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

**ABSTRACT** 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.

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**ABSTRACT:**In this paper, design of autotransformer based 24 Step AC-DC converter fed vector controlled Induction motor drive is presented and its Matlab/Simulink model is given. Also these results are compared with 12-pulse AC-DC converter fed vector controlled Induction motor drive. This paper deals with various multipulse AC-DC converters for improving the power quality in vector-controlled induction motor drives (VCIMDs) at the point of common coupling. These multipulse AC-DC converters are realized using a reduced rating autotransformer. Moreover, DC ripple reinjection is used to double the rectification pulses resulting in an effective harmonic mitigation. The proposed AC-DC converter is able to eliminate 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 the DC bus for a VCIMD fed from different AC-DC converters is also given to compare their performance. Simulation results of VCIMD were obtained in MATLAB & SIMULINK with NO LOAD & ON LOAD.01/2012; -
##### Conference Paper: A 12-pulse converter featuring a rotating magnetic field transformer

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**ABSTRACT:**A 12-Pulse Converter generally uses a phase-shifting transformer to get two sets of three-phase voltages, but the magnitude of the line current harmonic is too high. In this paper, a new type of 12-Pulse Converter featuring a rotating magnetic field transformer is presented. The design is based on the rationale of the induction machine, which can effectively reduce the line current harmonic and improve the power quality of the converter's DC output voltage.Modelling, Identification & Control (ICMIC), 2012 Proceedings of International Conference on; 01/2012 -
##### Conference Paper: A new design methodology for multipulse rectifiers with Delta auto-connected transformers and a retrofit application in Adjustable Speed Drives (ASDs)

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**ABSTRACT:**Multipulse rectifiers can replace a conventional six pulse three-phase rectifier (diode bridge) providing a DC voltage with low ripple, low Total Harmonic Distortion of current (THDi) and a high Power Factor (PF). In this context is presented a multipulse rectifier with generalized Delta-differential autotransformer topology, which can provide any level of DC output voltage for any level of three-phase AC input voltage. This paper presents all the possible configurations for Delta topology in order to choose, through graphics, one configuration that presents reduced weight and volume. The average voltage on the DC bus must be compatible with the DC voltage in the six pulse rectifier used in commercial ASDs. Therefore, it is possible to apply the retrofit technique to replace the conventional bridge rectifier by the proposed multipulse rectifier. Based on mathematic models and simulation results, an 18-pulse rectifier with Delta topology, 220 V of line voltage, 315 V of DC output, and rating 2.5 kW of power was designed, implemented and applied for three different commercial ASDs. Experimental results as voltage and current waveforms and results about PF and THDi will be presented.Industry Applications (INDUSCON), 2012 10th IEEE/IAS International Conference on; 01/2012

Page 1

IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 21, NO. 3, JULY 2006

1483

Harmonic Mitigation Using 12-Pulse

AC–DC Converter in Vector-Controlled

Induction Motor Drives

Bhim Singh, Senior Member, IEEE, G. Bhuvaneswari, Senior Member, IEEE, and Vipin Garg, Member, IEEE

Abstract—In this paper, a novel autotransformer with a reduced

kilovolt-ampere rating is presented for harmonic current reduc-

tion in twelve-pulse ac-dc converter-fed vector-controlled induc-

tion motor drives (VCIMDs). Different transformer arrangements

for 12-pulse-based rectification are also studied and a novel har-

monic mitigator capable of suppressing fifth, seventh, and 11th

(mostdominantharmonics)inthesupplycurrentispresented.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-pulsediodebridgerectifierisbeingused.Theeffectofloadvari-

ation 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.

Index Terms—Autotransformer, multipulse AC–DC converter,

power-quality improvement, vector-controlled induction motor

drive (VCIMD).

I. INTRODUCTION

W

quencyinductionmotor drives.These variablefrequencyinduc-

tion motor drives are generally operated in vector control [1],

as it is an elegant way of achieving high-performance control

of induction motors in a way similar to the dc motor. These

vector-controlled induction motor drives (VCIMDs) are fed by

an uncontrolled ac–dc converter which results in injection of

current harmonics into the supply system. These current har-

monics, while propogating through the finite source impedance,

result in voltage distortion at the point of common coupling,

thereby affecting the nearby consumers.

