POWER FACTOR CORRECTION IN PERMANENT MAGNET BRUSHLESS DC MOTOR DRIVE USING SINGLEPHASE CUK CONVERTER
ABSTRACT Permanent magnet brushless DC motor (PMBLDCM) drives are being employed in many variable speed applications due to their high efficiency, silent operation, compact size, high reliability, ease of control, and low maintenance requirements. These drives have power quality problems and poor power factor at input AC mains as they are mostly fed through diode bridge rectifier based voltage source inverters. To overcome such problems a singlephase singleswitch power factor correction ACDC converter topology based on a Cuk converter is proposed to feed voltage source inverters based PMBLDCM. It focuses on the analysis, design and performance evaluation of the proposed PFC converter topology for a 1.5 kW, 1500 rpm, 400 V PMBLDCM drive used for an airconditioning system. The proposed PFC converter topology is modelled and its performance is simulated in MatlabSimulink environment and results show an improved power quality and good power factor in wide speed range of the drive.
 Citations (12)
 Cited In (0)
 [Show abstract] [Hide abstract]
ABSTRACT: For pt.I see ibid., vol.25, no.2, p.26573 (1989). The authors develop a phase variable model of the BDCM (brushless DC motor) and use it to examine the performance of a BDCM speed servo drive system when fed by hysteresis and pulsewidthmodulated (PWM) current controllers. Particular attention was paid to the motor largesignal and smallsignal dynamics and motor torque pulsations. The simulation included the statespace model of the motor and speed controller and realtime model of the inverter switches. Every instance of a power device turning on or off was simulated to calculate the current oscillations and resulting torque pulsations. The results indicate that the small and largesignal responses are very similar. This result is only true when the timing of the input phase currents with the back EMF (electromotive force) is correct. The largesignal and smallsignal speed response is the same whether PWM or hysteresis current controllers are used. This is because, even though the torque pulsations may be different due to the use of different current controllers, the average value which determines the overall speed response is the sameIEEE Transactions on Industry Applications 04/1989; · 2.05 Impact Factor 
Conference Paper: Input current shaper using Cuk converter
[Show abstract] [Hide abstract]
ABSTRACT: The Cuk converter with integrated magnetics when used for input current shaping exhibits advantages over other topologies. When the `ripple steering' mechanism is employed, essentially zero input and output current ripples are obtained for all operating conditions, and the size of the magnetics can be significantly reduced. The discontinuous inductor current mode (DICM) with no current feedback loop is analyzed. Current shaping takes place automatically by keeping the duty cycle and switching frequency constant when the converter operates in DICM. The high input power factor and high overall conversion efficiency suggest operation in DICM for lowpower applications. Experimental results obtained on a 200W prototype are presentedTelecommunications Energy Conference, 1992. INTELEC '92., 14th International; 11/1992  SourceAvailable from: Jose A. Cobos[Show abstract] [Hide abstract]
ABSTRACT: The determination of the boundaries between both modes of conduction (continuous and discontinuous) in PWM DCtoDC switching power converters used as power factor preregulators (PFP) is presented in this paper. When a DCtoDC switching power converter works as a power factor preregulator, its operating point is constantly changing due to the fact that both the DC voltage conversion ratio and the load “seen” by the power converter are constantly changing in each halfsinusoid of the line voltage (input voltage of the converter). In these conditions, the conduction mode cannot be directly determined. In this paper, the boundaries between both conduction modes in each angle of the halfsinusoidal input voltage have been determined. The conditions to always operate in continuous or in discontinuous conduction modes have been determined as well. Finally, these results have been verified by simulations and experimental resultsIEEE Transactions on Power Electronics 10/1995; · 5.73 Impact Factor
Page 1
Journal of Engineering Science and Technology
Vol. 5, No. 4 (2010) 412  425
© School of Engineering, Taylor’s University
412
POWER FACTOR CORRECTION IN PERMANENT
MAGNET BRUSHLESS DC MOTOR DRIVE USING
SINGLEPHASE CUK CONVERTER
SANJEEV SINGH*, BHIM SINGH
Electrical Engineering Department, Indian Institute of Technology Delhi,
Hauz Khas, New Delhi110016, India
*Corresponding Author: sschauhan.sdl@gmail.com
Abstract
Permanent magnet brushless DC motor (PMBLDCM) drives are being employed
in many variable speed applications due to their high efficiency, silent operation,
compact size, high reliability, ease of control, and low maintenance requirements.
