Research Paper
Volume 2
February 2015
Issue 6
International Journal of Informative & Futuristic Research
ISSN (Online): 2347-1697
A Canonical Switching cell Converter fed
PMBLDC Drive for low and Medium
Power Applications
Electrical &
Electronics Engg.
Key Words Canonical Switching cell Converter (CSC), Power Factor Correction (PFC),
Voltage Source Inverter (VSI), Discontinuous Inductor Current Mode (DICM)
Paper ID
IJIFR/ V2/ E6/ 071
G. Shyam Shankar
R. Karthikeyan 2
1
Page No.
1920-1929
Subject Area
M.E. Scholar
Department of Electrical & Electronics Engg.
Sri Venkateswara College of Engineering,
Pennalur, Sriperumbudur Taluk -Tamilnadu
Associate Professor
Department of Electrical & Electronics Engg.
Sri Venkateswara College of Engineering,
Pennalur, Sriperumbudur Taluk -Tamilnadu
Abstract
Boost Power Factor Correction (PFC) converter was the popular methodology
in driving the Permanent Magnet Brushless DC Motor. It was used to control
the speed of the motor and also power factor correction. However, due to the
high switching losses in Voltage Source Inverter (VSI) this method is not
efficient. In order to reduce the switching losses in VSI and to improve the
power factor a new method is proposed. This method employs a Canonical
Switching Cell (CSC) Converter which operates in Discontinuous Inductor
Current Mode (DICM). The main advantage of the proposed converter is it
operates the Voltage Source Inverter in low frequency switching by
electronically commutating the Brushless DC Motor for reducing the
switching losses in Voltage Source Inverter which share the major portion of
overall losses in the Permanent Magnet Brushless DC drive. The proposed
converter operates in Discontinuous Inductor Current Mode to achieve unity
power factor and maintains the DC link voltage control at ac mains by using
Pulse Width Modulation technique. The proposed converter is simulated and
the results are compared with the conventional converter.
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Copyright © IJIFR 2015
1920
ISSN (Online): 2347-1697
International Journal of Informative & Futuristic Research (IJIFR)
Volume - 2, Issue - 6, February 2015
18th Edition, Page No: 1920-1929
1.
Introduction
Brushless DC Motors are preferred in a wide array of applications in industries such as appliances,
automotives , aerospace , consumer ,medical ,industrial automation for its reliability, high
efficiency, high power density, low maintenance requirements ,lower weight and low cost. As the
name implies, BLDC motors do not have brushes for commutation. Instead they are electronically
commutated. BLDC motors have many advantages over brushed DC motors and induction motors,
like better speed-torque characteristics, high dynamic response, high efficiency, noiseless operation
and wide speed ranges. Various topologies have been introduced for power factor correction. A
review of single phase improved power quality ac-dc converters [5] was proposed for adjustable
speed drives, battery charging for electric vehicles and power supplies for telecommunication
systems. This topology has various Improved Power Quality Converters, Switch Mode Rectifiers,
Power factor correctors, pulse width-modulation rectifiers, multilevel rectifiers. The topology
based classification was categorized on the basis of buck, boost, buck-boost, multilevel with
unidirectional and bidirectional voltage, current and power flow. These converters have given the
feature of universal input to the number of products which can have input power either from ac
mains of a varying voltage of 90 to 300 V with a varying frequency from 40 to 70 Hz or dc input.
Later a dual mode strategy was proposed [9] for BLDC motor drives with power factor used in
high efficiency compressor applications. The output inverter stage is operated in Pulse Amplitude
Modulation or Pulse Width Modulation mode with reduced switching frequency for efficiency
optimization of the compressor motor drive to maintain a constant V/Hz ratio with specified
current ripples. The proposed control scheme has been verified with a DSP-controlled Variable
Output Power Factor Converter (VOPFC) inverter motor driver with an efficiency improvement of
3% has been achieved. A high power factor brushless DC motor drive was proposed [4]. The
proposed power factor controller can achieve smooth output dc link voltage, which is supplied to
the BLDC motor drive and obtain the sinusoidal line current waveform with lower harmonic
distortion. The experimental results are preceded for motor drive with and without active PFC
under full load applications are demonstrated and feasibility of each design procedure and prove
the integrity of whole system. An optimum circuit configuration for power factor correction is
proposed. The various types of converters are applied to the single phase power factor correction.
It is found that the Canonical Switching Cell (CSC) is the best choice and selected as the optimum
PFC.
