Optimal harmonic reduction in AC/AC chopper converters

An optimal control strategy for selecting firing and commutation angles in pulsewidth-modulated (PWM) AC-AC chopper-type, single-phase converters is proposed. The method minimizes output-voltage harmonic distortion through numerical techniques, and can also simultaneously eliminate certain chosen harmonics. Best results are obtained when no harmonics are completely eliminated, but instead are allowed to have small residual values. The method yields lower weighted harmonic distortion than the harmonic elimination techniques. Freeing the solution from the usual constraint of quarter-wave symmetry results in even lower harmonic distortion