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fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TIA.2018.2851566, IEEE
Transactions on Industry Applications

Power Quality Enhancement Using Current Injection Technique in a Zigzag

Configured Autotransformer Based 12-Pulse Rectifier
R Kalpana, MIEEE Khimavath Sai Chethana Saravana Prakash P, SIEEE Bhim Singh, FIEEE
Department of Electrical Department of Electrical Department of Electrical Department of Electrical
and Electronics and Electronics and Electronics Engineering
Engineering Engineering Engineering IIT Delhi, India
NITK Surathkal, India NITK Surathkal, India NITK Surathkal, India bsingh@ee.iitd.ac.in
kalpana@nitk.edu.in ksaichethana@gmail.com saravanaprakshpv@ieee.org

Abstract–This paper proposes a DC side circuit configuration failure of equipment’s. Several methods were adopted to
that improves the harmonic suppression ability of a 12-pulse mitigate the aforementioned problems.
diode bridge rectifier (DBR) using a zigzag configured Normally in the existing installations filters are preferred
autotransformer. The DC side circuit uses a 1-phase DBR along [3], but in some cases design of filters may not be a feasible
with interphase transformer which generates the required
solution as the rating of the filter is equivalent to rating of the
circulating current thereby modifies the DC currents at the DBR
output, in turn shapes the input line current near to a sine wave. system. So, in new installation it is recommended to transform
The proposed 1-phase DBR is connected in parallel with the load the converter arrangement at the design stage, one such
which enables to reuse the harmonic energy thus improving the transformation is, use of passive wave shaping of input AC
energy conversion efficiency. The zigzag configured line currents [4]. These, passive wave shaping method gained
autotransformer used for 12-pulse DBR possesses the inbuilt its importance as it is simple in construction and it is the most
ability to hinder the zero sequence components which expels the economical way to address the power quality issues. This
need of zero sequence blocking transformer. The proposed technique uses the magnetics for power quality improvement
configuration is analyzed, simulated in MATLAB Simulink and and the resulting system is called multipulse converter (MPC)
the simulation results are presented, which confirms the [5].
reduction of THD in the input line current and thereby
improving power quality under large load variations. Further,
Multiple AC-DC converters are connected in such a way that
the viability of the proposed configuration is verified by harmonics generated by one converter can be cancelled by the
experimental results which confirms the suitability of the other converter [6] and the order of harmonics eliminated in
proposed configuration in industrial applications. the input AC source depends on the number of converters
used. The concept involved in MPC is to mitigate the
Index Terms–DC side circuit configuration, diode bridge harmonics by increasing the pulse number which is achieved
rectifier, interphase transformer, multipulse converter, power by increasing the number of converters. Phase shifting
factor, power quality, zigzag configured autotransformer. transformer is the essential component in MPC and provides a
technique for the cancellation of different harmonic orders
I. INTRODUCTION like (6k±1), (12k±1), (24k±1) and so on where k=1, 2, 3…
Phase shifting transformers may have combination of
Development in power electronic equipments led the transformer windings like star, delta, zigzag, fork, polygon
converters to be an integral part of industrial drives, power etc., [7]. Moreover, MPC can reduce the magnitude of higher
supplies, electric traction systems and automobile control order harmonics besides mitigating the lower order harmonics
equipment’s etc... With growing technology most of the [8]. Furthermore, MPCs are widely employed in high power
applications require DC power supply for its operation, applications due to various advantages like reduction in input
furthermore some applications need DC power supply at its AC line current harmonics, reduction in DC output voltage
intermediate stages, as in AC drives. Thus, among the ripple, minimal or no control is required as diodes are used,
varieties of power converters, AC-DC converters gained its high efficiency with reduced magnetic ratings [9], [10]. But
importance. The primary application of AC-DC converters is higher pulse number makes the system configuration more
to derive DC power from an AC supply [1]. These AC-DC complex with increased kVA rating of transformer. Because
converters uses solid state switches to control AC power and of the aforementioned reasons 12-pulses diode bridge rectifier
feed this controlled power to electrical loads such as lightning (DBR) is considered as an effective and economical way of
devices with electronic ballasts, controlled heating elements, improving the harmonic reduction ability and hence used in
battery charges, computer power supplies, adjustable speed most of the industrial applications like electric traction,
drives, high voltage DC and so on. These converters draw aircraft [11], variable frequency drives [12] and electric
non-sinusoidal currents from the AC mains and results in high furnace.
%THD, poor power factor (PF), distortion in supply voltage, A 12-pulse DBR can effectively eliminate (6k±1)
maloperation of protection systems, premature ageing of harmonics in the input AC line current [13], but it possess
equipments causing poor power quality [2] leading to severe (12k±1) (where k=1, 2,..) harmonics and other higher order
problems in case of sensitive loads and sometimes even the harmonics with %THD in AC input line current as 15%
without any additional equipment connected at the front-end,

