Computationally efficient predictive control of three-level NPC converters with DC-link voltage balancing: A priori state selection approach

We propose a novel framework for multistep predictive current control for induction machines. The main contribution of this work is the achievement of the control goal over a long prediction horizon while reaching DC-link balancing for the accompanying three-level neutral point clamped (3L-NPC) inverters at the same time. The multistep prediction horizon is implemented using a sphere decoding algorithm. The DC-link balancing is guaranteed by modifying the sphere decoder such that only neutral point affecting states are selected if the DC-link voltage is imbalanced. Since those states are not uniquely defined for the 3L-NPC inverter, the state that minimizes the DC-link voltage is then selected within a preprocessing stage. The framework is verified by means of simulations.