电网故障时双馈风力发电机励磁改进控制策略

Improved Control Strategy for a Doubly-fed Generation System Under Grid Fault

双馈风力发电机(DFIG)在风能捕获过程中,传统的定子磁链定向控制都假定电网上的电压恒定不变,定子磁链也恒定不变,没有考虑定子励磁电流的动态响应过程,这个误差在电网故障时会对系统产生极不稳定的作用。为此应考虑该响应过程,对控制檳型进行修正,提出一种应对电网电压跌落时的励磁改迸策略,即在建立转子侧变换器控制模型时,把反映励磁电流过渡过程的定子电压变化量考虑进来。通过推导定子磁场定向下的转子电压方程,搭建定子磁链定向矢量控制模型,经过仿真结果比较,说明在加入励磁补偿电压项后,风电系统在应对电网电压故障时的电流控制性能得到明显改善,有效提升了系统的低电压穿越能力。

Dynamic response of the stator excitation current is neglected in traditional stator-flux oriented control scheme, for assuming the constant of network voltage and stator flux linkage, in the process of wind energy capture of Doubly Fed Induction Generator. This inaccuracy would result in terrible performance during grid fault. Therefore, a improved control strategy is raised. That is, take the stator voltage changes into account, which reflect the field current transition process, in establishing the rotor side converter control mode. Through deducing the rotor voltage equation and building the vector control model, Simulation results indicate that the current control performance and the ability of low voltage ride-through have been improved obviously when wind power system in dealing with grid voltage faul.