ISSN 2348–2370
Vol.07,Issue.07,
July-2015,
Pages:1222-1227
www.ijatir.org
Improve PFC Bridgeless Buck–Boost Converter-Fed Adjustable-Speed Drive
TOKALA RAGHU1, N. KIRAN KUMAR 2
1
PG Scholar, Vaageswari College of Engineering, Ramakrishna Colony, Karimnagar(Dt), Telangana, India.
Assistant Professor, Vaageswari College of Engineering, Ramakrishna Colony, Karimnagar(Dt), Telangana, India.
2
Abstract: This papers presents a power factor remedied
(PFC) bridgeless (BL) buck–boost converter-fed brushless
direct current (BLDC) power plant get as a cost-effective
remedy regarding low-power software. A method of pace
command of the BLDC powerplant simply by managing
the dc url voltage of the voltage supplier inverter (VSI) is
needed having a single voltage sensor. This allows for the
procedure of VSI at essential volume transferring utilizing
the automated commutation of the BLDC powerplant that
provides decreased transferring failures. Any BL setting of
the buck–boost converter will be recommended that
provides the removing of the diode fill rectifier, hence
minimizing the conduction failures connected with this.
Any PFC BL buck–boost converter was designed to work
throughout discontinuous inductor current method (DICM)
to deliver a built in PFC at hvac mains. This functionality
of the recommended get will be looked at around a wide
range of pace command in addition to various supply
voltages (universal hvac mains at 90–265V) with much
better electric power high quality at hvac mains. This
acquired electric power high quality indices are inside the
suitable restrictions of worldwide electric power high
quality standards these kinds of since the IEC 61000-3-2.
This functionality of the recommended get will be
simulated
throughout
MATLAB/Simulink
natural
environment, plus the acquired email address particulars
are checked.
position is used rather than a mechanical commutation which
has disadvantages like sparking and wear and tear of brushes
and commutator assembly. Power quality problems have
become important issues to be considered due to the
recommended limits of harmonics in supply current by
various international power quality standards such as the
International Electro technical Commission (IEC) 61000-3-2.
For class-A equipment (< 600 W, 16 A per phase) which
includes household equipment, IEC 61000-3-2 restricts the
harmonic current of different order such that the total
harmonic distortion (THD) of the supply current should be
below 19%. A BLDC motor when fed by a diode bridge
rectifier (DBR) with a high value of dc link capacitor draws
peaky current which can lead to a THD of supply current of
the order of 65% and power factor as low as 0.8. Hence, a
DBR followed by a power factor corrected (PFC) converter is
utilized for improving the power quality at ac mains. Many
topologies of the single-stage PFC converter are reported in
the literature which has gained importance because of high
efficiency as compared to two-stage PFC converters due to
low component count and a single switch for dc link voltage
control and PFC operation.
II. CONVENTIONAL SCHEME
A. Schematic Diagram
Keywords: PFC, DICM, THD, Buck-Boost Converter.
I. INTRODUCTION
Efficiency and cost are the major concerns in the
development of low-power motor drives targeting
household applications such as fans, water pumps, blowers,
mixers, etc. The use of the brushless direct current (BLDC)
motor in these applications is becoming very common due
to features of high efficiency, high flux density per unit
volume, low maintenance requirements, and low electromagnetic-interference problems. These BLDC motors are
not limited to household applications, but these are suitable
for other applications such as medical equipment,
transportation, HVAC, motion control, and many industrial
tools. A BLDC motor has three phase windings on the
stator and permanent magnets on the rotor. The BLDC
motor is also known as an electronically commutated
motor because an electronic commutation based on rotor
Fig1. Control scheme of Cuk PFC converter-fed VSIbased PMBLDCMD.
This paper deals with an application of a PFC converter for
the speed control of a PMBLDCMD. For this voltage
controlled drive, a Cuk dc–dc converter is used as a PFC
Copyright @ 2015 IJATIR. All rights reserved.