Various methods based on the principle of increasing the

number of pulses in ac–dc converters have been reported in

the literature to mitigate current harmonics [2]–[4]. These

methods use two or more converters, where the harmonics

generated by one converter are cancelled by another converter,

by proper phase shift. The autotransformer-based configu-

rations [2] provide the reduction in magnetics rating, as the

transformer magnetic coupling transfers only a small portion

of the total kilovolt-ampere of the induction motor drive. These

autotransformer-based schemes considerably reduce the size

ITHtheproliferationofpower-electronicconverters,the

majority of dc drives are being replaced by variable fre-

Manuscript received February 9, 2005. Paper no. TPWRD-00077-2005.

The authors are with the Department of Electrical Engineering, Indian Insti-

tuteofTechnology,NewDelhi110016,India(e-mail:bhim_singh@yahoo.com;

bhuvan225@gmail.com; vipin123123@gmail.com).

Digital Object Identifier 10.1109/TPWRD.2005.860265

and weight of the transformer. Autotransformer-based 12-pulse

ac–dc converters have been reported [4] for reducing the total

harmonic distortion (THD) of the ac mains current. To ensure

equal power sharing between the diode bridges and to achieve

good harmonic cancellation, this topology needs interphase

transformers and impedance-matching inductors, resulting in

increased complexity and cost. Moreover, the dc-link voltage

is higher, making the scheme nonapplicable for retrofit appli-

cations. To overcome the problem of higher dc-link voltage,

Hammond [5] has proposed a new topology, but the transformer

design is very complex. To simplify the transformer design,

Paice [6] has reported a new topology for 12-pulse ac-dc

converters. But this topology requires higher rating magnetics,

resulting in the enhancement of capital cost. Steffan et al. [7]

have reported a quasi 12-pulse rectifier for harmonic reduction,

but here also the THD of the ac mains current at full load is

10.5% and at 40% load, it is around 20%. Kamath et al. [8]

have also reported a 12-pulse converter, but the THD of the

ac mains current is high even at full load (10.1%) and as load

decreases, the THD increases further (17% THD at 50% load).

In this paper, a novel autotransformer-based 12-pulse ac–dc

converter with reduced kilovolt-ampere (kVA) rating is pro-

posed to feed the VCIMD. The presented technique for the

design of the autotransformer provides flexibility in design to

vary the output voltages to make it suitable for retrofit applica-

tions (where presently, a six-pulse converter is being used, as

shown in Fig. 1) without much alterations in the system layout.

This topology results in improvement in THD of ac mains

current and power factor even under light load conditions.

II. TWELVE-PULSE AC–DC CONVERTER-BASED

HARMONIC MITIGATORS

For harmonic elimination, the required minimum phase shift

is given by [2]

Phase shift

Number of converters

For achieving 12-pulse rectification, the phase shift between

the two sets of voltages may be either 0 and 30 or

this paper, various topologies based on

been studied to reduce the size of the magnetics.

Fig. 2 shows the schematic diagram of a 12-pulse autotrans-

former-based ac–dc converter with a phase shift of

, referred as Topology “A” [3]. Similarly, Fig. 3 shows

the schematic diagram of a 12-pulse autotransformer-based

ac–dc converter with a phase shift of

. In

haveand

and

andreferred

0885-8977/$20.00 © 2006 IEEE

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1484IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 21, NO. 3, JULY 2006

Fig. 1.

drive.

Six-pulse diode bridge rectifier-fed vector-controlled induction motor

Fig.2.

and ??? ) fed VCIMD. (Topology A).

Autotransformer-based12-pulseconverter-(withaphaseshiftof???

as Topology “B” as per [4] and Fig. 4 shows the schematic

diagram of a 12-pulse autotransformer-based ac–dc converter

with a phase shift of

and

as per [6]. In all of these topologies, the voltages produced by

the autotransformer

,, and

to supply voltages

,, and

voltages

, , andare at

voltages, resulting in 12-pulse rectification.

referred as Topology “C”

are at

, where as the other set of

with respect to supply

with respect

III. DESIGN OF PROPOSED 12-PULSE AC–DC CONVERTER

This section deals with the autotransformer arrangement for

the proposed 12-pulse ac–dc converter-based harmonic miti-

gator referred as Topology “D”. Various issues related to the

design of the suitable autotransformer for 12-pulse configura-

tion are presented here.

