International Conference on Electrical, Electronics, and Optimization Techniques (ICEEOT) - 2016
Comparison of Cuk And Buck Converter Fed
Electronically Commuted Motor Drive
Amit Dodke
EE department ,
DESCOET, Dhamangaon
Rahul Argelwar
EE department ,
PCE, Nagpur
B.S. Dani
EE deparment
PCE,Nagpur
e-mail: dodkeamit@ymail.com
e-mail:rahulpargelwar@gmail.com
e-mail:bs_dani@rediffmail.com
Abstract— In this paper novel technique of Controlling
electronically commutated motor drive(PMBLDCMD) using cuk
converter explain. A DC-DC converter topology is employed for
speed control BLDC MOTOR and operated with voltage follower
Approach in discontinuous conduction mode (DCM). This paper
give comparative performance of speed controlling of BLDC
motor using Buck and cuk converter. The performance of BLDC
motor is studied using MATLAB Simulation for wide range of
speed control.
Keywords—BLDC motor, cuk converter , Voltage Control, VSI
I.
INTRODUCTION
High torque and low power applications mostly prefer
low voltage PMBLDCMs operated at constant current. Such
applications require the DC link voltage lower than the
average output of a DBR fed from a single-phase AC mains. A
DC-DC converter is connected between the VSI and the DBR
fed from single phase AC supply to provide controlled voltage
at DC link capacitor. There are many DC –DC converter
topologies available such as buck, boost, buck-boost, cuk
converter amongst which the cuk converter topology is used in
this work. It provides controlled DC voltage to the
PMBLDCM drive from an uncontrolled DC output of a single
phase AC mains fed DBR while improving the PQ at AC
mains [1]. The cuk converter topology has advantages of its
simplest construction and minimum component requirement
over other topologies. The merits of cuk converter topology
has input and output Current is ripple free. So that smooth
speed control of BLDC Motor is possible .The cuk converter
is designed for DCM operation to result in reduced sensor
requirement with the desired speed control.
it suitable for household application such as , water pump, fan,
mixers, etc.[2]. It not only used in household application but
also these are suitable for other application such as computer
automobile starter ,disc drives, , automobile wipers, medical
equipment and many other industrial tools. The BLDC motor
is also known as electronically commutated motor because an
electronic commutation based on rotor position is used for
controlling the speed
Permanent
magnet
brushless
DC
motors
(PMBLDCMs) are preferred motors for a compressor of an
air-conditioning system due to its features like high efficiency,
wide speed range and low maintenance requirements. The
978-1-4673-9939-5/16/$31.00 ©2016 IEEE
Dr.S.P.Muley
EE department
PEC,Nagpur
operation of the compressor with the speed control results in
an improved efficiency of the system while maintaining the
temperature in the air-conditioned zone at the set reference
consistently. Whereas, the existing air conditioners mostly
have a single-phase induction motor to drive the compressor in
on/off control mode. This results in increased losses due to
frequent on/off operation with increased mechanical and
electrical stresses on the motor, thereby poor efficiency and
reduced life of the motor. Moreover, the temperature of the air
conditioned zone is regulated in a hysteresis band. Therefore,
improved efficiency of the Air-Conditioning system will
certainly reduce the cost of living and energy demand to copeup with ever-increasing power crisis . Because of numerous
application of BLDC motor in low power need to be smooth
speed control. propose methodology use dc dc cuk converter
for smooth speed controlling and compare with buck
converter topology. [4]
II. PROPOSED CONTROL SCHEME
DC-DC converter feeding permanent magnet brushless
motor drive is proposed here for low power application. A cuk
converter comes under the category of DC to DC converter. In
proposed circuit single phase supply is feeding to uncontrolled
rectifier and DC converter is to control the voltage of DC link
capacitor. Voltage of DC link capacitor is used to control the
speed of BLDC motor. The output of DC link capacitor is fed
to inverter and then BLDC motor to control the speed. A
voltage follower technique is used to control the speed of
BLDC motor.
Fig1.block diagram of cuk converter fed BLDC motor drive.
