PWM control and input characteristics of three-phase multi-level AC/DC converter

The authors discuss the current control and pulse width modulation (PWM) pattern generation of a multilevel power converter which is capable of producing three levels of phase voltage. In the proposed current control, fast response is realized by introducing a converter model in the control algorithm and the effect of parameter difference between the model and an actual system is compensated for through proportional-plus-integral control of current difference. In PWM pattern generation, the balance of two capacitor voltages is taken into account. For the same sampling period, the current distortion factor of the proposed system can be approximately reduced to 60% of that of a conventional two-level power converter. The prototype was made using a digital signal processor, and simulation and experimental results were compared