Fig. 3.

and ??? ) fed VCIMD. (Topology B).

Autotransformer-based 12-pulse converter- (with a phase shift of 15

Fig.4.

and ??? ) fed VCIMD. (Topology C).

Autotransformer-based12-pulseconverter-(withaphaseshiftof???

A. Design of Autotransformer for Twelve-Pulse Converter

Toachievethe12-pulserectification,thefollowingconditions

have to be satisfied.

a) Two sets of balanced three-phase line voltages are to be

produced, which are either

with respect to each other. Here,

to reduce the size of the magnetics.

b) The magnitude of these line voltages should be equal to

each other to result in symmetrical pulses and reduced

ripple in output dc voltage.

Fig. 5 shows the winding connection diagram of the pro-

posed autotransformer for achieving the 12-pulse rectification.

The phasor diagram shown in Fig. 6 represents the relationship

among various phase voltages.

From the supply voltages, two sets of three-phase voltages

(phase shifted through

and

number of turns required for

calculated as follows. Consider phase “a” voltages as

or out of phase

phase shift is used

) are produced. The

phase shift areand

(1)

(2)

Assume the following set of voltages:

(3)

Similarly

(4)

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SINGH et al.: HARMONIC MITIGATION USING CONVERTER IN MOTOR DRIVES1485

Fig. 5. Proposed autotransformer winding connection diagram.

Fig. 6.

harmonic mitigator.

Vector diagram of phasor voltages for 12-pulse-based proposed

(5)

where, V is the root-mean-square (rms) value of the phase

voltage.

Using above equations,

and

equationsresultin

phaseshiftinanautotransformer.Thephase-shiftedvoltagesfor

phase “a” are

can be calculated. These

forthedesiredand

(6)

(7)

Thus, the autotransformer uses two auxiliary windings per

phase. A phase-shifted voltage (e.g.,

the following arrangements.

a) Tapping a portion (0.0227) of line voltage

b) Connecting one end of an approximate 0.138 times of line

voltage (e.g.,

) to this tap.

To ensure the independent operation of the rectifier groups,

interphase transformers (IPTs), which are relatively small in

size, are connected at the output of the rectifier bridges. With

thisarrangement,therectifierdiodesconductfor120 percycle.

With this transformer arrangement, the dc-link voltage obtained

is slightly higher than that of a six-pulse diode bridge recti-

fier output voltage due to 12-pulse rectification. To make the

) is obtained by using

.

Fig. 7.

harmonic mitigator for retrofit applications.

Vector diagram of phasor voltages for 12-pulse-based proposed

proposed harmonic mitigator suitable for retrofit applications,

the transformer design has been modified to make the dc-link

voltage the same as that of the six-pulse diode bridge rectifier.

The phasor diagram shown in Fig. 7 represents the generalized

diagramshowingtherelationshipamongvariousphasevoltages

for achieving the variable magnitude transformer output volt-

ages, which are phase shifted through

12-pulse operation).

By following the above procedure, for the same dc-link

voltage as that of a six-pulse diode bridge rectifier, the values

of

and are as

and are the new constants for achieving the same dc-link

voltage as that of the six-pulse diode bridge rectifier. Now, the

phase-shifted voltages for phase ”a” are as

(for achieving the

and , where

(8)

(9)

Now, a phase-shifted voltage (e.g.,

the following arrangements.

a) Tapping a portion (0.0195) of line voltage

b) Connecting one end of an approximate 0.1402 times of

line voltage (e.g.,

) to this tap.

Thus, by simply changing the transformer winding tapping,

the same dc-link voltage as that of the six-pulse diode bridge

rectifier is obtained. Fig. 8 shows the winding connection dia-

gram of the proposed autotransformer for designing the auto-

transformer suitable for retrofit applications. Fig. 9 shows the

proposed 12-pulse rectification-based harmonic mitigator-fed

VCIMD referred as topology “D.” The kVA rating of the trans-

former is calculated as [2]

) is obtained by using

.