International Conference on Electrical, Electronics, and Optimization Techniques (ICEEOT) - 2016
III. CUK CONVERTER
Fig. 2: Cuk Converter Circuit Representation with input and output current
waveforms
The Cuk converter is named for Slobodan Cuk of the
California Institute of Technology. It is the result of applying
the duality principle to the buck-boost converter to use a
capacitor instead of an inductor as the primary energy storage
device. As a result, the DC transfer function is nominally the
same as that of the Buck-Boost converter
Vo = -DVs/ (1-D )where, Vo is output voltage
Vs is input voltage of cuk converter
Output voltage polarity of cuk converter is similar to
that of buck boost converter. An advantage of the Cuk
converter topology is that the current pulsing occurs within the
converter itself and both the input and output currents are not
pulsed. Furthermore, if integrated magnetic are used, the input
or output current can (theoretically) be nullified as the ripple is
transferred to the other side of the converter. Because only one
capacitor suffers the losses associated with (internal) current
pulsing, the Cuk converter is more efficient than a filtered
Buck-Boost converter.
The operation of Cuk converter in DCM is described
Interval I: When switch is turned off, the energy stored in
inductor Li is transferred to capacitor C1 via diode D, till it is
completely discharged to enter DCM operation.
Interval II: When switch is turned on, inductor Li stores
energy while capacitor C1 discharges through Switch S to
transfer its energy to the DC link capacitor Cd. Input inductor
current iLi increases while the voltage across the capacitor C1
decreases .
Interval III: During this interval, no energy is left in input
inductor Li, hence current iLi becomes zero. Moreover,
inductor Lo operates in continuous conduction to transfer its
energy to DC link capacitor Cd.
=197.95 Volts
where VS is the rms value of the supply voltage.
Voltage rating = Kb * ωrated *10-3
= 156 Volts.
Current rating = Trated (Rated Torque) /Kt
= 1.62 Amp
The duty ratio D for the Cuk converter is given as,
D = Vdc / (Vin +Vdc)
= 156/198+156
= 0.44
where Vdc represents the DC link voltage of Cuk converter.
The dc link voltage of the PFC converter is given as
Vdc = Vin D/(1 − D)
(1)
where Vin is the average output of the DBR for a given ac
input voltage (Vs) related as
Vin = 2√2Vs/π.
(2)
The Cuk converter uses a boost inductor (Li) and a capacitor
(C1) for energy transfer. Their values are given as
Li =D Vin/ {fs(ΔILi)
(3)
C1 =D Idc/{fsΔVC1
(4)
A ripple filter is designed for ripple-free voltage at the dc link
of the Cuk converter. The inductance (Lo) of the ripple filter
restricts the inductor peak-to-peak ripple current (ΔILo) within
a specified value for the given switching frequency (fs),
whereas the capacitance (Cd) is calculated for the allowed
ripple in the dc link voltage (ΔVCd) [7], [8]. The values of the
ripple filter inductor and capacitor are given as
Lo =(1 − D)Vdc/ {fs(ΔILo)}
Cd =Idc/(2ωΔVCd).
(6)
The PFC converter is designed for a base dc link voltage
of Vdc = 200 V at Vs = 220 V for fs = 20kHz, Is = 4.5 A,
ΔILi = 0.45 A (10% of Idc), Idc = 3.5 A, ΔILo = 3.5 A (≈ Idc),
ΔVCd = 4 V (1% of Vo), and ΔVC1 = 220 V (≈ Vs).
The design values are obtained as Li = 2.5 mH, C1 = 0.66 μF,
Lo = 4.3 mH, and Cd = 2200 μF
The simulation diagram for Cuk converter is shown in fig .3.
Mosfet is used in cuk converter for high frequency and
operating frequency is 20 kHz
IV. DESIGN OF PFC CUK CONVERTER
The proposed drive system is designed for Cuk converter as
PFC converter fed BLDC motor drive operating in DICM. The
output inductor value is selected such that the current remains
discontinuous in a single switching cycle. The average input
voltage Vin after the rectifier is given as,
Vin = 2*1.414*VS / π
=2*1.414*220/ π
978-1-4673-9939-5/16/$31.00 ©2016 IEEE
(5)
Fig.3. Simulation of Cuk converter
International Conference on Electrical, Electronics, and Optimization Techniques (ICEEOT) - 2016
V. CONTROL OF CUK CONVERTER FED BLDC
MOTOR DRIVE
The control for dc-dc cuk converter is given below. The
following are the three block give the control of cuk converter
for Electronically commuted motor drive.
