A bridgeless cuk converter based induction motor drive for pfc applications

1. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
30-31, December, 2014, Ernakulam, India
191
A BRIDGELESS CUK CONVERTER BASED INDUCTION
MOTOR DRIVE FOR PFC APPLICATIONS
RAICHEL MATHEW1
, ASWATHY MOHANDAS P2
1
PG Scholar, Electrical and Electronics Department, Sree Narayana Gurukulam College of Engineering,
Kolenchery, India
2
Assistant Professor, Electrical and Electronics Department, Sree Narayana Gurukulam College of Engineering,
Kolenchery, India
ABSTRACT
A new bridgeless topology for power factor correction is proposed here. Induction motor drives are widely
employed in industrial sectors because of their high efficiency, reliability, output etc. They are considered as the major
prime movers and consume about 70% to 80% of the total electricity. As a result these drives face many problems related
to power quality and power factor. The main reason is the input rectifier bridge. Unity power factor is the main goal of all
company. If it is less than unity, then more current has to be supplied. For the power factor improvement a new
bridgeless topology is introduced here were input bridge section is absent. Cuk converter is used as the PFC converter
which operates in its (DCM) discontinuous conduction mode which offers zero current ON for switches. Proposed model
is simulated in Simulink model with suitable control strategies. Comparisons based on performances of conventional and
proposed circuits are included.
Keywords: Bridgeless Topology, CUK Converter, Discontinuous Conduction Mode DCM, Induction Motor, Zero
Current Switching ZCS
1. INTRODUCTION
Induction motors are the most suitable electric motors in industrial sector. They are well known for their
performance characteristics. Generally they are supplied from an input rectifier section with proper filtering methods [1].
When current flows through the diodes, conduction losses occur due to the voltage drop across it. This will in turn
degrades its efficiency especially at low voltages. So the input bridge section is completely eliminated for power factor
correction. Thus a new bridgeless topology is introduced. The number of semiconductor devices in the current path is
thus reduced. This will in turn reduce losses and improves power factor. PFC also leads to cost savings as well as energy
savings. It is inevitable for every converter in order to satisfy the regulatory standards IEC 61000-3-2.
For good power quality and power factor active power factor correction circuits are necessary. In conventional
methods single phase rectifiers are used. They operate by rectifying the input voltage and then filter it with large
capacitors. Capacitors always maintain a constant voltage approximately as its peak. Currents are drawn in narrow pulses
by the capacitors which results in major harmonic issues. It will also leads to severe power quality problems. Harmonics
not only destroys its line but also disrupts other devices connected to it [2]. Since pulsated currents are drawn. PFC
converters are employed to provide a constant DC source. Many topologies are proposed to sort out the problem of
power factor and also for harmonics. In most of PFC circuits, the converter used is boost converter. Boost converter has a
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2. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
step up conversion ratio [3]. It can be used in both CCM (continuous conduction mode) and DCM (discontinuous
conduction mode). But the disadvantage is that it can be applied for boost operations only. Apart from this it is suffered
from high inrush current and isolation problems. As an advance in technology in this paper Cuk converter is used as a
PFC converter [4].
The topology based on Cuk converter offers many advantages when compared to other converter topologies. It
includes automatic current shaping, both input and
implementation, protection from inrush currents etc. Proposed Cuk converter is subjected to be operated in discontinuous
conduction mode (DCM) which aids to achieve near unity power fac
zero current switching (ZCS) turn ON and turn OFF are possible
three semiconductors in current path. Compared with SEPIC converter
currents even at low ripple. So Cuk converter acts as a common selector in major basic topologies.
2. CONVENTIONAL CUK PFC CONVERTER
A conventional PFC Cuk rectifier is drawn in Fig 1. From the circuit, when switch Q
through three power semiconductor devices. That is two bridge diodes and one switch. Likewise when the switch is OFF,
current will flow through three diodes. So in every switching period current flow through three semiconductor devices
this will result in conduction losses and poor efficiency.
Fig 1: Conventional PFC Cuk converter
3. PROPOSED TOPOLOGY
In order to reduce the conduction losses and to improve the power supply efficiency, a Cuk converter bridgeless
topology is employed. The Cuk converter in DCM offers improved current shaping properties as compared with other fly
back converters .apart from all of this the major advantage is concerned with losses in switches and diodes. The
performance of new topology is compared with that of the conventional
Fig 2. Along with it block diagram regarding the proposed system is also shown.