(10)

The kVA rating of the interphase transformer is also calcu-

lated using the above relationship.

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1486 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 21, NO. 3, JULY 2006

Fig.8.

for retrofit applications.

Windingconnectiondiagramfortheproposedautotransformersuitable

Fig. 9.

fed VCIMD based on an autotransformer. (Topology D).

Proposed 12-pulse converter- (with a phase shift of ??? and ??? )

B. Design of Passive Tuned Filter

To improve the power quality, a passive shunt filter has been

designed in accordance with IEEE Standard 1531-2003 [9].

Fig. 10 shows the schematic diagram of the proposed harmonic

mitigator with a passive filter connected at the input. This

Topology is referred as “E.” Various issues involved with the

design of passive filters are given here.

1) Design Equations: The passive shunt filter is governed

by the following design equations [9], [10].

The impedance of the filter branch is given as

(11)

The resonance frequency can be written as

(12)

The inductor and capacitor impedances for th harmonic are

and

Quality factor: The quality of the filter is a measure of the

sharpness of tuning. A high value of quality factor results in a

very sharp tuned filter, whereas a low value results in high-pass

wide bandwidth performance, resulting in higher losses.

. At resonance,.

Fig. 10.

shift of ??? and ??? ) fed VCIMD. (Topology E).

Autotransformer-based proposed 12-pulse converter- (with a phase

It is defined as

(13)

The kVA of the filter capacitor at power frequency (60 Hz) is

given as

(14)

where

the point of connection of the filter, C is the capacitance of the

filter capacitor,

is the reactance of inductor, and

reactance of the capacitor at the resonant frequency.

is the nominal line-to-line voltage of the system at

is the

IV. VECTOR-CONTROLLED INDUCTION MOTOR DRIVE

Fig. 1 shows the schematic diagram of an indirect vector-

controlledinductionmotordrive(VCIMD).Thistechniqueuses

two currents of motor phases, namely

speedsignal

.TheclosedloopPIspeedcontrollercompares

the reference speed

with motor speed

reference torque

(after limiting it to a suitable value)

andand the motor

and generates

(15)

where

limiting it to a suitable value) and

speed error at the th and

proportional and integral gain constants.

The flux control signal

vector controller which calculates the torque component of and

the flux angle

as follows:

andare the output of the PI controller (after

and

instants.

refer to

are theand

along with are fed to the

(16)

(17)

(18)

(19)

(20)

where

rotor;

number of poles, mutual inductance, and rotor leakage factor,

respectively;

andare the value of rotor flux angles

is the magnetizing current;

is the angular velocity of rotor; P, M, and

is the slip speed of

are the

Page 5

SINGH et al.: HARMONIC MITIGATION USING CONVERTER IN MOTOR DRIVES 1487

Fig. 11. MATLAB block diagram of VCIMD.

Fig. 12.

VCIMD (topology “D”).

MATLAB block diagram of the proposed harmonic mitigator-fed

Fig. 13.

VCIMD (Topology “E”).

MATLAB block diagram of the proposed harmonic mitigator-fed

at thand( -1)thinstants,respectively,and

time taken as 100

s.

These currents (

,

converted to stationary frame three-phase currents (

as given below

isthesampling

), in synchronously rotating frame, are

,,)

(21)

(22)

(23)

where

These three-phase reference currents generated by the vector

controller are compared with the sensed motor currents (

and). The calculated current errors are

,, and are the three-phase reference currents.

,,

where(24)

ThesecurrenterrorsareamplifiedandfedtothePWMcurrent

controller which controls the duty ratio of different switches

in VSI. The VSI generates the PWM voltages being fed to the

Fig.14.

perturbation.

Dynamicresponseofasix-pulsedioderectifier-fedVCIMDwithload

Fig. 15.

load in a six-pulse diode bridge rectifier-fed VCIMD.

AC mains current waveform along with its harmonic spectrum at full

motor to develop the necessary torque for running the motor at

a given speed under given loading conditions.

V. MATLAB-BASED SIMULATION

The proposed harmonic mitigators, along with the VCIMD,

are simulated in a MATLAB environment along with

SIMULINK and power-system-blockset (PSB) toolboxes.

