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Volume IV/Issue2/OCT2014
P.G. scholar, Dept of EEE
Assistant Professor & HOD (EEE)
ABSTRACT: The brushless dc (BLDC) servomotor drives
have been widely used in aeronautics, electric vehicles,
robotics, and food and chemical industries. The use of a
permanent-magnet (PM) brushless dc motor (PMBLDCM)
in low-power appliances is increasing because of its features
of high efficiency, wide speed range, and low maintenance.
Brushless DC Motors are driven by DC voltage but current
commutation is controlled by solid state switches. The
commutation instants are determined by the rotor position.
The rotor shaft position is sensed by a Hall Effect sensor,
which provides signals to the respective switches. Hall
Effect sensors are used to ascertain the rotor position and
from the Hall sensor outputs, it is determined whether the
machine has reversed its direction. This is the ideal moment
for energizing the stator phase so that the machine can start
motoring in the counter clockwise direction. There are very
few publications regarding PFC in PMBLDCMDs despite
many PFC topologies for switched mode power supply and
battery charging applications. This work deals with an
application of a PFC converter for the speed control of a
PMBLDCMD. For the proposed voltage controlled drive, a
Boost dc–dc converter is used as a PFC converter because of
its continuous input and output currents, small output filter,
and wide output voltage range as compared to other single
switch converters. This work presents design and digital
implementation of a controller for achieving improved
performance of Brushless dc (BLDC) servomotor drive. The
proposed controller based BLDC motor is operated in four
quadrant operation and in the extension to this work Power
Factor correction is also achieved.
Index Terms: BLDC Motor, Cuk Converter, PI Controller,
VSI (Voltage Source Inverter).
The use of a permanent-magnet (PM) brushless dc motor
(PMBLDCM) in low-power appliances is increasing
because of its features of high efficiency, wide speed range,
and low maintenance. It is a rugged three-phase synchronous
motor due to the use of PMs on the rotor. The commutation
in a PMBLDCM is accomplished by solid state switches of a
three-phase voltage-source inverter (VSI). The brushless dc
motor has a rotor with permanent magnets and a stator with
windings. It is essentially a DC motor turned inside out. The
brushes and commutator have been eliminated and the
windings are connected to the control electronics. The
control electronics replace the function of the commutator
and energize the proper winding. The motor has less inertia,
therefore easier to start and stop. BLDC motors are
potentially cleaner, faster,more efficient, less noisy and
more reliable.
Fig. 1. Current waveform at ac mains and its harmonic spectra for the
PMBLDCM drive (PMBLDCMD) without PFC
A PMBLDCM has the developed torque proportional to its
phase current and its back electromotive force (EMF), which
is proportional to the speed [1]-[4]. Therefore, a constant
current in its stator windings with variable voltage across its
terminals maintains constant torque in a PMBLDCM under
variable speed operation. A speed control scheme is
proposed which uses a reference voltage at dc link
proportional to the desired speed of the permanent-magnet
brushless direct current (PMBLDC) motor. However, the
control of VSI is only used for electronic commutation
based on the rotor position signals of the PMBLDC motor.
The PMBLDCMD is fed from a single-phase ac supply
through a diode bridge rectifier (DBR) followed by a
capacitor at dc link.
Fig. 2. BLDC motor showing the commutation sequence.
Hysteresis current control and pulse width modulation
(PWM) control coupled with continuous control theory have
produced the most widely used BLDC motor control
techniques [4]. Hysteresis current control is essential toward
instantaneous torque control, yielding faster speed response
compared to PWM control. For most applications,
proportional-integral (PI) current and speed compensators
are sufficient to establish a well-regulated speed/torque
The Brushless DC motor is driven by rectangular or
trapezoidal voltage strokes coupled with the given rotor
position. The voltage strokes must be properly aligned
between the phases, so that the angle between the stator flux
and the rotor flux is kept close to 90 to get the maximum
developed torque. BLDC motors often incorporate either
internal or external position sensors to sense the actual rotor
position or its position can also be detected without sensors.
BLDC motors are used in Automotive, Aerospace,
Consumer, Medical, Industrial Automation equipments and
instrumentation. This paper is organized as follows: Section
II describes the Four-quadrant control and operation of the
BLDC drive.
