International Journal of Research and Engineering Volume 2, Issue 4
57 http://www.ijre.org
ISSN 2348-7852 (Print) | ISSN 2348-7860 (Online)
Bridgeless PFC Cuk Derived Converter Fed BLDC Motor with PID and Fuzzy Logic
Controller 1J. Pearly Catherine,
2R. Balamurugan
Department of Power Electronics and Drives, K.S.Rangasamy College of Technology (Autonomous)
K.S.R Kalvi Nagar, Tiruchengode, Namakkal, Tamilnadu, India, Ph./Fax: 04288 274741-44/04288 274860 1J. Pearly Catherine, R. Balamurugan, email:
Abstract—A bridgeless single phase ac-dc rectifier based
Cuk derived converter topology fed BLDC motor is
proposed to improvepower factor at the AC mains near to
the unity with low THD for PFC applications. It utilizes one control signal over the whole line cycle. In addition, the
proposed converter exhibits low inrush current and low
magnetic emissions as classical Cuk topology. The partial
elimination of diodes in DBR in the bridgeless topology
results in lower conduction losses as compared with
conventional Cuk converter. The proposed method is
simulated in MATLAB/Simulink with PID and fuzzy logic
controller for precise speed control. Simulation results are
presented along with the theoretical analysis.
Keywords— Power Factor Correction(PFC), Total
Harmonic Distortion (THD), Diode Bridge
Rectifier(DBR), Cuk Derived Converter, Fuzzy Logic
Control (FLC)
Introduction
BLDC motors are most popular in household appliances
over the last few decades [1-3]. As the name indicates, it has
no brushes for commutation thus eliminates the
disadvantages of wear and tear in conventional DC motors.
The switches are electronically commutated with the help of
rotor position detected using hall sensors. Hence the BLDC
motor is also known as electronically commutated motor [4-5]. Power quality problems have become important issues in
these motors 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 [6]. Combination of motor
with inverter is the BLDC motor setup.BLDC motor is
powered with two level inverter.The two level inverter
composed of 6 switches. Based on rotor position obtained
from hall sensors/optical encoders/resolvers, the power
electronic switches are commutated.
A BLDC motor when fed by a diode bridge rectifier
(DBR) has higher conduction losses. The high conduction loss caused by the high forward voltage drop of the bridge
diode begins to degrade the overall system efficiency.The
heat generated within the bridge rectifier may destroy the
individual diodes. Hence, it becomes necessary to utilize a
bridge rectifier with higher current handling capability or
heat dissipating characteristics. This increases the size and
cost of the power supply, which is unacceptable for an
efficient design. Bridgeless topologies seems to be the best
solution for reducing the conduction and switching losses of
the converter.
Several bridgeless topologies are introduced. Bridgeless boost converter requires an additional converter or an
isolation transformer to step down the voltage [10-
11].Bridgeless buck
converter is limited for step down applications [12-13].
Bridgeless SEPIC converter has large number of
semiconductor devices in the current conduction path during
each switching cycle and has discontinuous output current resulting in a relatively high output ripple.Bridgeless buck-
boost converter operates with high peak current in power
components and poor transient response that makes it less
efficient [15-16].
This paper presents a BL Cuk converter-fed BLDC
motor drive with constant dc link voltage of VSI for
improved power quality at ac mains with reduced
components. Section II deals with Cuk derived converter
topologies, Section III deals with simulation analysis of the
proposed method with PID Controller, Section IV deals with
simulation analysis of the proposed method with FLC,
Section VI deals with conclusion and future scope of the paper.
CUK DERIVED CONVERTER TOPOLOGIES
Bridgeless Cuk converter has the following advantages
because of its features:
1. Easy implementation of transformer isolation.
2. Natural protection against inrush current occurring
at start up or overload current, lower input current
ripple.
3. Less electromagnetic interference associated with
discontinuous conduction mode (DCM) topology.
4. Cuk converter has both input and output currents with a low current ripple.
5. Can achieve power factor near to the unity.
For applications, which require a low current ripple at
the input and output ports of the converter, the Cuk
converter seems to be a potential candidate in the basic
converter topologies.
The three new Cuk derived topologies are derived
from the conventional PFC Cuk rectifiers [17-19]. The
bridgeless Cuk derived converter is a combination of two
dc-dc converters. One for each half line period (T/2) of the
input voltage. There are one or two semiconductor switches
in the current flowing path. Current stresses in the active and passive switches are further reduced. Circuit efficiency is
improved as compared to conventional Cuk rectifier. They
do not suffer from high common mode noise problem and
common mode emission performance is similar to the
conventional PFC topologies. . Power Factor Correction
rectifiers are used to improve the rectifier power density and
to reduce noise emissions via soft switching techniques or
coupled magnetic topologies [7-9].
