Indian Journal of Science and Technology, Vol 8(16), DOI: 10.17485/ijst/2015/v8i16/70427, July 2015
ISSN (Print) : 0974-6846
ISSN (Online) : 0974-5645
PFC-based Control Strategies for Four Switch
VSI fed BLDC Motor
V. Ramesh* and Y. Kusuma Latha
Department of Electrical and Electronics Engineering, KL University, Vaddeswaram-522502, India;
rameshvaddi6013@kluniversity.in, kusumalathay@gmail.com
Abstract
In this paper, two control strategies for BLDC motor drive have been implemented. One of the control strategies is based
on PFC-CUK converter fed PMBLDCM drive and another one is PFC-interleaved boost converter fed BLDC motor drive.
Comparison has been made between the two control strategies in terms of Torque ripple, Power factor for different
operating speeds. The proposed work has been implemented under MATLAB/simulink environment. Simulation results
are presented to validate proposed work. From the results, it is observed that PFC interleaved Boost converter fed BLDC
motor drive is more effective compared to CUK converter fed BLDC motor drive.
Keywords: BLDC Motor Drive, CUK Converter, Interleaved Boost Converter, Torque Ripple, Two Leg Inverter
1. Introduction
BLDC motor is three phase AC motor with electronic
commutation and rotor position feedback. In general
BLDC motor is implemented by using six switches, three
phase inverter. The Hall Effect sensors are used to provide
the information related to rotor position. The wide usage
of BLDC motor due its inherent advantages like high efficiency, high flux density, optimal cost etc. this archived
by reduction in the number of switches and sensors1. A
new topology called Four Switches, Three Phase Inverter
(FSTPI) is being considered for BLDC drive system2,3.
This topology reduces decreases the requirement of power
electronic switches, thereby reducing the overall losses
and cost4,5. The Minimization of conducting currents is
difficult to asymmetric voltage PWM4. The existing PWM
schemes cannot be used for FSTPI. Therefore, a new converter topology for three phase BLDC motor drive is to
be developed.
The Back EMF wave form of BLDC motor is
trapezoidal in shape. And the stator current wave form
*Author for correspondence
is rectangular in shape. Hysteresis current control is
employ to maintain the actual motor currents close
to rectangular reference values7. All through steady
state analysis FSTPI fed BLDC motor is studied8,
themodeling, simulation and practical realization is to be
explored. PI control is method of speed control of BLDC
motor which reduces the steady state error to zero9, PI
controller does not respond to quick variation of speed
and reaches the set point slowly. The PI controller can
be easily implemented because simplicity and most
common usage since long time10.
In this paper, two control strategies for BLDC motor
based on CUK converter for Four Switch VSI Fed
PMBLDCM Drive and interleaved boost converter for
four Switches VSI fed PMBLDCM Drive has been developed and comparison is made between this two control
strategies for different operating speeds. The performance
of the BLDC motor with interleaved boost converter for
four switch VSI fed PMBLDCM motor is found to be
quite effective due to improve power quality, less torque
ripple and smooth control of speed of BLDC motor.
PFC-based Control Strategies for Four Switch VSI fed BLDC Motor
2. Proposed Control Schemes
of Four Switches VSI fed
PMBLDCM Drive
2.2 CUK Converter for Four Switch VSI fed
PMBLDCM Drive
2.1 Interleaved Boost Converter for Four
Switches VSI fed PMBLDCM Drive
The Figure 1 shows the interleaved boost converter for
four switches VSI fed BLDC motor drive system. The
control scheme employs hysteresis current control. For
each phase of 3-hystersis current controller, four power
electronic switches are used and hence low cost and less
switching losses and also reductions in torque ripple, as
well as voltage stress and improved dynamic response.
The variable DC output of bridge rectifier is fed to interleaved boost converter. The output of the interleaved
boost converter is fed two leg VSI inverter which drives
BLDC motor. The power factor correction control scheme
is based on the principle of current multiplier approach.
This involves the presence of current loop inside speed
control loop, in case of continuous conduction of the converter. The control loop starts with processing of speed
obtained by comparing the actual, speed with the desired
reference speed. The error is fed to the PI controller to
obtain the reference torque and compared with actual
torque of BLDC motor. The resultant torque error is multiplied with suitable constant and amplified is order to
provide input to reference current block. The reference
current is compared with phase a current which is gives
to hysteresis current control. The hysteresis current controller generates pluses for operation of two leg inverter
and a rate limiter is introduced, which limits the current
within specified limits.