These drives have power quality problems and poor power factor at input AC
mains as they are mostly fed through diode bridge rectifier based voltage source
inverters. To overcome such problems a singlephase singleswitch power factor
correction ACDC converter topology based on a Cuk converter is proposed to
feed voltage source inverters based PMBLDCM. It focuses on the analysis, design
and performance evaluation of the proposed PFC converter topology for a 1.5
kW, 1500 rpm, 400 V PMBLDCM drive used for an airconditioning system. The
proposed PFC converter topology is modelled and its performance is simulated in
MatlabSimulink environment and results show an improved power quality and
good power factor in wide speed range of the drive.
Keywords: PMBLDCM drive, Power factor correction, Cuk converter,
Airconditioning, VSI.
1. Introduction
A permanent magnet brushless DC motor (PMBLDCM) is a kind of threephase
synchronous motor having permanent magnets on the rotor [15]. It is regarded as
a rugged and efficient machine for variety of applications. Usually, the
PMBLDCMs are powered from singlephase AC mains through a diode bridge
rectifier (DBR) with smoothening DC capacitor and a threephase voltage source
inverter (VSI) [23, 5]. Due to the uncontrolled charging of DC link capacitor, the
AC mains current waveform is a pulsed waveform featuring a peak value higher
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Power Factor Correction in Permanent Magnet Brushless DC Motor Drive 413
Journal of Engineering Science and Technology December 2010, Vol. 5(4)
Nomenclatures
Co
C1
D
ex
fs
Iav
*
dc
I
Is
ix
J
Kb
Kpv, Kiv
Kpω, Kiω
kdc
Li
Lo
Ls
M
md
P
p
R
Ra
S
Te
Tl
uvi
*
dc
V
Vdc
Vdc
Ve
Vin
Vs
Greek Symbols
ILi
ILo
VCo
VC1
ω
*
r
ωe
ωr
Capacitor of the output ripple filter, µF
Intermediate capacitor, µF
Duty ratio
Back emf of phase x of PMBLDCM
Switching frequency, Hz
Average motor current from DC link, A
Reference inductor current, A
Input AC Current (RMS), A
Current in phase x of PMBLDCM, A
Inertia of PMBLDC motor, kgm2
Back EMF constant of the PMBLDCM
Proportional and integral gains of the voltage PI controller
Proportional and integral gains of the speed PI controller
Gain
Boost inductor, mH
Inductance of output ripple filter, mH
Selfinductance of the PMBLDCM/phase
Mutual inductance of the PMBLDCM
Carrier waveform
Number of poles in the PMBLDCM
Differential operator (d/dt)
Equivalent Output Resistance at DC Link, Ω
Resistance of motor winding/phase, Ω
Switching function
Electromagnetic torque of PMBLDCM
Load torque on the PMBLDC motor
Unit template of the input AC
Reference DC link voltage, V
Output voltage, V
Sensed DC link voltage, V
Voltage error at DC Link, V
Output voltage of DBR, V
Input AC Voltage (RMS), V
Peak to peak current ripple in boost inductor, A
Inductor peak to peak current ripple, A
Peak to peak ripple in output voltage, V
Peak to peak voltage ripple of intermediate capacitor, V
Rotor position
Frequency at input AC mains, rad/s
Reference speed of the PMBLDCM, rad/s
Speed error, rad/s
Rotor speed of the PMBLDCM, rad/s
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414 S. Singh and B. Singh
Journal of Engineering Science and Technology December 2010, Vol. 5(4)
Abbreviations
CCM
CF
DBR
IGBTs
PF
PFC
PI
PMBLDCM
PQ
PWM
THD
VSI
Continuous conduction mode
Crest factor
Diode bridge rectifier
Insulated gate bipolar transistors
Power factor
Power factor correction
Proportionalintegral
Permanent magnet brushless DC motor
Power quality
Pulse width modulation
Total harmonic distortion
Voltage source inverters
than the peak of the fundamental input current as shown in Fig. 1. The power
factor (PF) is 0.738, crest factor (CF) is 2.24 with 67% efficiency of the drive.
Fig. 1. Supply Current and Harmonic Spectrum (at 220 VAC) of a DBR Fed
PMBLDCM Drive at Rated Torque and 1000 rpm.
