A Digital Predictive Current Control With Improved Sampled Inductor Current for Cascaded Inverters

This paper proposes a current-control technique with a predictive control method for multilevel inverters. The proposed current-control method adopts a variable sampling point scheme for inductor current sensing. It is able to avoid the switching noise caused by the turn-on or turn-off of power devices. The measured value of the inductor current is used to estimate the inverter output voltage at the next switching period with a simple linear extrapolation to force the output current to follow the current reference. Compared to the conventional predictive current controllers, the proposed control features are as follows: 1) only the inductor current measurement is required, and it is able to achieve a cost-effective and less-complex circuit (the output voltage and current measurements are required for a conventional controller) and 2) the proposed variable sampling technique is designed to avoid the switching noise, thus a robust current-control system can be achieved. Finally, a seven-level cascaded inverter with three dc-ac converter modules was constructed and tested. Analysis, simulations, and experimental results are presented to demonstrate the superiority of the proposed system.