基于边界特性的多端柔性直流配电系统单端量保护方案
Single-ended Protection Scheme Based on Boundary Characteristic for the Multi-terminal VSC-based DC Distribution System
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摘要: 多端柔性直流配电系统的发展尚面临几大技术难点亟待解决,在继电保护方面主要问题在于直流故障的可靠识别。传统交流配电系统、高压直流输电系统保护原理无法适用于多端柔性直流配电系统。因此,该文设计了一种新型的多端柔性直流配电系统直流线路保护方法。利用线路边界特性,通过小波变换提取区、内外故障的暂态特征差异,实现故障的快速、可靠识别;并利用直流电抗器压降判据实现保护的方向性。该方法基于单端电气量实现全线路保护,动作速度快,无需通信,能够满足直流配电系统对保护的速动性、可靠性和选择性要求。最后,大量的仿真算例验证了所设计方案的可行性。Abstract: Several technical difficulties are still confronting us when it comes to the multi-terminal flexible DC distribution system, among which is the DC fault identification. The protection principles for the AC system and conventional DC transmission system are not applicable to the multi-terminal flexible DC distribution system. Thus the paper designed a novel DC line protection scheme. Based on the boundary characteristic, it extracted the transient characteristic difference between the internal fault and external fault to realize the fault identification. And the directionality of the protection was achieved by the DC-reactor voltage-drop criteria. The proposed scheme could identify the internal fault and external fault quickly without communication, which could satisfy the speed, reliability and selectivity requirement of the DC distribution system. Corresponding simulation cases were carried out to verify the feasibility and superiority of the proposed scheme.
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