Sanjeev Singh and Bhim Singh focused on the Cuk dc-dc converter as a single stage power factor
correction converter for a PMBLDCM drive fed through diode bridge rectifier from a single phase
ac mains. The speed of the compressor is controlled to achieve optimum air-conditioning using a
concept of the voltage control at dc link proportional to the desired speed of the PMBLDCM[8].
The speed of the PMBLDC motor drive has been found to be proportional to the dc link voltage,
thereby a smooth speed control is observed while controlling the dc link voltage. The introduction
of the rate limiter in the reference dc link voltage effectively limits the motor current within the
desired value during the transient conditions. The PFC Cuk converter provides nearly unity PF for
a wide range of speed and dc link voltage. Hence it is very useful in Railway fans, Air
Conditioners to avoid inrush current and improved power factor. The main objective of the project
is to design a Canonical Switching Cell Converter which is fed through with the PMBLDC drive
for improving the power factor correction and to reduce the overall switching losses of the system.
The simulation of the proposed converter is done using Matlab-Simulink.
G. Shyam Shankar, R. Karthikeyan :: A Canonical Switching cell Converter
fed PMBLDC Drive for low and Medium Power Applications
1921
ISSN (Online): 2347-1697
International Journal of Informative & Futuristic Research (IJIFR)
Volume - 2, Issue - 6, February 2015
18th Edition, Page No: 1920-1929
2. Operating Principle of the converter
The block diagram of the canonical converter fed PMBLDCM drive is shown in Fig 1. Here 220 V
is given as an input to the converter and the pulse generator is used to supply pulses to the
converter. The output voltage of the converter acts as a source to the voltage source inverter which
feds the PMBLDC motor.
Figure 2.1: Block diagram
The block diagram of the proposed converter shown in figure 1is PFC-based canonical switching
cell (CSC) converter. A CSC converter operating in DICM acts as an inherent power factor preregulator for attaining a unity power factor at ac mains. A variable dc-bus voltage of the VSI is
used for controlling the speed of the BLDCM. This operates the VSI in low-frequency switching
by electronically commutating the BLDCM for reducing the switching losses in six insulated gate
bipolar transistor’s (IGBT’s) of VSI which share the major portion of overall losses in the BLDCM
drive. The front-end CSC converter is designed and its parameters are selected to operate in a
DICM for obtaining a high-power factor at wide range of speed control. The proposed Canonical
Switching cell circuit consists of a Switch (Sw), an intermediate Capacitor (Cd), a diode, an
Inductor (Li), and a DC link Capacitor (Cdc).
3. Modes of Operation
The proposed BLDCM drive uses a CSC converter operating in DICM. In DICM, the current in
inductor becomes discontinuous in a switching period (Ts ). Three states of CSC converter are
shown in Fig. Waveforms of inductor current and intermediate capacitor’s voltage for a complete
cycle of line frequency are shown in Fig. 2, whereas Fig.3 shows the variation in different
variables of CSC converter such as switch gate voltage (Vg ), inductor current (iLi ), intermediate
capacitor’s voltage (Vc1), and dc-link voltage (Vdc) in a complete switching period. Three modes of
operation are described as follows.
3.1
Mode I: As shown in Figure 3.1, when switch is turned on, the energy from the
supply and stored energy in the intermediate capacitor are transferred to inductor. In this process,
the voltage across the intermediate capacitor reduces, while inductor current and dc-link voltage
are increased as shown in Fig. 2 The designed value of intermediate capacitor is large enough to
hold enough energy such that the voltage across it does not become discontinuous.
G. Shyam Shankar, R. Karthikeyan :: A Canonical Switching cell Converter
fed PMBLDC Drive for low and Medium Power Applications
1922
ISSN (Online): 2347-1697
International Journal of Informative & Futuristic Research (IJIFR)
Volume - 2, Issue - 6, February 2015
18th Edition, Page No: 1920-1929
Figure 3.1: Equivalent Circuit for mode 1
3.2
Mode II:
Figure 3.2: Equivalent Circuit for mode 2
G. Shyam Shankar, R. Karthikeyan :: A Canonical Switching cell Converter
fed PMBLDC Drive for low and Medium Power Applications
1923
ISSN (Online): 2347-1697
International Journal of Informative & Futuristic Research (IJIFR)
Volume - 2, Issue - 6, February 2015
18th Edition, Page No: 1920-1929
The switch is turned OFF in this mode of operation as shown in Fig 3. The intermediate capacitor
is charged through the supply current while inductor starts discharging hence voltage starts
increasing, while current decreases in this mode of operation as shown in Fig. 3 Moreover, the
voltage across the dc-link capacitor continues to increase due to discharging of inductor.