A. Reference Voltage Generator
It generates voltage which is proportional to the output speed
of BLDC motor. The reference voltage generator produces a
voltage(Vdc*) by multiplying the speed with a constant value
known as the voltage constant (Kb) of the BLDC motor. This
voltage is compare with dc link voltage(Vdc) of cuk converter
for required speed.
B. Voltage Controller
similar. There is a hall effect sensor is used to detect the rotor
position. the sensor are mounted at 60° electrical interval. The
sensor used in trapezoidal motor is cheaper than sinusoidal
PMAC motor.
The switching sequence of VSI for different positions of the
rotor is shown in Table I and II. Decoder module in the
simulation diagram implements the following truth table.
TABLE.1
Truth table for decoder module
The errors produces by the Vdc* and Vdc is given to a
Proportional Integral( speed controller) which generates a
controlled output corresponding to the error signal. The value
Ki and Kp is set by using trial and errors method in matalab
simulink.
C. PWM Generator
The output of the PI controller Vc is given to the PWM
generator which produces a PWM signal of fixed frequency
and varying duty ratio. A saw tooth waveform is compared
with the output of PI controller .
If md(t)<Vc(t) then S= 1 else S= 0
where S denotes the switching signals as 1 and 0 for MOSFET
to switch on and off respectively.
ha
hb
hc
Emf_a
Emf_b
0
0
0
0
0
Emf_c
0
0
0
1
0
-1
+1
0
0
1
0
-1
+1
0
1
1
-1
0
1
1
0
0
+1
0
-1
1
0
1
+1
-1
0
1
1
0
0
+1
-1
1
1
1
0
0
0
The gate pulse generation for inverter implements the
following truth table.
TABLE.II
Truth table for gate pulse generation
emf a
emf b
Emfc
Q1
Q2
Q3
Q4
Q5
Q6
0
0
0
0
0
0
0
0
0
0
-1
+1
0
0
0
1
1
0
-1
+1
0
0
0
1
1
0
0
-1
0
1
0
1
0
0
1
0
+1
0
-1
1
0
0
0
0
1
+1
-1
0
1
0
0
1
0
0
0
+1
-1
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
Fig.4.Simulation of PWM generator
Where d is output of PI controller and c is input to gate
terminal of MOSFET of Cuk converter.
VI. ELECTRONICS COMMUTATION.
The BLDC motor employ a voltage source inverter & a
trapezoidal PMAC motor is shown in fig.3.4. The stator
winding of star connected .it will have rotor position sensor
which are not shown in figure. Let the stator winding is fed
with current pulses which are 120° duration. since theair gap
flux is constant ,the voltage induced is proportional to the
speed of rotor.[7] During period 0 to 60°,switch T1 & T4 are
ON at that time winding A & B connected to dc source. for
next 60° operation,T1 & T6 is ON, at that time winding A &
C is connected to dc source. the operation for next duration is
978-1-4673-9939-5/16/$31.00 ©2016 IEEE
The Brushless DC motor normally consists of stator windings,
where the arrangement is determined by rotor pole pairs made
of permanent magnets. In the Brushless DC motor, the
commutation sequence plays an important role in enabling the
rotor rotation.[2] Each commutation has one of the stator
windings energized to positive power (current enters into the
winding), the second winding as negative. In order to keep the
motor running, the magnetic field produced by the windings
should shift position, as the rotor moves to catch up with the
stator field. Hens we have to excite winding sequentially for
maintaining rotor in running condition .This is done by
electronic switches, ON& OFF sequentially. In other words,
the process of activating current flow in six directions through
the appropriate motor phase windings to produce an output
torque is called as commutation.[8]
International Conference on Electrical, Electronics, and Optimization Techniques (ICEEOT) - 2016
VII. CIRCUIT DESCRIPTION.
Fig.5. Cuk converter fed BLDC Motor Drive
The proposed Cuk converter based PMBLDCM drive operated
with voltage follower control. The proposed controller is
operated to maintain a constant DC link voltage with PFC
action at AC mains. The DC link voltage is sensed and
compared with a reference voltage which results in a voltage
error. This voltage error is passed through a voltage controller
to give a modulating signal which is amplified and compared
with saw-tooth carrier wave of fixed frequency to generate a
pulse width modulated signal for the switching device of the
DC-DC converter.
