ABSTRACT: Power electronic devices are non-linear loads; the non linear nature of these switching devices causes harmonic current injection into the ac mains there by polluting the Power Quality (PQ) at the Point of Common Coupling (PCC). This PQ improvement is achieved by using multi-pulse converters in THREE-PHASE AC-DC Converters (ADCs). The proposed multi-pulse ac-dc converter is based on autotransformer configurations and is able to eliminate lower order harmonics in the ac supply current. This paper describes the comparative analysis of different types of multipulse converters in vector controlled induction motor drives (VCIMD). The proposed multi-pulse ac-dc converter is designed and the simulation model is developed in MATLAB. Keywords: Autotransformer, multi-pulse AC-DC converter, passive filter, harmonic mitigator, power quality improvement and Vector-Controlled Induction Motor Drive (VCIMD). I.INTRODUCTION The use of induction motors has been increased in industrial applications due to their advantages such as improved efficiency, ruggedness, reliability and low cost. So for variable speed drives dc motors have been used because of their flexible characteristics  The proposed multi-pulse ac-dc converters those are suitable for retrofit re to feed vector controlled induction motor drive (VCIMD)  II. DESIGN OF PROPOSED 12-PULSE AND 24-PULSE AC-DC CONVERTERS The design of the suitable autotransformer for these proposed multi-pulse ac-dc converters along with the design of a reduced rating passive tuned filter for effective harmonic filtering. A. Design Of the Proposed 12-Pulse Ac-Dc Converter: To design the 12-pulse ac-dc converter, we have to select the mainly two conditions. First condition is, Two sets of balanced three-phase line voltages are to be produced, which are either or out of phase with respect to each other. Second the magnitude of these line voltages should be equal to each other to result in reduced ripple in output dc voltage. Simulink model of 12-pulse ac-dc converter based proposed harmonic mitigator fed VCIMD is shown i

M Karthika

V V Vijetha Inti

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       ISSN (Print)  : 2320 – 3765 
       ISSN (Online): 2278 – 8875 
 
International Journal of Advanced Research in  Electrical, 
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Vol. 2, Issue 9, September 2013 
 
Copyright to IJAREEIE                                                            www.ijareeie.com                                                                            4186          
 
COMPARATIVE ANALYSIS OF 
MULTIPULSE AC-DC CONVERTERS IN 
VCIMD 
M. Karthika
1
, V.V. Vijetha Inti
2
  
Assistant professor, Dept of EEE, Vishnu Institute of Technology, Bhimavaram, W.G.Dist, AP, India
1
 
Assistant professor, Dept of EEE Vishnu Institute of Technology, Bhimavaram, W.G.Dist, AP, India
2
 
ABSTRACT: Power electronic devices are non-linear loads; the non linear nature of these switching devices causes 
harmonic current injection into the ac mains there by polluting the Power Quality (PQ) at the Point of Common 
Coupling (PCC). This PQ improvement is achieved by using multi-pulse converters in THREE-PHASE AC-DC 
Converters (ADCs). The proposed multi-pulse ac-dc converter is based on autotransformer configurations and is able to 
eliminate lower order harmonics in the ac supply current. This paper describes the comparative analysis of different 
types of multipulse converters in vector controlled induction motor drives (VCIMD). The proposed multi-pulse ac-dc 
converter is designed and the simulation model is developed in MATLAB. 
 
Keywords: Autotransformer, multi-pulse AC–DC converter, passive filter, harmonic mitigator, power quality 
improvement and Vector-Controlled Induction Motor Drive (VCIMD). 
 
I.INTRODUCTION 
The use of induction motors has been increased in industrial applications due to their advantages such as improved 
efficiency, ruggedness, reliability and low cost. So for variable speed drives dc motors have been used because of their 
flexible characteristics [1]. To incorporate the flexible characteristics of a dc motor into an induction motor, vector 
control technique has been used in many industries. Various methods based on the principle of increasing the number 
of pulses in ac–dc converters to mitigate current harmonics [2]. These methods use two or more converters where the 
harmonics generated by one converter are cancelled by another converter through proper phase shift [3].These 
autotransformer based schemes considerably reduce the size and weight of the transformer. Autotransformer-based 
multi-pulse ac–dc converters have been introduced for reducing the total harmonic distortion (THD) of the ac mains 
current [4]. To provide equal power sharing between the diode bridges and to achieve good harmonic cancellation, 
interphase transformers are needed [5][6]. 
 
