不对称故障下双馈式风电机组转子励磁控制的极限分析

Limit analysis of RSC control for DFIG-based wind turbines with asymmetrical faults

对于双馈式风电机组而言,当采用转子励磁这一类控制方法进行低压穿越(low voltage ride-through,LVRT)时,根据具体控制方法的不同,其LVRT能力不同。但是由于转子电压幅值的限制,使得转子励磁控制方法存在一个极限。为了分析不对称电压跌落故障下转子励磁控制方法的极限,该文以最小化转子电流为目标,基于最优控制理论设计了一种转子励磁最优控制方法。基于该方法可以得到不对称故障下转子励磁控制方法的极限,进而衡量转子励磁控制下系统对于不对称故障的穿越能力。最后以典型的1.5MW双馈式风电机组为例,分析了3种不对称故障下转子励磁控制的故障穿越能力。由分析结果可得:在相同的电压跌落深度下,相间短路故障最难穿越,两相接地故障次之,单相接地故障最容易穿越。

For doubly-fed induction generator （DFIG）-based wind turbines, the low voltage ride-through （LVRT） capabilities of different rotor side converter （RSC） control methods vary depending on the specific RSC control methods. However, there is a limit for RSC control methods due to the limited voltage output of the RSC. The control limit for asymmetrical voltage dips is analyzed using an optimal RSC control method based on optimal control theory to minimize the rotor current. The RSC control limit for asymmetrical faults is obtained and the LVRT capabilities of RSC control methods are evaluated. Finally, a typical 1.5 MW DFIG based wind turbine is used to analyze the limits of RSC control for three types of asymmetrical voltage dips. The results show that for the same voltage dip depth, phase-to-phase faults are the most difficult to ride through, while single-phase to ground faults are the easiest.