M.Subhash, et al. Power Factor Correction for Buck-Boost Converter Fed BLDC Motor Drive
REVIEW ARTICAL
Power Factor Correction for Buck-Boost
Converter Fed BLDC Motor Drive
M.Subhash1, M.Raju2
1
Student, Control Systems in Electrical and Electronics Engineering Department, JNTU Hyderabad,
India
1
subhash.mandha@gmail.com
2
Asst. Prof., Electrical and Electronics Engineering Department, Aurora’s Research & Technological Institute
Warangal, India.
2
raju.moutam@gmail.com
Abstract:- This Article provides an power factor corrected
bridgeless buck–boost converter-fed brushless direct current
motor as a cost-effective alternative pertaining to low-power
apps. A technique of pace handle on the BLDC motor by
managing the particular dc link voltage on the voltage source
inverter (VSI) is employed with a sole voltage sensor. This kind
of allows for the particular operation of VSI on essential volume
moving over using the electric commutation on the BLDC motor
that offers reduced moving over loss. The BL setting on the
buck–boost converter is actually offered that offers the
particular reduction on the diode fill rectifier, hence decreasing
the particular conduction loss linked to it. The PFC BL buck–
boost converter was designed to work throughout discontinuous
inductor recent function (DICM) to provide the natural PFC on
ac mains. This functionality on the offered get is actually
examined on the wide range of pace handle and different present
voltages (universal ac mains on 90–265 V) with improved energy
quality on ac mains. This acquired energy quality indices usually
are from the satisfactory restricts of worldwide energy quality
requirements for example the IEC 61000-3-2. This functionality
on the offered get is actually simulated throughout
MATLAB/Simulink surroundings.
Keywords: Power Factor Corrected (PFC), Voltage Source
Inverter (VSI), DICM.
I. INTRODUCTION
Permanent magnet brushless DC motors (PMBLDCMs)
are more preferable for a compressor motor of an airconditioning system because it gives more efficiency, very
low maintenance requirements and high speed range. The
compressor operation is the speed control which results in an
improved efficiency of the system while maintaining the
temperature in the air-conditioned zone at the fixed reference
time to time. Whereas, the normal air conditioners regularly
having a single-phase induction motor to drive the compressor
in „on/off‟ control mode which results in increased losses due
to frequent „on/off‟ operation with increased electrical and
mechanical stresses on the motor, and it will results in low
efficiency and reduced life of the motor. Moreover, the
temperature of the air conditioned zone will be regulated in a
hysteresis band. Therefore, the improved efficiency of the AirConditional system will be certainly reduces the cost of living
and the energy demand to cope up with ever-increasing power
crisis.
PMBLDCM is one type of a three-phase synchronous
motor with permanent magnets (PMs) on the rotor and the
trapezoidal back EMF waveform will be operated on
electronic commutation which is accomplished by solid state
switches, and is powered through a three-phase voltage source
inverter (VSI) which is fed with single-phase AC supply using
a diode bridge rectifier (DBR) followed by smoothening the
DC link capacitor. The compressor will exerts the constant
torque (i.e. rated torque) on the PMBLDCM and will be
operated in speed control mode to improve the efficiency of
the Air-Con system as the back-emf of the PMBLDCM is
proportional to the motor speed and the torque developed is
directly proportional to its phase current, therefore, a constant
torque will be maintained by the constant current in the stator
winding of the PMBLDCM whereas the speed is controlled by
varying the terminal voltage of the motor. With regarding to
this logic the speed control scheme is proposed in this paper
which uses a reference voltage at DC link which is
proportional to the desired speed of the PMBLDC motor.