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which deteriorates the performance of the devices in case of

sensitive loads. Though increase in pulse number by
employing multiple converters reduces %THD, it is not a
feasible solution to bring %THD to the acceptable level
because of size, cost, circuit complexity, kVA rating and
number of components. Therefore, researchers carried several
studies over the past years and emerged with several methods
to reduce the %THD in the input AC line current of a 12-
pulse DBR to an acceptable range. Various methods based on
pulse multiplication technique came into existence. Pulse
multiplication method improves power quality at both input
and output side of a AC-DC converter [14], [15]. This method
usually uses an interphase reactor (IPR) [16] with a secondary Fig. 1. Schematic of the proposed zigzag autotransformer based 12-pulse
circuit which enables to inject the desired current that can converter with a DC side circuit configuration.
shape the input AC line current near to a sine wave. Further,
many techniques came into practice for reducing the of ±15˚with respect to supply voltage. The output of this
harmonics which includes DC side ripple re-injection zigzag configured autotransformer is given as an input to two
technique [17], pulse doubling method [18], active IPR with 3-phase DBR units. The positive output terminals of the two
auxiliary circuits [19], IPR with a secondary circuit which 3-phase DBR units are connected to IPT, and negative
acts as a low kVA pulse width modulated (PWM) current terminals are connected together, to the negative terminal of
source to shape the input line current [20], DC side current load as shown in Fig. 1. The primary side of the IPT has a
injection [21], harmonic reduction using passive devices [22] center tap which is connected to positive terminal of the load.
and active IPR with auxiliary circuit consisting of energy The secondary of the IPT enables to connect the proposed
storage element [23]. All these pulse multiplication methods current injection circuit at the DC side of a 12-pulse DBR;
improve harmonic suppression ability in a most economical this circuit with optimally designed IPT injects the required
way by reducing design complexity and kVA rating of an current that shapes the output current of two 3-phase DBR
autotransformer but possess disadvantages like magnitude of units which in turn modifies the output currents of zigzag
higher order harmonics gets doubled. configured autotransformer, thus finally shapes the input AC
In addition, there are some active front-end harmonic line current near to a sine wave thereby reducing the %THD.
rejection techniques like active power filter [24], active PFC The proposed circuit at secondary side of IPT uses a 1-phase
[25] and Vienna rectifier [26] which can enhance the power DBR. The output terminals of this 1-phase DBR are
quality of MPC. However, these methods have limitations like connected in parallel with the load such that the harmonic
complex control strategies, computational complexity and power drawn is again being fed back to the system thus
accuracy in measuring the control variables which results in reducing the power losses and thereby effectively increasing
more engineer effort. Even without IPR, the harmonic the energy conversion efficiency [23].
reduction in the input line current can be achieved by
incorporating the PWM circuits at the output of MPC. But III. THEORETICAL ANALYSIS AND DESIGN OF THE PROPOSED
these techniques are also requires complex control structure TOPOLOGY
with accurate sensing effort [27], [28].
Furthermore, zero sequence blocking transformers (ZSBT) The following considerations are made for the theoretical
are employed to assure the independent operation of the two analysis: the diodes are ideal, leakage inductance and
DBR units [29] whereas, the proposed method uses zigzag resistance of the transformer are negligible, balanced 3-phase
configured autotransformer that hinders the zero sequence supply with negligible source inductance and ripple free load
components and hence expelled the need of ZSBT thereby current.
reducing the overall magnetic rating. This paper also presents
a simple DC side circuit configuration for a 12-pulse zigzag A. Analysis of Zigzag Configured Autotransformer
configured autotransformer based DBR. The design mainly
deals in determining the optimal turns ratio ‘n’ of interphase The 3-phase supply voltages are given by,
transformer (IPT) at which %THD is minimum and analyzing vR = vm sin (ω t ) (1)
the power quality indices of the proposed configuration for
 2π 
wide load variations. vY vm sin  ω t − 
= (2)
 3 
II. PROPOSED SYSTEM TOPOLOGY
 2π 
vB = v m sin  ω t +  (3)
The proposed zigzag based 12-pulse DBR with a DC side  3 
circuit configuration is shown in Fig. 1. It consists of a where vm is the peak value of phase voltage and line to line
3-phase AC supply connected to a zigzag configured auto voltages of 3-phase supply system are given by,
transformer to provide a multiphase supply with a phase shift

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(a) (b) (a) (b)

Fig. 2. Schematic of zigzag configured autotransformer (a) Winding Fig. 3. Schematic of the IPT (a) Winding configuration. (b) DC side circuit
configuration. (b) Phasor diagram with phase shifted voltages. configuration.
The output voltages of the two 3-phase DBR units are
obtained by Fourier analysis and the output voltages are given
 π
vRY = 3 vm sin  ω t +  (4) as,
 6
 π 
 kπ  
( )
3 2  2
Vdc1 = 3 − 1 vml 1 −  cos   cos  ω t −  (14)
 π π  k=6,12,18.... k − 1  6  
2
12 
vYB = 3 vm sin  ω t −  (5)
 2   kπ   π 
( )
3 2  2
Vdc2 = 3 − 1 vml 1 −  cos   cos  ω t +  (15)
π  k 2
− 1  6   12 
 5π  k=6,12,18...

