分析了直流换相失败的机理，指出交流系统故障导致的换流母线电压跌落是换相失败的主要诱因，而负荷模型的不同又将导致故障后系统电压跌落幅度的不同，从而影响换相失败的发生。分析了现有的两种常用负荷模型ZIP模型和电动机模型对电压跌落的影响机理，指出电动机模型可为系统提供机械惯量，在故障瞬间相比于ZIP模型更有利于抑制系统电压跌落，降低换相失败发生概率；但在故障持续期间，电动机负荷会吸收更多无功，危及系统稳定性。基于南方电网方式数据，计算了不同负荷模型下可能导致多回直流同时换相失败的故障区域以及系统的极限切除时间，并对以上论述进行了仿真验证。%This paper analyzes the mechanism of commutation failure and points out that the voltage sag of commutation bus in inverter station caused by AC system fault is a main factor. Different load models will lead to different amplitude of voltage sag, which will influence the occurrence of commutation failure. This paper analyses the impact on system voltage sag of two common used load models —— ZIP load and motor load, and points out that compared with ZIP model, the motor load model is more beneficial for preventing voltage sag at the instant of fault as the motor load can provide mechanical inertia to the system. While in the duration of fault, the motor load will absorb large amount of reactive power, which will do harm to the system stability. Based on the data of China Southern Power Grid (CSG), this paper calculates the fault regions that can cause commutation failure and the system critical clearance time under different load models to verify the view point proposed. This work is supported by National High-tech R & D Program of China (863 Program) (No. 2011AA05A102) and Fundamental Research Funds for the Central Universities (No. 2013ZM0028).
展开▼