This is due to the fact that, the DBR does not draw any current from the AC
mains when the AC voltage is less than the DC link voltage, as the diodes are
reverse biased during that period; however, it draws a large current when the AC
voltage is higher than the DC link voltage. Therefore, many power quality (PQ)
problems arise at input AC mains including poor power factor, increased total
harmonic distortion (THD) and high crest factor (CF) of AC mains current etc.
These PQ problems become more severe for the utility when many such drives
are employed simultaneously at various places.
To mitigate PQ and associated problems several international standards have
come up in the recent past including IEC 6100032 [6] which is specially meant
for low power drives. Therefore, the drive system having inherent power factor
correction (PFC) are more in demand and PFC converters have become preferred
feature of new drives. Since the PMBLDCM drives have to be operated from the
utility supply, therefore they should conform to the international PQ standards.
To comply with the PQ standards in the low power range, the power factor
correction (PFC) converter topology using active wave shaping techniques is a
popular and preferred solution in domestic applications. The PFC converter forces
the drive to draw sinusoidal AC mains current in phase with its voltage.
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Power Factor Correction in Permanent Magnet Brushless DC Motor Drive 415
Journal of Engineering Science and Technology December 2010, Vol. 5(4)
Moreover, for PFC converter fed PMBLDCM drives, the additional cost and
complexity of the PFC converter are not justified, therefore, converter topologies
with inherent feature of PFC are preferred in these drives. Therefore, a DCDC
converter topology is mostly preferred amongst several available topologies [7
15] e.g., buck, boost, buckboost, Cuk, SEPIC, zeta converters with variations of
capacitive/inductive energy transfer. The net result is improved performance, such
as reduction of AC mains current harmonics, reduction of acoustic noise and
electromagnetic pollution, minimum number of components, enhanced efficiency,
utilization of the full input voltage range etc.
Few efforts [9,11,13,15] have been made to introduce PFC feature in PMBLDC
motors using unipolar excitation [13] and bipolar excitation [9,11,15] of
PMBLDCMs. For airconditioners, a PMBLDCM with boost PFC converter [11] and
PMSM with improved power quality converter [12] have been reported for power
quality improvement. However, a PMBLDCM is best suited for airconditioning
system due to simple control, high average torque produced and few torque ripples.
This paper deals with a Cuk converter as PFC ACDC converter to feed
PMBLDCM driven airconditioner. Because, the Cuk converter with PFC inherits
advantages like low current and voltage ripple in output, near unity power factor
with simple control and reduced size magnetics [7]. A detailed design and
performance evaluation of the proposed PFC converter for feeding PMBLDCM
drive are presented for airconditioning system. The paper is organized in six
main parts, namely introduction, operation and control of Cuk converter fed
PMBLDCM, their design, modeling of the proposed PMBLDCM drive,
performance evaluation and conclusion.
2. Operation and Control of Cuk Converter fed PMBLDCM
Figure 2 shows the proposed topology of Cuk PFC converter fed PMBLDCM
drive with control scheme for the speed control as well as PFC with DC link
voltage control. For the speed control of the PMBLDCM, a proportionalintegral
(PI) controller [3] is used to drive a constant torque compressor in air
conditioning system. The rotor position of PMBLDCM is sensed using Hall effect
sensors and converted to speed signal, which is compared with a reference speed.
The speed error signal is passed through a speed controller to give the torque
equivalent which is converted to current equivalent signal. This signal is
multiplied with a rectangular unit template in phase with top flat portion of
motor‟s back EMF to get reference currents of the motor. The reference motor
currents are compared with the sensed motor currents. These current errors are
amplified and amplified signals are then compared with triangular carrier wave to
generate the PWM pulses for turning on/off the VSI switches. The control of
PMBLDCM requires rotorposition information only at the commutation points,
e.g., every 60°electrical in the threephases [15], therefore, comparatively simple
controller is required for commutation and current control.
The Cuk PFC converter topology has a conventional DBR fed from single
phase AC mains followed by the Cuk DCDC converter, an output ripple filter
and a threephase VSI to feed the PMBLDC motor. The DCDC converter
provides a controlled DC voltage from uncontrolled DC output of DBR, while
controlling the power factor (PF) through high frequency switching of the PFC
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416 S. Singh and B. Singh
Journal of Engineering Science and Technology December 2010, Vol. 5(4)
switch. The regulated output DC voltage from the DCDC converter is decided by
its duty ratio (D). The switching frequency (fs) is decided by the switching device
used, operating voltage, power level and switching losses of the device. In this
work, a set of insulated gate bipolar transistors (IGBTs) are used as the switching
devices in the PFC switch as well as in VSI bridge, because IGBTs can operate in
wide switching frequency range to make optimum balance between magnetics,
size of filter components and switching losses.
