An Improved Finite Control Set Model Predictive Control with Common-Mode Voltage Reduction for Four-Level Nested Neutral-Point Clamped Inverters

This article introduces an enhanced finite control set model predictive control (FCS-MPC) technique that allows for reducing common mode voltage (CMV) in a four-level inverter. At the same time, this approach lessens the workload on the computer, lowers harmonic currents, and maintains balanced flying capacitors (FC) voltage levels. Initially, after examining all potential voltage vectors in a four-level NNPC system, 20 voltage vectors with high CMV are eliminated, while the remaining vectors are chosen as potential voltage vectors for the suggested scheme. Next, in different sectors of the space vector graph, different PWM modes are adopted according to the difference of selected vectors. The combination of five-segment and seven-segment wave is adopted, which not only reduces the CMV, but also improves the current quality. Finally, the FC voltage is balanced by the selection of redundant switching states. The effectiveness of the proposed FCS-MPC method is confirmed through simulations.