3.3
Mode III:
Figure 3.3: Equivalent Circuit for mode 3
This is the discontinuous conduction mode of operation as inductor is completely discharged and
current becomes zero as shown in Figure 3.3. The voltage across intermediate capacitor continues
to increase, while dc-link capacitor supplies the required energy to the load, hence starts decreasing
as shown in Figure 3.3.
4. Simulation of Canonical Converter fed PMBLDC Motor
The closed loop control is employed in order to regulate the error in output voltage by providing
the feedback loop. The feedback loop consists of rate limiter, P I controller, PWM controller and a
voltage controller. The dc voltage of the canonical converter is now measured and the error voltage
is generated. The error voltage is amplified by using amplifier with the gain value for the desired
output voltage. The Simulation of the Canonical converter fed PMBLDC motor is shown in figure
4.1.The input voltage 230 Volt is given to the uncontrolled rectifier which converts ac to
unregulated dc. Then the uncontrolled dc canonical converter which is converted into dc link
voltage. The dc link voltage which is fed through the voltage source inverter (VSI) which is fed
through the PMBLDC motor drive.
G. Shyam Shankar, R. Karthikeyan :: A Canonical Switching cell Converter
fed PMBLDC Drive for low and Medium Power Applications
1924
ISSN (Online): 2347-1697
International Journal of Informative & Futuristic Research (IJIFR)
Volume - 2, Issue - 6, February 2015
18th Edition, Page No: 1920-1929
Figure 4.1: Simulation Circuit of the Canonical Converter fed PMBLDC Drive
4.1
Simulation results
The dc link voltage coming from the converter acts as a voltage source for the inverter.
The selection of switching frequency is a trade-off between the permitted losses in the PFC
converter switches and the size of the input inductor. A high switching frequency reduces the size
and the value of the input side inductor. But it also increases the switching losses of the solid state
devices and therefore requires a large size of the heat sink. Moreover, a low value of inductance
increases the current stress on the PFC converter switch in DICM operation. Therefore the
switching frequency is selected as 20 KHz such that the losses and current stress of PFC converter
switches are low and it also meets the desired performance.
G. Shyam Shankar, R. Karthikeyan :: A Canonical Switching cell Converter
fed PMBLDC Drive for low and Medium Power Applications
1925
ISSN (Online): 2347-1697
International Journal of Informative & Futuristic Research (IJIFR)
Volume - 2, Issue - 6, February 2015
18th Edition, Page No: 1920-1929
Figure 4.2: Stator Current
Figure 4.2 shows the waveform of stator current. The stator current reaches at 1.5A and is
maintained constant due to the fixed stator resistance of the winding.
Figure 4.3: Stator back-emf
Since the motor used here is the BLDC the back emf should be trapezoidal as shown in figure 4.3.
Figure 4.4: Electromagnetic Torque
G. Shyam Shankar, R. Karthikeyan :: A Canonical Switching cell Converter
fed PMBLDC Drive for low and Medium Power Applications
1926
ISSN (Online): 2347-1697
International Journal of Informative & Futuristic Research (IJIFR)
Volume - 2, Issue - 6, February 2015
18th Edition, Page No: 1920-1929
The torque reaches at 1.5 Nm and is maintained constant with little torque pulsation. Hence the
motor runs at stable electromagnetic torque.
Figure 4.5: Rotor Speed
Figure 4.5 shows the rotor speed overshoots till 2300 rpm and then settles at 2000 rpm and is
maintained constant.so the machine maintains at a constant speed.
5. Hardware Simulation
This project may be extended to perform hardware implementation using PIC16F1877A
microcontroller. An opto-isolation circuitry based on 6N136 opto-coupler is used to provide the
required isolation between the microcontroller and the switches used in PFC converter and Voltage
Source Inverter. The waveform is analysed by using proteus simulation software and the hardware
kit. The USART acts as an interface between software and the hardware.
The speed of the BLDC motor is varied by varying the duty cycle of the converter Switch
are listed in Fig 5.1, 5.2 and 5.3.
