Model predictive control based selective harmonic mitigation technique for multilevel cascaded H-bridge converters

The selective harmonic elimination (SHE) strategy is specially well suited for high-power applications where the power losses must be kept below strict limits. The SHE technique is based on offline calculations and the generation of a pre-programmed voltage waveforms eliminating some low order harmonics. An evolution of SHE is the selective harmonic mitigation (SHM) technique which is based on pre-programmed waveforms non eliminating the low order harmonics but reducing the distortion below the limits imposed by a grid code. However, the main drawback of these pre-programmed SHE and SHM techniques is a low dynamic performance. In a recent paper, an online SHE technique based on the model predictive control (MPC) has been presented improving the dynamic performance of the conventional SHE method. In this paper, the online version of the SHM technique is introduced. It is based also in the MPC strategy and has been tested in a cascaded multilevel converter obtaining a high performance with very low switching frequency.