Co
Ref.
Speed
PMBLDC
Motor
Speed
Controller
Position
to Speed
Position
Sensing
Ref. Current Generator
PWM Current Controller
i*
a
i*
b
Vdc

+
Ref.
Voltage
ia
VSI
Current
Sensing
ib

+
Lo
C1
Li
Ls
is
Voltage
Controller
Vs
Ref.
Current
Generator
PWM
Controller
Idc
Cuk Converter
PFC Control Scheme
Vdc
i*
c
ic
ωr
ωe
ω*
r
I*
I*
dc
I
Vin
V*
dc
Ve
Fig. 2. Control Schematic of PFC Cuk Converter Fed PMBLDCM Drive.
The use of current multiplier approach with average current control scheme in
continuous conduction mode (CCM) of the PFC converter makes this topology an
efficient option. The control loop employed to execute PFC action involves outer
voltage loop and inner current loop. For control action, the DC link voltage is
sensed and compared with the set reference voltage at DC link. The error voltage
is passed through a voltage PI controller to give the modulating current signal.
This signal is multiplied with a unit template of input AC voltage which is
compared with DC current sensed after the DBR. Hall effect voltage and current
sensors are employed for voltage and current sensing. This current error is
amplified and amplified signal is then compared with sawtooth carrier wave to
generate the PWM pulses for turning on/off the DCDC converter switch. The
complete control strategy consists of selection of sensors, design of control
algorithm and PWM controller for the drive.
3. Design of Cuk PFC Converter for PMBLDCM
Figure 2 shows the proposed topology of Cuk converter fed PMBLDCM drive. In
the Cuk converter, the inductance, Lo, of output ripple filter restricts the inductor
peak to peak current ripple, ILo, within specified value for a given switching
frequency, fs. The capacitor, Co, of the output ripple filter is considered to be very
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Power Factor Correction in Permanent Magnet Brushless DC Motor Drive 417
Journal of Engineering Science and Technology December 2010, Vol. 5(4)
large for ripple free output voltage. However, in practical situations the output
voltage cannot be ripple free due to finite value of the capacitor, Co, which can be
calculated for a specified ripple in output voltage, VCo. Suitable snubbers are
also designed for active switches along with the input and output ripple filters.
The Cuk converter belongs to the buckboost converter family and has
inverted voltage polarity at the output. It operates on the principle of capacitive
energy transfer and uses inductors on both sides of the switch to reduce current
ripple [7,10]. The Cuk DCDC converter provides a regulated DC output voltage
for wide range of input DC voltage. It is designed for constant voltage across the
intermediate capacitor, C1, as it operates on the principle of capacitive energy
transfer. The boost inductor, Li, output filter inductor, Lo, and capacitor, Co, are
designed according to maximum allowable current and voltage ripple during
transient conditions of the PMBLDCM drive. The design equations governing the
duty ratio and other component values are as follows.
Output voltage
D
DV
DV
V
in
dc
1
(1)
Boost inductor
Lis
in
I
i
f
L
(2)
Intermediate capacitor
oC
V
s
VV
D
Rf
D
C
/
1
1
(3)
Output filter inductor
Los
I
o
o
If
L
1
(4)
Output filter capacitor
o
av
o
V
C
2
(5)
For Vdc = 400 V, Vin = 198 V for Vac = 220 Vrms, fs = 40 kHz, Iav = 4 A,
R= (Vo/Iav) = 100 Ω, ΔILi= 1.5 A, ΔILo= 2.0 A (50% of Iav), ΔVo= 4.25 V (1.06% of
Vo), ΔVC1= 15 V (3.75% of Vo), the design parameters are calculated on the basis
of above equations as Li=2.21 mH, C1=4.45 µF, Lo=1.6 mH, Co=1500 µF.
4. Modeling of The Proposed PFC Converter for PMBLDCM Drive
The modeling of the proposed PFC converter fed PMBLDCM drive involves
modeling of a PFC converter and modeling of PMBLDCM drive. The PFC
converter consists of a DBR at front end and a Cuk converter with output ripple
filter. Therefore, its modeling mainly includes the modeling of the voltage
controller, reference current generator and PWM controller. The various
components of PMBLDCM drive are a speed controller, a reference current
generator, a PWM current controller and a PMBLDC motor. Each of the above
components of a PMBLDCM drive are modeled by mathematical equations and
combination of such models represent complete PMBLDCM drive.