However, the control of VSI is only for electronic
commutation which is based on the position of rotar signals of
the PMBLDC motor. The PMBLDCM drive is fed from a
single-phase AC mains through a diode bridge rectifier (DBR)
followed by a DC link capacitor which will suffers from
power quality (PQ) disturbances such as poor power factor
(PF), increased total harmonic distortion (THD) of current at
input AC mains and with high crest factor (CF). It is mainly
due to the uncontrolled charging of DC link capacitor which
resulting in the pulsed current waveform having a peak value
higher than the amplitude of the fundamental input current at
AC mains. Moreover, the standards of power quality for low
power equipments emphasize on lower harmonic contents and
near to unity power factor current to be drawn from AC mains
by these motors. The proposed PMBLDCM drive is modeled
in Mat lab- Simulink environment and will be evaluated for an
air conditioning compressor load. The compressor load is
considered as a constant torque load equal to rated torque with
the speed control required by air conditioning system. A 1.5
kW rating PMBLDCM is used to drive the air conditioner
compressor, speed which is controlled effectively by
controlling the DC link voltage. The detailed data of the motor
and simulation parameters are given in the Appendix. The
performance operation of the proposed PFC drive is evaluated
on the basis of various parameters such as total harmonic
distortion (THD) and the crest factor (CF) of the current at
input AC mains, displacement power factor (DPF), power
factor (PF) and efficiency of the drive system (ηdrive) at
different speeds of the motor.
Aurora’s International Journal of Computing | 2015 | Vol. 2. Issue 2 | July-December 2015.
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M.Subhash, et al. Power Factor Correction for Buck-Boost Converter Fed BLDC Motor Drive
II. LITERATURE SURVEY
An electric utility's power load on the electrical distribution
system falls into one of three categories of resistive, inductive
or capacitive. In most industrial facilities, the most common
inductive loads use a conductive coil winding to produce emf
which permits for motor functioning. All inductive loads
requires two different types of power for motor to operate ie.,
Active power (measured in kW or kilowatts) - this power
produces the motive force Reactive power (kvar) which
energizes the magnetic field of the motor. The operating
power from the distribution system constitutes both active
(working) and reactive (non-working) elements. The active
power is useful in driving the motor whereas the reactive
power only provides the magnetic field. Unfortunately,
electric utility's customers will be charged for both active and
reactive power.
For example drop from 1.0 to 0.9 results in 15%
more current being required for the same load. A power factor
of 0.7 requires approximately 40% more current; and a power
factor of 0.5 requires approximately 100% (twice as much) to
handle the same load. The solution for these problems is to
reduce the reactive power drawn from the supply by
improving the power factor. If an AC motor is 100% efficient
it would consume only active power. However, since most AC
motors are only 75% to 80% efficient, which operate at a
lower power factor. This means inefficient and even waste of
energy usage and cost efficiency because most electric utilities
charge penalties for poor, inefficient power factor. Simply
installing capacitors will improve a commercial or industrial
company's power factor and will result in savings on their
electricity bill monthly. An additional potential benefit for
correcting poor power factor includes the reduction of heating
losses in transformers and distribution equipment longer
equipment life.
A. BLDC motors
BLDC motors have very vast applications in the market. They
are Automotive, appliance, industrial controls, automation,
aviation and so on. Out of these, we can categorize the type of
BLDC motor control into three major types
• Constant load
• Varying loads
• Positioning applications.
III. INVERTER OPERATION
Inverter is power electronic circuit which converts a
direct current into an alternative current of desired magnitude
and frequency by using appropriate transformers, switching
and control circuits. Inverters find their application in modern
ac motor and uninterruptible power supplies. Static inverters
which do not have moving parts are used in a wide range of
applications, from small switching power supplies in
computers, to large electric utility high voltage applications
which transport bulk power. Inverters commonly draw AC
power from DC sources such as solar panels or batteries. The
electrical inverter is a high-power electronic oscillator. It is
named as electronic oscillator because in early days
mechanical AC to DC converters was made to work in
reverse, and thus were “inverted", to convert DC to AC. As
inverter performs as reverse of rectifier.