vBR = 3 vm sin  ω t +  (6) where Vdc1 and Vdc2 are the output voltages of DBR-1 and
 6 
DBR-2 respectively and vml is the peak value of line to line
The required multiphase supply for the operation of two voltage.
3-phase DBR units is provided by zigzag configured Average output load voltage is given by,
autotransformer windings as shown in Fig. 2(a). The two π
DBR units are phase shifted by 30o, by providing a phase shift 64  π (16)
VL =  3 v m sin  ω t +  d(ωt)
of -15o to DBR-1 with respect to supply voltage and a phase ππ  12 
shift of +15o to DBR-2 with respect to supply voltage. The 12

phasor diagram shown in Fig. 2(b) depicts the two sets of The magnetic rating of the zigzag configured autotransformer
phase shifted voltages that are built for the operation of two is calculated as follows,
1
3-phase DBR units. From the phasor diagram, the phase Zigzag transformer kVA rating =  v1 i1 + v2 i 2 + v3 i3 +.....103 (17)
shifted voltages of R-phase are given as 2
where v1, v2, v3…. are the RMS voltages across each winding
vR1 = m1 (vRY − vBR ) + m2 vYB (7) and i1, i2, i3 …. are the RMS currents through the each
vR2 = m1 (vRY − vBR ) − m2 vYB (8) winding. The magnetic rating of the proposed zigzag
where vRY, vYB, vBR are the line to line voltages of 3-phase configured autotransformer is calculated as follows,
supply, by solving (7) and (8) the constants m1 and m2 can be 1 (18)
Zigzag transformer kVA rating = {3[2(vRY i1 + vR1 i R1 )]}
obtained as m1=0.5773, m2=0.2679. During the design stage 2
of zigzag autotransformer number of turns for each winding is Thus, the kVA rating of the zigzag configured
determined based on these m1 and m2 values. By auto transformer is 26.6% of the rated load.
incorporating m1 and m2 values in (7) and (8) we get,
 π B. IPT and DC Side Circuit Configuration
( 
)
vR1 = 3 − 1 v m sin  ω t − 
12 
(9)
Fig. 3(a) shows the winding configuration of IPT and
 π
(
vR2 = 3 − 1 vm sin  ω t + 

)
12 
(10)
Fig. 3(b) shows IPT with DC circuit configuration. IPT
primary has a center tap which is connected to load and the
Similarly, the phase shifted equations of the other two phases other two terminals are connected to the outputs of the two
can also be obtained. In Fig. 2(a) applying KCL at the input 3-phase DBR units as shown in Fig. 3(b). Hence, the
phase R, the current iR is given by, instantaneous difference of voltages of the two DBR units
appears across the primary of IPT and it is calculated by (20).
iR =i R1 + i R2 + i1 (11)
and the winding current can be obtained by applying Ampere
vp =Vdc1 − Vdc2 (19)
   kπ   kπ  
turns balance law as follows,
m1i1 = m2 (iR1 + i R2 ) (12)
vp =
3 2
π
( 
)
3 − 1 vml  
 
−4
 
k=6,12,18.... k − 1
2
(20)
cos   sin kωt sin   
6 12

i1 = ( 2 3−3) ( i R1 + i R 2 ) (13) Instantaneous difference of currents of the two DBR units

flows through the primary winding of IPT and it is given as
Similarly, other phase currents can be determined. The phase
shifted voltages acts as an input to the two 3-phase DBR i p = idc1 − idc2 (21)
units.

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Thus, the value of DBR output current, idc1 during positive

half cycle is calculated from (28).
(ii) During negative half cycle
Fig. 4(b) shows the equivalent circuit of IPT with current
injection circuit during negative half cycle. The diodes D1 and
D4 gets reverse biased and diodes D2 and D3 gets forward
(a) (b) biased and conducts for the negative half cycle thereby
Fig. 4. Operation of the 1-phase DBR (a) Equivalent circuit during positive resulting in current circulation. Considering the current
half cycle. (b) Equivalent circuit during negative half cycle. flowing through the secondary of IPT, is2 is equals to iDBR and
The voltage is buildup on the secondary side of IPT by DBR-I current tends to zero during this cycle. By Ampere
Faradays laws of electromagnetic induction, which enables to turns balance law,
connect a current injection circuit for wave shaping of the 1
2
N p i p = Ns is2 (29)
input AC line current. The load current can be obtained by
applying KCL at load terminal in Fig. 3(b) and it is given by, From (21) and (29),
1
IL = idc1 + idc2 (22) idc2 
is2 = (30)
2n
The equivalent magnetic rating of the IPT is calculated as
By applying KCL at load terminal
follows,
1 idc 2 + is 2 = IL (31)
IPT kVA rating =  primary VA +secondary VA 103 (23)
2 From (30) and (31),
1 3
IPT kVA rating = vp i p + vs is 
2  10 (24) idc = 
2
2n 
 IL (32)
 2n +1 
where vp and ip are the RMS value of instantaneous voltage
and current differences of the two DBR units and vs and is are Thus, the value of negative half cycle DBR output current idc2
the RMS value of voltage and current at the secondary side of is calculated from (32).
IPT. Thus, the kVA rating of the IPT is obtained as 3.7% of D. Wave Shaping of Input AC Line Current
the rated load by considering the simulation values of winding
voltages and currents. The 1-phase DBR connected at secondary of the optimally
designed IPT injects the required circulating currents into the
C. Operation of DC Current Injection Circuit primary winding of IPT which helps in shaping the input AC
line current to a sine wave.
The secondary output current of the IPT is a symmetrical
AC wave with a period of 30o. This output is applied as an
input to the 1-phase DBR which acts as a current injection
circuit and injects the required current into the system. The
operation of 1-phase DBR can be explained by considering
positive and negative half cycles of the conduction period.
(i) During positive half cycle
Fig. 4(a) shows the equivalent circuit of IPT with current
injection circuit during positive half cycle. The diodes D1 and
D4 are forward biased and conducts for the positive half cycle
thereby current flows through the secondary of IPT, i.e., iDBR
is equal to is1. In addition, during this operation DBR- II
current tends to zero. By Ampere turns balance law,
1
2
N p i p = Ns is1 (25)
From (21) and (25),
1
is1 = idc1 (26)
2n
By applying KCL at the load terminal
idc1 + is1 = IL (27)
From (26) and (27),
Fig. 5. Theoretical waveforms resulting in wave shaping of input AC line
 
