A simple capacitor votage balancing scheme for the cascaded five-level inverter fed AC machine drive

This paper proposes a simple scheme for balancing the series capacitor voltages at the three-phase cascaded five-level inverter fed an induction motor by using the logic circuits. Using switching patterns based on the multi-carrier technique, two series-capacitor voltages can be only balanced during one cycle. However, they have a ripple voltage, which may cause the induction motor drive to be unstable. The proposed scheme for balancing capacitor voltages can be implemented by simple logic circuits. It can be verified that the series capacitor voltages are maintained constant at wide frequency range through experimental results with 32-bit DSP and Cyclone-III FPGA.