Volume IV/Issue2/OCT2014
A large amount of literature exists on four quadrant control
of conventional BLDC drives with high degree of freedom
in the machine converter. This is due to the absence of the
converter itself on the scene so far. Significant features
peculiar to this converter are limited direct current control of
the main phase and its heavy dependence on the auxiliary
phase winding and auxiliary capacitor state. Likewise, the
auxiliary winding current control is dependent on the duty
cycle of the controllable switch, motor speed and load, and
state of the auxiliary capacitor. These constraints have to be
managed very tightly in order to implement a four-quadrant
variable speed operation in this motor drive. It is discussed
in this section
A. Clockwise Motoring And Regeneration Mode :
In order to achieve motoring in the forward direction, for
example, the CW direction, the stator winding should be
excited when the rotor is moving from the unaligned to the
aligned position. Assuming that the rotor poles reach the
unaligned position (almost in alignment with the auxiliary
stator poles) of the main phase winding and such a position
is detected, the main phase winding is energized. When the
rotor poles have reached near he aligned position with the
main poles, the current in the main phase is turned off. The
machine spins then, for example, in the CW direction and,
during this time, the main winding is energized as the rotor
poles move from the auxiliary stator poles to the main stator
poles. The regenerative braking [12], on the contrary, is
achieved by excitation of the stator windings when the rotor
moves from the aligned position toward the unaligned
position. During this time, the kinetic energy in the machine
is transferred to the dc-link source via the auxiliary winding.
Note that the machine is still in the CW direction of rotation
but its speed rapidly decreases toward standstill.
B. Counter Clockwise (CCW) Direction and
When the speed reversal command is obtained, the control
goes into the CW regeneration mode as explained in the
paragraph above. That brings the rotor to the standstill
position. Instead of waiting for the absolute standstill
position, continuous energization of the main phase is
attempted during the time rotor poles move from aligned to
unaligned rotor positions. This not only slows the rotor to
standstill rapidly but also provides an opportunity for
reversal if the rotor poles come to a stop between the main
and auxiliary poles. Therefore, there is the necessity for
determining the instant when the rotor of the machine is
ideally positioned for reversal. Hall-effect sensors are used
to ascertain the rotor position and speed and they are located
at the main winding and auxiliary winding. From the Hall
sensor outputs, it is determined whether the machine has
reversed its direction. Crucial to this is finding the aligned
rotor position of the rotor poles with the auxiliary poles.
This is the ideal moment for energizing the main stator
phase so that the machine can start motoring in the CCW
Volume IV/Issue2/OCT2014
conducts currents of the inductors L1 and L2, whereas
capacitor C1 is charged by the inductor L1 current.
Fig.3: Operating Modes
Fig.6: Cuk converter: (a) circuit diagram
To obtain the dc voltage transfer function of the converter,
we shall use the principle that the average current through a
capacitor is zero for steady-state operation. Let us assume
that inductors L1 and L2 are large enough that their ripple
current can be neglected. Capacitor C1 is in steady state if
IL2DT =IL1(1-D)T
For a lossless converter
Fig.4: Four Quadrants of operation
Combining these two equations, the dc voltage transfer
function Of the Cuk converter is
MV=VO/VS= D/(1-D)
This voltage transfer function is the same as that for the
buck-boost converter.
The boundaries between the continuous conduction mode
(CCM) and
Discontinuous conduction mode (DCM) are determined by
For L1
Fig.5: Equivalent Circuit of power stage of BLDC
And for L2.
The circuit of the Cuk converter is shown in Fig.a. It
consists of dc input voltage source VS, input inductor L1,
controllable switch S, energy transfer capacitor C1, diode D,
filter inductor L2, filter capacitor Cand load resistance R. An
important advantage of this topology is a continuous current
at both the input and the output of the converter.
Disadvantages of the Cuk converter are a high number of
reactive components and high current stresses on the switch,
the diode, and the capacitor C1. When the switch is on, the
diode is off and the capacitor C1 is discharged by the
inductor L2 current. With the switch in the off state, the
The output part of the Cuk converter is similar to that of the
buck converter. Hence, the expression for the filter capacitor
C is
Cmin = (
The peak-to-peak ripple voltage in the capacitor C1can be
estimated as
Vr1= (
A transformer (isolated) version of the Cuk converter can
beobtained by splitting capacitor C1 and inserting a high
frequency transformer between the split capacitors.
Volume IV/Issue2/OCT2014
overshoot in the actual speed, which means it aids the motor
to run. At other times the speed is stabilized with the
reference speed. The reference speed is 1500 rpm. The speed
comparison between the actual speed and the reference
speed is shown in Fig. 10.
Fig.9: Output simulink model-Rotor speed(rpm), Stator
current (A), Stator back emf (V)
The Hall sensor signals and the phase current (of one phase)
of three phase Brushless DC motor are shown in Fig. 13.
The Pulse Width Modulation (PWM) pulses applied to the
inverter circuit at the appropriate time to trigger the
appropriate switches are the control signals to the circuit. It
Fig.7: simulink Model of PFC based BLDC Drive
depicts that the motor is running in the forward direction,
after a time interval brake is applied, the motor stops
decelerating at this point the battery starts charging. Once
the brake is released the motor starts to run. Only four of six
PWM pulses are shown in the scope. The capacitor is placed
in between the DBR and inverter some problem has been
occurred in the currents at the input side. This problem as
shown in the Fig:12. The problem in the input current is
rectified by using cuk converter and the power factor should
become unity. The input side of the inverter got pure dc as
shown in Fig:11 (a) and (b) .