idc1 =  2n  IL (28)
current (a) Injected current of IPT. (b) Output currents of 3-phase DBR.
 2n + 1 
(c) Input currents of 3-phase DBR. (d) Source current. (e) Output voltages
of 3-phase DBR. (f) Load voltage.

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TABLE I SIMULATED RESULTS ON VARIATION IN THE IPT TURNS RATIO FOR AC line current is 3.12%. Further, the PF is maintained near
VARIOUS INPUT POWER QUALITY INDICES
to unity, thus resulting in improvement of power quality
Turns Average Average parameters. Fig. 6 shows the variation of THD in the input
ratio load load
of IPT current, voltage, %THD DPF DF PF current and PF with respect to IPT turns ratio. Therefore, an
(n) IL (A) VL (V) IPT with turns ratio, n=14 is optimally determined for the
2 10.70 556.0 11.36 0.9964 0.9936 0.9902 proposed system configuration that results in reduced THD of
4 10.70 556.0 11.34 0.9964 0.9936 0.9902 the input AC line current.
6 10.70 556.0 11.31 0.9964 0.9937 0.9904
8 10.66 557.0 10.64 0.9964 0.9944 0.9909 IV. RESULTS AND DISCUSSION
10 10.60 557.5 7.520 0.9958 0.9972 0.9930
12 10.57 558.0 4.270 0.9944 0.9991 0.9935 A. Discussion on Simulation Results
14 10.57 558.0 3.120 0.9945 0.9995 0.9939
The proposed DC side circuit configuration is designed and
15 10.58 559.0 3.260 0.9934 0.9995 0.9929
simulated for a 6 kW system with an input voltage of 400 V,
16 10.58 559.0 3.590 0.9932 0.9994 0.9926
resulting in an output voltage of 559 V. The DC side circuit is
18 10.60 560.0 4.410 0.9930 0.9991 0.9923
modeled as a 1-phase DBR which is connected at the
20 10.60 561.0 4.990 0.9929 0.9988 0.9917 secondary of the IPT with optimally designed values given in
22 10.65 561.8 5.540 0.9926 0.9985 0.9911 Appendix.

Fig. 6. Variation of THD and PF with respect to turns ratio ‘n’.

Fig. 5 explains the theoretical wave shaping of source

current. Fig. 5(a) represents the waveform of injected
circulating current is. This injected current modifies the shape
of two 3-phase DBR output currents resulting a unipolar
characteristics of the waveforms idc1, idc2 which are
represented in the Fig. 5 (b). The modified output currents of
two 3-phase DBR units idc1, idc2 modifies the nature of the
DBR input currents iR1, iR2 as shown in Fig. 5(c). Finally,
these DBR input currents iR1, iR2 modifies the input AC line to
a near sine wave. It can be observed from Fig. 5(d) that after Fig. 7. Waveforms of currents without IPT and 1-phase DBR (a) Output
wave shaping, the source current has 24 pulses thus the currents of 3-phase DBR units idc1, idc2.(b) Input DBR currents of 3-phase
characteristic of the pulse doubling is achieved by the DBR units iR1,iR2. (c) Winding current, i1. (d) Source current, iR.
proposed current injection technique which leads to the
reduction in the input current THD. Fig. 5(e) and (f) shows
the output voltages of 3-phase DBR units and load voltage
respectively.

E. Determination of Optimal Turns Ratio of IPT

The optimal value of IPT turns ratio is calculated using

simulated values. For an appropriate turns ratio of IPT, the
voltage developed at the secondary of IPT makes the 1-phase
DBR to operate and inject the circulating currents which are
required for shaping of the input AC line current nearly sine
wave. The variation in IPT turns ratio for different power
quality indices are given in Table I. From Table I, it is evident Fig. 8. Harmonic spectrum of R-phase input line current without IPT and
1-phase DBR.
that when IPT turns ratio, n equals to 14, the THD of input

