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Three-phase multipulse ac-dc converters (MPC) are developed for improving power quality to reduce harmonics in ac mains and ripples in dc output. This paper deals with the multipulse ac-dc converter configurations, state of art, their performance, power quality aspects, components selection considerations, latest trends, future developments, and potential applications. It is targeted to provide broad perspective on multipulse converter technology to the researchers, engineers, and designers dealing with them. A classified fist of more than 250 research publications on the subject is also given for quick reference. Index Terms--AC-DC converters, harmonics reduction, multi-pulse, power quality, rectifiers.

This paper proposes a new control algorithm resuiting in significant advantages toward smooth control of an active filter (AF). The majority of existing feedforward control methods of the AF system result in switching notches (sharp-rising ripples) in the supply current during transitions of stepped waveshaped nonlinear load current. This is due to switching signals for the AF devices, which are obtained by comparison of the sensed and reference currents of the AF. The proposed control algorithm is based on feedback control, wherein, switching signals for the AF devices are obtained by comparing sensed and reference supply currents. This not only eliminates switching notches in the supply currents but also reduces the supply current total demand distortion below the 5% mark recommended by the IEEE-519 standard. A TMS320C31 digital signal processor is used for real-time implementation of the proposed algorithm. To establish its viability and flexibility, the proposed algorithm is also experimented with a laboratory prototype of the AF system made of a reduced number of switches. Index Terms--Active filter (AF), direct current control, harmonics, indirect current control, power quality.

Three-phase ac-dc converters have been developed to a matured level with improved power quality in terms of power-factor correction, reduced total harmonic distortion at input ac mains, and regulated dc output in buck, boost, buck--boost, multilevel, and multipulse modes with unidirectional and bidirectional power flow. This paper presents an exhaustive review of three-phase improved power quality ac-dc converters (IPQCs) configurations, control strategies, selection of components, comparative factors, recent trends, their suitability, and selection for specific applications. It is aimed at presenting a state of the art on the IPQC technology to researchers, designers, and application engineers dealing with three-phase ac-dc converters. A classified list of around 450 research articles on IPQCs is also appended for a quick reference. Index Terms--Harmonic reduction, improved power quality, power-factor correction, switch-mode rectifiers, three-phase ac--dc converters.

Solid-state switch-mode rectification converters have reached a matured level for improving power quality in terms of power-factor correction (PFC), reduced total harmonic distortion at input ac mains and precisely regulated dc output in buck, boost, buck--boost and multilevel modes with unidirectional and bidirectional power flow. This paper deals with a comprehensive review of improved power quality converters (IPQCs) configurations, control approaches, design features, selection of components, other related considerations, and their suitability and selection for specific applications. It is targeted to provide a wide spectrum on the status of IPQC technology to researchers, designers and application engineers working on switched-mode ac-dc converters. A classified list of more than 450 research publications on the state of art of IPQC is also given for a quick reference. Index Terms--AC-DC converters, harmonic reduction, improved power quality, power-factor correction, switch-mode rectifiers (SMRs).