环状柔直配网线路的单端量保护原理

Single-terminal Quantity Based Line Protection for Ring Flexible DC Distribution System

直流线路故障的快速、可靠识别是多端柔性直流配网发展面临的技术难点之一。针对模块化多电平换流器、电压源换流器共存的环状直流配网的中压直流线路,提出利用附加电感电压的故障识别方法。首先,提出基于模量网络的故障后线路附加电感电压初始值计算方法。其次,利用线路附加电感电压初始值在区内、外故障时的差异,实现故障的快速识别;并利用故障极和非故障极上电感电压初始值的差异进行选极。该方案采用单端电气量快速、准确识别故障,无需通信,可靠性高。最后,在PSCAD/ETMDC平台搭建仿真模型,验证所提计算方法的正确性和保护方案的可行性。

The fast and reliable identification of DC line faults is one of the key points in the development of multi-terminal flexible DC distribution networks.With regard to MVDC lines in a multi-terminal ring DC distribution network with MMCs and VSCs,a fault identification approach based on the voltage of the additional inductor was proposed. Firstly,the calculation method of the initial voltage across the additional inductor after pole-to-ground and pole-to-pole faults, was elaborated based on modulus networks of the system. Subsequently,the difference of the initial voltage across the additional inductor between internal and external faults was used to realize the fault identification.Furthermore,the fault pole was discriminated based on the difference between the initial voltage across the additional inductor of the faulted pole and that of the normal pole.The proposed protection scheme can identify the fault quickly and reliably without communication systems.Finally,the proposed calculation method and the feasibility of the protection scheme are verified via PSCAD/EMTDC based simulation.