International Journal of Research and Engineering Volume 2, Issue 4
58 http://www.ijre.org
ISSN 2348-7852 (Print) | ISSN 2348-7860 (Online)
(a) Type I
(b) Type II
(c) TypeIII
Figure 1. CUK Derived Converter Topologies
The three new Cuk rectifiers are compared based on
components count, mode of operation in DCM and driver circuit complexity as tabulated in Table 1. The bridgeless
PFC Cuk rectifiers of Fig. 1 utilize two power switches (Q1
and Q2). However, the two power switches can be driven by
the same control signal, which significantly simplifies the
control circuitry.
TABLE I. CUK CONVERTERTOPOLOGIES IN DCM
MODE
Item Conv.
Cuk
Type-I Type-
II
Type-
III
Diode 4 slow+1
fast
2
slow+3
fast
2 fast 2
slow+2
fast
Switch
1 2(with
unidirec
tional
current
capabili
ties)
2 2
Current
Conducti
on Path
when SW
on
2 slow
diodes
and 1
switch
1 slow
diode
and 1
switch
with
series
diode
1 body
diode
and 1
switch
1
slow
diode
and 1
switch
Current
Conducti
on Path
when SW
on
3 diodes
( 2 slow
and 1 fast)
2 diodes
( 1 slow
and 1 fast)
1 fast
diode
2
diodes(
1 slow and 1
fast)
Current
Conducti
on Path
in DCM
2 slow
diodes
1 slow
diode
- 1 slow
diode
Compone
nt Count
10 11 11 13
Number
of
Capacito
rs
2 3 4 3
Driver
circuit
Complexi
ty
1 non-
floating
2 non-
floating
1
floatin
g + 1
non-floatin
g
2
non-
floatin
g
Operation of bl cuk converters
The choice of mode of operation of a PFC converter is a
critical issue because it directly affects the cost and rating of
the components used in the PFC converter [20] - [22].
Continuous Conduction Mode (CCM) and Discontinuous
Conduction Mode (DCM) are widely used in practice. In
CCM or DCM, the inductor‟s current or the voltage across
intermediate capacitor in a PFC converter remains
continuous or discontinuous in a switching period
respectively. To operate a PFC converter in CCM, one requires three sensors (two voltage, one current) while a
DCM operation can be achieved using a single voltage
sensor. The stresses on PFC converter switch operating in
DCM are comparatively higher as compared with its
operation in CCM.By operating the rectifier in DCM,
several advantages can be gained such as:
1. Natural near-unity power factor.
2. The power switches are turned ON at zero current
and the output diodes are turned OFF at zero
current.
(a)
International Journal of Research and Engineering Volume 2, Issue 4
59 http://www.ijre.org
ISSN 2348-7852 (Print) | ISSN 2348-7860 (Online)
(b)
Figure 2. Circuits of Type I Cuk rectifier (a)During positive half cycle.
(b)During negative half cycle.
The mode of operation is an application dependent.
CCM is suitable for high power applications and DCM for
low power applications. Thus, the losses due to the turn-on
switching and the reverse recovery of the output diodes are
considerably reduced. Conversely, DCM operation
significantly increases the conduction losses due to the
increased current stress through circuit components. As a
result, this leads to one disadvantage of the DCM operation, which limits its use to low-power applications (less than 300
W). Hence, DCM is preferred for low-power applications.
(a)
(b)
Figure 3. Circuits of Type II Cuk rectifier
(a)During positive half cycle.
(b)During negative half cycle.
(a)
(b)
Figure 4. Circuits of Type III Cuk rectifier
(a)During positive half cycle.
(b)During negative half cycle.
IV. SIMULATION OF CUK CONVERTER FED
BLDC MOTOR DRIVE USING PID CONTROLLER
A computer simulation model for PFC Cuk converter
fed BLDC motor drive is developed using the
MATLAB/SIMULINK software is shown in figure. 5. The
switching pulse for Cuk converter is generated with the
help of PID controller. Single phase ac voltage is given as
input to the Cuk rectifier. The voltage source inverter boost
the DC voltage of the rectifier and is fed to the BLDC
Motor.
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ISSN 2348-7852 (Print) | ISSN 2348-7860 (Online)
Figure 5. Simulink Model Using PID Controller
The speed control can be achieved by varying the DC
link voltage of the inverter. The power factor calculation
block is shown in figure 6.
Figure 6. Power Factor Calculation Block
The power factor of AC mains is 0.88, which is not
good. Hence the power quality gets affected.
Figure 7. Sub Block for Power Factor Calculation
The sub block of power factor calculation is shown in
figure 7.The line side voltage and current is taken as input and it is converted into corresponding real and reactive
power and the power factor is calculated with the help of
math operator blocks.
Figure 8. Speed Response
The speed response of the BLDC motor is shown in
figure 8. Depending upon the loading condition, the PID
controller controls the DC link voltage to obtain the
constant speed response. Initially the speed is gradually
increased and settled to reference value.
