Vipin Garg

A Novel T-Connected Autotransformer-Based 18-Pulse AC–DC Converter for Harmonic Mitigation in Adjustable-Speed Induction-Motor Drives

This paper presents the design, analysis, and development of a novel autotransformer-based 18-pulse AC-DC converter with reduced kilovoltampere rating, feeding vector-controlled induction-motor drives (VCIMDs) for power-quality improvement at the point of common coupling (PCC). The proposed autotransformer consists of only two single-phase transformers for its realization against three single-phase transformers required in other configurations. The proposed 18-pulse AC-DC converter is suitable for retrofit applications, where, presently, a six-pulse diode bridge rectifier is being used. A set of power-quality parameters, such as total harmonic distortion (THD) and crest factor of AC mains current, power factor, displacement factor, and distortion factor at AC mains, THD of supply voltage at PCC, and DC-bus-voltage ripple factor for a VCIMD fed from an 18-pulse AC-DC converter, are computed to observe its performance. The presented design technique provides flexibility to give an average DC output from the proposed converter, which is the same as that of a conventional three-phase diode bridge rectifier. However, it is also possible to step-up or step-down the output voltage as required. The effect of load variation on VCIMD is also studied to observe the effectiveness of the proposed harmonic mitigator. A laboratory prototype of the proposed autotransformer-based 18-pulse AC-DC converter is developed to validate the design and simulation model.

Harmonic mitigation using 12-pulse AC-DC converter in vector-controlled induction motor drives

In this paper, a novel autotransformer with a reduced kilovolt-ampere rating is presented for harmonic current reduction in twelve-pulse ac-dc converter-fed vector-controlled induction motor drives (VCIMDs). Different transformer arrangements for 12-pulse-based rectification are also studied and a novel harmonic mitigator capable of suppressing fifth, seventh, and 11th (most dominant harmonics) in the supply current is presented. The design procedure for the proposed autotransformer is presented to show the flexibility in the design for making it a cost-effective replacement suitable for retrofit applications, where presently a six-pulse diode bridge rectifier is being used. The effect of load variation on VCIMD is also studied to demonstrate the effectiveness of the proposed harmonic mitigator. A set of power-quality indices on input ac mains and on a dc bus for a VCIMD fed from different 12-pulse ac-dc converters is given to compare their performance.

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.

A Novel Polygon Based 18-Pulse AC–DC Converter for Vector Controlled Induction Motor Drives

This paper presents a novel configuration of an autotransformer based 18-pulse ac-dc converter for improving the power quality at the point of common coupling (PCC) in variable frequency induction motor drives (VFIMDs). The polygon based connection of autotransformer for achieving 18-pulse rectification is utilized to result in reduction in rating of the magnetics. The design of the autotransformer is carried out for an 18-pulse ac-dc converter feeding a vector controlled induction motor drive (VCIMD). Moreover, the autotransformer design is modified for making it suitable for retrofit applications, where presently a 6-pulse diode bridge rectifier is used. The effect of load variation on VCIMD is also studied and the performance of the proposed 18-pulse ac-dc converter is compared in terms of different power quality indices on both ac as well as dc side with other ac-dc converters. A laboratory prototype of the proposed autotransformer based 18-pulse ac-dc converter feeding a 10-hp induction motor drive is developed to verify the design and simulated results

Power-quality improvements in vector-controlled induction motor drive employing pulse multiplication in AC-DC converters

This paper deals with the pulse doubling in a 12-pulse ac-dc converter for improving power quality in vector-controlled induction motor drives (VCIMDs). The design of proposed magnetics shows the flexibility in varying the voltage ratio of the autotransformer for making it suitable for retrofit applications, where presently a six-pulse diode bridge rectifier is being used. The proposed ac-dc converter is capable of eliminating up to 21st harmonics in the supply current. 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 proposed ac-dc converter are also given to compare its performance with six-pulse and twelve-pulse ac-dc converters.