The proposed multi-pulse ac-dc converters those are suitable for retrofit re to feed vector controlled induction motor 
drive (VCIMD) [7].This proposed multi-pulse ac-dc converter results in the elimination of 5th, 7th, 11th, 13th, 17th and 
21th harmonics. It results in near unity power factor operation in the wide operating range of the drive with the THD of 
ac mains current always less than 5%. 
 
II. DESIGN OF PROPOSED 12-PULSE AND 24-PULSE AC–DC CONVERTERS 
The design of the suitable autotransformer for these proposed multi-pulse ac-dc converters along with the design of a 
reduced rating passive tuned filter for effective harmonic filtering.  
 
A. Design Of the Proposed 12-Pulse Ac–Dc Converter: 
To design the 12-pulse ac-dc converter, we have to select the mainly two conditions. First condition is, Two sets of 
balanced three-phase line voltages are to be produced, which are either  or out of phase with respect to each 
other. Second the magnitude of these line voltages should be equal to each other to result in reduced ripple in output dc 
voltage. Simulink model of 12-pulse ac–dc converter based proposed harmonic mitigator fed VCIMD is shown in fig-1 
 
       ISSN (Print)  : 2320 – 3765 
       ISSN (Online): 2278 – 8875 
 
International Journal of Advanced Research in  Electrical, 
Electronics and Instrumentation Engineering 
(An ISO 3297: 2007 Certified Organization) 
Vol. 2, Issue 9, September 2013 
 
Copyright to IJAREEIE                                                            www.ijareeie.com                                                                            4187          
 
C
o
n
n
1
C
o
n
n
2
C
o
n
n
3
tuned fi lter1
Discrete,
Ts = 5e-005 s.
powergui
A1
B1
C1
A2
B2
C2
+
_
 +
_ 
bridge rectifier
VA
VB
VC
VA1
VB1
VC1
VA2
VB2
VC2
autotransformer
speedpulses
Vector Control
v
+
-
Vab2
v
+
-
Vab1
z
1
Torque
step1
Speed
step1
Scope
L1
Tm
m
A
B
C
Induction Motor
30 HP / 415 V
i
+
-
Ii
g
A
B
C
+
-
IGBT based inverter
Speed
Iabc
C
N
A
B
C
415V 50Hz
<Rotor speed (wm)>
<Electromagnetic torque Te (N*m)>
 
Fig. 1 Simulink model of 12-pulse ac–dc converter based proposed harmonic mitigator fed VCIMD 
The number of turns required for and phase shift are calculated as follows. Consider phase “a” voltages as 
     (1) 
                                     (2) 
Assume the following set of voltages: 
, ,                            (3) 
Similarly 
, ,    (4) 
, ,    (5) 
 
Using above equations, and  can be calculated. These equations result in  and   for the 
desired phase shift in an autotransformer. The phase-shifted voltages for phase “a” are 
                     (6) 
                     (7) 
 
Thus, the autotransformer uses two auxiliary windings per phase. A phase-shifted voltage (e.g.  ) is obtained by 
Tapping a portion (0.0227) of line voltage  and Connecting one end of an approximate 0.138 times of line voltage 
(e.g.,  ) to this tap. 
 
 
       ISSN (Print)  : 2320 – 3765 
       ISSN (Online): 2278 – 8875 
 
International Journal of Advanced Research in  Electrical, 
Electronics and Instrumentation Engineering 
(An ISO 3297: 2007 Certified Organization) 
Vol. 2, Issue 9, September 2013 
 
Copyright to IJAREEIE                                                            www.ijareeie.com                                                                            4188          
 
 
B. Design Of the Proposed 24-Pulse Ac–Dc Converter: 
For achieving the 24-pulse operation, four sets of 3-phase voltages (phase shifted through an angle of +15
◦
) are 
produced. The number of turns required for achieving these phase shifts among different phase voltages is calculated as 
follows. 
Consider phase 'a' voltages as: 
    (8) 
    (9) 
    (10) 
    (11) 
 