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(a) (b)
Fig. 11. Simulation waveform and harmonic spectrum with IPT and 1-phase
DBR (a) R-phase input line current. (b) Input line voltage.
The harmonic spectrum shows that %THD of the input line
current as 10.60% which creates power quality issues in case
of sensitive loads. For sensitive loads, the limits on the
%THD of the input line current is more stringently followed
and hence the proposed configuration has been developed for
such sensitive loads.
The simulation results presented in Fig. 9 shows the wave
shaping of input line current for the proposed circuit
configuration with IPT and 1-phase DBR. The operation of
1-phase DBR results in sinusoidal shaping of the input AC
line current. Fig. 9 (a) shows the secondary IPT current which
is responsible for injecting the required current, that circulates
Fig. 9. Simulation waveforms resulting in wave shaping of input AC line in the primary of IPT. This current modifies the output
current with IPT and 1-phase DBR (a) Injected current. (b) Output currents currents of two 3-phase DBR units idc1, idc2 as shown in Fig.
of 3-phase DBR units. (c) Input currents of 3-phase DBR units. (d) Winding 9(b), though the characteristics of waveform gets altered, the
current, i1. (e) Source current, iR. mean value of currents idc1, idc2 remains unchanged. Further,
idc1 and idc2 modifies iR1 and iR2 currents as shown in Fig. 9
(c). Fig. 9(d) shows the winding current of R-phase of a
zigzag configured autotransformer. By adding up the currents
iR1, iR2, i1 the input AC line current is shaped near to a sine
wave as shown in Fig. 9(e). Fig. 10 shows the simulation
results of load voltage and load current. Fig. 11(a) represents
the harmonic spectrum of the input AC line current (R-phase)
from which it can be inferred that (6k±1), (12k±1) harmonics
are mitigated but (24k±1) where k=1, 2,.. harmonics and all
other higher order harmonics are present with reduced
Fig. 10. Simulation waveforms of (a) Output load voltage, VL. (b) Output magnitudes which confirms the pulse doubling operation.
load current, IL. From the harmonic spectrum it is evident that the %THD of
input AC line current is 3.12%. Fig. 11(b) represents the
The simulation results presented in Fig. 7 shows the harmonic spectrum of input AC line to line voltage from
performance of the proposed circuit configuration without which it can be inferred that %THD is 3.82%. Thus, the
IPT and 1-phase DBR. Fig. 7(a) represents the output current proposed system with IPT and 1-phase DBR provides better
waveforms of the two 3-phase DBR units idc1, idc2 that are operation with sensitive loads when compared to system
unidirectional in nature. Fig. 7(b) represents the current without IPT and 1-phase DBR.
waveforms iR1, iR2 at the output side of a zigzag
autotransformer which is bidirectional in nature. The B. Discussion on Harmonic Reduction Capability for a Wide
waveforms iR1, iR2 are phase shifted by 15o with respect to Variation in Load
supply voltage which are required for the operation of two
3-phase DBR units connected in parallel. Fig. 7(c) represents The turns ratio of IPT is kept constant at the designed
the waveform of current through the winding of the zigzag optimal value and the system is analyzed for a wide variation
autotransformer, i1. The vector sum of currents iR1, iR2 and i1 in load. The variation in %THD of input AC line current with
results in the R-phase supply current, iR is shown in Fig. 7(d). the load variation is presented in Table II. From Table II it is
Fig. 8 shows the harmonic spectrum of input supply current of observed that at 20% of load, the %THD of the input AC line
R-phase from which it can be inferred that (6k ± 1) harmonics current is 4.82% and at 100% of load, %THD of input AC
are mitigated but (12k±1), (24k±1) where k=1, 2... harmonics line current is 3.12%. In both the cases %THD of input
and all other higher order harmonics are present.

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TABLE II SIMULATION RESULTS OF INPUT AC LINE CURRENT, VOLTAGE, current. Fig. 13(c) represents the winding current in R-phase
%THD AND PF FOR A WIDE VARIATIONS IN LOAD of a zigzag configured autotransformer. Fig. 13(d) represents
% IL VL %
Load (A) (V) THDi
PF the phase shifted currents of zigzag configured
20 2.138 562.7 4.82 0.992 autotransformer iR1, iR2. Fig. 13(e) shows the output load
40 4.257 561.5 4.35 0.993 current and the R-phase input line current of the proposed
60 6.371 560.3 3.84 0.994 system. Fig. 13(f) and (g) represents the harmonic spectrum
80 8.871 558.8 3.36 0.996 of input current and voltage respectively. Fig. 13(h) shows the
100 10.56 558.9 3.12 0.997
input voltage and current of the R-phase of a 3-phase supply
system which is in-phase with each other. The experimental
results of the proposed system follows similar trends as that
of simulation results.

Fig. 12. Variation of load voltage with percentage change in load.

(a)
AC line current is < 5%, hence the proposed circuit
configuration is suitable for sensitive loads wherein the
allowable limits on input line current THD are stringent.
Furthermore, it is evident that variation in %THD is very low
i.e, 1.7% for a wide variation in load. This reduction in
%THD even under load variation is because, when load
changes the voltage across the primary of IPT also changes
which in turn induces corresponding voltage across secondary
of IPT by Faradays laws of electromagnetic induction.
Thereby, the 1-phase DBR circuit acts accordingly and
induces appropriate circulating current, thus modifies the
(b)
input line current near to a sine wave. Fig. 12 shows the
variation in load voltage VL corresponding to percentage
change in load, it can be inferred from the graph that the
percentage change in output voltage is 0.679% hence voltage
regulation is very low. Therefore, the optimally designed IPT
with DC side current injection circuit configuration can
withstand a wide variation in load by generating an
appropriate circulating current which can shape the input AC
line current near to a sine wave.

