SHE-PWM and optimized DC voltage levels for cascaded multilevel inverters control

This paper presents a new formulation of selective harmonic elimination pulse width modulation (SHE-PWM) technique suitable for cascaded multilevel inverters with optimized DC voltage levels. The paper reformulates the problem in a way which the levels of the DC sources are made variables within certain constraints. Therefore, the degrees of freedom for specifying the cost function are increased when compared to existing family of SHE-based multilevel control for the same physical structure. Moreover, with the proposed approach, the solution of the switching angles can be sought for the entire range of the modulation index without affecting the number of harmonics being eliminated or the number of the output voltage waveform. The theoretical and the simulation findings are validated through experiments and the results were in good agreement.