Analysis of Common-mode Voltage during Switching of Individual IGBTs in Three-phase Inverter

The impedance-balancing method is a way of reducing common-mode voltage. However, when it is applied to a three-phase inverter circuit, the inductances of the two conductor lines supplying the power affect the common-mode voltage. Here, we investigated the effect of the inductance of the conductor lines supplying power on the common-mode voltage in the impedance balancing method by using a circuit simulation. The results show that when the balance of the inductances of the two conductor lines changes, the value of the balancing element that reduces the common-mode voltage also changes. An analysis of the common-mode voltage during individual switching of the insulated-gate bipolar transistors constituting the three-phase inverter shows that it is reduced under all switching conditions.