中文摘要：

为降低机电类负载共模电压,对多电平变流器零序电压优化控制算法进行了研究。首先,采用了一种将经典αβ坐标系中的α和β坐标值分别拉伸为原值的3和√3倍的新型mn坐标系,推导了多电平空间矢量脉宽调制（SVPWM）在这种新型坐标系中的实现方法;其次,根据引入的零序电压约束条件,推导了多电平电路输出状态。实验结果表明,在mn坐标系中,所有基本矢量的坐标为整数,零序电压优化控制算法能确保零序电压的值在-E/3、0和E/3之间来回切换（E为单级电平）,且该算法与多电平的电平数无关。

英文摘要：

In order to reduce the impact of common-mode voltages for mechanical-electronic load, we presented a ze- ro-order voltage optimized control algorithm for multilevel converter. Firstly, we proposed a new stretched αβ coordinate system, name mn coordinate system, in which α and β coordinate values were stretched to 3 and √3 times the original value, respectively. Then we deduced the implementation method of multilevel space vector pulse width modula- tion（SVPWM） in the mn coordinate system. On the basis of the constraint of zero-order voltage, we calculated the output state of multilevel circuit. The experimental results show that the converter voltage vectors have only integer entries in the new coordinate system; the zero-order voltage values for E/3, O, or E/3 （E is single-stage level ） by using the proposed op- timized control algorithm; and the computation load of the presented optimized control algorithm is irrelevant to the number of cell.