I have a 13-level output staircase multilevel inverter. I applied the selective harmonic elimination using the Newton Raphson method to eliminate the 3rd, 5th, 7th, 9th, and 11th low order harmonics. However, the 3rd order harmonic was not completely eliminated. It is 1.26% to the fundamental. Is it a normal thing with selective harmonic elimination or there is a problem in my scheme and the 3rd harmonic should be eliminated?
Thanks for your help.
I think it is normal. Because as the order of the harmonics decreases, the impedance offered to them decreases and so they are greater in magnitude compared to higher order harmonics.
If the angles were chosen properly, the 3rd, 5th, 7th, 9th, and 11th low order harmonics should be eliminated and their magnitudes should be very close to zero, including the 3rd harmonic.
https://ieeexplore.ieee.org/document/9244313
the harmonics will be removed completely if the angles are chosen correctly. an effective optimization algorithm is required to findout the correct switching angles. try genetic algorithm for instance. the third order harmonics are automatically removed in three-phase system's line to line voltages. so don't worry about them.
https://ieeexplore.ieee.org/document/8695981
Normally 3rd harmonics impact is more than others due to sum up in R, Y & B phases instead of cancellation. Use of transformer in circuit may reduce 3rd harmonics or cancel it.
3rd harmonics are more dangerous for electronics and distribution systems.
Algorithm detecting 3rd harmonics frequency and reduce it sufficiently may give harmonics free output.
3rd harmonic will be eliminate by selecting the angle properly....I totally agree with sheen
depending on number of switching angles which eliminate low order harmonics equal (N-1) where N is the number of switching angles .
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