Title :
Bandwidth considerations for multilevel converters
Author :
Walker, Geoff ; Ledwich, Gerard
Author_Institution :
Dept. of Comput. Sci. & Electr. Eng., Queensland Univ., St. Lucia, Qld., Australia
fDate :
1/1/1999 12:00:00 AM
Abstract :
Multilevel converters can achieve an overall effective switch frequency multiplication and consequent ripple reduction through the cancellation of the lowest order switch frequency terms. This paper investigates the harmonic content and the frequency response of these multimodulator converters. It is shown that the transfer function of uniformly sampled modulators is a bessel function associated with the inherent sampling process. Naturally sampled modulators have a flat transfer function, but multiple switchings per switch cycle will occur unless the input is slew-rate limited. Lower sideband harmonics of the effective carrier frequency and, in uniform converters, harmonics of the input signal also limit the useful bandwidth. Observations about the effect of the number of converters, their type (naturally or uniformly sampled), and the ratio of modulating frequency and switch frequency are made
Keywords :
PWM power convertors; frequency response; harmonic distortion; power conversion harmonics; switching circuits; transfer functions; bandwidth considerations; bessel function; carrier frequency; frequency response; harmonic content; input signal harmonics; lowest order switch frequency; modulating frequency; multilevel power converters; ripple reduction; sampling process; sideband harmonics; slew-rate limited input; switch frequency; switch frequency multiplication; transfer function; Bandwidth; Capacitors; Frequency conversion; Pulse width modulation; Pulse width modulation converters; Pulse width modulation inverters; Switches; Switching converters; Switching frequency; Transfer functions;
Journal_Title :
Power Electronics, IEEE Transactions on