适用于逆变型分布式电源T接的配电网线路纵联保护方案

针对逆变型分布式电源(IIDG)T接于配电网导致双端电流纵联差动保护难以适用的问题，提出一种基于线路端点正序电流的新型纵联保护方案。建立以并网点正序电压主导的IIDG压控电流源模型。根据线路本端保护测量所得正序电气量分别求解对端正序电流计算值。在此基础上，将同一端点测量值与计算值的相量差幅值作为保护动作量，并利用发生区、内外故障时保护动作量的差异形成故障识别判据。考虑计算误差及互感器传变误差对保护整定值的影响构建完整的保护方案。该方案在保护动作量计算过程中无须实时获取IIDG运行状态，仅在现有双端纵联通道内对线路两端的电气量进行通信即可准确识别区内、外故障，通信压力小。仿真结果表明所提保护方案可靠有效，受IIDG出力影响小且具备一定抗过渡电阻能力。

Line pilot protection scheme for distribution network with inverter-interfaced distributed generation in T-connection mode

Aiming at the issue that the dual-terminal current differential protection is not applicable to distribution network with T-connected inverter-interfaced distributed generation(IIDG),a new pilot protection scheme based on the positive-sequence current of the line terminal is proposed. An IIDG voltage-controlled current-source model dominated by the positive-sequence voltage of the point of common coupling(PCC) is established. According to the positive-sequence electrical quantities measured by the protection at local terminal, the positive-sequence current at the opposite terminal is calculated. On this basis, the amplitude of the phasor difference between the measured and the calculated values at the same terminal is taken as the protection operation quantity, and the fault identification criterion is formed by using the difference of the protection operation quantities under internal and external faults. Considering the influence of calculation error and the transmission error of transformers on the protection threshold, a complete protection scheme is constructed, which does not need to obtain the real-time operation status of IIDGs during the protection decision-making process. By communicating electrical quantities at both terminals of the line in existing dual-terminal pilot channels, the internal and external faults can be accurately identified, and the communication pressure is small. The simulative results show that the proposed protection scheme is reliable and effective, which is less affected by the IIDG output and has certain tolerance against transition resistance.