Figure 9. Electromagnetic Torque with PID Controller
The electromagnetic torque waveform is shown in
figure 9. It contains more amount of ripple content in its
waveform which degrade the performance of the motor. At the time of starting the acceleration of the motor is high
because of high starting torque.
Figure 10. Stator Back EMF with PID Controller
The trapezoidal shape back EMF waveform was
shown in figure 10. The back EMF waveform is departed from its ideal shape at the time of starting. Later then it
regains its original form.
V. SIMULATION OF CUK CONVERTER FED
BLDC MOTOR DRIVE USING PID
CONTROLLER
A computer simulation model for PFC Cuk converter fed
BLDC motor drive is developed using the
MATLAB/SIMULINK software is shown in figure 11. The
switching pulse for Cuk converter is generated with the
help of hall signals obtained from hall sensors. The speed of
the motor is controlled by controlling the DC link voltage of the inverter with the help of fuzzy logic controller.
Single phase ac voltage is given as input to the Cuk
rectifier. The voltage source inverter boost the DC voltage
of the rectifier and is fed to the BLDC Motor.
Figure 11. Simulink block of BLDC motor drive with
Fuzzy logic controller
The simulation block for AC mains power factor
calculation block is shown in figure 12. The display shows the AC mains power factor which could be affected when
the motor is connected to the mains. With the help of cuk
converter with fuzzy logic switching pulse, the power factor
has been improved to 0.98 which is nearer to unity.
Figure 12. Power Factor Calculation Block
The sub block of power factor calculation is shown in
figure 13.The line side voltage and current is taken as input and it is converted into corresponding real and reactive
power using real and reactive power Simulink
International Journal of Research and Engineering Volume 2, Issue 4
61 http://www.ijre.org
ISSN 2348-7852 (Print) | ISSN 2348-7860 (Online)
block.
Figure 13. Sub block for power factor calculation
The two inputs are taken as speed error and change in
speed error for fuzzy logic controller. Thus the decision
making rules for FLC for obtaining controlled signal
comprises of 11x3 matrices. Based upon these rules the
switching pulse for cuk converter is generated corresponding to speed variation. The cuk converter
regulates the supply given to the inverter, so that the speed
should be maintained at the reference value.
TABLE II. RULES TABLE FOR FLC
As said earlier compared to other bridgeless converters,
the type III cuk converter effectively regulates the inverter
supply and improves the power factor at AC mains near to unity. The ac-dc bridgeless converter thus reduces the
conduction losses and the use of PWM inverter makes it
possible to operate at the fundamental switching frequency.
The artificial intelligent fuzzy logic controller generates the
switching pulses for the Cuk converter.
The speed is controlled effectively by controlling the
DC link voltage. For the performance evaluation of the
proposed drive under input ac voltage variation, the DC link
voltage is kept constant as shown in figure 14.
Figure 14. Speed Response
The speed should be linearly varied and settled at
0.07ms. Compared to other controllers, the settling time of
the artificial intelligent controllers is minimum.
The electromagnetic torque waveform is shown in figure
15. At a time of starting, the torque should be maximum and
reduced to nominal value after the motor settled to reference
speed.
Figure 15. Electromagnetic Torque waveform
Due to commutation of inverter, the generated
electromagnetic torque contains significant amount of ripple
in its waveform. This causes acoustic noise in the motor and
performance of the motor gets degraded.
Figure 16. Back EMF Waveform
The trapezoidal shape back EMF waveform is shown in
figure 16. The shape of the back EMF waveform gets collapsed at the time of starting. After the motor settles to
the reference value, the non-linearity in the back EMF
waveform gets reduced.
Figure 17. Total Harmonic Distortion
The Total Harmonic Distortion (THD) is achieved as
5.46% is represented in figure 17. For any type of load the harmonic level is almost constant.
VI. CONCLUSION
A comparative analysis of different types of converter
topologies for power factor correction in BLDC motors has
been discussed. A suitable Type III Cuk Converter seems to
be a potential candidate for PFC.The bridgeless Cuk
International Journal of Research and Engineering Volume 2, Issue 4
62 http://www.ijre.org
ISSN 2348-7852 (Print) | ISSN 2348-7860 (Online)
converter fed BLDC motor drive improves the power factor
at the AC mains near to the unity with precise speed control
of fuzzy logic controller with low THD. The suitable
controller for PFC operation of BLDC motor drives has
been analysed. FLC seems to be the best controller in
performance improvement of BLDC motor drives for
attaining the power factor near to unity.Hence the overall
system can be implemented in Air-conditioning System.In the future work, renewable energy like Solar, Fuel cell can
be used as the source for the system which is useful to
reduce the demand of electricity. It also reduces the
pollution and greenhouse effect. Controller performance
may further improved by using other intelligent control
algorithms like genetic-fuzzy and neuro-genetic. As far as
the environment aspects are concerned, this kind of hybrid
systems have to be wide spread in order to cover the energy
demands and in the way to help reduce the greenhouse gases
and the pollution of the environment.
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