Where, V is the rms value of phase voltage. Using above equations K1, K2, K3 and K4 can be calculated. These 
equations result in K1 =0.005706, K2 = 0.07041, K3 =0.0508 and K4 = 0.196375 for the desired phase shift in 
autotransformer. Simulink model of 24-pulse ac–dc converter based proposed harmonic mitigator fed VCIMD is shown 
in fig-2 
C
o
n
n
1
C
o
n
n
2
C
o
n
n
3
tuned fi lter
Discrete,
Ts = 5e-005 s.
powergui
speedpulses
Vector Control
v
+
-
Vab2
v
+
-
Vab1
z
1
Torque
step1Speed
step1
Scope
L2
Tm
m
A
B
C
Induction Motor
30 HP / 415 V
i
+
-
Ii
g
A
B
C
+
-
IGBT based inverter
Speed
Iabc
C
A1
B1
C1
A2
B2
C2
A3
B3
C3
A4
B4
C4
+
_
+ 
_ 
 +
 _
 + 
 _ 
BRIDGE RECTIFIER
VA
VB
VC
VA1
VB1
VC1
VA2
VB2
VC2
VA3
VB3
VC3
VA4
VB4
VC4
AUTO T/F
N
A
B
C
415V 50Hz
<Rotor speed (wm)>
<Electromagnetic torque Te (N*m)>
 
Fig. 2 Simulink model of 24-pulse ac–dc converter based proposed harmonic mitigator fed VCIMD 
A phase shifted voltage (e.g. Val) is obtained by tapping a portion (0.005706) of line voltage Vca and connecting one 
end of an approximately (0.07041) of line voltage (e.g. Vbc) to this tap. Thus the autotransformer can be designed with 
these known values of winding constants. 
 
       ISSN (Print)  : 2320 – 3765 
       ISSN (Online): 2278 – 8875 
 
International Journal of Advanced Research in  Electrical, 
Electronics and Instrumentation Engineering 
(An ISO 3297: 2007 Certified Organization) 
Vol. 2, Issue 9, September 2013 
 
Copyright to IJAREEIE                                                            www.ijareeie.com                                                                            4189          
 
III. VECTOR CONTROLLED INDUCTION MOTOR DRIVE 
Indirect vector controlling technique is very popular in industrial applications.Fig.3 shows the MATLAB diagram of 
an indirect vector controlled induction motor drive (VCIMD).The power circuit consists of a front-end diode rectifier 
and a PWM inverter with a dynamic brake in the DC link. A hysteresis-band current controller PWM is used. The 
speed control loop generates the torque component of current. 
 
The speed control range in indirect vector control can easily be extended from stand-still (Zero speed) to the field 
weakening region. In this case, closed loop flux control is needed. In the constant torque region, the flux is constant. 
However in the field-weakening region, the flux is programmed such that the inverter always operates in PWM 
mode. In the rotor flux oriented reference frame the reference vector ids (flux component of the stator current) is 
obtained. 
1
pulses
Phir
Te*
Iq*
iqs*
calculation
Phir* Id*
id*
Calculation
Teta
Id*
Iq*
Iabc*
dq to ABC
conversion
z
1
Phir
wm
Iq
Teta
Teta
Calculation
w
w*
Te*
Speed
controller
0.96
Phir*
Iabc
Iabc
Speed
Speed
IdPhir
Flux
Calculation
Iabc
Iabc*
Pulses
Current
Regulator
Iabc
Teta
Id
Iq
ABC to dq
conversion
1
speed
 
Fig. 3 MATLAB block diagram of VCIMD 
The closed loop PI speed controller compares the reference speed (ωr
*
) with motor speed (ωr) and generates the 
reference torque T
*
(after limiting it to a suitable value). The torque component of the stator current reference vector iqs 
is obtained from the output of the PI controller. These current components (ids
*
 and iqs
*
) are converted to stationary 
reference frame using rotor flux angle calculated as sum of the rotor angle and the value of slip angle. 
 
These currents (ids
*
, iqs
*
) in synchronously rotating frame are converted to stationary frame three phase currents (ias
*
, 
ibs
*
, ics
*
). These three phase reference currents (ias
*
, ibs
*
 and ics
*
)  along with the sensed motor currents (ias, ibs and ics) are 
fed to the PWM current controller which provides the gating signals to different switches of VSI to develop necessary 
voltages. These voltages are being fed to the motor to develop the necessary torque for running the motor at a given 
speed under given load conditions. 
IV.RESULTS 
The proposed autotransformer based harmonic mitigators along with the VCIMD are simulated to demonstrate the 
performance of the proposed converter systems. The THD of the ac mains current at full load is 30.10%, which 
decreases to 65.9% at light load and the power factor at full load is 0.933, which decreases to 0. 816 at light load (20% 
of full load). The supply current waveform at full load along with its harmonic spectrum of 6-pulse converter is shown 
in Fig. 5, and shows that the THD of ac mains current is 30.10%, these results show the need for improving the power 
quality at ac mains using some harmonic mitigators which can easily replace the existing 6-pulse converter. 
 