C. Discussion on Experimental Results

(c)
The laboratory prototype of the proposed configuration has
been developed and system behavior is examined by
conducting extensive tests. Tests are conducted at a reduced
voltage and results are recorded by a FLUKE 434-II power
quality analyzer. The experiment is performed at a reduced
input voltage of 150 V (line to line), 50 Hz, resulting in
output load voltage and current of 210 V and 4 A
respectively. Fig. 13 shows the test results of the proposed
configuration. Fig. 13(a) represents IPT primary voltage vp
and source current iR. Fig. 13(b) shows the IPT primary
current ip which is responsible for wave shaping of input AC
(d)

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This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TIA.2018.2851566, IEEE
Transactions on Industry Applications

(e)
(g)

(f) (h)
Fig. 13. Test results of (a) Voltage across IPT Primary winding, vp and source current, iR. (b) Current through primary winding of IPT, ip. (c) Winding current
through zigzag transformer, i1. (d) Phase shifted output currents of zigzag configured autotransformer. (e) Current through the load, IL and source current, iR.
(f) Harmonic spectrum of input ac line current. (g) Harmonic spectrum of input source voltage. (h) Source voltage and source current.

TABLE III COMPARISON OF THE PROPOSED CONFIGURATION WITH THE EXISTING HIGHER PULSE CONFIGURATION

Number of Magnetic ratings Total kVA

System % input Approxima Complexity of
rating of
Reference configurati current te total cost autotransformer
Diodes Switches Transformer IPT Total the system
on THD ($)* configuration
(kVA)
[15] 12-pulse 12 - 130.9% 1.66% 132.6% 9.40% 10.00 620.2 Low
(isolated)
[30] 18-pulse 21 3 18.00% - 18.00% 8.03% 2.400 84.10 Medium
[31] 18-pulse 18 - 55.00% - 55.00% 5.40% 30.77 293.1 High
[33] 24-pulse 24 16 27.70% - 27.70% 3.12% 12.00 129.5 High
[34] 36-pulse 21 - 130.0% 1.24% 131.2% 1.36% 5.000 613.8 High
[35] 40-pulse 42 - 61.29% 0.54% 61.73% 2.55% 5.000 288.7 High
Proposed 12-pulse 16 - 26.66% 3.70% 30.30% 3.12% 6.000 141.7 Low

TABLE IV COST AND SIZE COMPARISON OF THE PROPOSED CONFIGURATION WITH THE EXISTING 12-PULSE CONFIGURATIONS

Part Model name Unit cost ($)** [15] [19] [21] [22] Proposed
Diode 750KBPC1010W 2.23 12 12 16 16 16
MOSFET FCP650N80Z 3.11 - 5 1 - -
Driver TLP250 2.00 - 2 1 - -
Transformer kVA - - 7956 2118 1734 2376 1818
rating (VA)
Transformer kVA - - 132.6% 35.30% 28.90% 39.60% 30.3%
rating (in terms of
load)
Total cost ($)** 646.9 211.4 178.0 220.0 177.0

* The total cost estimation of the transformer is done by following the thumb rule. Cost of the transformer is estimated as 5 times the kVA rating of
transformer and for comparison purpose kVA rating of all the transformers are taken for a common load of 6 kW.
** The prices may vary based on market growth.

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This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TIA.2018.2851566, IEEE
Transactions on Industry Applications