TOKALA RAGHU, N. KIRAN KUMAR
converter because of its continuous input and output
is achieved by the dc link voltage control of VSI using a BL
currents, small output filter, and wide output voltage range
buck–boost converter. This reduces the switching losses in
as compared to other single switch converters. Moreover,
VSI due to the low frequency operation of VSI for the
apart from PQ improvement at ac mains, it controls the
electronic commutation of the BLDC motor.
voltage at dc link for the desired speed of the Air-Con. The
detailed modeling, design, and performance evaluation of
the proposed drive are presented for an air-conditioner
driven by a 0.816-kW 1500-r/min PMBLDC motor.
B. Proposed Speed Control Scheme of PMBLDC Motor
for Air-Conditioner:
Fig1 shows the proposed speed control scheme which is
based on the control of the dc link voltage reference as an
equivalent to the reference speed. However, the rotor
position signals acquired by Hall-effect sensors are used by
an electronic commutator to generate switching sequence
for the VSI feeding the PMBLDC motor, and therefore,
rotor position is required only at the commutation points.
The Cuk dc–dc converter controls the dc link voltage using
capacitive energy transfer which results in no pulsating
input and output currents . The proposed PFC converter is
operated at a high switching frequency for fast and
effective control with additional advantage of a small size
filter. For high-frequency operation, a metal–oxide–
semiconductor field-effect transistor (MOSFET) is used in
the proposed PFC converter, whereas Insulated gate bipolar
transistors (IGBTs) are used in the VSI Bridge feeding the
PMBLDCM because of its operation at lower frequency
compared to the PFC converter. The PFC control scheme
uses a current multiplier approach with a current control
loop inside the speed control loop for continuousconduction-mode operation of the converter.
The control loop begins with the processing of voltage
error (Ve), obtained after the comparison of sensed dc link
voltage (Vdc) (and a voltage (V*dc) equivalent to the
reference speed, through a proportional–integral (PI)
controller to give the modulating control signal Ic). This
signal (Ic) is multiplied with a unit template of input ac
voltage to get the reference dc current (I*d) and compared
with the dc current (Id) sensed after the DBR. The resultant
current error (Ie) is amplified and compared with a saw
tooth carrier wave of fixed frequency (fs) to generate the
pulse width modulation (PWM) pulse for the Cuk
converter. Its duty ratio (D) at a switching frequency (fs)
controls the dc link voltage at the desired value. For the
control of current to PMBLDCM through VSI during the
step change of the reference voltage due to the change in
the reference speed, a rate limiter is introduced, which
limits the stator current of the PMBLDCM within the
specified value which is considered as double the rated
current in this work.
III. OPERATION OF THE PROPOSED CIRCUIT
A. Schematic Diagram
The parameters of the BL buck–boost converter are
designed such that it operates in discontinuous inductor
current mode (DICM) to achieve an inherent power factor
correction at ac mains. The speed control Of BLDC motor
Fig2. The proposed BL buck–boost converter-based VSIfed BLDC motor drive.
Table1. Comparative Analysis of Proposed BL Buck–
Boost Converter with Existing Topologies
The performance of the proposed drive is evaluated for a
wide range of speed control with improved power quality at
ac mains. Moreover, the effect of supply voltage variation at
universal ac mains is also studied to demonstrate the
performance of the drive in practical supply conditions.
Voltage and current stresses on the PFC converter switch are
also evaluated for determining the switch rating and heat sink
design. Finally, a hardware implementation of the proposed
BLDC motor drive is carried out to demonstrate the feasibility
of the proposed drive over a wide range of speed control with
improved power quality at ac mains. A brief comparison of
various configurations reported in the literature is tabulated in
Table 3.1. The comparison is carried out on the basis of the
total number of components (switch- Sw, diode-D, inductorL, and capacitor-C) and total number of components
International Journal of Advanced Technology and Innovative Research
Volume.07, IssueNo.07, July-2015, Pages: 1222-1227
Improve PFC Bridgeless Buck–Boost Converter-Fed Adjustable-Speed Drive
conducting during each half cycle of supply voltage. The
BL buck and boost converter configurations are not
suitable for the required application due to the requirement
of high voltage conversion ratio. The proposed
configuration of the BL buck–boost converter has the
minimum number of components and least number of
conduction devices during each half cycle of supply
voltage which governs the choice of the BL buck–boost
converter for this application.