T-connected autotransformer-based 24-pulse AC-DC converter for variable frequency induction motor drives

A new robust passive waveshaper based on 24-pulse ac-dc conversion is proposed to feed voltage source inverter (VSI) supplying squirrel-cage induction motor drive. The passive waveshaper consists of a newly designed T-connected autotransformer with less number of windings resulting in simplicity in design and manufacturing. The proposed 24-pulse ac-dc converter is found capable of suppressing less than 23rd harmonics in the supply current. The power factor is also improved to near unity in the wide operating range of the vector-controlled induction motor drive (VCIMD). Finally, the design of the autotransformer is modified to make it suitable for applications, where presently a 6-pulse diode bridge rectifier is used. A laboratory prototype of proposed T-connected autotransformer-based 24-pulse ac-dc converter is developed and test results are presented to validate the developed design procedure and the simulation models of this ac-dc converter under varying loads

Harmonic Mitigation in AC–DC Converters for Vector Controlled Induction Motor Drives

This paper deals with autotransformer-based multipulse ac--dc converters with reduced magnetics feeding vector controlled induction motor drives for improving the power quality at the point of common coupling. The proposed 12-pulse ac--dc converter-based harmonic mitigator consists of an autotransformer alongwith a passive shunt filter tuned for 11th harmonic frequency. This results in the elimination of 5th, 7th, and 11th harmonic currents. Similarly, the proposed 18-pulse ac--dc converter-based harmonic mitigator eliminates the 5th, 7th, 11th, 13th, and 17th harmonic currents, thereby improving the power quality at ac mains. The experimentation is carried out on the developed prototype of autotransformers-based ac--dc converters. Different power quality indexes of the proposed 12-pulse and 18-pulse ac--dc converters are obtained from simulation and verified from experimental results.

Improved power quality AC-DC converter for electric multiple units in electric traction

This paper presents the performance analysis of an improved power quality AC-DC converter (IPQC) fed vector controlled induction motor drive (VCIMD) for electric multiple units (EMU) application in electric traction of Indian railways. The IPQC enhances the input power factor close to unity and also reduces the total harmonic distortion (THD) of AC mains current. The converter provides bi-directional power flow capability during regenerative braking resulting in energy efficient operation of the drive. It also provides constant DC-link voltage during transient and steady state conditions. Detailed modeling and simulated results of the proposed converter fed induction motor drive are presented to demonstrate the features of improved power quality and energy conservation

Polygon-Connected Autotransformer-Based 24-Pulse AC–DC Converter for Vector-Controlled Induction-Motor Drives

This paper presents a novel autotransformer-based 24-pulse AC-DC converter feeding vector-controlled induction motor drives (VCIMDs) for improving power quality at the point of common coupling. The DC-ripple-reinjection technique is used in achieving the pulse multiplication in a 12-pulse AC-DC converter. The design of the proposed autotransformer is given, and necessary modifications are made in it to provide the same output DC voltage as a 6-pulse diode-bridge AC-DC converter to make it suitable for retrofit applications. The proposed 24-pulse AC-DC converter is found capable of suppressing up to the 21st harmonics in the supply current along with the power-factor improvement close to unity in the wide operating range of the drive. A set of power-quality indexes at input AC mains and on DC bus for a VCIMD fed from various AC-DC converters are also given to compare their performance. A prototype of the proposed autotransformer-based 24-pulse AC-DC converter is developed, and test results are presented to validate the developed design procedure and the simulation models of this AC-DC converter under varying loads.

An Improved Power-Quality 30-Pulse AC–DC for Varying Loads

This paper presents the design and analysis of a novel 30-pulse ac-dc converter for harmonic mitigation under varying loads. The proposed 30-pulse ac-dc converter is based on a polygon-connected autotransformer with reduced magnetics. The proposed ac-dc converter is able to eliminate lower than 29th order harmonics in the ac supply current. The resulting supply current is near sinusoidal in shape with low total harmonic distortion and a nearly unity power factor. Moreover, the design of an autotransformer is modified to make it suitable for retrofit applications, where presently a 6-pulse diode bridge rectifier is used. To validate the proposed approach, various power-quality indices are presented under varying loads. The proposed ac-dc converter is found to be suitable for retrofit applications with a large load variation and where harmonic reduction is more stringent. The laboratory prototype of the proposed autotransformer-based 30-pulse ac-dc converter is developed and test results are presented which validate the developed design procedure and the simulation models of this ac-dc converter