Fig. 11 shows the MATLAB model of a vector-controlled

induction motor drive. The VCIMD consists of an induction

motor drive controlled using an indirect vector-control tech-

nique. Fig. 12 shows the MATLAB model of the proposed

harmonic mitigator based on 12-pulse rectification to simulate

its performance. Fig. 13 shows the MATLAB model of the pro-

posed harmonic mitigator along with a passive filter connected

on the supply side to further improve various power-quality

indices. The simulated results have been analyzed to study the

effect of load variation on the drive on various power-quality

indices as well as to show the reduction in rating of magnetics

in the proposed configuration.

Page 6

1488 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 21, NO. 3, JULY 2006

Fig.16.

load (20%) in a six-pulse diode bridge rectifier-fed VCIMD.

ACmains currentwaveformalongwithitsharmonicspectrumatlight

Fig. 17.

load for Topology “A.”

AC mains current waveform along with its harmonic spectrum at full

VI. RESULTS AND DISCUSSION

The proposed harmonic mitigator along with the VCIMD

have been simulated to demonstrate the performance of the

proposed system. Fig. 14 shows the dynamic performance

along with load perturbation on the VCIMD fed by a six-pulse

diode bridge rectifier. It consists of supply voltage

current

, rotor speed “” (in electrical rad/sec), three-phase

motor currents

, motor-developed torque “

and dc-link voltage

(V). Fig. 15 shows the supply current

waveform along with its harmonic spectrum at full load. The

THD of the ac mains current at full load is 31.2%, which dete-

riorates to 57.7% at light load as shown in Fig. 16. Moreover,

the power factor at full load is 0.937, which deteriorates to

0.848 as the load is reduced. These results show that there is

a need for improving the power quality at the ac mains using

some harmonic mitigators which can easily replace the existing

six-pulse converter.

, supply

” (in N-m)

Fig.18.

load (20%) for Topology “A.”

ACmainscurrentwaveformalongwithitsharmonicspectrumatlight

Fig. 19.

load for Topology “B.”

AC mains current waveform along with its harmonic spectrum at full

Fig.20.

load (20%) for Topology “B.”

ACmainscurrentwaveformalongwithitsharmonicspectrumatlight

Page 7

SINGH et al.: HARMONIC MITIGATION USING CONVERTER IN MOTOR DRIVES 1489

Fig. 21.

load for Topology “C.”

AC mains current waveform along with its harmonic spectrum at full

Fig. 22.

load (20%) for Topology “C.”

ACmainscurrentwaveformalongwithitsharmonicspectrumatlight

A. Performance of Twelve-Pulse Rectification-Based

Harmonic Mitigators

Different configurations of 12-pulse ac–dc converters have

been modeled and simulated to compare their relative perfor-

mance in terms of different power-quality indices.

1) Autotransformer With

simulation results of an autotransformer (with phase shift of

and)-based ac–dc converter (Topology “A”)-fed

VCIMD are shown in Figs. 17 and 18. Fig. 17 shows the wave-

form of the supply current along with its harmonic spectrum

at full load and Fig. 18 shows these parameters at light load

(20%) in topology “A.” The THD of supply current at full load

is 7.02% and that at light load is 10.23%, whereas the power

factor under these conditions is 0.973 and 0.975, respectively.

Here, the dc-link voltage is higher than that of a 6-pulse diode

bridge rectifier. In topology “B”, the THD of the ac mains cur-

rent at full load is 6.24%and at light load, it is 14.25% as shown

in Figs. 19 and 20, respectively. Here again, the dc-link voltage

is high. In topology “C”, the THD of the ac mains current at

full load is 6.59% and 13.13% at light load (20%) as shown in

andPhase Shift: The

Fig. 23.

load for Topology “D.”

AC mains current waveform along with its harmonic spectrum at full

Fig.24.

load (20%) for Topology “D.”

ACmainscurrentwaveformalongwithitsharmonicspectrumatlight

Figs. 21 and 22, respectively. This topology needs magnetics as

high as 43.56% of the drive rating. There is a need for a suitable

ac–dc converter which has the same dc-link voltage as that of

a six-pulse diode bridge rectifier (for retrofit applications) and

which needs small magnetics.