B. Operating Principle of PFC BL Buck–Boost
Converter
The operation of the PFC BL buck–boost converter is
classified into two parts which include the operation during
the positive and negative half cycles of supply voltage and
during the complete switching cycle.
1. Operation During Positive and Negative Half Cycles
of Supply Voltage:
In the proposed scheme of the BL buck–boost converter,
switches Sw1 and Sw2 operate for the positive and negative
half cycles of the supply voltage, respectively. During the
positive half cycle of the supply voltage, switch Sw1,
inductor Li1, and diodes D1 and Dp are operated to transfer
energy to dc link capacitor Cd as shown in Fig3(a)–(c).
Similarly, for the negative half cycle of the supply voltage,
switch Sw2, inductor Li2, and diodes D2 and Dn conduct
as shown in Fig. 3(a)–(c). In the DICM operation of the BL
buck–boost converter, the current in inductor Li becomes
discontinuous for a certain duration in a switching period.
Fig.3 shows the waveforms of different parameters during
the positive and negative half cycles of supply voltage.
Fig3. Operation of the proposed converter in different
modes (a)–(c) for a positive half cycle of supply voltage
and (d) the associated waveforms. (a) Mode I. (b) Mode
II.(c) Mode III.
IV. DESIGNING
A. Design of PFC BL Buck–Boost Converter:
A PFC BL buck–boost converter is designed to operate in
DICM such that the current in inductors Li1 and Li2 becomes
discontinuous in a switching period. For a BLDC of power
rating 241W (complete specifications of the BLDC motor are
given in the Appendix), a power converter of 340 W (Po) is
designed. For a supply voltage with an rms value of 220V, the
average voltage appearing at the input side is given as
3.2.2. Operation During Complete Switching Cycle:
Three modes of operation during a complete switching
cycle are discussed for the positive half cycle of supply
voltage as shown here in after.
The relation governing the voltage conversion ratio for a
buck–boost converter is given as
Mode I: In this mode, switch Sw1 conducts to charge the
inductor Li1; hence, an inductor current iLi1 increases in this
mode as shown in Fig3(a). Diode Dp completes the input
side circuitry, whereas the dc link capacitor Cd is
discharged by the VSI-fed BLDC motor as shown in Fig. 3.
Mode II: As shown in Fig3(b), in this mode of operation,
switch Sw1 is turned off, and the stored energy in inductor
Li1 is transferred to dc link capacitor Cd until the inductor is
completely discharged. The current in inductor Li1 reduces
and reaches zero as shown in Fig3.
Mode III: In this mode, inductor Li1 enters discontinuous
conduction, i.e., no energy is left in the inductor; hence,
current iLi1 becomes zero for the rest of the switching
period. As shown in Fig. 3.2(c), none of the switch or
diode is conducting in this mode, and dc link capacitor Cd
supplies energy to the load; hence, voltage Vdc across dc
link capacitor Cd starts decreasing. The operation is
repeated when switch Sw1 is turned on again after a
complete switching cycle.
Fig4. Supply current at the rated load on BLDC motor for
different values of input side inductors with supply voltage
as 220V and dc link voltage as 40.
International Journal of Advanced Technology and Innovative Research
Volume.07, IssueNo.07, July-2015, Pages: 1222-1227
TOKALA RAGHU, N. KIRAN KUMAR
B. Design of Input Inductors (Li1 and Li2)
The value of inductance Lic1, to operate in critical
conduction mode in the buck–boost converter, is given as
Hence, the nearest possible value of dc link capacitor Cd is
selected as 2200μF.
Here R is the equivalent load resistance, d is the duty ratio,
and fs is the switching frequency. Now, the value of Lic1 is
calculated at the worst duty ratio of dmin such that the
converter operates in DICM even at very low duty ratio. At
minimum duty ratio, i.e., the BLDC motor operating at 40
V(Vdcmin), the power (Pmin) is given as 90 W (i.e., for
constant torque, the load power is proportional to speed).