A. Classification of Inverters
1. Based on the source used
 Voltage source inverter
 Current source inverter
2. Based on methods of switching
 Pulse width modulation inverters
 Square wave inverters
3. Based on switching devices used
 Transistorized inverter
 Thyristorized inverter
4. Based on the inversion principle
 Resonant inverter
 Non- Resonant inverter
IV. PROPOSED SPEED CONTROL SCHEME OF PMBLDC
MOTOR FOR AIR CONDITIONER
The proposed speed control method (as shown in
Fig1).controls reference voltage at DC link as an equivalent
reference speed, thereby it replaces the conventional control
of the motor speed and stator current involving various
sensors for voltage and current signals. Moreover, the rotor
position signals are used to generate the switching sequence
for the VSI as an electronic commutator of the PMBLDC
motor. Therefore, rotor-position information is required only
at the commutation points, e.g., every 60degrees electrical in
the three phase. The rotor position of PMBLDCM is sensed
by using hall effect. as shown in Table-I. The DC link voltage
is controlled by a half-bridge buck DC-DC converter based on
the duty ratio (D) of the converter.
For a fast and effective control small size of magnetic
and filters and high switching frequency is used. The
switching frequency (fs) is limited by the switching device
used, operating power level and switching losses of the
device. Metal oxide field effect transistors (MOSFETs) are
used as the switching device for high switching frequency in
the proposed PFC converter. However, insulated gate bipolar
transistors (IGBTs) are used in VSI bridge feeding
PMBLDCM, to reduce the switching stress, as it is operated at
lower frequency when compared to PFC switches. The PFC
control scheme uses the current control loop inside a speed
control loop with current multiplier approach which operates
in continuous conduction mode (CCM) with average current
control.
Aurora’s International Journal of Computing | 2015 | Vol. 2. Issue 2 | July-December 2015.
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ISSN: Online: 2395 – 0420
Print : 2395 - 0412
M.Subhash, et al. Power Factor Correction for Buck-Boost Converter Fed BLDC Motor Drive
The control loop begins with the comparison of
sensed DC link voltage with equivalent voltage to the
reference speed. The resultant voltage error is passed through
a proportional-integral (PI) controller to give a modulating
current signal. This signal is multiplied with a unit template of
input AC voltage and compared with DC current sensed after
the DBR . The resultant current error is amplified and
compared with saw-tooth carrier wave of fixed frequency (fs)
in unipolar scheme (as shown in Fig.4.2) to generate the PWM
pulses for half-bridge converter. For current control of the
PMBLDCM while step change of reference voltage due to the
change in reference speed, the voltage gradient less than 800
V/s is introduced for the change of DC link voltage, which
ensures the stator current of the PMBLDCM within the
specified limits.
inductance (Lo) of the ripple filter restricts the inductor peak
to peak ripple current (ΔILo) within specified value for the
given switching frequency (fs), whereas, the capacitance (Cd)
is calculated for a specified ripple in the output voltage
(ΔVCd). The output filter inductor and capacitor are given as,
(3)
(4)
The PFC converter is designed for a base DC link voltage
of Vdc = 400 V at Vin = 198 V from Vs = 220 Vrms. The
turn‟s ratio of the high frequency transformer (N2/N1) is
taken as 6:1 to maintain the desired DC link voltage at low
input AC voltages typically at 170V. Other design data are fs
= 40 kHz, Io = 4 A, ΔVCd= 4 V (1% of Vdc), ΔILo= 0.8 A
(20% of Io). The design parameters are calculated as Lo=2.0
mH, Cd=1600 μF.
Fig1. Control schematic of Proposed Bridge-buck PFC converter fed
PMBLDCM drive.
Fig 2. PWM control of the buck half-bridge converter.
B. Design of PFC Buck Half-Bridge Converter Based
PMBLDCM Drive
The proposed PFC buck half-bridge converter is designed
for a PMBLDCM drive by considering PQ constraints at AC
mains and allowable ripple in DC link voltage. The DC link
voltage of the PFC converter is given as
(1)
Where N1, N21, N22 are number of turns in primary,
secondary upper and lower windings of the high frequency
(HF) isolation transformer, respectively Vin is the average
output of the DBR for a given AC input voltage (Vs) related
as,
V. RESULTS AND DISCUSSIONS
A. Simulation Model
(2)
The ripple filter is designed to reduce the ripples
introduced in the output voltage due to high switching
frequency for constant of the buck half-bridge converter. The
Fig3. Simulation Model
Aurora’s International Journal of Computing | 2015 | Vol. 2. Issue 2 | July-December 2015.
