ADVANCES in NATURAL and APPLIED SCIENCES ISSN: 1995-0772 Published BY AENSI Publication EISSN: 1998-1090 http://www.aensiweb.com/anas 2016 March 10(3): pages 190-197 Open Access Journal Power Factor Correction Based Bridgeless Single Switch SEPIC Converter Fed BLDC Motor 1 Nazar Ali. A, Assistant Professor, 2 Gowri.N, PG Scholor 1 Department of Electrical and Electronics K. Ramakrishnan College Of Technology 2 Department of Electrical and Electronics K. Ramakrishnan College Of Technology Received 25 January 2016; Accepted 28 March 2016; Available 10 April 2016 Address For Correspondence: Nazar Ali. A, Assistant Professor, Department of Electrical and Electronics K. Ramakrishnan College Of Technology E-mail: krcthodeee@gmail.com Copyright 2016 by authors and American-Eurasian Network for Scientific Information (AENSI Publication). This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/ ABSTRACT In this paper, a Bridgeless (BL) Single Switch Single Ended Primary Inductance (SEPIC) converter fed Brushless DC (BLDC) motor drive is proposed. The proposed topology uses a single active switch for power factor correction (PFC) and DC link voltage control. The speed of the BLDC motor is controlled by the concept of variable DC link voltage. The proposed converter is designed to operate in a continuous conduction mode (CCM) which increases the static gain at low input voltage without extreme switch duty cycle. The conduction losses are reduced by eliminating the front end diode bridge. Besides the application cost and total harmonic distortion (THD) are less with high PF. The performance of the proposed topology is compared with the conventional bridgeless PFC Luo converter. The results show that the proposed topology succeeds wide range of speed control with power factor correction at the AC mains using single switch. KEYWORDS: Bridgeless SEPIC rectifier, total hormonic distortion,continuous conduction mode, power factor correction. INTRODUCTION Brushless DC motor is a three phase synchronous motor having torque-speed characteristics of DC motor. Its stator has three phase winding excited by a voltage source inverter (VSI) and rotor has permanent magnet. It does not require any brushes and commutator assembly rather An electronic commutation based on the rotor position as sensed by Hall Effect position sensors is used[1,2]. Hence the problem of wear and tear of brushes, EMI and noise interference are eliminated. The BLDC motor has the advantages such as high efficiency, high power density, low maintenance, compact size, and their immunity to electro-magnetic interference (EMI) problems. The conventional BLDC motor drive using front-end diode bridge rectifier and high value of DC link capacitor draws high distorted current with harmonics. Such configuration leads to low power factor and high total harmonic of supply current at AC mains. Such power quality indices are not acceptable under the limits of international power quality standards such as IEC 61000-3-2[3]. Moreover, such power quality indices increases the EMI in the PFC converter. The EMI causes problems such as skin effect, hysteresis loss, transients, eddy current loss and reduces the efficiency and performance of the system. Therefore the converter with power factor improving in the AC mains in required. Power factor correction topologies to drive the BLDC motor such as boost type configurations are preferred most because of its low cost and simplicity. However it utilizes a constant DC link voltage with PWM based VSI for speed control. This scheme suffer from high switching loss due to front end diode bridge rectifier and have high THD which reduces the power factor[4,5]. Hence with the elimination of front end diode bridge rectifier the bridgeless configuration is introduced in the past decade as its efficiency is high[6,7]. The To Cite This Article: Nazar Ali. A, Assistant Professor, Gowri.N, PG Scholor., Power Factor Correction Based Bridgeless Single Switch SEPIC Converter Fed BLDC Motor. Advances in Natural and Applied Sciences. 10(3);