4.1. PFC converter
The modeling of a PFC converter mainly consists of the modeling of the voltage
controller, reference current generator and a PWM controller. These components
require various signals sensed from the system e.g. DC link voltage, current after
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418 S. Singh and B. Singh
Journal of Engineering Science and Technology December 2010, Vol. 5(4)
DBR and input voltage template. The accuracy of the controller depends on these
sensed signals.
4.1.1.
Voltage controller
The modeling of a voltage controller is of prime importance as the performance of
the PMBLDCM drive depends on this controller. The proportional integral (PI)
controller is used to control the DC link voltage. At kth instant of time,
reference DC link voltage, Vdc(k) is sensed DC link voltage then the voltage error
Ve(k) is calculated as,
)(
*kVdc
is
)()()(
*
dc
kVkVkV
dce
Ve(k) (6)
This voltage error is processed through the voltage controller to get desired
control signal. The output of the PI controller at kth instant I(k) is given as,
I(k) = I(k1) + Kpv[Ve(k) – Ve(k1)] + KivVe(k) (7)
where Kpv and Kiv are the proportional and integral gains of the voltage controller.
4.1.2.
The reference inductor current,
vi dc
ukII
(8)
where uvi is the unit template of the input AC mains voltage calculated as,
Reference current generator
*
dc
I
, of the Cuk converter is given as,
*
in
d
vi
V
V
u
;
id
VV
; Vi= Vin sin ωt (9)
where ω is frequency in rad/s at input AC mains.
4.1.3.
PWM controller
The reference Cuk converter current is compared with its sensed current to
generate the current error
dc dcdc
IIi
kdc and compared with carrier waveform md(t). The switching signals for the
IGBT of the PFC converter are generated by comparing this amplified current
error with sawtooth carrier waveform of 20 kHz.
*
. This current error is amplified by gain
If
kdc idc > md (t) then S = 1 (10)
If
kdc idc ≤ md (t) then S = 0 (11)
where S is the switching function of the switch used in Cuk converter
representing „on‟ position with S = 1 and its „off‟ position with S = 0.
4.2. PMBLDCM drive
The modeling of a speed controller is quite important as the performance of the
system depends on this controller. If at kth instant of time,
speed, ωr(k) is rotor speed then the speed error ωe(k) can be calculated as,
)()(
kkk
rre
k
r
*
is reference
*
(12)
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Power Factor Correction in Permanent Magnet Brushless DC Motor Drive 419
Journal of Engineering Science and Technology December 2010, Vol. 5(4)
This speed error is processed through a speed controller to get desired
control signal.
4.2.1.
Speed controller
The PI controller is the simplest and most commonly used speed controller. The
output of the PI controller at kth instant T(k) is given as,
T(k) = T(k1) + Kpω[ωe(k) – ωe(k1)] + Kiω ωe(k) (13)
where Kpω and Kiω are the proportional and integral gains of the speed controller.
4.2.2.
Reference winding currents
The amplitude of stator winding current is as,
K
2
b
kT
I
*
(14)
where Kb is the back emf constant of the PMBLDCM.
The reference phase currents of the motor winding are denoted by
,, ,
cb
ii
for phases a, b, c respectively. For duration of 060º the reference
currents can be given as,
***
a
i
0 and , , 1
*
c
*
b
*
a
iIii
(15)
Similarly, the reference winding currents during other 60º duration are generated
in rectangular 120º block form in phase with trapezoidal voltage of respective
phases. These reference currents are compared with sensed phase currents to
generate the current errors
aaa
iii
phases of the motor.
*
,
bbb
iii
*
,
ccc
iii
*
for three
4.2.3.
PWM current controller
The PWM current controller compares these amplified current errors of each
phase with carrier waveform of a fixed frequency and generates the switching
sequence for the voltage source inverter. These current errors ia, ib, ic are
amplified by gain k1 before comparing with carrier waveform m(t). The switching
sequence is generated based on the logic given for phase “a” as,
If
k1 ia > m(t) then Sa = 1 (16)
If
k1 ia ≤ m(t) then Sa = 0 (17)
The switching sequences Sb and Sc are generated using similar logic for other
two phases of the motor. For the projectile configuration comprising conical
forebody and boattail, the effect
4.2.4.