Interleaved Boost Converter
L1
The Figure 2 shows the block diagram of CUK converter
for four switches VSI fed BLDC motor. The performance
of the motor is enhanced due to less ripple content in
torque wave form, reduced voltage stress on the power
electronic switches and improved dynamic response.
The AC supply is given to the diode bridge rectifier.
The variable DC output of bridge rectifier is fed to CUK
converter. The output of CUK converter goes to three
leg inverter which drives BLDC motor. The power factor
correction control scheme is based on the principle of
current multiplier approach. Involves in the presence
of current loop inside speed control loop in case of
continuous conduction of the converter. The control
loop starts with processing of speed error obtained by
comparing the actual speed with the desired reference
speed. The error is fed to the PI controller to obtain the
reference torque and compared with actual torque of
BLDC motor. The resultant torque error is multiplied
with suitable constant amplified is order to provide
input to reference current block. The reference current
is compared with phase currents fed to BLDC motor
which is fed to hysteresis current control. The hysteresis
current controller generates pluses for operation of two
leg inverter for current control of BLDC motor drive.
A rate limiter is introduced, which limits the current
within specified limits.
CUCK Converter
L1
2LEG Inverter
L0
C1
S1
SW
2 LEG Inverter
D
S1
D2
S3
Cd
S2
C1
S2
S1
S2
S4
C2
BLDC
MOTOR
Position
encoder
+
i a*
Tref
Reference
Speed
+
-
G
PI
Gain
Te
ib*
ia
i c*
-
+
ib
+
ic
-
Vol 8 (16) | July 2015 | www.indjst.org
BLDC
MOTOR
Position
encoder
+
i a*
Tref
Reference
Speed
+
-
G
PI
Gain
Te
-
Figure 1. Interleaved Boost Converter for four switches
VSI fed PMBLDCM drive.
2
C2
Hysteresis
Current
controller
Diode
Bridge
Rectifier
Hysteresis
Current
controller
S4
Diode
Bridge
Rectifier
Vs
C0
C1
r
D1
L2
S3
Vs
ib*
ia
-
+
ib i c*
+
ic
-
Figure 2. CUK converter for fourswitchesVSI fed
PMBLDCM drive.
Indian Journal of Science and Technology
V. Ramesh and Y. Kusuma Latha
3. Description and
Implementation of Proposed
Control Schemes
Table1. Operting modes Switching tates and output
phase voltage of BLDC motor
Switching sequence
Figure 1 and Figure 2 show the schematic diagrams of
two leg inverter fed PMBLDC drive with CUK converter
and Interleaved Boost converters respectively. The actual
speed of BLDC motor and reference speed is compared to
obtain error in speed and gives as input to PI controller.
The output of PI controller is reference torque which is
compared with actual torque. The magnitude of reference
currents is obtainedwith the help of torque and appropriate gain values. The hysteresis current control is employed
to control 2 leg inverter fed BLDC motor.
3.1 Speed Controller
The reference torque is given by
Tr (n) = T (n − 1) + K Psc We (n) − We (n − 1) + KiscWe (n) (1)
Where Kpsc = Speed controller Proportional Gain
Kisc = Speed controller of the Integral Gain
I ref = K te ∗ Tr (2)
Where Tr = Reference Torque
Kte = Constant Torque
The Iref is compared with actual motor current and the
error is fed hysteresis current controller to produce pulses
for 2-Leg inverter
3.4 Two Leg Inverter
V
Van = dc ( 4SW1 − 2SW 2 − 1) 3
(3)
Vdc
( −2SW1 + 4SW 2 − 1) 3
(4)
Vol 8 (16) | July 2015 | www.indjst.org
2Vdc
3
–Vdc
Vdc
0
0
Vdc
–Vdc
0
1
Vdc
3
Vdc
3
0
0
1
1
1
−
Vdc
3
−
−
Vdc
( −2SW1 − 2SW 2 + 2) 3
2Vdc
3
(5)
Van 
  Vdc
 vbn  = 3
Vcn 
 
 4 −2

  SW1 Vdc
 −2 4  SW 2 + 3

 −2 −2 


 −1
 
 −1 2
 
(6)
The various operating modes and corresponding output
voltage of BLDC motor are presented in Table 1.
