Predictive control based selective harmonic elimination with low switching frequency for multilevel converters

This paper presents a new low switching frequency modulation technique for multilevel power converters. The proposed algorithm is based on model predictive control and uses the sliding discrete Fourier transform to calculate harmonic components in real time in order to eliminate undesired harmonics at the output voltage. In this way the cost function of the predictive control can achieve similar results to traditional selective harmonic elimination, but without the need of off-line calculations and interpolation tables. The algorithm is executed online in real time, improving the dynamic performance of the system. In addition, no predefined switching patterns need to be designed, making the generalization for multilevel converters an easy task even for any modulation index or converters with different number of levels. Simulations results for three and seven level inverters are presented.