一种考虑短路电流指标的动态等值方法

摘要

When DFIG(Doubly-Fed Induction Generator) works steadily,its rotor current frequency is low,so the influence of dead-time is notable. The influence of dead-time on converter output voltage,the phenomenon of zero-current clamping and the asymmetry caused by dead-time are analyzed,based on which, the existing dead-time compensation strategy is improved. The space of current vector is divided into six regions and only one phase voltage is compensated. The zero-current clamping phenomenon is compensated as well. The comparative value of PWM generator is modified twice in a switching period to avoid the asymmetry caused by dead-time. Tests are carried out on the DFIG experiment platform and the results demonstrate the proposed dead-time compensation method reduces the harmonic components of rotor current effectively and eliminates the zero-current clamping phenomenon.%短路电流反映了交流系统的强度,为了简化原系统并保留原系统的短路电流特性,提出了一种考虑短路电流指标的动态等值方法.首先将外部系统根据机组的同调性划分为若干外部等值子系统,然后将短路电流作为等值过程中的一个重要量化指标,利用改进的Ward等值法对每个等值子系统化简,最后根据外部系统中的发电机与边界母线的电气距离来确定等值发电机的参数.算例表明,所提出的动态等值方法不仅能使等值前后研究系统的对称和不对称短路电流完全一致,还非常好地保留了原系统动态特性.