191Nazar Ali. A, Assistant Professor, Gowri.N, PG Scholor., 2016/ Advances in Natural and Applied Sciences. 10(3) March 2016, bridgeless buck and boost converters in [8] suffer from limited voltage conversion ratio. The bridgeless Cuk and SEPIC converter has high voltage conversion ratio but it suffers from high total harmonic distortion[9]. The Luo converter for PFC suffer from high switching loss and THD. Besides, the cost is high[10]. The conventional SEPIC PFC converter requires two active switches therefore the cost and the switching loss is high[11,12]. This paper presents a single switch SEPIC PFC converter to drive the BLDC motor. The proposed converter reduces the switching loss and THD. It has high efficiency and improves the power factor with low cost. The proposed converter utilizes single active switch for controlling variable DC link voltage. However two diodes are used compared to the conventional PFC SEPIC converter on the current path to avoid short circuit condition, but the number of active switches are reduced whose cost is higher than the diode. Therefore the application cost can be reduced. Fig. 1: Proposed block diagram II Proposed Bl- Single Switch Sepic Pfc Converter For Bldc Motor Drive: Fig. 2: Proposed PFC BL-Single Switch SEPIC Converter fed BLDC motor drive Fig 2 shows the proposed bridgeless single switch SEPIC PFC converter fed BLDC motor drive. A singlephase supply followed by filter and a Single switch BL-SEPIC converter used to feed a VSI driving a BLDC motor. The BL-single switch SEPIC converter is designed to operate in CCM to act as an inherent power factor pre-regulator. The speed of the BLDC motor is controlled by adjusting the dc-link voltage of VSI using a single voltage sensor. This allows VSI to operate at fundamental frequency switching (i.e., electronic commutation of the BLDC motor) and hence has low switching losses in it, which are considerably high in a PWM-based VSI feeding a BLDC motor. The proposed scheme is designed, and its performance is simulated for achieving an improved power quality at ac mains for a wide range of speed control and supply voltage variations.
192Nazar Ali. A, Assistant Professor, Gowri.N, PG Scholor., 2016/ Advances in Natural and Applied Sciences. 10(3) March 2016, III Principle of Operation: The operation of proposed PFC BL-Single Switch SEPIC converter is classified into two parts which include the operation during positive and negative half cycle of the supply voltage(figs. 3(a) and 3(b) ). During the positive half-line cycle, L1-S1-C1-L0-D0 is active through diode Dn, which connects the input ac source to the output. During the negative half-line cycle, L2-S2-C2-L0-D0, is active through diode Dp, which connects the input ac source to the output. Thus, due to the symmetry of the circuit, it is sufficient to analyze the circuit during the positive half-period of the input voltage. The rectifier is operated when the switch S1, is turned on then diode Dn is forward biased by the sum inductor currents il1and il2. As a result, diode Dp is reverse biased by the input voltage. The output diode is reverse biased by the reverse voltage (Vac + Vo). A common DC-link capacitor Cd is used for both the positive and negative half cycle of operation. The undesired circulating current from the capacitive coupling loop, shown in Figure3 (a) and 3(b) by the green line. A. Operation during switch on: Fig3(a) shows the on-time diagram for switch S1, for which switch S1 is on, and diode D1 is off. The input side inductor L1 is charged from the input voltage in this stage, the charged C1 transfers energy into the output side inductor Lo, and Lo is charging in this stage. In addition, the load current comes from the charged output capacitor Co. B.Operation during switch off: Fig3(b)shows the off-state diagram for switch S1, in which switch S1 is off and the diode D1 is on. Inductor L1 charges the capacitor C1 and provides the load current. The Inductor L2 is connected to the load: it charges the output capacitor Co and provides the load current. Fig. 3: (a) Diagram of the bridgeless SEPIC PFC converter (switch-on). Fig. 3: (b) Diagram of the bridgeless SEPIC PFC converter (switch-off). VI Design Of Bl-Single Switch Pfc Converter: The PFC BL-single switch SEPIC converter is designed for its operation in CCM. There are many factors involved in the design process of SEPIC PFC. The input AC voltage is 230v. The converter is designed to control the DC link voltage from 50v( Vdc min) to 400v (Vdc max). The line frequency is 50HZ and the