Figure 5.1: Speed of the PMBLDC motor at a duty cycle of 0.2
G. Shyam Shankar, R. Karthikeyan :: A Canonical Switching cell Converter
fed PMBLDC Drive for low and Medium Power Applications
1927
ISSN (Online): 2347-1697
International Journal of Informative & Futuristic Research (IJIFR)
Volume - 2, Issue - 6, February 2015
18th Edition, Page No: 1920-1929
Figure 5.2: Speed of the PMBLDC motor at a duty cycle of 0.65
Figure 5.3: Speed of the PMBLDC motor at a duty cycle of 0.75
G. Shyam Shankar, R. Karthikeyan :: A Canonical Switching cell Converter
fed PMBLDC Drive for low and Medium Power Applications
1928
ISSN (Online): 2347-1697
International Journal of Informative & Futuristic Research (IJIFR)
Volume - 2, Issue - 6, February 2015
18th Edition, Page No: 1920-1929
6. Conclusion
A PFC-based CSC converter-fed BLDCM drive has been proposed for targeting low-power
household applications. A variable voltage of dc bus has been used for controlling the speed of
BLDCM which operates VSI in low-frequency switching mode for reduced switching losses. A
front-end CSC converter operating in DICM has been used for dual objectives of dc-link voltage
control and achieving a unity power factor at ac mains. The performance of the proposed drive has
been found quite well for its operation at variation of speed over a wide range.
7. References
[1] K. Ando, Y. Watanabe, I. Fujimatsu, M. Matsuo, K. Matsui, O. Sago, L. Yamamoto, and H. Mori,
“Power factor correction using CSC converter,” in Proc. 26th Annu. Int. Telecommun. Energy
Conf. (INTELEC), Chicago, IL, USA, 2004, pp. 117–124.
[2] P. Alaeinovin and J. Jatskevich, “Filtering of hall-sensor signals for improved operation of
brushless dc motors,” IEEE Trans. Energy Convers., vol. 27, no. 2, pp. 547–549, Jun. 2012.
[3] T. F. Chan, L.-T. Yan, and S.-Y. Fang, “In-wheel permanent-magnet brushless DC motor drive for
an electric bicycle,” IEEE Trans. Energy Convers., vol. 17, no. 2, pp. 229–233, Jun. 2002.
[4] T.Gopalarathnam and H.A.Toliyat,”A new topology for unipolar brushless dc motor drive with
high power factor,” IEEE Trans. Power Electron., vol. 18, no. 6, pp. 1397–1404, Nov. 2003.
[5] T. Y. Ho, M. S. Chen, L. H. Yang, and W. L. Lin, “The design of a high power factor brushless DC
motor drive,” in Proc. 2012 Int. Symp. Comput. Consum. Control., Taiwan, Jun. 4– 6, 2012, pp.
345–348.
[6] P. Pillay and R. Krishnan, “Application characteristics of permanent magnet synchronous and
brushless DC motors for servo drives,” IEEE Trans Ind.Appl., vol. 27, no. 5, pp. 986–996, Sep./Oct.
1991.
[7] 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.
[8] 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.
[9] Singh and B. Singh, “A voltage-controlled PFC CUK converter based PMBLDCM drive for airconditioners,” IEEE Trans. Ind. Appl., vol. 48,no. 2, pp. 832–838, Mar./Apr. 2012.
[10] V. Vlatkovic, D. Borojevic, and F. C. Lee, “Input filter design for power factor correction circuits,”
IEEE Trans. Power Electron., vol. 11, no. 1,pp. 199–205, Jan. 1996.
[11] C. H. Wu and Y. Y. Tzou, “Digital control strategy for efficiency optimization of a BLDC motor
driver with VOPFC,” in Proc. IEEE Energy Conves. Congr. Expo.( ECCE), San Jose, CA, USA,
2009, pp. 2528–2534.
[12] Z. Q. Zhu and D. Howe, “Electrical machines and drives for electric, hybrid, and fuel cell
vehicles,” IEEE Proc., vol. 95, no. 4, pp. 746–765,Apr. 2007.
Biographies:
Shyam Shankar G received B.E. Electrical and Electronics Engineering from Cape Institute of Technology under Anna
University Chennai in 2012.He is currently pursuing M.E. in Power Electronics and Drives at Sri Venkateswara College
of Engineering under Anna University Chennai . His research interests include Power Electronics, Electrical machines,
and Drives .
R.Karthikeyan received his B.E. Electronics and communication Engineering from National Engineering College in
1989.He completed M.E in Power Systems from Annamalai Uinversity in 1991.He has finished his Ph.D from Anna
University Chennai in 2015. He has been working as an Associate Professor at Sri Venkateswara College of Engineering
for 20 years.His research interests include Power Electronics, Special Electrical Machines and Drives.
G. Shyam Shankar, R. Karthikeyan :: A Canonical Switching cell Converter
fed PMBLDC Drive for low and Medium Power Applications
1929