基于快速开关的串联谐振型故障限流器的仿真

Simulation of an Series Resonant Type FCL Based on Fast Transfer Switch

为限制电力系统短路电流,提出了一种开关作为电容器短路元件的串联谐振型故障电流限制器拓扑。以220kV单相线路为例,利用EMTP软件对这种限流器拓扑的动态工作特性进行仿真分析。提出了2种有效措施,以抑制电流转移过程由杂散振荡导致的电容支路高频过电流和过电压现象,仿真结果表明,在电容支路中串入电抗器比在快速开关支路中串入效果更佳。快速开关的合闸时间对限流效果至为关键,对此做了具体分析。结果指出,快速开关的合闸时间须足够短(10ms以内),才能有效实现故障限流。该故障限流器拓扑结构简单、响应速度快,其中的快速开关只进行快速合闸操作,不需要具备电流开断能力,易设计,造价低廉。

To give an effective solution to fault current suppressing, an series resonant type fault current limiter （FCL） topology based on fast transfer switch is presented, in which a fast transfer switch is used as the short-circuit element for the capacitor. Simulations through EMTP are carried out to verify the dynamic performance of the proposed current-limiting topology, regarding a single-phase equivalent circuit of 220 kV system. Two effective measures are proposed to suppress the over-voltage and over-current in the capacitor branch caused by stray oscillations occurring in the short current transfer process, and the simulation results demonstrate that an series inductor in capacitor branch is preferable to that in the fast transfer switch branch, because in the latter case the short-circuit current is harder to transfer and thus the short-circuit current can not be suppressed effectively. Also, the series inductor must be optimally selected to achieve a balance between the over-current and the over-voltage across the capacitor. The impact on current limiting effect of the closing time of fast transfer switch is analyzed in detail, which indicates that a closing time of less than 10 seconds is compulsory for practicable fault current limiting applications. The proposed FCL topology is of simple structure and fast response, and further, the transfer switch is simply to complete a fast closing operation without additional requirement of its current breaking capacity, and therefore convenient design and low cost can be achieved.