新型直驱风电系统中3L-NPC变流器中点平衡控制的研究

RESEARCH ON NEUTRAL-POINT BALANCE CONTROL OF 3L-NPC VSC FOR NOVEL DIRECT-DRIVE WIND POWER SYSTEM

提出一种基于多相永磁同步发电机和二极管中点箝位三电平变流器构成的风电变换系统,并着重研究其中三电平变流器的中点平衡控制问题。通过比较现有各种不同平衡控制策略的谐波和损耗性能,提出新的解决方案。推荐的全功率变流器拓扑,通过三电平变流器的并联和串联组合及功率均衡控制,不仅可分摊发电机的功率,而且可自动抵消电容中点的低频脉动及直流漂移,谐波和损耗性能不受影响。最后,通过实验验证了新方案的有效性。

A novel wind power conversion system was proposed based on a multi-phase permanent synchronous generator （MPPMSG） and the hybrid three-level neutral-point-clamped converters, stressing on the neutral-point balance control problems. By comparisons of harmonics and power losses for the different balance control methods, a new better solution was suggested. The proposed full-size converter topology will not only apportion the generator power, but also eliminate the neutral-point low-frequency voltage fluctuation and DC voltage shifts by means of series- and parallel-connection of 3 L converters, as well as power balance control with harmonic and power loss properties unaffected. Finally, the experiment was made to verify the effectiveness of the new method.