Abstract

This article proposes a simplified optimal switching sequence model predictive control (OSS-MPC) without weighting coefficients for off-grid T-type single-phase three-level inverters. To eliminate the tedious weight-tuning process when constructing the switching sequences, the different effects of redundant small voltage vectors on the upper and lower dc bus capacitors' voltages are considered. Each switching sequence consists of two symmetrical redundant small voltage vectors with opposite effects on dc bus capacitors' voltages so that the neutral point voltage balance of the inverter can be achieved by tuning the dwelling time of two redundant small voltage vectors with opposite effects. According to the different effects of the switching sequence, the candidate switching sequences can be obtained by a simple division of the switching sequences through the reference. Then, the OSS can be selected by minimizing a cost function, which considerably simplifies the optimization process. Finally, the effectiveness of the proposed simplified OSS-MPC algorithm is experimentally evaluated based on a laboratory prototype in terms of code execution time, steady-state performance, transient performance, and neutral point potential balance performance.