PMBLDC motor
The PMBLDC motor can be modeled in the form of a set of differential equations
given as,
pix = (vx  ix Ra – ex)/(Ls+M) (18)
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420 S. Singh and B. Singh
Journal of Engineering Science and Technology December 2010, Vol. 5(4)
pr = (P/2) (TeTl)/ J
p = r
The back emfs may be expressed as a function of position () as,
(19)
(20)
ex= Kb fx() r (21)
where x can be phase a, b or c and accordingly fx() represents function of
rotor position with a maximum value ±1, identical to trapezoidal induced emf
given as,
fa(θ) = 1 for 0 < θ < 2π/3 (22)
fa(θ) = (6/ π)( π θ) 1
for 2π/3 < θ < π (23)
fa(θ) = 1
for π < θ < 5π/3 (24)
fa(θ) = (6/π)(θ 2π) +1
for 5π/3 < θ < 2π (25)
The functions fb(θ) and fc(θ) are similar to fa(θ) with a phase difference of 120º
and 240º respectively. Therefore, the electromagnetic torque expressed as,
Te = Kb[fa(θ) ia + fb(θ) ib+ fc(θ) ic] (26)
Equations (1826) represent the model of the PMBLDC motor.
5. Performance Evaluation
The performance of the proposed PMBLDCM drive is evaluated for a compressor
load of an airconditioner in MatlabSimulink environment. The compressor
behaves as a constant torque equal to rated torque load and runs at variable speed
as per requirement of air conditioning system. The PMBLDCM of 1.5 kW, 400 V
rating, with 1500 rpm and 10 Nm torque is used to drive such load. The detailed
data of the PMBLDC motor are given in Appendix A. The performance of the
drive is simulated for constant rated torque (10 Nm) at reference speed of 1000
rpm. The DC link voltage is kept constant at 400 V with the input AC voltage of
220 Vrms. The components of Cuk converter are selected on the basis of PQ
constraints at AC mains and allowable ripple in DClink voltage as discussed in
Section 3. The controller parameters have been tuned to get the desired PQ
parameters and the values of controller gains are given in Appendix A. The
performance evaluation is made on the basis of various PQ parameters i.e. current
total harmonic distortion (THDi) at input AC mains, distortion factor (DF),
displacement power factor (DPF), power factor (PF), crest factor (CF), input AC
current rms value (Isrms) and efficiency of the drive.
5.1. Performance during starting
Figure 3(a) shows that the starting of the drive is smooth with rated torque (10
Nm) and PFC is achieved during the starting of the drive. The motor is started
from 220 Vrms AC input at rated torque with a reference speed of 1000 rpm. The
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Power Factor Correction in Permanent Magnet Brushless DC Motor Drive 421
Journal of Engineering Science and Technology December 2010, Vol. 5(4)
maximum allowable torque and the stator current are limited to double the rated
value. The motor speed reaches the reference speed within 0.2 s. Thereafter, the
stator current and motor torque resumes the rated value within 0.01 s.
5.2. Performance during speed change
The speed is increased and decreased at rated torque for detailed evaluation of the
drive as shown in Figs. 3(b)(d). The motor speed is increased to 1200 rpm, as
shown in Fig. 3(b) and decreased to 750 rpm, as shown in Fig. 3(c) from 1000
rpm. The motor attains the reference speed within couple of cycles of AC mains
frequency during these changes. Moreover, the motor speed is reduced to 300 rpm
(20% of its rated value) from 750 rpm within 0.02 s. while achieving the PFC at
input AC mains, as shown in Fig. 3(d).
Fig. 3(a) Starting of PMBLDCM Drive at 1000 rpm (104.7 rad/s).
Fig. 3(b) Speed Change from 10001200 rpm (104.7 125.7 rad/s).
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422 S. Singh and B. Singh
Journal of Engineering Science and Technology December 2010, Vol. 5(4)
Fig. 3(c) Speed Change from 1000750 rpm (104.778.5 rad/s).
Fig. 3(d) Speed Change from 750300 rpm (78.531.4 rad/s).
Fig. 3. Performance of a Cuk Converter Fed PMBLDCM Drive during
Transient Conditions at Rated Torque (10Nm) with 220 VAC Input.