193Nazar Ali. A, Assistant Professor, Gowri.N, PG Scholor., 2016/ Advances in Natural and Applied Sciences. 10(3) March 2016, switching frequency Fsw is 20kHZ. If efficiency is set equal to 95%, from the converter the following equation calculations are made to select the appropriate values of the components. The relationship between the input and the output is given as D = Vin (1) Vin+Vdc The input inductors L1 and L2 is given as L1 = L2 = D Vin = 0.5 198 =1mH (2) [ Fsw(Δ IL1)] 20000 4.95 The capacitors C1 and C2 is given by C1 = C2 = D Idc = 0.5 0.4 =1μF (3) [ Fsw(ΔVc1)] 20000 10 The output capacitor Co is given by Co = D Idc = 0.5 0.4 = 3000 μf (4) [ Fsw(ΔVco)] 20000 0.0033 The output inductor Lo is given by Lo = (1-D) Vdc = (1-0.5) 340 = 22μH (5) [ Fsw(Δ ILo)] 20000 30 A.Control Circuit: The fig.4 shows the controller circuit simulation. The PI controller is used in the control circuit. The sensed DC link voltage Vdc is compared with the voltage Vdc equivalent to the reference speed and the voltage error is obtained. The PI controller give the modulating control signal. This signal is compared with a high frequency sawtooth signal to generate the switching signal to the active switch. It also generates the gate signal to the switches in the VSI. Fig. 4: PI Control Circuit V Simulation Results: The parameter of the SEPIC PFC converter are summarized in Table I. The proposed bridgeless single switch SEPIC PFC converter is compared with the BL-Luo PFC converter. MATLAB is used to verify the steady state waveforms of each component. Table 1: Parameters of the Simulation Circuit Parameters L1,L2 C1,C2 Lo Co Value 1Mh 1μF 22μH 3000 μf A. Simulation of Conventional BL-Luo converter fed BLDC motor drive: The Fig 5 shows the simulation circuit of conventional BL- Luo converter. It is a negative output Luo converter. Its duty cycle is 0.2 to 0.5. The switching frequency is 20kHZ.
194Nazar Ali. A, Assistant Professor, Gowri.N, PG Scholor., 2016/ Advances in Natural and Applied Sciences. 10(3) March 2016, Fig. 5: Simulation of Conventional BL-Luo Converter The Fig 6 shows the input voltage and current waveform. It shows the input voltage is 230v and source current is affected with harmonics. The THD is 60% and the power factor is 0.85. Fig. 6: Input voltage and current for conventional SEPIC The Fig 7 shows the output voltage waveform for the BL-Luo converter. The output voltage is Vdc= -312v. From the fig the output voltage with ripple voltage is seen. Fig. 7: Output voltage for conventional SEPIC B. Simulation of Proposed BL- SEPIC Converter fed BLDC motor drive: The Fig.8 shows the simulation of proposed BL- single switch SEPIC PFC converter. The switching frequency is 20kHZ.
195Nazar Ali. A, Assistant Professor, Gowri.N, PG Scholor., 2016/ Advances in Natural and Applied Sciences. 10(3) March 2016, Fig. 8: Simulation of Proposed BL-SEPIC Converter The Fig 9 shows the input voltage and current waveform. It shows the input voltage is 230v. The THD is 45% and the power factor is 0.92. Fig. 9: Input voltage and current for SEPIC Converter The Fig 10 shows the output voltage waveform for the BL- SEPIC converter. The output voltage is Vdc= 340v. From the fig the output voltage has less ripple voltage is seen. Fig. 10: Output voltage for SEPIC Converter The Fig 11 shows the VSI simulation circuit. The output of VSI is fed to the BLDC motor. The Fig 12 shows the speed and torque of proposed converter. The speed upto 2000rpm is obtained. The torque waveform is also shown. The Fig 13 and 14 shows the stator current and EMF waveform.