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ISSN: Online: 2395 – 0420
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M.Subhash, et al. Power Factor Correction for Buck-Boost Converter Fed BLDC Motor Drive
speed control is fast and smooth for both acceleration and
retardation with power factor maintained at nearly unity value.
Moreover, the current of PMBLDCM stator is within the
limits (twice the rated current) due to the introduction of a rate
limiter in the reference voltage. the results are shown like
voltage (vs) and current (is) waveforms at AC mains, DC link
voltage (Vdc), Motor Speed (N), developed electromagnetic
torque of the motor (Te), the stator current of the motor for
phase „a‟ (Ia), and shaft power output (Po).
Fig4. Proposed speed control scheme of PMBLDC motor for air conditioner.
B. Discussion on Simulation Results
1. Starting performance of the PMBLDCM drive at 900rpm.
Fig 6. PMBLDCM drive under speed variation from 900 rpm to 1500 rpm.
Fig 5. Starting performance of the PMBLDCM drive at 900 rpm.
3. PMBLDCM drive under speed variation from 900 to
300 rpm
The performance operation of proposed PMBLDCM
drive fed from 220 V AC mains during starting at rated torque
and 900 rpm speed is shown in Fig. 5. A rate limiter of 800
V/s is introduced as reference voltage to limit the starting
current of the motor as well as the charging current of the DC
link capacitor. The PI controller closely tracks the reference
speed so that the motor attains reference speed smoothly
within 0.35 sec while keeping the stator current within the
desired limits i.e. double the rated value. The current (is)
waveform at input AC mains is in phase with the supply
voltage (vs) demonstrating nearly to unity power factor during
the starting.
2. PMBLDCM drives under speed variation from 900 to
1500 rpm.
During Transient Condition the performance of the drive
during the speed control of the compressor. The reference
speed is varied from 900 rpm to 1500 rpm for the rated load
performance of the compressor. By this it is observed that the
Fig 7. PMBLDCM drive under speed variation from 900 rpm to 300 rpm.
In transient Condition the performance of the drive
during the speed control of the compressor. The reference
speed varied from 900 rpm to 300 rpm for performance of the
compressor at light load. It is observed that the speed control
is fast and smooth for both acceleration and retardation with
Aurora’s International Journal of Computing | 2015 | Vol. 2. Issue 2 | July-December 2015.
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ISSN: Online: 2395 – 0420
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M.Subhash, et al. Power Factor Correction for Buck-Boost Converter Fed BLDC Motor Drive
power factor maintained at nearly unity value. Moreover, the
stator current of PMBLDCM is within the allowed limit
(twice the rated current) due to the introduction of a rate
limiter in the reference voltage. The results are shown as
voltage (vs) and current (is) waveforms at AC mains, speed of
the motor (N), DC link voltage (Vdc), developed
electromagnetic torque of the motor (Te), the stator current of
the motor for phase „a‟ (Ia), and shaft power output (Po).
like this. i.e., voltage (vs) and current (Is) waveforms at AC
mains, the stator current of the motor for phase „a‟ (Ia), DC
link voltage (Vdc), speed of the motor (N), developed
electromagnetic torque of the motor (Te), and shaft power
output (Po).
6. Performance of the PMBLDCM drive at 1500 rpm
4. Performance of the PMBLDCM drive at 300 rpm
Fig 8. Performance of the PMBLDCM drive at 300 rpm.
During Steady State Condition: The speed control of
the compressor driven by PMBLDCM under steady state
condition is carried out with speed at 300 rpm and the results
are shown as voltage (vs) and DC link voltage (Vdc), current
(Is) waveforms at AC mains, motor speed (N), enhanced
electromagnetic torque of the motor (Te), the stator current of
the motor for phase „a‟ (Ia), and shaft power output (Po).