Hence, from (4), the value of inductance Licmin
corresponding to Vdc min is calculated as
The values of inductances Li1 and Li2 are taken less
than 1/10th of the minimum critical value of inductance to
ensure a deep DICM condition [24]. The analysis of supply
current at minimum duty ratio (i.e., supply voltage as 220
V and dc link voltage as 40V) is carried out for different
values of the inductor (Li1 and Li2). Fig. 4 shows the supply
current at the input inductor’s value as Lic, Lic/2, Lic/4, and
Lic/10, respectively. The supply current at higher values of
the input side inductor is highly distorted due to the
inability of the converter to operate in DICM at peak
values of supply voltages. Hence, the values of inductors
Li1 and Li2 are selected around 1/10th of the critical
inductance and are taken as 34 μH. It reduces the size, cost,
and weight of the PFC converter.
C. Design of DC Link Capacitor (Cd)
The design of the dc link capacitor is governed by the
amount of the second-order harmonic (lowest) current
flowing in the capacitor and is derived as follows. For the
PFC operation, the supply current (is) is in phase with the
supply voltage (vs). Hence, the input power Pin is given as
where the latter term corresponds to the second-order
harmonic, which is reflected in the dc link capacitor as
The dc link voltage ripple corresponding to this capacitor
current is given as
For a maximum value of voltage ripple at the dc link
capacitor, Sin(ωt) is taken as 1. Hence, (7) is rewritten as
4.4. Design of Input Filter (Lf and Cf ):
A second-order low-pass LC filter is used at the input side to
absorb the higher order harmonics such that it is not reflected
in the supply current. The maximum value of filter
capacitance is given as
where Ipeak, Vpeak, ωL, and θ represent the peak value of supply
current, peak value of supply voltage, line frequency in
radians per second, and displacement angle between the
supply voltage and supply current, respectively. Hence, a
value of Cf is taken as 330 nF. Now, the value of inductor Lf is
calculated as follows. The value of the filter inductor is
designed by considering the source impedance (Ls) of 4%–4%
of the base impedance. Hence, the additional value of
inductance required is given as
Where fc is the cutoff frequency of the designed filter which is
selected as
fL < fc < fsw
(12)
Hence, a value of fc is taken as fsw/10. Finally, a low-pass
filter with inductor and capacitor of 1.6mH and 330nF is
selected for this particular application.
D. Comparative Analysis of Different Configurations:
A comparative analysis of the proposed BL buck–boost
converter-fed BLDC motor drive is carried out with
conventional schemes. Two conventional schemes of the
DBR-fed BLDC motor drive and a single-switch PFC using a
constant dc bus voltage are used for comparative performance
evaluation. The analysis is classified into two subcategories as
follows.
1. Comparison on Basis of Losses and Efficiency
The losses in the complete BLDC motor drive are classified
as losses in various sections such as DBR, PFC converter,
VSI, and the BLDC motor. The losses in different parts of the
BLDC motor are measured for three different configurations
of the BLDC motor drive. As shown in Fig. 4.2(a), the losses
in two conventional schemes of the BLDC motor drive are
higher in VSI due to the use of PWM-based switching of VSI
which increases the switching losses in the system. This
accounts for an increase in the efficiency of the proposed
system as shown in Fig. 4.2(b). The conventional scheme of
the BLDC motor drive with PFC has the lowest efficiency due
to the high amount of losses in the VSI as well as in the DBR
and PFC converter.
Now, the value of the dc link capacitor is calculated for
the designed value Vdc des with permitted ripple in the dc
link voltage (ΔVdc) taken as 3% as
International Journal of Advanced Technology and Innovative Research
Volume.07, IssueNo.07, July-2015, Pages: 1222-1227
Improve PFC Bridgeless Buck–Boost Converter-Fed Adjustable-Speed Drive
V. SIMULATION CIRCUIT AND RESULTS
Fig8. TORQUE (Te).
Fig5. Simulation Model Diagram.
Fig9. Vdc(v).
Fig6. Stator Current(Ia) & Electromotive Force(Ea).
Fig7. SPEED(N)rpm.
VI. CONCLUSION
A PFC BL buck–boost converter-based VSI-fed BLDC
motor drive has been proposed targeting low-power
applications. A new method of speed control has been utilized
by controlling the voltage at dc bus and operating the VSI at
fundamental frequency for the electronic commutation of the
BLDC motor for reducing the switching losses in VSI. The
front-end BL buck–boost converter has been operated in
DICM for achieving an inherent power factor correction at ac
mains. A satisfactory performance has been achieved for
speed control and supply voltage variation with power quality
indices within the acceptable limits of IEC 61000-3-2.
