International Journal of Revolution in Electrical and Electronic Engineering (IJREEE)
ISSN (Online): 2350 –0220, ISSN (Print): 2350 –0212
Volume 2 Issue 1Mar 2015
AN ADJUSTABLE SPEED PFC BRIDGELESS BUCK BOOST
CONVERTER FED BLDC MOTOR DRIVES WITH SIX
SWITCH VSI INVERTER
A.Anitha1, S.Kamachi2
1
PG Scholar, Department of Electrical and Electronics Engineering, Dhanalakshmi Srinivasan
College of Engineering & Technology, Chennai.
2
Assistant Professor, Department of Electrical and Electronics Engineering, Dhanalakshmi
Srinivasan College of Engineering & Technology, Chennai
Abstract: This paper presents a power factor corrected (PFC) bridgeless (BL) Sepic converter-fed
brushless direct current (BLDC) motor with multi drive option as a cost-effective solution for lowpower application. An approach of speed control of the BLDC motor by controlling the dc link
voltage of the voltage source inverter (VSI) is used with a single voltage sensor .A BL configuration of
the Sepic converter is proposed which offers the elimination of the diode bridge rectifier, thus
reducing the conduction losses associated with it. A PFC BL Sepic converter is designed to operate in
discontinuous inductor current mode (DICM) to provide an inherent PFC at ac mains.
Index Terms—Bridgeless (BL) buck–boost converter, brushless direct current (BLDC) motor,
discontinuous inductor current mode (DICM), power factor corrected (PFC), power quality.
1. 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 problem. 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 position is used rather than a mechanical
commutation which has disadvantages like sparking and wear and tear of brushes and commutator
assembly.
Brushless DC electric motor (BLDC motors, BL motors) also known as electronically commutated
motors (ECMs, EC motors) are synchronous motors that are powered by a DC electric source via an
integrated inverter/switching power supply, which produces an AC electric signal to drive the motor.
In this context, AC, alternating current, does not imply a sinusoidal waveform, but rather a bidirectional current with no restriction on waveform. Additional sensors and electronics control the
inverter output amplitude and waveform (and therefore percent of DC bus usage/efficiency) and
frequency (i.e. rotor speed).
The rotor part of a brushless motor is often a permanent magnet synchronous motor, but can also be a
switched reluctance motor, or induction motor [citation needed].
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ijreee
International Journal of Revolution in Electrical and Electronic Engineering (IJREEE)
ISSN (Online): 2350 –0220, ISSN (Print): 2350 –0212
Volume 2 Issue 1Mar 2015
Brushless motors may be described as stepper motors; however, the term stepper motor tends to be
used for motors that are designed specifically to be operated in a mode where they are frequently
stopped with the rotor in a defined angular position. This page describes more general brushless motor
principles, though there is overlap. Two key performance parameters of brushless DC motors are the
motor constants Kv and Km.
Electrical equipment often has at least one motor used to rotate or displace an object from its initial
position. There are a variety of motor types available in the market, including induction motors,
servomotors, DC motors (brushed and brushless), etc. Depending upon the application requirements, a
particular motor can be selected. However, a current trend is that most new designs are moving
towards Brushless DC motors, popularly known as BLDC motors.
2. PROPOSED BLDC MOTOR DRIVE WITH BL BUCK–BOOST CONVERTER
The proposed BL buck–boost converter-based VSI-fed BLDC motor drive is shown in the fig. 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 is achieved by the dc link voltage control of VSI using a BL buck–boost
converter. This reduces the switching losses in VSI due to the low frequency operation of VSI for the
electronic commutation of the BLDC motor. The performance of the proposed drive is evaluated for a
wide range of speed control with improved power quality at ac mains.
Fig.1 Proposed BLDC motor drive with BL buck–boost converter
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ijreee
International Journal of Revolution in Electrical and Electronic Engineering (IJREEE)
ISSN (Online): 2350 –0220, ISSN (Print): 2350 –0212
Volume 2 Issue 1Mar 2015
3. SIMULATION DIAGRAM
The MATLAB-Simulink model of the BLDC Motor drive with BL Buck-Boost converter fig.2. As
shown in the MATLAB-Simulink circuit, a total of 9 MOSET’s are used and each MOSET is given
separate pulses via the pulse generator block present in MATLAB.
Fig.2 Simulation Diagram
4. RESULTS AND DISCUSION
The performance of the proposed BLDC motor drive is simulated in MATLAB/Simulink environment
using the Sim- Power-System toolbox. The performance evaluation of the pro- posed drive is
categorized in terms of the performance of the BLDC motor and BL buck–boost converter and the
achieved power quality indices obtained at ac mains.
Fig.3 BLDC Output Stator Current
40
ijreee
International Journal of Revolution in Electrical and Electronic Engineering (IJREEE)
ISSN (Online): 2350 –0220, ISSN (Print): 2350 –0212
Volume 2 Issue 1Mar 2015
Fig.4 Rotor Speed Output Waveform
Fig.5 Rotor Speed Output Waveform
4.1 Steady-State Performance
The steady-state behavior of the proposed BLDC motor drive for two cycles of supply voltage at
rated condition (rateddclink voltage of 200 V). The discontinuous induc- tor currents (iLi1 and iLi2)
are obtained, confirming the DICM operation of the BL buck–boost converter. The performance of
the proposed BLDC motor drive at speed control by varying dc link voltage from 50 to 200 V is
tabulated in Table III. The harmonic spectra of the supply current at rated and light load conditions
,i.e.,dc link voltages of 200 and 50V which shows that the THD of supply current obtained is under
the acceptable limits of IEC 61000-3-2.
4.2 Dynamic Performance of Proposed BLDC Motor Drive
The dynamic behavior of the proposed drive system during a starting at 50 V, step change in dc link
voltage from 100 to 150 V, and supply voltage change from 270 to 170 V. A smooth transition of
speed and dc link voltage is achieved with a small overshoot in supply current under the acceptable
limit of the maximum allowable stator winding current of the BLDC motor.
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ijreee
International Journal of Revolution in Electrical and Electronic Engineering (IJREEE)
ISSN (Online): 2350 –0220, ISSN (Print): 2350 –0212
Volume 2 Issue 1Mar 2015
5. COMPARATIVE ANALYSIS
5.1 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. 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. 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.
5.2 Comparison on Basis of Power Quality
The harmonic distortion in a conventional scheme of the DBR- fed BLDC motor drive is as high as
80%–100%, which is not a recommended solution as per the guidelines of IEC 61000- 3-2 [7].The
power quality will be increased.
6. CONCLUSIONS
A PFC BL Sepic converter- nine switch based VSI-fed BLDC motor drive has been proposed
targeting low-power applications. A new method of speed control has been utilized such as hysteresis
control and 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.
7. FEATURES




Switching losses and Conduction losses are reduced.
Power factor is improved.
Power quality will be high.
Sensorless control is possible.
REFERENCES
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3552, Sep. 2012.
3. Pragasan Pillay, Member, Ieee,andr. Krishnan ―Modeling of Permanent Magnet Motor Drives‖ at
IEEE Trans Ind Elec.vol 35,no4,Nov 1988
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ijreee
International Journal of Revolution in Electrical and Electronic Engineering (IJREEE)
ISSN (Online): 2350 –0220, ISSN (Print): 2350 –0212
Volume 2 Issue 1Mar 2015
4. E. Afjei*, O. Hashemipour, M. A. Saati and M. M. Nezamabadi ―A New Hybrid Brushless Dc
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