Model Predictive Control of Nested Neutral Point Clamped (NNPC) Converter

This paper proposes a model predictive control (MPC) strategy for a nested neutral point clamped (NNPC) converter. The NNPC converter is a four-level topology that is very attractive for medium-voltage (MV) applications. This is because it has less number of components in compare to other classic four-level topologies. In this paper, the MPC strategy is developed for the NNPC converter to control output currents and voltages of flying capacitors. First, a discrete-time model of the converters is presented and then all the control objectives are formulated in terms of the switching states. The cost function is defined to express the control goals. The best switching state will be chosen to minimize the cost function and the selected switching state will be applied to the converter during next sampling interval. Performance of the proposed control strategy is investigated in the MATLAB/SIMULINK environment for different operating conditions.