基于信息指纹的柔性直流线路差动保护

Differential Protection of Flexible DC Line Based on Information Fingerprint

柔性直流电网以其灵活可控特性受到广泛关注,保护是其安全可靠运行的关键。柔性直流电网要求线路保护数毫秒内有选择地隔离故障,现有保护性能有待进一步提升。差动电流波形富含丰富的故障信息,区内、外故障的差流时频特性存在较大差异。基于此特征,提出差动电流指纹的概念,并利用指纹匹配技术实现了保护判别和故障测距。该方案充分利用了差动电流时–频域特征,相对于基于单一故障特征的保护方案更具优势,可耐受线路分布电容电流的影响。大量仿真结果表明,该保护方案能在6ms内准确识别区内外故障同时可以实现故障测距的功能,测距误差在3%以内。在300Ω过渡电阻接地故障下仍能准确动作,具有30dB的抗噪声能力和20μs的耐同步误差能力。

Flexible DC grid has received wide attention due to its flexible and controllable characteristics, and protection is the key to its safe and reliable operation. It requires line protection to isolate faults within a few milliseconds selectively, and the existing protection performance needs to be further improved. The differential current waveform has abundant fault information, and the time-frequency characteristics of the differential current of internal and external faults are quite different. Based on this feature, the differential current fingerprint concept was proposed, and the fingerprint matching technology was used to realize protection discrimination and fault location. This scheme made full use of the differential current’s time-frequency domain characteristics, which can be more advantageous than the protection scheme based on single fault characteristics and can withstand the influence of the line distributed capacitive current. Many simulation results show that the protection scheme can accurately identify the internal and external faults within 6ms and realize the fault location function simultaneously. The ranging error is within 3%. It can still act accurately under the ground fault of 300Ω fault resistance, with 30d B anti-noise ability and 20μs anti-synchronization error ability.