中点箝位型逆变器控制方法的综合研究

本文深入研究了空间矢量调制模式下的三电平逆变器中点电压波动的机理，建立了平均中点电流数学模型，为中点电压平衡控制提供了理论依据，并提出基于电压中矢量合成的中点电压平衡控制方法，该方法对于系统动态过程中出现的电压不平衡，可以通过调整冗余小矢量的相对作用时间进行补偿，由于电压中矢量的部分作用时间被均分给相应的小矢量，因此其补偿效果明显。实验结果证实了本文研究方法的正确性。

Variation Mechanism and its Balancing Control Method of Neutralpoint Potential for Three-level NPC Inverter

This paper investigates the variation mechanism of neutral point(NP)potential in detail,establishes the average NP current model,therefore,thus the theory base is built for the balancing control of neutral point potential,and several important conclusions about variation of NP potential are given.Then,a novel balancing control of NP potential,based on space vector modulation pattern where a middle vectors are synthesized by redundant small vectors,is proposed. Theoretical analysis and experimental results indicate that the proposed method for NP balancing control vector synthe- sizing concept based can make the average NP current zero,and do not influence the NP potential within every sample period.Moreover,the effectiveness of compensation for departure of the NP potential during the system dynamic processes is significant because of the distribution of active time of middle voltage vectors to that of corresponding small voltage vectors.Finally,experimental results are given to verify the validity of the proposed method.