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Sigma-delta modulation (SDM) schemes are presented as a powerful approach to attain sinusoidal input current in a boost-type rectifier (BTR). The SDM schemes generate long on-state duration of the switch at the start of each half-cycle in a BTR. They also have harmonic-spreading effects. By virtue of these advantages, the dominant low-frequency harmonics in the input current are effectively reduced. The difference between the sinusoidal reference and the actual input current in a BTR is estimated after voltage zero crossings. The input current waveforms and their spectra are compared in cases of SDM and the conventional PWM. The performances of the SDM schemes have been validated on a 1.6 kW BTR using a computer simulation package. The total harmonic distortion in the input current confirms that the SDM schemes yield more sinusoidal input current waveform than the fixed switching frequency PWM scheme.
Date of Publication: 7 Nov. 2004