Optimal Vector Sequence Model Predictive Control to Suppress Common-Mode Voltage for Five-Level Converters

In this paper, an optimal vector sequence model predictive control (OVS-MPC) is proposed for the five-level active neutral-point-clamped (5L-ANPC) converter to suppress the common-mode voltage (CMV). OVS-MPC not only reduces the amplitude of CMV but also decreases its <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> value. The step CMV value per sampling period has only two types: greater than zero or less than zero, which greatly reduces the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv/dt</i> value. The OVS-MPC achieves a fixed switching frequency, with one phase state remaining unchanged and the other two phases changing only once per sampling period. In addition, the switching sequence is redesigned in the OVS-MPC to reduce the switching losses between adjacent sampling periods. The cost function does not contain any weighting factors, and it can determine the sub-sectors, select the candidate vectors, and calculate the duty ratios. Finally, the simulation and experiment are conducted on a 5L-ANPC platform. Compared with existing MPC strategies, the OVS-MPC can significantly reduce the RMS value of CMV, and the CMV amplitude will not increase under all modulation indices.