International Conference on Emerging Trends in Engineering and Management (ICETEM14)
30-31, December, 2014, Ernakulam, India
192
can be used in both CCM (continuous conduction mode) and DCM (discontinuous
conduction mode). But the disadvantage is that it can be applied for boost operations only. Apart from this it is suffered
problems. As an advance in technology in this paper Cuk converter is used as a
The topology based on Cuk converter offers many advantages when compared to other converter topologies. It
includes automatic current shaping, both input and output continuous currents, less ripple content in input current, easy
implementation, protection from inrush currents etc. Proposed Cuk converter is subjected to be operated in discontinuous
conduction mode (DCM) which aids to achieve near unity power factor and reduced total harmonic distortion (THD). Also
nd turn OFF are possible. Moreover the selected topology still has a problem those
three semiconductors in current path. Compared with SEPIC converter [8], Cuk converter has continuous input and output
currents even at low ripple. So Cuk converter acts as a common selector in major basic topologies.
CONVENTIONAL CUK PFC CONVERTER
A conventional PFC Cuk rectifier is drawn in Fig 1. From the circuit, when switch Q
through three power semiconductor devices. That is two bridge diodes and one switch. Likewise when the switch is OFF,
current will flow through three diodes. So in every switching period current flow through three semiconductor devices
this will result in conduction losses and poor efficiency.
Fig 1: Conventional PFC Cuk converter
In order to reduce the conduction losses and to improve the power supply efficiency, a Cuk converter bridgeless
topology is employed. The Cuk converter in DCM offers improved current shaping properties as compared with other fly
back converters .apart from all of this the major advantage is concerned with losses in switches and diodes. The
y is compared with that of the conventional type [9]. The proposed circuit
Fig 2. Along with it block diagram regarding the proposed system is also shown.
Fig 3: Bridgeless Cuk Rectifier
International Conference on Emerging Trends in Engineering and Management (ICETEM14)
, December, 2014, Ernakulam, India
can be used in both CCM (continuous conduction mode) and DCM (discontinuous
conduction mode). But the disadvantage is that it can be applied for boost operations only. Apart from this it is suffered
problems. As an advance in technology in this paper Cuk converter is used as a
The topology based on Cuk converter offers many advantages when compared to other converter topologies. It
output continuous currents, less ripple content in input current, easy
implementation, protection from inrush currents etc. Proposed Cuk converter is subjected to be operated in discontinuous
tor and reduced total harmonic distortion (THD). Also
. Moreover the selected topology still has a problem those
erter has continuous input and output
currents even at low ripple. So Cuk converter acts as a common selector in major basic topologies.
A conventional PFC Cuk rectifier is drawn in Fig 1. From the circuit, when switch Q is ON current flows
through three power semiconductor devices. That is two bridge diodes and one switch. Likewise when the switch is OFF,
current will flow through three diodes. So in every switching period current flow through three semiconductor devices,
In order to reduce the conduction losses and to improve the power supply efficiency, a Cuk converter bridgeless
topology is employed. The Cuk converter in DCM offers improved current shaping properties as compared with other fly
back converters .apart from all of this the major advantage is concerned with losses in switches and diodes. The
]. The proposed circuit is shown below in

3. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
30-31, December, 2014, Ernakulam, India
193
The bridgeless Cuk rectifier is formed by connecting two DC-DC converters together. For every switching cycle
each converter operates for time (T/2) of the total time. From figure, when switch is ON, the current Iac flows through
L1, Q1 and Dp. Likewise when switch is OFF, current flows through diode D01.So in each case, current flows through one
or more semiconductor device. As a result the conduction losses in active and passive switches are reduced and circuit
efficiency is considerably reduced. Here the slow recovery diodes Dp and Dn always connect the output voltage to input
ac line voltage in order to prevent the common mode noise problems. Thus the circuit is free from noise and EMI
problems [8]. Also by the reduction of conduction losses, energy savings as well as cost savings can be achieved. In fig
(3), there are two recovery diodes along with the two switches. The switches are operated with same control circuitry.
That is switch Q1 is turned ON for positive cycle and Q2 vice versa. As a result the complexity of the circuit can be
reduced [10].
