直流系统换相失败仿真研究

Study on Commutation Failure of DC System Based on PSCAD/EMTDC

在直流输电系统中,逆变侧交流系统的各种不对称故障会对逆变站中各换相阀的正常运行带来不同程度的影响,将导致各换相阀呈现不同的换相失败几率。由换相电压时间面积得出换相电压的幅值和过零点前移角是决定换相成功与否的两个重要因素。利用EMTDC/PSCAD仿真得到在各种故障情况下各阀的换相失败几率,结果显示:各换相失败几率与换相电压的幅值和相位直接相关,换相电压幅值跌落越大,角度超前越大,其换相失败几率则越大。

In DC transmission system , the various kinds of unsymmetrical faults in AC system behind invert side will bring diflerent inference to each converter valves in inverter station , which can result in diflerent probabilities of commutation failure in each converter valves . Infer from the area of commutating voltages time that the amplitude and phase advanced quantity of the commutating voltages is two determinate factors which decide commutating success or not . The oflsets in the amplitude and phase of the commutating voltages before and after faults is calculated by using the symmetrical component method , and deduce the probabilities of commutation failure in each converter valves base on the oflsets .The EMTDC / PSCAD simulation is used to obtain the commutation failure probability of each valve under various fault conditions.The results show that the larger the amplitude of the commutation voltage falls, the bigger the angle is, and the greater the chance of commutation failure.