D. Discussion on Comparison of the Proposed Configuration the associated driver circuit. Moreover, the proposed
with the Existing Configurations configuration provides various added advantages when
compared to [21] such as better voltage regulation,
The following considerations are made for the calculation satisfactory performance even under wide load variation,
and comparison: increased energy conversion efficiency since the absorbed
1. The VA ratings of the transformers are calculated on a power is fed back into the system, no complex control, less
common load of 6 kW, for which the proposed system is computational complexity and simple design. Hence from the
designed. above comparison, it can be concluded that the proposed
2. All the diodes and MOSFETs have same part number. system results as a better solution for improving the
performance of the 12-pulse converter configuration.
Table III presents a comparison of the proposed
configuration with conventional 12-pulse converter [15], 18-
The proposed configuration provides the following
pulse converter [30], 18-pulse converter [31], 24-pulse
features:
converter [33], 36-pulse converter [34], and 40-pulse
converter [35]. From Table III, it is evident that as the pulse
1. The proposed 12-pulse DBR uses a zigzag configured
number increases, the number of components used increases
autotransformer which has the inbuilt ability to hinder the
and kVA rating also increases. In Table III though the
zero sequence components thus the need for ZSBT is
proposed configuration cost is higher than [30] and [33], it is
expelled.
the approximate estimation by considering only magnetics of
2. The proposed system acts as a normal 12-pulse DBR
the circuit. Moreover, [30] requires three 3-phase DBR units
without any secondary side circuit whereas, with the 1-
and [33] employs four 3-phase DBR units and sixteen IGBTs
phase DBR at the secondary of IPT, the input line current
thus increases complexity in design. All these factors
hold 24-pulses thus reducing the input line current THD.
aggregate and results in increased size and cost of the entire
3. The proposed configuration offers a very low voltage
setup in case of [30] and [33]. But proposed configuration
regulation of 0.679%, thus maintaining nearly a constant
requires only two 3-phase DBR units. Further, when
output voltage under load variations.
compared to [15], [31] and [32], the proposed configuration
4. Even for a wide variation of load, the proposed system
provides better performance in all aspects and it is
provides satisfactory result on the input power quality
economical also. It is evident from the comparison of the
parameters.
proposed configuration with [34] and [35] that, the %THD is
5. Since the output of the 1-phase DBR is connected to the
less in case of [34] and [35] but variation in %THD of the
load, the harmonic power absorbed is reused by the
proposed system is small. Moreover, the total cost of [34] and
system thus improving the energy conversion efficiency
[35] is higher than the proposed system and hence [34] and
and reduced losses.
[35] doesn’t offer an economically feasible solution.
Furthermore, the proposed configuration requires less
V. CONCLUSION
components when compared to [36], though it incorporates
only two diodes at the DC side, but the peak inverse voltage
A DC side circuit using 1-phase DBR along with optimally
(PIV) rating of the diode is twice the secondary voltage of
designed IPT is presented in this paper. The proposes DC
IPT. Whereas the proposed system uses four diodes and
circuit improves the harmonic reduction capability of a zigzag
hence the PIV rating of the diode is brought down to the
configured autotransformer based 12-pulse DBR and thereby
secondary voltage of IPT. In addition, the proposed system
improving power quality indices. Moreover, the output of DC
offers less %THD when compared to [36]. From the above
side current injection circuit is connected to the load thereby
discussion, it can be summarized that the proposed
the harmonic energy absorbed is reutilized by the system thus
configuration is able to provide effective performance similar
improving the energy conversion efficiency. The magnetic
to the higher pulse systems with reduced number of
rating of the proposed system is only 30.3% of the load rating
components, less complexity in design and simple injection
thereby reduces the space and volume required by the system.
circuit, thus resulting in an economical solution.
The need of ZSBT has been eliminated by the proposed
Table IV presents the detailed cost analysis of the proposed
zigzag transformer-based system. Also, the proposed system
system with some of the available 12-pulse DBR system.
works satisfactorily even under wide load variation and
From Table IV, it is evident that transformer provides major
maintains pulse doubling for the optimally designed value of
contribution to the total cost and size of the system. In spite of
IPT turns ratio. The experimental setup of the proposed
[21], [22] and the proposed configuration uses same number
configuration has been developed in the laboratory and the
of diodes, [21] requires an active switch and a driver circuit
system behavior was examined for a wide load variation. The
which increases the design complexity and [22] requires
tests results have affirmed the similar trend in theoretical and
higher kVA rating autotransformer which increases the cost of
simulation results which confirms the suitability of the
the system. From Table IV it is evident that the proposed
proposed system for industrial applications.
configuration is economical and possess less kVA rating
when compared to [15], [19] and [22]. Even though, the kVA
rating of the proposed configuration is slightly higher than
[21], the total cost is less due the absence of active switch and

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This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TIA.2018.2851566, IEEE
Transactions on Industry Applications

APPENDIX Multiplication," in 2007 IEEE International Symposium on Industrial

Electronics, Vigo, 2007, pp. 889-894.
Supply voltage – 400 V (L-L); Source inductance - 1.5 mH; DC load – 6 kW [15] B. Singh, S. Gairola, A. Chandra and K. Al-Haddad, "Power Quality
Zigzag Improvements in Isolated Twelve-Pulse AC-DC Converters Using
Transformer details IPT Delta/Double-Polygon Transformer," in 2007 IEEE Power Electronics
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Flux density 0.8 T 0.8 T Specialists Conference, Orlando, FL, 2007, pp. 2848-2853.
[16] S. Yang, F. Meng and W. Yang, "Optimum Design of Interphase Reactor
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75 mm Harmonic Reduction in Hvdc Converters By Direct Ripple Reinjection,"
I - laminations (l x w) 171.4 mm x 50.8 mm 100 mm x in Sixth International Conference on AC and DC Power Transmission,
25 mm London, UK, 1996, pp. 197-201.
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delta/polygon-connected transformer-based 36-pulse ac-dc converter for
Winding leakage 0.02 p.u 0.02 p.u
power quality improvement," in 2012 3rd Power Electronics and Drive
inductance
Systems Technology (PEDSTC), Tehran, 2012, pp. 428-434.
Core magnetization 500 p.u 500 p.u
[19] F. Meng, W. Yang, S. Yang and L. Gao, "Active Harmonic Reduction for
inductance
12-Pulse Diode Bridge Rectifier at DC Side With Two-Stage Auxiliary
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Energy Conference, Nanjing, 2009, pp. 1-5. Unit With Impressed Output Voltage," IEEE Trans. on Power Electron.,
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Asymmetric Multiphase Staggering Autoconfigured Transformer For blocking transformers for multi-pulse rectifier in aerospace applications,"
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[11] M. Alnajjar and D. Gerling, "Predictive control of variable frequency [30] A. C. Lourenço, F. J. M. Seixas, J. C. Pelicer and P. S. Oliveira, "18-pulse
brushless excited synchronous generator for more electric aircraft power autotransformer rectifier unit using SEPIC converters for regulated DC-
system," in 2014 International Conference on Electrical Machines bus and high frequency isolation," in 2015 IEEE 13th Brazilian Power
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Autotransformer Based Controlled AC-DC Converter for Pulse [33] R. Kalpana, B. Singh and G. Bhuvaneswari, "An improved power quality
converter for three-phase switched mode power supplies," in Electrical,

