One-cycle controlled three-phase PWM rectifiers with improved regulation under unbalanced and distorted input voltage conditions

This paper proposes a modified one-cycle-control (OCC) scheme for regulation of three-phase pulsewidth-modulated (PWM) rectifiers under unbalanced and distorted supply conditions. Mathematical analysis is presented to show the dominant harmonic voltage across the dc-link of PWM rectifier when controlled by the existing OCC scheme. Such ripple voltage may aggravate the harmonic distortion in input currents. To address these problems, the concept concerning with the reconstruction of reference signals in OCC core is introduced. With minor modifications made into the OCC control equation, the overall proposed control scheme can effectively minimize the harmonic components found in the input currents and smoothen output ripple imposed on the dc-link voltage without using large capacitance. Furthermore, previously identified advantages of OCC can all be preserved by the new control scheme. Finally, all the theoretical findings are supported by the experimental results obtained from a 1.2 kW three-phase PWM rectifier developed in the laboratory.