5. Performance of the PMBLDCM drive at 900 rpm
Fig 9. Performance of the PMBLDCM drive at 900 rpm.
During Steady State Condition: The speed control of
the PMBLDCM driven compressor under steady state
condition is carried out at speed 900 rpm and which results as
Fig 10. Performance of the PMBLDCM drive at 1500 rpm.
During Steady State Condition: The speed of the
compressor driven by PMBLDCM under steady state
condition is carried out at 1500 rpm and the results are shown
as voltage (vs) and current (is) waveforms at AC mains, speed
of the motor (N), DC link voltage (Vdc), developed
electromagnetic torque of the motor (Te), the stator current of
the motor for phase „a‟ (Ia), and shaft power output (Po).
VI. CONCLUSION
A new speed control strategy of a drive PMBLDCM
is validated for compressor load of air conditioner which uses
the reference speed as an equivalent reference voltage at DC
link point. The control of speed is directly proportional to the
control voltage at DC link. The rated limiter introduced in the
reference voltage at DC link point is effectively limits the
motor current in the desired value at the transient condition
(speed control & starting). The additional PFC property to the
proposed drive ensures almost unity PF in wide range of speed
and input AC voltage. Moreover, power quality parameters of
this PMBLDCM drive are in conformity to Global standard
IEC 61000-3-2. The proposed drive has demonstrated
improved speed control with most energy efficient operation
of the drive system in the wide range of speed and input AC
voltage. This drive has been found as a best candidate for a
PMBLDCM driving Air-Con load in 1-2 kW power range.
Aurora’s International Journal of Computing | 2015 | Vol. 2. Issue 2 | July-December 2015.
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ISSN: Online: 2395 – 0420
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M.Subhash, et al. Power Factor Correction for Buck-Boost
Buck Boost Converter Fed BLDC Motor Drive
VII.
FUTURE SCOPE
The proposed drive has demonstrated good speed
control with energy efficient operation of thee drive system in
the complete range of speed and input AC voltages.
voltage
Moreover, power quality indices of the proposed drive
PMBLDCM is inconformity to the Global standard IEC
61000-3-2.
2. The proposed drive has been found as a most
promising drive for a variable
ble speed application of an air
conditioner 1-2
2 kW power range. Improved power quality is
observed with almost all unity power factor and efficiency
improved of the drive in a wide range of the speed and an AC
input voltage. A bridge DC-DC
DC converter, conne
connected between
the VSI and the DBR fed from single-phase
phase AC mains
controls DC link voltage of the VSI feeding the PMBLDCM
while maintaining near unity power factor at input AC mains.
The bridge converter is selected for PFC amongst many DC
DCDC converter topologies
ogies due to its features of high voltage
conversion ratio, continuous input current and low input
current ripple. There by performance evaluation of the
proposed drive for an air conditioner compressor driven by a
PMBLDC motor of 3.75 kW, 1500 rpm rating.
converters with symmetrically driven transformer,” IEEE Trans.
Ind. Appl., vol. 37, no. 2, pp. 592 – 600, March
March-April 2001.
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“Small signal modelling of a half bridge converter with an
active
ve input current shaper,” in Proc. IEEE PESC, 2002, vol.1,
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[13] S.K. Han, H.K. Yoon, G.W. Moon, M.J. Youn, Y.H. Kim and
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AUTHOR
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M.Subhash Is Pursuing
His M. Tech. Degree In
Electrical & Electronics Engineering Department From
Aurora’s
Research & Technological Institute
Affiliated To JNTU Hyderabad.
Raju Moutam presently working as Assistant Pro
Professor
in Aurora’s Research & Technological Institute in
Warangal. He received his M.TECH degree with
specialization in Electrical Power Systems from JNTU
Ananthapur
Aurora’s International Journal of Computing | 2015
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December 2015.
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ISSN: Online: 2395 – 0420
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