Fig.8: Modelling of co
The Simulink model of the BLDC motor [13]. The closed
loop controller for a three phase brushless DC motor is
modelled using MATLAB/Simulink [14] and [15] is shown
in Fig. 7. Permanent Magnet Synchronous motor with
trapezoidal back EMF is modelled as a Brushless DC
Motor.The model of the controller shown in Fig. 8, receives
the Hall signals as its input, converts it in to appropriate
voltage signals.
The simulation results shown in Fig. 9 indicates that, when a
negative torque is applied at time 0.6s, there is a peak
Fig.10: Reference speed and actual speed in rpm.
Volume IV/Issue2/OCT2014
(a)input voltage and current
Fig.13:Hall Sensor signals and Phase Current
In this paper, the power factor of the BLDC drive is
(b) Dc output voltage
Fig.11: After connecting the cuk converter at the rectifier
corrected by controlling the input power. A control scheme
is proposed for BLDC motor to change the direction from
CW to CCW and the speed control is achieved both for
servo response and regulator response. The motor reverses
its direction almost instantaneously, it will pass through
zero, but the transition is too quick.
(a) Input voltage and current
(b) Dc output voltage
Fig.12: After connecting the capacitor at the rectifier end
Volume IV/Issue2/OCT2014
[1] T. Kenjo and S. Nagamori, Permanent Magnet Brushless DC Motors. Oxford, U.K.: Clarendon, 1985.
[2] . J. Sokira and W. Jaffe, Brushless DC Motors: Electronic Commutation and Control. New York: Tab, 1989.
[3] J. R. Hendershort and T. J. E. Miller, Design of Brushless Permanent- Magnet Motors. Oxford, U.K.: Clarendon,
[4] J. F. Gieras and M. Wing, Permanent Magnet Motor Technology—Design and Application. New York: Marcel
Dekker, 2002.
[5] F. Rodriguez and A. Emadi, “A novel digital control technique for brushless DC motor drives,” IEEE Trans. Ind.
Electron., vol. 54, no. 5,pp. 2365–2373, Oct. 2007.
[6] N. Mohan, M. Undeland, andW. P. Robbins, Power Electronics: Converters, Applications and Design. Hoboken,
NJ: Wiley, 1995.
[7] S. Cuk and R. D. Middlebrook, “Advances in switched-mode power conversion Part-I,” IEEE Trans. Ind. Electron.,
vol. IE-30, no. 1, pp. 10–19, Feb. 1983.
[8] S. Hossain, I. Husain, H. Klode, B. Lequesne, and A. Omekanda, “Fourquadrant control of a switched reluctance
motor for a highly dynamic actuator load,” in Proc. IEEE APEC’02, 2002, pp. 41–47.
[9] C. J. Tseng and C. L. Chen, “A novel ZVT PWM Cuk power factor corrector,” IEEE Trans. Ind. Electron., vol. 46,
no. 4, pp. 780–787, Aug. 1999.
[10] A.Sathyan, N. Milivojevic, Y.-J. Lee, M. Krishnamurthy, and A. Emadi, “An FPGA-based novel digital PWM
control scheme for BLDC
[11] motor drives,” IEEE Trans. Ind. Electron., vol. 56, no. 8, pp. 3040–3049, Aug. 2009.
[12] W. Cui, H. Zhang, Y.-L. Ma, and Y.-J. Zhang, “Regenerative braking control method and optimal scheme for
electric motorcycle,” in Proc.Int. Conf. Power Engineering, Energy and Electrical Drives, Spain, 2011, pp. 1–6.
[13] V. U, S. Pola, and K. P. Vittal, “Simulation of four quadrant operation& speed control of BLDC motor on
MATLAB/SIMULINK,” in Proc.IEEE Region 10 Conference, 2008, pp. 1–6.
[14] C. S. Joice and Dr. S. R. Paranjothi, “Simulation of closed loop control of four quadrant operation in three phase
brushless DC motor using MATLAB/simulink,” in Proc. ICPCES, 2010, pp. 259–263.
[15] M.-F. Tsai, T. PhuQuy, B.-F. Wu, and C.-S. Tseng, “Model construction and verification of a BLDC motor using
MATLAB/SIMULINK and FPGA control,” in Proc. 6th IEEE Conf. Ind. Electron. Appl., Beijing, 2011, pp. 1797
M.Rakesh received the B.TECH degree in electrical and electronics engineering from SREE
CHAITHANYA COLLEGE OF ENGINEERING (JNTU university), Karimnagar, Telangana,India .
And M.TECH from ANURAG COLLEGE OF ENGINEERING (JNTU university)Hyderabad, India.
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