2) Proposed Harmonic Mitigator: The supply current

waveform at full load along with its harmonic spectrum is

shown in Fig. 23 (Topology “D”), which shows that the THD

of the ac mains current is 8.17% and the power factor obtained

is 0.975. Fig. 24 shows the supply current waveform along with

its harmonic spectrum under light load condition (20%). At

light load condition, the THD of the ac mains current is 9.40%

and the power factor is 0.969. To improve the power-quality

indices further, a passive shunt filter has been connected at

the supply input (Topology “E”). Fig. 25 shows the dynamic

performance of the proposed harmonic mitigator (Topology

“E”) at starting and load perturbation. Fig. 26 shows the supply

current waveform along with its harmonic spectrum at full load

condition, showing a THD of 6.68% and a power factor of

0.982. The supply current waveform under light load condition

Page 8

1490 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 21, NO. 3, JULY 2006

Fig. 25.

converter-fed VCIMD with load perturbation for Topology “E.”

Dynamic response ofproposed 12-pulse autotransformer-based ac-dc

Fig. 26.

load for Topology “E.”

AC mains current waveform along with its harmonic spectrum at full

(20%), along with its harmonic spectrum, is shown in Fig. 27,

which shows that the THD of the ac mains current is 7.52% and

the power factor is 0.98.

Table I shows the effect of load variation on the VCIMD to

study various power-quality indices. It shows that the proposed

harmonic mitigator is able to perform satisfactorily under load

variation on VCIMD with almost unity power factor (always

higher than 0.98) and a THD of supply current always less than

8%. This is within the IEEE Standard 519 [11] limits for SCR

20.TableIIshowsthevariationofsupplycurrent

verter input current

with a load on VCIMD. It can be ob-

served that the supply current

verter input current

.

The variation of THD of the ac mains current and power

factor in VCIMD fed from a six-pulse and the proposed

12-pulse ac–dc converters is shown in Figs. 28 and 29,

respectively, showing a remarkable improvement in these

power-quality indices. Table III shows a comparative study

andcon-

is always less than the con-

Fig.27.

load (20%) for Topology “E.”

ACmainscurrentwaveformalongwithitsharmonicspectrumatlight

TABLE I

POWER-QUALITY INDICES UNDER VARYING LOADS IN PROPOSED

HARMONIC MITIGATOR-FED VCIMD

TABLE II

COMPARISON OF SUPPLY CURRENT AND CONVERTER INPUT

CURRENT IN DIFFERENT CONVERTERS

of different power-quality indices of a VCIMD fed from a

six-pulse converter and different 12-pulse converters.

The converters in topologies A and B result in a higher

dc-link voltage than a six-pulse diode bridge rectifier. So these

topologies cannot be used in retrofit applications. The auto-

transformer in Topology “C” results in a dc-link voltage that is

almost the same as that of a six-pulse diode bridge rectifier, but

the rating of the magnetics is high 20.825 kVA (43.56% of the

drive rating), which is on a higher side as shown in Table IV.

The proposed autotransformer-based 12-pulse ac–dc converter

gives the same dc-link voltage as that of a six-pulse diode

bridge rectifier, making it suitable for retrofit applications.

Moreover, the rating of the autotransformer is 9.3 kVA. It needs

Page 9

SINGH et al.: HARMONIC MITIGATION USING CONVERTER IN MOTOR DRIVES 1491

TABLE III

COMPARISON OF POWER-QUALITY PARAMETERS OF A VCIMD FED FROM DIFFERENT 12-PULSE CONVERTERS

Fig. 28.

six-pulse and proposed 12-pulse ac-dc converter- (Topology “E”) fed VCIMD.

Variation of THD of the ac mains current with load on VCIMD in

Fig. 29.

proposed 12-pulse ac–dc converter- (Topology “E”’) fed VCIMD.

Variation of power factor with load on VCIMD in six-pulse and

TABLE IV

RATING OF MAGNETICS IN DIFFERENT CONVERTER TOPOLOGIES

a small rating interphase transformer of 1.38 kVA, resulting in

total magnetics of 10.68 kVA (22.34% of drive rating).