Dynamic response of 12-pulse converter based proposed harmonic mitigator fed VCIMD with load perturbation is 
shown in Fig. 4, these results shows the improvement of characteristics with respect to 6-pulse converter system in 
 
       ISSN (Print)  : 2320 – 3765 
       ISSN (Online): 2278 – 8875 
 
International Journal of Advanced Research in  Electrical, 
Electronics and Instrumentation Engineering 
(An ISO 3297: 2007 Certified Organization) 
Vol. 2, Issue 9, September 2013 
 
Copyright to IJAREEIE                                                            www.ijareeie.com                                                                            4190          
 
terms of THD and power factor. 
The supply current waveform at full load along with its harmonic spectrum of 12-pulse converter is shown in Fig. 6, 
and shows that the THD of ac mains current is 4.45%, and the power factor obtained is 0.988.  
 
 
Fig. 4 Dynamic response of 12-pulse ac–dc converter based proposed harmonic mitigator fed VCIMD with load 
perturbation. 
 
 
Fig. 5 AC mains current waveform along with its harmonic spectrum at full load in a six-pulse diode bridge 
rectifier-fed VCIMD. 
From these results that the proposed 12-pulse harmonic mitigator is able to perform satisfactorily on VCIMD with 
power factor always higher than 0.98 and THD of supply current less than 5%. 
 
 
       ISSN (Print)  : 2320 – 3765 
       ISSN (Online): 2278 – 8875 
 
International Journal of Advanced Research in  Electrical, 
Electronics and Instrumentation Engineering 
(An ISO 3297: 2007 Certified Organization) 
Vol. 2, Issue 9, September 2013 
 
Copyright to IJAREEIE                                                            www.ijareeie.com                                                                            4191          
 
 
 
Fig. 6 AC mains current waveform along with its harmonic spectrum at full load with 12-pulse ac–dc converter on 
ac side. 
 
 
Fig. 7 AC mains current waveform along with its harmonic spectrum at full load with 18-pulse ac–dc converter on ac 
side. 
 
 
Fig. 8 AC mains current waveform along with its harmonic spectrum at full load with 24-pulse ac–dc converter on 
ac side. 
 
 
 
 
 
       ISSN (Print)  : 2320 – 3765 
       ISSN (Online): 2278 – 8875 
 
International Journal of Advanced Research in  Electrical, 
Electronics and Instrumentation Engineering 
(An ISO 3297: 2007 Certified Organization) 
Vol. 2, Issue 9, September 2013 
 
Copyright to IJAREEIE                                                            www.ijareeie.com                                                                            4192          
 
Table-1comparison of Power Quality Indexes of A VCIMD Fed from Different Converters 
S.No. ZS Topology 
IS(A) 
 
THD of IS 
(%) 
Distortion 
Factor (DF) 
Displacement 
Factor (DPF) 
Power 
Factor(PF) 
DC Link 
Voltage (V) 
Full 
Load 
Light 
load 
(20%) 
Full 
Load 
Light 
load 
(20%) 
Full 
Load 
Light 
load 
(20%) 
Full 
Load 
Light 
load 
(20%) 
Full 
Load 
Light 
load 
(20%) 
Full 
Load 
Light 
load 
(20%) 
1 3% 6-pulse 43.31 10.1 30.9 65.9 0.955 0.835 0.977 0.977 0.933 0.816 545 557 
2 3% 12-pulse 42.54 8.84 4.42 8.10 0.999 0.997 0.988 0.947 0.988 0.944 545 563 
3 3% 18-pulse 41.60 8.29 3.25 4.60 0.999 0.999 0.983 0.998 0.982 0.998 544 559 
4 3% 24-pulse 40.45 7.92 1.12 2.21 0.999 0.999 0.980 0.999 0.992 0.999 540 560 
 
However, under light load condition, these power quality indexes start decreasing, which shows that the supply current 
(Is) is always less than the converter input current (Ic), thus, showing the effectiveness of the designed passive filter. 
The supply current waveform at full load along with its harmonic spectrum of 18-pulse converter is shown in Fig. 7, 
showing THD of ac mains current as 3.27% and the power factor obtained as 0.982. So that the proposed harmonic 
mitigator operates satisfactorily under varying load conditions, the load on VCIMD is varied.  
 
