliably and rapidly, and has obvious advantages over DC line differential protection and derivative under-voltage protection. This work is supported by National Natural Science Foundation of China (No. 51377104).