级联多电平逆变器空间矢量调制算法零序电压分布及优化算法

Zero Order Voltage Distribution and Optimized Algorithm of SVPWM Method for Multi-Level Cascaded Inverter

逆变器输出电压中的零序分量在电机中形成共模电压,它通过寄生回路产生的共模电流会损坏电机轴承、造成绕组绝缘的破坏以及产生电磁干扰。本文在将常规dq0坐标旋转45°后的新坐标平面中,研究了空间矢量对应的零序分量的分布规律。结果表明,只要适当地减小调制系数,逆变器输出电压矢量的零序分量幅值就可以小于一定的限制值。基于该规律,提出了一种将级联型多电平逆变器输出零序电压幅值的相对值限制为1/3的空间矢量调制算法。仿真和实验结果表明,该调制方法对零序电压的抑制是有效的,并且计算简单、易于实现。

The zero order voltage output from inverter will form common mode voltage, which drives the common mode current through the parasitic circuit loop in motors. The common mode current can damage the motor bearings and the winding insulations, and can generate electromagnetic interference （EMI）. In the new coordinator platform which is rotated from traditional dq0 coordinator by 45 degrees, this paper drew out the distribution of the space vectors＇ zero order voltage component. The result shows that, the zero order voltage component can be restricted to a suitable value by reducing the modulation coefficient. Based on the distributions, an algorithm is deduced, which can limit the inverter＇s output zero order voltage to one third of the DC supply voltage of one cascaded unit of the multi-level cascaded inverter. The simulation and the experimental results prove that the algorithm is worked well to depress the zero order voltage of multilevel inverter, and it shows that the algorithm is simple to be completed.