电网电压骤降故障下双馈风力发电机建模与控制

Modeling and Control of DFIG Wind Energy Generation System Under Grid Voltage Dip

双馈感应发电机(DFIG)在变速恒频风力发电中得到广泛应用,对DFIG采用矢量控制可使风电系统实现最大风能追踪和有功、无功解耦调节,从而获得优良的发电运行性能。但在传统的矢量控制方式中,通常认为是无穷大理想电网,忽略了定子励磁电流变化的动态过程,从而得到简化的DFIG数学模型,并以此作为电流内环控制器的设计依据。这种控制器在电网正常的情况下可使系统获得优良的动静态特性,但当电网出现故障时,其控制性能将恶化。为了提高电网电压故障情况下DFIG不间断运行能力,文中以DFIG的精确数学模型为依据,针对传统的2种矢量控制方式的不足,提出了改进的控制方案,并对改进前后电网电压骤降情况下DFIG的动态过程进行了仿真对比,结果表明改进方案可以有效控制转子电流,保护转子励磁变频器,提高DFIG变速恒频风电系统在电网故障下的不间断运行能力,是并网DFIG风力发电机的一种有效、实用的控制策略。

Doubly-fed induction generator （DFIG） has been widely used in the variable-speed constant- frequency （VSCF） wind energy generation system. Vector control is already applied in the DFIG control, which makes the DFIG achieve good performance in the wind energy generation. But in two typical traditional vector control schemes, the stator magnetizing current is considered invariant to simplify the design of rotor current inner-loop controller. The two schemes are capable of performing very well when the grid is in normal condition. However, when the grid disturbance, such as grid voltage dip or swell fault, occurs, the control performance will be getting worse, the rotor over current will appear, which will reduce the ride-through capability of the DFIG wind energy generation system. Based on the precise model of the DFIG, the deficiency of the traditional vector control is also deeply investigated. The improved control schemes for the two typical traditional vector control used in DFIG are proposed, and the simulation study of the proposed and traditional control schemes is carried out. The validity of the proposed modified schemes to control the rotor current and improve the ride-through ability of the DFIG wind energy generation system is proved by the comparative study.