Moreover, voltage and current stresses on the PFC switch
have been evaluated for determining the practical application
of the proposed scheme. Finally, an experimental prototype of
the proposed drive has been developed to validate the
performance of the proposed BLDC motor drive under speed
control with improved power quality at ac mains. The
proposed scheme has shown satisfactory performance, and it
is a recommended solution applicable to low-power BLDC
motor drives.
International Journal of Advanced Technology and Innovative Research
Volume.07, IssueNo.07, July-2015, Pages: 1222-1227
TOKALA RAGHU, N. KIRAN KUMAR
VII. REFERENCES
[1] C. L. Xia, Permanent Magnet Brushless DC Motor
Drives and Controls. Hoboken, NJ, USA: Wiley, 2012.
[2] J. Moreno, M. E. Ortuzar, and J. W. Dixon, “Energymanagement system for a hybrid electric vehicle, using
ultracapacitors and neural networks,” IEEE Trans. Ind.
Electron., vol. 53, no. 2, pp. 614–623, Apr. 2006.
[3] Y. Chen, C. Chiu, Y. Jhang, Z. Tang, and R. Liang, “A
driver for the singlephase brushless dc fan motor with
hybrid winding structure,” IEEE Trans. Ind. Electron., vol.
60, no. 10, pp. 4369–4375, Oct. 2013.
[4] X. Huang, A. Goodman, C. Gerada, Y. Fang, and Q.
Lu, “A single sided matrix converter drive for a brushless
dc motor in aerospace applications,” IEEE Trans. Ind.
Electron., vol. 59, no. 9, pp. 3542–3552, Sep. 2012.
[5] H. A. Toliyat and S. Campbell, DSP-Based
Electromechanical Motion Control. Boca Raton, FL, USA:
CRC Press, 2004.
[6] P. Pillay and R. Krishnan, “Modeling of permanent
magnet motor drives,” IEEE Trans. Ind. Electron., vol. 35,
no. 4, pp. 537–541, Nov. 1988.
[7] Limits for Harmonic Current Emissions (Equipment
Input Current ≤16 A Per Phase), Int. Std. IEC 61000-3-2,
2000.
[8] S. Singh and B. Singh, “A voltage-controlled PFC Cuk
converter based PMBLDCM drive for air-conditioners,”
IEEE Trans. Ind. Appl., vol. 48, no. 2, pp. 832–838,
Mar./Apr. 2012.
[9] B. Singh, B. N. Singh, A. Chandra, K. Al-Haddad, A.
Pandey, and D. P. Kothari, “A review of single-phase
improved power quality ac dc converters,” IEEE Trans.
Ind. Electron., vol. 50, no. 5, pp. 962–981, Oct. 2003.
[10] B. Singh, S. Singh, A. Chandra, and K. Al-Haddad,
“Comprehensive study of single-phase ac-dc power factor
corrected converters with high-frequency isolation,” IEEE
Trans. Ind. Informat., vol. 7, no. 4, pp. 540–556, Nov.
2011.
Author’s Profile:
Tokala Raghu, received B.Tech
degree in Electrical and Electronics
Engineering from Sindhura College
of Engg. &Tech, NTPC, Ramagundam, Karimnagar,T.S. Andcurrently
pursuing
M.Tech
in
Power
Electronics at Vaageswari College of
Engineering, T.S. My areas of interest
are Power Systems, and Power
Electronics, Electrical Machines.
N.Kiran Kumar, working as Assistant Professor in
Vaageswari College of Engineering, Karimnagar,T.S. He
received the P.G. in Power Engineering and an Energy
system is specialization at Sri Chaithanya Engineering
College at Karimnagar, T.S. And he received B.Tech in
Electrical & Electronics Engineering at Kakathiya Institute
of Technology & Science at Warangal. He areas of interest
are Power Systems, Power Electronics, and Electrical
Machines.
International Journal of Advanced Technology and Innovative Research
Volume.07, IssueNo.07, July-2015, Pages: 1222-1227