For the speed control, the speed signal derived from rotor
position of the PMBLDCM, sensed using Hall effect sensor, is
compared with a reference speed. The resultant speed error is
passed through a speed controller to get the torque equivalent
which is converted to an equivalent current signal using motor
torque constant [8].
This current signal is multiplied with a rectangular unit
template waveform which is in phase with top flat portion of
motor’s back EMF so that reference three phase current of the
motor are generated .These reference current are compared
with the sensed motor current and current error are generated
which is amplified and compared with triangular carrier waves
to generate the PWM signals for the VSI switches [7]
VIII.
Fig. 6.Simulation diagram of Cuk converter fed BLDC motor drive
IX. SIMULATION OF BUCK CONVERTER FED
BLDC MOTOR DRIVE
The MATLAB simulation of Buck converter fed BLDC motor
drive is as shown in fig.7. Diode bridge rectifier is fed by 220
Volts AC supply. The output of Diode bridge rectifier is fed to
buck converter. The duty cycle for buck converter is provided
by pulse generator. Three phase voltage source inverter is fed
output of buck converter. The BLDC motor is fed by this three
phase voltage source inverter.
SIMULATION OF CUK CONVERTER FED
BLDC MOTOR
The MATLAB simulation of Buck converter fed BLDC motor
drive is as shown in fig.4. Diode bridge rectifier is fed by 220
Volts AC supply. The output of Diode bridge rectifier is fed to
buck converter. The duty cycle for Cuk converter is provided
by pulse generator. Three phase voltage source inverter is fed
output of cuk converter. The BLDC motor is fed by this three
phase voltage source inverter
Fig.7.Simulation diagram of Buck converter fed BLDC motor drive
978-1-4673-9939-5/16/$31.00 ©2016 IEEE
International Conference on Electrical, Electronics, and Optimization Techniques (ICEEOT) - 2016
IX .RESULTS
The comparitive analysis of results of both system is
given below. Following fig shows the comparitive result of
Cuk and buck converer fed BLDC Motor drive .
6
4
c u rre n t
2
0
Vo
-2
200
-4
0
V o lt a g e ( V )
300
0.02
0.04
0.06
0.08
100
0
0.1 0.12
Time(sec)
0.14
0.16
0.18
0.2
0.16
0.18
Stator current ia
5
4
-100
0
0.02
0.04
0.06
0.08
0.1
Time (Sec)
0.12
0.14
0.16
0.18
0.2
3
2
Vo
Ia
1
250
0
200
v o lt a g e ( V o )
-1
150
-2
-3
100
50
0
0
0.02
0.04
0.06
0.08
0.1
Time(sec)
0.12
0.14
0.16
0.18
0.2
0.02
0.04
0.06
0.08
0.1
Time
0.12
0.14
0.2
Fig.9 .Comparison of stator current of cuk and buck converter fed BLDC
motor drive
TABLE .III.
Performance of cuk and buck converter fed BLDC motor
Fig. 8. Comparison of output voltages cuk and buck
converter fed bldc motor drive
Vdc
Output speed using
converter (RPM)
140
1095
1089
160
1332
1326
180
1542
1536
200
1866
1860
2000
1500
S p e e d (rp m )
0
1000
500
Cuk
Output speed using
converter (RPM)
Buck
0
-500
0
0.02
0.04
0.06
0.08
0.1
Time (sec)
0.12
0.14
0.16
0.18
0.2
Rotor speed (rpm)
2000
s p e e d (rp m )
1500
1000
X.