4. MODE OF OPERATION
Before the explanation some assumptions has to be made. The converter should be operated in steady state
condition. The components should be ideal and lossless. The value of output capacitor should be large enough to
withstand the voltage stresses. Due to symmetry only positive half cycle is to be analyzed. During the positive half cycle,
the first half of the circuit involves in the operation. That is the path L1-Q1-C1-L01-D01 is active through diode Dp which
connects input source and output. Likewise during the negative half cycle, the path L2-Q2-C2-L02-D02 is active which
connects input and output. The Cuk converter is operating in its discontinuous conduction mode which offers additional
advantages like natural near unity power factor, zero current switching etc [10].
5. CONVERTER DESIGN
For DCM operation the following condition should be satisfied.
Ke<Ke-crict=1/2(M+sin(ωt))2
(1)
Where Ke is the dimension parameter and is given by,
Ke=2Le/RL.TS (2)
Let the other parameters be:
Input voltage = 100Vrms, output voltage = 48V, power = 150W.
From this, output current I0 = 3.12A. the load resistance is given by V = I × R and obtained as 15.3Ω. Assume the output
voltage is less than 1% and the switching frequency be 50KHZ.
∆iL1 < 10% IL1 (3)
∆IL2 = (1-D)/F.L2 (4)
∆VC1 = D.Vd.Id/V0.C.F (5)
∆IL1 = D.Vin/ L.F1 (6)
From the above equations the values of inductor and capacitor are obtained as:
L1= L2=1mH
L01=L02=22µH
C1=C2=1µF
Cout=12000Μf

4. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
6. SIMULATION AND MODELLING
Fig 4: Simulation diagram of conventional Cuk converter
International Conference on Emerging Trends in Engineering and Management (ICETEM14)
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SIMULATION AND MODELLING
Fig 4: Simulation diagram of conventional Cuk converter
Fig 5: Output voltage and current
Fig 6: THD of conventional Cuk
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5. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
In fig 4, simulation diagram of conventional Cuk converter is shown. And in
waveforms of voltages and THD are shown. The power factor is measured in terms of THD. Apart from this in figures
7,8,9 the proposed topology is shown. When compared the THD is reduced from 14.17% to 5.26%, which shows that the
proposed system has reduced losses.bas a result the efficiency is higher than that of conventional system.
Input voltage
Switching Frequency
Input inductors L1
Output inductors L
Energy transfer capacitors C
Filter capacitors C
Active Switches Q
Output diodes Do, D
Input diodes Dp and D
Filter L & C
International Conference on Emerging Trends in Engineering and Management (ICETEM14)
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195
Fig 7: Bridgeless Cuk Converter
Fig 8: Output voltage and current
TABLE I: SIMULATION DETAILS
In fig 4, simulation diagram of conventional Cuk converter is shown. And in fig 5 & 6 the corresponding
waveforms of voltages and THD are shown. The power factor is measured in terms of THD. Apart from this in figures
7,8,9 the proposed topology is shown. When compared the THD is reduced from 14.17% to 5.26%, which shows that the
proposed system has reduced losses.bas a result the efficiency is higher than that of conventional system.
180V
Switching Frequency 20 kHz
1 and L2 1Mh
Output inductors Lo1 and Lo2 22µH
Energy transfer capacitors C1 and C2 1µF
capacitors Co 12000 µF
Active Switches Q1 and Q2 Rds-on=29mΏ
, Do1 and Do2 Vf =0.9V
and Dn Vf =0.7V
L=1e-4
& C=39e-2
International Conference on Emerging Trends in Engineering and Management (ICETEM14)
, December, 2014, Ernakulam, India
fig 5 & 6 the corresponding
waveforms of voltages and THD are shown. The power factor is measured in terms of THD. Apart from this in figures
7,8,9 the proposed topology is shown. When compared the THD is reduced from 14.17% to 5.26%, which shows that the
proposed system has reduced losses.bas a result the efficiency is higher than that of conventional system.

6. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
30-31, December, 2014, Ernakulam, India
196
Fig 9: THD of bridgeless converter
7. CONCLUSION
A new topology based on Cuk converter is proposed and simulated. The proposed topology is simulated with
induction motor load. By this the power factor of an IM is increased and considerable efficiency can be achieved. By
considering all other converter topologies, Cuk converter becomes the best solution. Apart from conventional systems,
bridgeless topologies yield more efficiency and energy savings. As IM are the most commonly used electric motors, the
increase in pf and efficiency had lead to tremendous changes in industrial sector
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