Title :
Opportunities for harmonic cancellation with carrier based PWM for two-level and multi-level cascaded inverters
Author :
Holmes, D.G. ; McGrath, B.P.
Author_Institution :
Dept. of Electr. & Comput. Syst. Eng., Monash Univ., Clayton, Vic., Australia
Abstract :
PWM strategies have been the subject of many years of research effort, and the merits of the various alternatives investigated have been argued extensively. In general, it is now accepted that natural or asymmetrical regular sampled PWM with a third harmonic injected or a space vector centered reference waveform gives the best harmonic performance, with discontinuous modulation having some advantages for higher modulation ratios. This paper uses a general analytical solution for carrier based PWM to mathematically identify the harmonic cancellation that occurs in various PWM implementations and converter topologies. This solution provides a formal justification for the superiority of natural and asymmetrical regular sampling techniques in eliminating half of their sideband harmonics simply by virtue of their phase leg switching. Then the use of fundamental reference phase shifting between phase legs to create single and three phase I-I output voltages is reviewed, and the harmonic cancellation that occurs is identified. One significant result from this analysis is the realisation that an odd/triplen carrier/fundamental ratio has no intrinsic harmonic benefit, contrary to the generally accepted wisdom. Finally, opportunities for harmonic elimination in multi-level cascaded inverter systems by carrier phase shifting are investigated, and the optimum phase shift is identified
Keywords :
DC-AC power convertors; PWM invertors; harmonic distortion; harmonics suppression; power conversion harmonics; switching circuits; PWM implementations; carrier based PWM; carrier phase shifting; converter topologies; discontinuous modulation; harmonic cancellation; modulation ratios; multi-level cascaded inverters; odd/triplen carrier/fundamental ratio; sideband harmonics elimination; space vector centered reference waveform; third harmonic injection; two-level cascaded inverters; Harmonic analysis; Leg; Pulse width modulation; Pulse width modulation converters; Pulse width modulation inverters; Sampling methods; Space vector pulse width modulation; Switches; Topology; Voltage;
Conference_Titel :
Industry Applications Conference, 1999. Thirty-Fourth IAS Annual Meeting. Conference Record of the 1999 IEEE
Conference_Location :
Phoenix, AZ
Print_ISBN :
0-7803-5589-X
DOI :
10.1109/IAS.1999.801595