500
-500
CONCLUSION
A simple control using a voltage follower approach has been
0
0
0.02
0.04
0.06
0.08
0.1
Time (sec)
0.12
0.14
0.16
0.18
0.2
Fig.7 Comparison of output speed cuk and buck converter fed bldc motor
drive
g
q ( )
drive. A novel scheme of speed control using a single voltage
sensor has been proposed. A single stage PFC converter
system has been designed and validated for the speed control
2.5
2
for a wide range of speed. The performance of the proposed
Tm
1.5
drive system has also been evaluated for varying input AC
1
0.5
0
0
used for voltage control of a Cuk converter fed BLDC motor
voltages and smooth performance of motor is obtained. The
0.02
0.04
0.06
0.08
0.1
Time (sec)
0.12
0.14
0.16
0.18
0.2
proposed drive system has been found a suitable control
Electromagnetic Torque (Nm)
technique among various adjustable speed drives for many
3
2.5
low power applications. With help of comparison with buck
T o rq u e (T )
2
1.5
converter it can be concluded that the Cuk converter fed
1
BLDC motor gives better performance.
0.5
0
0
0.02
0.04
0.06
0.08
0.1
Time
0.12
0.14
0.16
0.18
0.2
Fig.8. Comparison of electromagnetic torque cuk and buck converter BLDC
fed motor drive
978-1-4673-9939-5/16/$31.00 ©2016 IEEE
International Conference on Electrical, Electronics, and Optimization Techniques (ICEEOT) - 2016
APPENDIX
BLDC Motor Rating: 4 pole, Prated (Rated Power) =252.72W,
Trated (Rated Torque) = 1.2 Nm, Wrated (Rated
Speed) = 2000 rpm, Kb (Back EMF Constant) = 78 V/krpm,
Kt (Torque Constant) = 0.74 Nm/A, Rph (Phase Resistance)
=14.56Ω, L (Phase Inductance) = 25.71 mH, J (Moment of
Inertia) = 0.00013 kg-cm2.
REFERENCES
[[1] Singh, S.; Singh, B., "A Voltage-Controlled PFC Cuk ConverterBased
PMBLDCM
Drive
for
Air-Conditioners," Industry
Applications, IEEE Transactions on , vol.48, no.2, pp.832,838,
March-April 2012.
[2] Simonetti, D. S L; Sebastian, J.; dos Reis, F.S.; Uceda, J.,
"Design criteria for SEPIC and Cuk converters as power factor
preregulators in discontinuous conduction mode," Industrial
Electronics, Control, Instrumentation, and Automation, 1992.
Power Electronics and Motion Control., Proceedings of the
1992 International Conference on , vol., no., pp.283,288 vol.1,
9-13 Nov 1992.
[3] Singh, B.; Singh, B.N.; Chandra, A; Al-Haddad, K.; Pandey, A;
Kothari, D.P., "A review of single-phase improved power
quality
AC-DC
converters," Industrial
Electronics,
IEEE
Transactions on , vol.50, no.5, pp.962,981, Oct. 2003.
[4] Bist, V.; Singh, B., "An Adjustable-Speed PFC Bridgeless Buck–
Boost
Converter-Fed
Electronics,
IEEE
BLDC
Motor
Transactions
Drive," Industrial
on ,
vol.61,
no.6,
pp.2665,2677, June 2014.
[5] Singh, S.; Singh, B., "PFC buck converter fed PMBLDCM drive
for low power
[6] Rong-Jong Wai; Kun-Huai Jheng, "High-Efficiency Single-Input
Multiple-Output DC–DC Converter," Power Electronics, IEEE
Transactions on , vol.28, no.2, pp.886,898, Feb. 2013.
[7] M. M. Abdel Aziz, A. A. Mahfouz, D. M. Khorshied, “Simplified
approaches
for
controlling
dc-dc
power
Converters”
,
International Journal of Engineering Science and Technology
(IJEST), Vol. 4 No.02 February 2012, pp.792-804
[8] Tsai-Fu Wu, "The origin of converters," Future Energy
Electronics Conference (IFEEC), 2013 1st International , vol.,
no., pp.611,617, 3-6 Nov. 2013.
[9] Darwish, A; Holliday, D.; Ahmed, S.; Massoud, AM.; Williams,
B.W., "A Single-Stage Three-Phase Inverter Based on Cuk
Converters for PV Applications," Emerging and Selected Topics
in Power Electronics, IEEE Journal of , vol, no.99, pp.11 march
2014
978-1-4673-9939-5/16/$31.00 ©2016 IEEE
[
10] Krishnan Ramu, “Electric Motor Drives Modeling, Analysis, and
Control”, Prentice Hall, pp. 578 -582, 2001