The BLDC motor is modelled using differential equations
given by
di p
dt
(
)
= v p − i p R a − E p / (Ls + M ) (7)
Where a, b, c phases
Four electronic power switches Sw1, Sw2, Sw3 and Sw4
constitute 2 leg inverter. The two legs of the inverter are
connected to 2 phase of BLDC motor while the third
phase of two capacitor
Vbn =
Vdc
3
0
Van
3.5 PMBLDCM Drive
3.3 Hysteresis Controller
Vcn
SW2
Where Van, Vbn, Vcn are terminal voltage of BLDC
motor
The equations can be rewritten is matrix form as
3.2 Reference Current Single (Iref):
The current reference signal is given by
Vbn
SW1
Vcn =
Output phase voltages
dω r  P 
=   ( Tm − Tl ) / J  2
dt
(8)
Back EMF of BLDC motor is terms of rotor angle
position (θ) is given by
Ep = kb fp (θ) ωr
(9)
fp (θ) Is similar to induces EMF which is trapezoidal in
nature is given by
Indian Journal of Science and Technology
3
PFC-based Control Strategies for Four Switch VSI fed BLDC Motor
f p (θ ) = 1
for 0 < q < 2p / 3
 6
f p (θ ) =   ( π − θ ) − 1
 π
for 2p / 3 < q < p (11)
f p (θ ) = −1
for p < q < 5p / 3
 6
f p (θ ) =   (θ − 2 π ) + 1
 π
(10)
(12)
for 5p / 3 < q < 2p (13)
The equation of the electronic torque Tm is expressed
in equation from as
(
)
Tm = K b fa (θ) ia + fb (θ) i b + fc (θ) i c the BLDC motor fed CUK converter, the current reaches
to 1.8 Amp and gradually decreases to 1.6 Amps.
Figure 4 represents Back EMF wave form of BLDC
drive system with interleaved boost converter and CUK
converter. In case of interleaved boost converter, the back
EMF is maintained at 38V where as in case of CUK converter the value is 42V. During dynamic response the
EMF value reaches to 55.2V in case of interleaved Boost
­converter where as the value is 58V for CUK converter.
E lec tromagnetic Torque (Nm)
60
(14)
40
Stator Voltage(Volts)
20
4. Results Discussion
0
-20
-40
4.1 Interleaved Boost Converter and
CUK –converter Four Switches VSI fed
PMBLDC Motor
0
0. 1
0. 2
0. 3
0. 4
0. 5
Time in S ec s
0. 6
0. 7
0. 8
0. 9
1
(a)
E lec tromagnetic Torque (Nm)
60
40
20
0
-20
-40
-60
0
0. 1
0. 2
0. 3
0. 4
0. 5
Time In S ec s
0. 6
0. 7
0. 8
0. 9
1
(b)
E lec tromagnetic Torque (Nm)
10
-80
Stator Voltage(Volts)
Figure 3 shows the stator current of proposed BLDC
motor drive system with interleaved boost converter and
CUK converter. The current raises gradually to 1.4 Amps
initially t = 0.01secs. During the dynamic response of
BLDC motor the current value rapidly rises to 1.5 Amps
and falls to 1.4 Amps. In case of CUK converter fed BLDC
motor, the current is 1.8Amps and gradually reaches a
steady value 1.6Amps.During the dynamic response of
-60
8
Figure 4. Back EMF wave form one of the phase of BLDC
motor, (a). Interleaved Boost Converter and (b). CUK
Converter.
Current(Amps)
6
4
2
0
-2
-4
0
0. 1
0. 2
0. 3
0. 4
0. 5
Time in S ec s
0. 6
0. 7
0. 8
0. 9
1
(a)
2
1.5
1
Current(Amps)
0.5
0
-0.5
-1
-1.5
-2
0
0.1
0.2
0.3
0.4
0.5
Time In S ecs
0.6
0.7
0.8
0.9
1
(b)
Figure 3. Stator Current wave form one of the phases of
BLDC motor, (a). Interleaved Boost Converter and (b).
CUK Converter.
4
Vol 8 (16) | July 2015 | www.indjst.org
Figure 5 shows torque wave form of BLDC motor fed
by interleaved boost converter and CUK converter respectively. The torque is 1.75N-m in case of interleaved boost
converter where it is 2.2N-m CUK converter. During
dynamic response of BLDC motor in case of interleaved
boost converter the torque fluctuates between 2N-m to
2.2N-m and finally reaches a steady state value of 2 N-m
torque increase to 2.2N-m for certain instant of fixed
change but reaches the steady state value of 2 .2 N-m.
Figure 6 shows the speed response of BLDC motor fed
by interleaved boost converter as well as CUK converter.
The speed value is 300rpm in case of interleaved boot
whereas 300rpm in case of CUK converter. On observation of dynamic response of the drive for the interleaved
topology the speed changes instantaneously from 300rpm
Indian Journal of Science and Technology
V. Ramesh and Y. Kusuma Latha
to 750rpm.Whereas increase the CUK converter ­topology.
The speed change 300rpm to 750rpm gradually.
