基于差补调制方式的级联H桥逆变器单元故障控制方法

为了增加级联H桥型逆变器单元故障后的输出能力,采用逆变器中性点偏移的工作方式,使逆变器非故障部分继续工作,输出最大幅值的对称线电压,但同时中性点的偏移也造成了电压谐波的增加。该文以6单元串联H桥系统为例进行分析,提出中性点偏移前后采用差补调制方式来控制逆变器,可以减少电压的谐波含量,且参数易于调整。与目前所采用的其它控制方法相比,该方法不仅提升输出合成电压的幅值,而且有效控制了电压的谐波含量,从而减少故障对系统的影响,提高级联H桥逆变器系统的可靠性。系统故障前后的仿真和实验结果表明所提出的控制方法是正确和有效的。

Control Method for Cascaded H-Bridge Inverter With Faulty Cells Based on Differential PWM

To increase the output value of the cascaded H-bridge inverter after cell failure,neutral shift principle is often used.The phase angle of each inverter phase voltage can be adjusted to generate a set of balanced line voltage for the motor,but the harmonic is increased with the shifted neutral point.To decrease the harmonic,differential pulse width modulation(PWM)strategies used to control the cascaded H-bridge three phase inverter before and after cell faults are presented,the output voltage value is increased than that in traditional way,and the voltage keeps clean after cell fault by this strategy.The reliability of the system is then enhanced.The simulated results agree with the theoretical analysis.