ZDC控制方式下的永磁直驱风电机组高速运行特性

Operation Characteristics of Direct-drive Wind Turbine in High-speed Operation Area under ZDC Control

在经典的d轴电流给定为零(ZDC,Zero d-axis Current)的矢量控制方式下,永磁同步发电机在高转速运行区域会出现异常运行工况。该异常运行工况产生的原因是,机侧变流器在有限的直流母线利用率下无法有效地平衡较高的发电机定子感应电动势。本文通过仿真对比了采用过调制与否对系统稳定性的影响。仿真结果表明,在高速运行区域必须允许变流器进行过调制以保障永磁发电机的可控性和稳定性,但同时也发现采用过调制将会导致转矩出现较明显的6倍频波动。

Under the conventional ZDC （Zero d-axis Current） control, the Permanent Magnetic Synchronous Generator （PMSG） mav become abnormal when runs in high-speed range. This is because the machine-side converter, which is constrained by its dc-link voltage, can not effectively balance the stator EMF of the PMSG. Through simulation study, this paper investigates the said abnormal operation condition by considering both linear and nonliriear modulation strategies. The results indicate that in order to guarantee the controllability and safe operation of the PMSG, the control system has to allow over-modulation strategy. As a compromise, the oscillation of the electro-magnetic torque at 6th order harmonics will appear in high-speed range.