Linear-System-Based Selective Harmonic Elimination Solution for Multilevel Inverters

This paper proposes a general analytical method for the harmonic elimination in three-phase cascaded H-bridge inverters with $l=2\cdot 2^{n}+1$ levels. The solution, consisting of 2n switching angles, removes the first n low order harmonics and their multiples from the output, keeping the amplitude of the fundamental harmonic fixed by the modulation index, and is obtained for a wide range of modulation indices. If a switching angle is greater than $\pi/2$, it is modified such as to obtain a valid solution. The proposed method has been successfully verified with simulations issued with 5, 9, and 17 level inverters and with a 9-level experimental test rig.