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This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TIA.2018.2851566, IEEE
Transactions on Industry Applications

Electronics and Computer Science (SCEECS), 2014 IEEE Students' October 2012, has been a CEA Chair Professor. He was the Head of the
Conference on, Bhopal, 2014, pp. 1-5. Department of Electrical Engineering, IIT Delhi, from July 2014 to August
[34] B. Singh and S. Gairola, "Pulse Doubling in 18-Pulse AC-DC 2016. Since, August 2016, he has been the Dean of Academics with IIT
Converters," in 2007 7th International Conference on Power Electronics Delhi. His research interests include solar photovoltaic (PV) grid interface
and Drive Systems, Bangkok, 2007, pp. 533-539. systems, microgrids, power quality monitoring and mitigation, solar PV
[35] R. Abdollahi and G. B. Gharehpetian, "Inclusive Design and water pumping systems, improved power quality ac-dc converters, power
Implementation of Novel 40-Pulse AC–DC Converter for Retrofit electronics, electrical machines, drives, flexible ac transmission systems, and
Applications and Harmonic Mitigation," IEEE Trans. on Ind. Electron., high voltage direct current systems.
vol. 63, no. 2, pp. 667-677, Feb. 2016. Dr. Singh has been a JC Bose Fellow with the Department of Science
[36] S. Yang, J. Wang and W. Yang, "A Novel 24-Pulse Diode Rectifier with and Technology, Government of India, since December 2015; a Fellow of
an Auxiliary Single-Phase Full-Wave Rectifier at DC Side," IEEE Trans. the Indian National Academy of Engineering, the Indian National Science
on Power Electron., vol. 32, no. 3, pp. 1885-1893, March 2017. Academy, the National Academy of Science (India), the Indian Academy of
Sciences (India), the World Academy of Sciences, the Institute of Electrical
and Electronics Engineers, the Institute of Engineering and Technology, the
Institution of Engineers (India), and Institution of Electronics and
R. Kalpana (M’17) received the bachelor’s degree Telecommunication Engineers; and a Life Member of the Indian Society for
in electrical and electronics engineering from Technical Education, the System Society of India, and the National
Madras University, Chennai, India, in 1998; the Institution of Quality and Reliability.
Master’s degree in power systems form Anna
University, Chennai, in 2000; and the Ph.D. degree
in electrical engineering from Indian Institute of
Technology Delhi (IITD), New Delhi, India, in
2012.
She is currently working as an Assistant
Professor with the Department of Electrical and
Electronics Engineering, National Institute of Technology Karnataka
(NITK), Surathkal, Mangaluru, India. Her research interests include power
conditioning, photovoltaic grid interface systems and application of power
electronics to power systems.

Khimavath Sai Chethana received the B.Tech

degree in electrical and electronics engineering
from Jawaharlal Nehru Technological University
Anantapur (JNTUA), Anantapur, India in 2015.
She is currently working towards the M.Tech
degree in the department of electrical and
electronics engineering, National Institute of
Technology Karnataka (NITK), Surathkal, India.
Her research interests include power quality
improvement in multi-pulse AC-DC converters.

Saravana Prakash P (S’14) received the B.Tech.

degree in electrical and electronics engineering
from the Pondicherry University, Puducherry,
India, in 2007, and the M.Tech. degree in electrical
drives and control from the Pondicherry
Engineering College (PEC), Puducherry, India, in
2013. He is currently working towards the Ph.D.
degree with the Department of Electrical and
Electronics Engineering, National Institute of
Technology Karnataka (NITK), Surathkal,
Mangaluru, Karnataka, India.
His research interests include power electronics, power quality
improvement, and SMPS.

Bhim Singh (SM’99, F’10) was born in

Rahamapur, Bijnor (UP), India, in 1956. He
received the B.E. degree in electrical engineering
from the University of Roorkee, India, in 1977,
and the M.Tech. degree power apparatus and
systems and the Ph.D. degree in electrical
engineering from the Indian Institute of
Technology Delhi, New Delhi, India, in 1979 and
1983, respectively.
In 1983, he was a Lecturer in the Department
of Electrical Engineering, University of Roorkee (Now IIT Roorkee), where
he became a Reader in 1988. In December 1990, he was an Assistant
Professor in the Department of Electrical Engineering, IIT Delhi, where he
has become an Associate Professor in 1994 and a Professor in 1997, was an
ABB Chair Professor from September 2007 to September 2012 and since

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