A predictive current control technique for three-level NPC Voltage Source Inverters

In this paper a predictive current control technique for three-level Neutral Point Clamped (NPC) Voltage Source Inverters (VSI) is presented. The method is based on the prediction of the future value of load current by using a discrete-time model of the system and can be applied to any multilevel inverter for high-voltage high-power applications. The inverter is considered as a non-linear system with its 19 switching states. The proposed controller predicts the load current for all voltage vectors generated by the inverter. The current error for each voltage vector is calculated and the vector that ensures the smallest value of current error is selected as the inverter voltage vector for the next sampling time. The method allows optimum reference current tracking for all operating conditions under low current harmonic distortion as a result of many voltage vectors that participate in the control process. Furthermore, the proposed control ensures fast dynamic response and decoupling effect between the load current components. Finally, neutral-point voltage balancing with low ripple is also obtained.