The supply current waveform at full load along with its harmonic spectrum of 24-pulse converter is shown in Fig. 8, 
showing THD of ac mains current as 1.12% and the power factor obtained as 0.992. So that the proposed harmonic 
mitigator operates satisfactorily under varying load conditions, the load on VCIMD is varied. Table-1 shows the 
comparative analysis of different power quality indexes of a VCIMD is fed from 6, 12, 18, 24-pulse converters and it 
shows the power quality improvement. 
From these results that the proposed 24-pulse converter based harmonic mitigator performs well under load variation 
on VCIMD with a near-unity power factor and THD of supply current always less than 5%. 
IV.CONCLUSION 
The proposed harmonic mitigators have been designed, modeled, and developed with variable frequency induction 
motor drives operating under varying load conditions. The observed performance of the proposed harmonic mitigators 
has the capability of these converters to improve the power quality indexes at ac Mains in terms of supply current THD, 
supply voltage THD, power factor and crest factor.  
 
Moreover, the12-pulse-based harmonic mitigator can be used for retrofit applications where load variation is always 
higher than 50 the proposed 24-pulse ac-dc converter results in almost unity power factor in the wide operating range 
of the drive. Thus the proposed ac-dc converter can easily replace the existing 6-pulse converters without much 
alteration in the existing system layout and equipments. 
 
REFERENCES 
[1]. P. Vas, Sensorless Vector and Direct Torque Control. Oxford, U.K.: 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, and I. J. Pitel, “Polyphase transformer arrangements with reduced kVA capacities for harmonic current   reduction in 
rectifier type     
[4]. Utility interface” IEEE Trans. Power Electron., vol. 11, no. 5, pp. 680–689, Sep. 1996.  
[5]. G. R. Kamath, B. Runyan, and R. Wood, “A compact autotransformer based 12-pulse rectifier circuit,” in Proc. 2001 IEEE   IECON, pp1344–
1349 
[6]. D. A. Paice, “Multipulse converter system,” U.S. Patent 4 876 634, Oct. 24, 1989.  
[7]. S. M. Peeran and C. W. P. Cascadden, “Applications, design, and specifications of harmonic filters for variable frequency drives,” IEEE Trans. 
Ind. Appl, vol. 31, no. 4, pp. 841–847, Jul. /Aug. 1995. 
[8]. G. J. Wakileh, Power System Harmonics, Fundamentals, Analysis and Filter Design. New York: Springer, 2001, ch. 5, pp.  105–135. 
 
 
 
 
 
       ISSN (Print)  : 2320 – 3765 
       ISSN (Online): 2278 – 8875 
 
International Journal of Advanced Research in  Electrical, 
Electronics and Instrumentation Engineering 
(An ISO 3297: 2007 Certified Organization) 
Vol. 2, Issue 9, September 2013 
 
Copyright to IJAREEIE                                                            www.ijareeie.com                                                                            4193          
 
BIOGRAPHY 
 
 
Ms. M. Karthika obtained her Bachelor of Technology in Electrical and Electronics Engineering 
from V.R.S &Y.R.N College of Engineering and Technology, Chirala, Prakasam Dist., Andhra 
Pradesh, India. She completed her Master of Technology in Power Electronics from Shri Vishnu 
Engineering College for Women, Bhimavaram, West Godavari Dist., Andhra Pradesh, India. Her 
area of interest includes Power Electronics & Drives, Power Systems, Power Quality and Control 
Systems. She has 2 years of teaching experience. She is currently working as Assistant Professor in 
Electrical and Electronics Engineering Department at Vishnu institute of Technology, Bhimavaram, 
Andhra Pradesh, India. 
 
 
 
Mrs. I.V.V. Vijetha obtained her Bachelor of Technology in Electrical and Electronics 
Engineering from NOVA College of Engineering and Technology, Jangareddygudem, West 
Godavari Dist., Andhra Pradesh, India. She completed her Master of Technology in Power 
Electronics in NOVA College of Engineering and Technology, Andhra Pradesh, India. Her area of 
interest includes Power Electronics, Power Systems and Machines and FACTS. She has 6 years of 
teaching experience. She is currently working as Assistant Professor in Electrical and Electronics 
Engineering Department at Vishnu institute of Technology, Bhimavaram, Andhra Pradesh, India. 
 


COMPARATIVE ANALYSIS OF MULTIPULSE AC-DC CONVERTERS IN VCIMD

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COMPARATIVE ANALYSIS OF MULTIPULSE AC-DC CONVERTERS IN VCIMD

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