永磁直驱风电系统弱磁控制研究

Reaserch on field weakening control of PMSG for direct-drive WECS

永磁直驱风力发电系统中,机侧变流器输出电压受直流母线电压限制。在对最大风能捕获曲线进行跟踪过程中,当机侧变流器参考输出电压超过直流母线电压限幅值后,需要进行弱磁控制。弱磁控制可以采用开环弱磁和闭环弱磁,其中开环弱磁控制通过判断当前转速与转折速度的关系进行投切,闭环控制利用参考电压与直流母线电压反馈值进行控制。文章对两种方式进行了原理分析和对比,对比分析结果表明:相对于开环弱磁控制,闭环弱磁控制对电机参数依赖性小,数字控制实现容易,稳态条件精度更高,应用更具有普遍性。在Matlab环境和实验平台上分别对两种方案进行了仿真和实验验证,结果很好地吻合了理论分析的结论。

In direct-drive wind generation system,output voltage of generator side converter is limited by DC bus voltage. In the tracking of MPPT curve,field weakening（ FW） control is needed when output reference voltage is larger than the limitation decided by DC bus voltage. FW control can be realized either by open-loop FW or closedloop FW. The open-loop FW is switched by the relationship between generator speed and the transition speed,while the closed-loop FW contains a closed loop controller in which output reference voltage and DC bus voltage are feedback variables. Two approaches of FW control are analyzed and compared. The comparison result indicates that closed-loop FW is independent of generator parametres,easy to implement in DSP and has more accurate control performance in steady state,thus the closed-loop FW control has better prospect in the industrial application. Simulation and expermental verification are carried out in the Matlab and laboratory setup. The results are coincident with the theoretical analysis.