5.3. Performance during steady state condition
The current waveforms at AC input mains and its harmonic spectra during steady
state at 1200 rpm, 1000 rpm, 750 rpm and 300 rpm are shown in Figs. 4(a)(d).
The current THD at AC mains remains less than 3% up to 50% of rated speed.
However, the THD of AC mains current of the order of 5.57% is attained at 20%
of rated speed with near unity power factor in the wide range of speed control.
Moreover, the drive shows an improved performance in terms of reduced torque
ripple, current ripple and speed ripple during steady state operating conditions.
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Power Factor Correction in Permanent Magnet Brushless DC Motor Drive 423
Journal of Engineering Science and Technology December 2010, Vol. 5(4)
(a) Is and its THD at 1200 rpm. (b) Is and its THD at 1000 rpm.
(c) Is and its THD at 750 rpm. (d) Is and its THD at 300 rpm.
Fig. 4. Supply Current (Is) Waveform and its Harmonic Spectra
(at 220 VAC) of a Cuk Converter Fed PMBLDCM Drive
During Steadystate Condition at Rated Torque.
5.4. Performance during input voltage variation
The variation of PQ parameters is observed for variable input AC voltages (170
V270 V) with constant DC link voltage (400 V) to the drive for a speed of 1000
rpm as shown in Fig. 5. These results show reduced THD of AC mains current
and improved PF in wide range of input AC voltage. The transient and steady
state performances, current waveforms and its THD and PQ parameter variation
with input voltage are shown in Figs. 35 to provide an exhaustive evaluation of
the proposed topology. Moreover, the PQ parameters for variable AC input
voltage are also shown in Table 1 for comparison. The current THD at input AC
mains in steady state conditions always remains within the standards of IEC
6100032 and the power factor remains near unity.
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424 S. Singh and B. Singh
Journal of Engineering Science and Technology December 2010, Vol. 5(4)
Fig. 5. Variation of PQ Parameters of a Cuk Converter Fed PMBLDCM
Drive with Input Supply Voltage Variation (DC Link Voltage kept Constant
at 400 V) at 1000 rpm Speed and Rated Torque (10 Nm).
Table 1. Variation of PQ Parameters with Input AC Voltage (VAC) at 1000 rpm
Speed and Rated Torque (10 Nm) with Constant DC Link Voltage (400 V).
VAC (V)
THDi (%) DPF PF
170
1.59 0.9998 0.9997
180
1.69 0.9997 0.9996
190
1.78 0.9997 0.9995
200
1.97 0.9997 0.9995
210
2.19 0.9997 0.9995
220
2.24 0.9997 0.9994
230
2.36 0.9996 0.9993
240
2.53 0.9995 0.9992
250
2.63 0.9994 0.9991
260
2.73 0.9994 0.9990
270
2.90 0.9993 0.9989
CF
1.41
1.41
1.41
1.41
1.41
1.42
1.41
1.41
1.41
1.41
1.41
Is (A)
6.83
6.45
6.11
5.81
5.53
5.28
5.05
4.85
4.65
4.48
4.31
Drive (%)
91.2
91.1
91.1
91.1
91.1
91.1
91.0
91.0
91.0
90.9
90.8
6. Conclusion
A Cuk converter based PFC topology for a PMBLDCM drive has been proposed
and validated for a compressor load of an airconditioner. The PFC converter has
ensured reasonable high power factor of the order of 0.998 in wide range of the
speed as well as input AC voltage. Moreover, performance parameters show an
improved power quality with less torque ripple, smooth speed control of the
PMBLDCM drive. The THD of AC mains current has been observed well below
6% in most of the cases and completely satisfies the international norms [6]. The
performance of the drive has been found very good in the wide range of input AC
voltage with desired power quality parameters. This topology has been found
suitable for the applications involving speed control at constant torque load.
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Appendix A
PMBLDC Motor Data
Rated power
1.5 kW Resistance Rs
Rated voltage
400 VDC Inductance (Ls+M)
Rated speed
1500 rpm Inertia J
Rated torque
10 Nm Back EMF constant Kb
Poles
4
The circuit parameters used for simulations: source impedance: 0.03 pu,
switching frequency of PFC switch = 20 kHz. The gains of voltage and speed PI
controllers: Kpv= 0.09985, Kiv= 1.25, Kpω= 0.11, Kiω= 1.2.
2.8 Ω/ph.
5.21 mH/ph.
0.013 kgm2
0.615 V s/rad