Sanjay Gairola

Multipulse AC–DC Converters for Improving Power Quality: A Review

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 list of more than 250 research publications on the subject is also given for quick reference.

Pulse multiplication in AC-DC converters for harmonic mitigation in vector-controlled induction motor drives

In this paper, an autotransformer with reduced kilovoltampere rating for 24-pulse ac-dc converter fed vector controlled induction motor drives (VCIMDs) is presented for harmonic current reduction. The 24-pulse operation is achieved using dc ripple reinjection technique in 12-pulse ac-dc converters. The proposed novel harmonic mitigator is found capable of suppressing up to 21st harmonic in the supply current. The procedure for the design of autotransformer for proposed ac-dc converter is presented to show the flexibility in the design for making it a cost-effective replacement suitable for retrofit applications, where presently a 6-pulse diode bridge rectifier is used. The effect of load variation on VCIMD is also studied to demonstrate the effectiveness of the proposed ac-dc converter. A set of power quality indices on input ac mains and on dc bus for a VCIMD fed from other 24-pulse ac-dc converters are also given to compare their performance. The laboratory prototypes of proposed autotransformers based 12-pulse and 24-pulse ac-dc converters are developed and test results are presented to validate the developed design procedure and the simulation models of these ac-dc converters under varying loads.

Power Quality Improvement in Conventional Electronic Load Controller for an Isolated Power Generation

This paper deals with the power quality improvement in a conventional electronic load controller (ELC) used for isolated pico-hydropower generation based on an asynchronous generator (AG). The conventional ELC is based on a six-pulse uncontrolled diode bridge rectifier with a chopper and an auxiliary load. It causes harmonic currents injection resulting distortion in the current and terminal voltage of the generator. The proposed ELC employs a 24-pulse rectifier with 14 diodes and a chopper. A polygon wound autotransformer with reduced kilovolts ampere rating for 24-pulse ac-dc converter is designed and developed for harmonic current reduction to meet the power quality requirements as prescribed by IEEE standard-519. The comparative study of two topologies, conventional ELC (six-pulse bridge-rectifier-based ELC) and proposed ELC (24-pulse bridge-rectifier-based ELC) is carried out in MATLAB using SIMULINK and Power System Blockset toolboxes. Experimental validation is carried out for both ELCs for regulating the voltage and frequency of an isolated AG driven by uncontrolled pico-hydroturbine.

A 40-Pulse AC--DC Converter Fed Vector-Controlled Induction Motor Drive

In this paper, a novel autotransformer for a 40-pulse ac-dc converter configuration is designed, modeled, simulated, and implemented to feed vector-controlled induction motor drive (VCIMD). The proposed converter consists of two paralleled ten-pulse ac-dc converters along with pulse doubling circuit at dc bus. Each ten-pulse ac-dc converter involves five-phase diode bridge rectifiers. It improves power quality at ac mains, and it meets IEEE-519 standard requirements at varying loads. A set of power quality indexes on input ac mains and dc bus for a VCIMD fed from 20-pulse and 6-pulse converters is also given to compare their performance. It is observed that input current total harmonic distortion (THD) of much less than 5% is possible with the proposed topology at varying loads.

Autoconnected-Transformer-Based 20-Pulse AC–DC Converter for Telecommunication Power Supply

In this paper, an autoconnected-transformer-based 20-pulse ac-dc converter is proposed for harmonic current reduction in switched-mode power supplies (SMPSs) of moderate rating (10-15 kW). The proposed ac-dc converter is realized with a fractional magnetic rating of the load. The supply current is nearly sinusoidal with low total harmonic distortion, and the power factor is close to unity. A set of power quality indices at three-phase utility for an SMPS is presented for both 20- and 6-pulse converters to compare their performances. It is determined that the power quality indices at ac mains with a 20-pulse converter meet IEEE Standard 519 even at varying loads. A laboratory prototype of an autoconnected-transformer-based 20-pulse ac-dc converter has been designed and developed to validate the findings from simulation. Various tests have been conducted on it, and the test results conform to the simulation results.

An Autotransformer-Based 36-Pulse Controlled AC–DC Converter

Abstract This paper proposes a non-isolated 36-pulse controlled AC–DC converter for medium power rating drives. It involves pulse multiplication in a 12-pulse AC–DC converter. The approach employs a polygon autotransformer arrangement, which results in a near equal leakage reactance in series with each thyristor bridge. The volt–ampere rating of the autotransformer is observed to be small and the converter meets IEEE-519 standard power–quality requirements over a wide range of firing angle.

Design and Development of a 36-Pulse AC-DC Converter for Vector Controlled Induction Motor Drive

In this paper, an autotransformer based 36-pulse AC-DC converter fed vector controlled induction motor drives (VCIMDs) is presented for reduction of harmonic-currents. A 36-pulse converter is realized using a specially designed autotransformer and two 18-pulse diode bridge rectifiers. The effect of load variation on VCIMD is also studied to demonstrate the effectiveness of the proposed AC-DC converter. A set of power quality indices on input AC mains and on DC bus for a VCIMD fed from 6-pulse and 18-pulse AC-DC converters are also given to compare their performance. It is observed that input current total harmonic distortion (THD) less than 5% is possible with the proposed topology at varying-loads. A laboratory prototype of this 36-pulse AC-DC converter is developed and test results are presented to validate the design and simulation model. It improves power quality at AC mains and meets IEEE-519 standard requirements at varying loads.

Zigzag Connected Autotransformer Based Controlled AC-DC Converter for Pulse Multiplication

This paper deals with the analysis and design of a non-isolated 36-pulse controlled AC-DC converter for medium power rating drives, field winding supply of large alternators, magnet power supplies, etc. It consists of pulse multiplication in non-isolated 12-pulse AC-DC converter to get 36-pulse converter characteristics without employing zero-sequence blocking transformer (ZSBT). The proposed converter employs a zigzag connected autotransformer, which results in near equal leakage reactance in series with each thyristor bridge. The volt-ampere rating of the autotransformer is small and the converter meets IEEE-519 standard power-quality requirements over wide range of firing angle.

A fork connected auto-transformer based 24-pulse AC-DC converter

In this paper, a 24-pulse AC-DC converter is designed, modeled and simulated to feed non-isolated industrial loads. The proposed configuration consists of an auto-transformer based on fork connection to overcome current harmonic problems in AC mains. It improves power quality at AC mains and it meets IEEE-519 standard requirements at varying loads. A set of power quality indices on input AC mains and on DC bus for a load fed from 6-pulse and 12-pulse AC-DC converters is also given to compare their performance. It is observed that input current total harmonic distortion (THD) of less than 5% is possible with the proposed topology of AC-DC converter at varying loads.

A Novel Harmonic Mitigation Converter for Variable Frequency Drives

In this paper, a novel autotransformer for 56-pulse AC-DC converter configuration is designed, modeled and simulated to feed vector controlled induction motor drive (VCIMD). The proposed autotransformer configuration consists of two paralleled 14-pulse AC-DC converters involving seven-phase shifted uncontrolled diode bridges with pulse doubling circuit. It improves power quality at AC mains and it meets IEEE-519 standard requirements at varying loads.