VII. CONCLUSION

A novel autotransformer-based 12-pulse ac–dc converter has

been modeled with a VCIMD load. The design technique of the

proposed converter has shown the flexibility to design the trans-

former suitable for retrofit applications with variable frequency

induction motor drivesoperating undervaryingload conditions.

The proposed harmonic mitigator has resulted in the reduction

in rating of the magnetics, leading to the saving in overall cost

of the drive. The effect of load variation on the VCIMD on var-

ious power-quality indices has also shown the efficacy of the

proposed harmonic mitigator in improving these indices. The

observed performance of the proposed harmonic mitigator has

been found better than the existing 12-pulse converter config-

urations. The performance of the proposed harmonic mitigator

has demonstrated thecapabilityof this converterresulting inthe

improvement of power-quality indices at the ac mains in terms

oftheTHDofthesupplycurrent,THDofsupplyvoltage,power

factor, and crest factor. On the dc-link side too, it provides a re-

markable improvement in ripple factor of the dc-link voltage.

It can easily replace the existing six-pulse converters without

much alteration in the existing system layout and equipment.

APPENDIX

MOTOR AND CONTROLLER SPECIFICATIONS

Three-phase squirrel cage induction motor

(37.3 kW), three-phase, four-Pole, Y-connected, 460 V, 60

Hz,

,

,

Controller parameters

PI controller:

DC-link parameters:

Magnetics ratings

Twelve-pulse-based converter:

9.3 kVA, interphase transformer 1.38 kVA, passive filter

2.22 kVA.

50 HP

,,

,-.

,;

mH, F.

Autotransformerrating

REFERENCES

[1] P. Vas, Sensorless Vector and Direct Torque Control.

Oxford Univ. Press, 1998.

[2] D. A. Paice, Power Electronic Converter Harmonics: Multipulse

Methods for Clean Power. Piscataway, NJ: IEEE Press, 1996.

[3] S.Choi,P.N.Enjeti,andI.J.Pitel,“Polyphasetransformerarrangements

with reduced kVA capacities for harmonic current reduction in rectifier

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Bhim Singh (SM’99) was born in Rahamapur, India,

in 1956. He received the B.E. (electrical) degree

from the University of Roorkee, Roorkee, India, in

1977 and the M. Tech. and Ph.D. degrees from the

Indian Institute of Technology (IIT), Delhi, New

Delhi, India, in 1979 and 1983, respectively.

In 1983, he joined the Department of Electrical

Engineering, University of Roorkee, as a Lecturer,

and in 1988 became a Reader. In December 1990,

he joined the Department of Electrical Engineering,

IIT Delhi, as an Assistant Professor. He became an

Associate Professor in 1994 and a full Professor in 1997. His field of interest

includes power electronics, electrical machines and drives, active filters, static

VAR compensator, and analysis and digital control of electrical machines.

Dr. Singh is a Fellow of Indian National Academy of Engineering (INAE),

theInstitutionofEngineers(India)[IE(I)],andtheInstitutionofElectronicsand

Telecommunication Engineers (IETE), a Life Member of the Indian Society for

TechnicalEducation(ISTE),theSystemSocietyofIndia(SSI),andtheNational

Institution of Quality and Reliability (NIQR).

G. Bhuvaneswari (SM’99) received the M.Tech.

and Ph.D. degrees from the Indian Institute of

Technology (IIT), Madras, India, in 1988 and 1992,

respectively.

Currently, she is an Assistant Professor, Depart-

ment of Electrical Engineering, IIT Delhi, New

Delhi, India, where she has been since 1997. Her re-

search interests include power electronics, electrical

machines, and power conditioning. She is a fellow

of IETE.

Vipin Garg (M’05) was born in Kurushhetra,

Haryana, India, in 1972. He received the B.Tech.

(Electrical) and M.Tech. degrees from Regional

Engineering College, Kurukshetra, in 1994 and

1996, respectively, and is currently pursuing the

Ph.D. degree at the Indian Institute of Technology

Delhi, New Delhi.

HejoinedtheIndianRailwaysServiceofElectrical

Engineers (IRSEE),New Delhi, asan Assistant Elec-

trical Engineer and became Divisional Electrical En-

gineer in 2002. His research interests include power

electronics and electric traction and drives.

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