Method
Torue R es pons e
14
Table 2. Performance of CUK converter fed
PMBLDCM drive and interleaved boost converter for
speed control & torque ripple
Speed in Rpm
Torque Ripple
(N-m)
CUK converter
Four Switch VSI
fed BLDC Drive
300
0.18N-m
750
0.22N-m
Interleaved Boost
converter Four
Switch VSI fed
BLDC Drive
300
0.12N-m
750
0.20N-m
12
10
Torque(N-m)
8
6
4
2
0
-2
-4
0
0. 1
0. 2
0. 3
0. 4
0. 5
Time in s econds
0. 6
0. 7
0. 8
0. 9
1
(a)
5. Conclusion
E lec tromagnetic Torque (Nm)
3
2. 5
Torque(N-m)
2
1. 5
1
0. 5
0
-0. 5
0
0. 1
0. 2
0. 3
0. 4
0. 5
Time In S ec s
0. 6
0. 7
0. 8
0. 9
1
(b)
Figure 5. Torque output wave form at speed corresponding
to 300 rpm ad 750 rpm, (a). Interleaved Boost Converter and
(b). CUK Converter.
S peed R es pons e
1000
900
In this paper two PFC based control strategies have
been developed for four switches VSI fed PMBLDC
motor drive. The two control strategies one is based
on Interleaved Boost Converter and another one based
on CUK converter topology, both control strategies
have been applied to BLDC motor drive for different
operating speeds to ensure unity power factor under
wide rangeof speed and supply voltages. Comparison has
been made between the two proposed control strategies
of the BLDC motor and it is found that interleaved boost
converter based control strategies proved to be the best
compared to CUK converter based control strategy of
BLDC motor.
800
700
6. References
Speed in RPM
600
500
400
300
Motor Actual S peed
Motor R ederence S peed
200
100
0
0
0.25
0.5
0.75
1
1.25
Time in s ec
(a)
R otor s peed (rpm)
800
700
600
Speed(Rpm)
500
400
300
200
100
0
-100
0
0. 1
0. 2
0. 3
0. 4
0. 5
Time In S ec s
0. 6
0. 7
0. 8
0. 9
1
(b)
Figure 6. Speed output wave form of the drive at constant
load torque variable300 rpm and 750 rpm, (a). Interleaved
Boost Converter and (b). CUK Converter.
Vol 8 (16) | July 2015 | www.indjst.org
1. Lee BK, Kim TH, Ehsani M. On the feasibility of four-switch
three-phase BLDC motor drives for low cost commercial
applications: topology and control. IEEE Transactions on
Power Electron. 2003 Jan; 18(1):164–72.
2. Puviarasi R, Dhanasekaran D. Interleaved boost converter
fed DC machine with zero voltage switching and PWM
technique. Indian Journal of Science and Technology. 2015
Feb; 8(4):376–82.
3. Pushpavalli M, Abirami P, Vasanth K. Performance of fuzzy
controlled negative KY boost converter. Indian Journal of
Science and Technology. 2014 Aug; 7(8):1049–59.
4. Subramanian K, Kumar VKS, Saravanan EM, Dinesh E.
implementation of one cycle control technique in DC-DC
buck converter. Indian Journal of Science and Technology.
2015 Jan; 8(S2):200–6.
5. Krishnan R. Selection criteria for servo motor drives.
Proceedings of IEEE IAS Annual Meeting; 1986.
p. 301–8.
Indian Journal of Science and Technology
5
PFC-based Control Strategies for Four Switch VSI fed BLDC Motor
6. Jahns TM. Torque production in permanentmagnet
synchronous motor drives with rectangular current
excitation. IEEE Transactions on Industry Application.
1984 Jul/Aug; IA-20(4):803–13.
7. Pillay P, Krishnan R. Modeling, simulation and analysis
of permanent-magnet motor drives. II. The brushless DC
motor drive. IEEE Transactions on Industry Applications.
1989 Mar/Apr; 25(2):274–9.
8. Lin C-L, Jan H-Y, Shieh NC. GA-based multiobjective PID
control for a linear Brushless DC motor. IEEE Transactions
on Mechanical. 2003 Mar; 8(1):56–65.
6
Vol 8 (16) | July 2015 | www.indjst.org
9. Nasri M, Nezamabadi-Pour H, Malihemaghfoori.
A PSObasedoptimization of PID controller for a linearBLDC motor. Proceedings of World Academy of Science
Engineeringand Technicalogy; 2007 Apr; 20.
10. Ang K, Chong G, Li Y. PID control system analysis, design
and technology. IEEE Transactions on Control System
Technology; 2005 July; 13(4):559–76.
Indian Journal of Science and Technology