柔性直流配电系统线路保护与定值整定

目前，随着电力电子技术的逐渐成熟，柔性直流系统受到广泛关注。作为柔性直流配电系统发展的关键技术，保护所面临的主要挑战是如何利用受限和持续过程极短的故障电流可靠识别和快速隔离故障。文中针对基于具有直流故障隔离能力换流器的柔性直流配电系统，分析了直流线路发生单极接地故障、双极短路故障以及断线故障时的故障特性，提出直流线路的保护方案。同时依据继电保护对四性的要求以及各保护之间的配合关系，确定保护动作的边界条件，反推出保护定值的合理范围，最终形成直流保护定值整定原则和整定计算方法，为实际工程中的保护设计和应用提供了参考。最后，在PSCAD仿真平台搭建仿真模型，仿真结果验证了保护方案的可行性以及保护定值整定的合理性。

Line Protection and Setting Calculation for Flexible DC Distribution System

At present, with the gradual maturity of power electronics technology, flexible DC systems have attracted wide attention. As one of the key technologies in the development of flexible DC distribution system, the protection technology faces the main challenge of how to reliably identify and quickly isolate faults by using fault current with limited and very short duration. For the flexible DC distribution system based on converters with DC fault isolation capability, this paper analyzes the fault characteristics of single pole-to-ground fault, bipolar short-circuit fault and broken line fault of DC line, and proposes the protection scheme of DC line. Meanwhile, according to the requirements of the relay protection for the four characteristics and the coordination relationship between various protections, the boundary conditions of protection action are determined, and the reasonable range of protection setting value is deduced. The setting principle and calculation method of DC protection are formed, which provides a reference for the protection design and application in the practical engineering. Finally, a simulation model is built in the PSCAD simulation platform. The simulation results verify the feasibility of the protection scheme and the rationality of the setting value of the protection.