196Nazar Ali. A, Assistant Professor, Gowri.N, PG Scholor., 2016/ Advances in Natural and Applied Sciences. 10(3) March 2016, Fig. 11: VSI for SEPIC Converter Fig. 12: Speed and Torque of SEPIC Converter Fig. 13: Stator current of SEPIC Converter fed BLDC motor Fig. 14: EMF waveform of SEPIC Converter fed BLDC motor C. Comparison of conventional BL-Luo converter with proposed SEPIC converter fed BLDC motor: The Conventional BL-Luo converter and BL- SEPIC PFC converters are compared in Table 2. The PF and THD values for proposed converter are measured as respectively 0.92 and 45%. The switching loss and the ripple voltage are less when compared to the conventional BL-Luo converter fed BLDC motor drive. Also the number of active switch required is also less. The simulations show that it is an excellent option for proposed bridgeless SEPIC PFC with single active switch for lower power applications. Table 2: Comparison of Conventional and Proposed configuration fed BLDC motor drive Paramater Conventional PFC BL-Luo Converter Proposed PFC BL-SEPIC converter THD 60% 45% Power Factor 0.85 0.92 Speed(rpm) 1900 2000 Switching loss(w) 2.345 1.412 Ripple voltage(v) 7.42 1.30 Number of switches required 2 1
197Nazar Ali. A, Assistant Professor, Gowri.N, PG Scholor., 2016/ Advances in Natural and Applied Sciences. 10(3) March 2016, Conclusion: In this paper, a single phase bridgeless PFC based single switch SEPIC converter fed BLDC motor drive has been proposed. The speed of the BLDC motor is controlled with near unity PF at the AC mains. The converter requires less components and the application cost is low. The proposed PFC BL- converter is designed to operate with reduced switching loss.the ripple voltage is less in the proposed converter. The comparison of conventional BL-Luo converter with SEPIC PFC is made and it is proved that the proposed drive has low THD and high power factor. The design and performance of the proposed BLDC motor drive is simulated in MATLAB/Simulink for achieving an improved power quality over wide range of speed control. REFERENCES 1. Sokira, T.J. and W. Jaffe, 1989. Brushless DC Motors: Electronic Commutation and Control. Blue Ridge Summit, PA, USA: Tab Books. 2. Toliyat, H.A. and S. Campbell, 2004. DSP-Based Electromechanical Motion Control. New York, NY, USA: CRC Press. 3. Limits for Harmonic Current Emissions (Equipment input current 16 A per phase), International Std. IEC 61000-3-2, 2000. 4. Ozturk, S.B., O. Yang and H.A. Toliyat, 2007. Power factor correction of direct torque controlled brushless dc motor drive, in Conf. Rec. 42 nd IEEE IAS Annu. Meeting, pp: 297-304. 5. Ho, T.Y., M.S. Chen, L.H. Yang and W.L. Lin, 2012. The design of a high power factor brushless dc motor drive, in Int. Symp. Comput., Consum. Control, pp: 345-348. 6. Jang, Y. and M.M. Jovanovi c, 2011. Bridgeless high-power-factor buck converter, IEEE Trans. Power Electron., 26(2): 602-611. 7. Mahdavi, M. and H. Farzanehfard, 2011. Bridgeless SEPIC PFC rectifier with reduced components and conduction losses, IEEE Trans. Ind. Electron., 58(9): 4153-4160. 8. Huber, L., Y. Jang and M.M Jovanovic, 2008. Performance evaluation of bridgeless PFC boost rectifiers, IEEE Trans. Power Electron., 23(3): 1381-1390. 9. Fardoun, A.A., E.H. Ismail, A.J. Sabzali and M.A. Al-Saffar, 2012. New efficient bridgeless Cuk rectifiers for PFC applications, IEEE Trans. Power Electron., 27(7): 3292-3301. 10. Yamamoto, I., K. Matsui and M. Matsuo, 2002. A comparison of various dc-dc converters and their application to power factor correction, in Proc. PCC, Osaka, Japan, 1: 128-135. 11. Mahdavi, M., H. Farzanehfard, 2011. "Bridgeless SEPIC PFC rectifier with reduced components and conduction losses", IEEE Trans. Ind. Electron., 58(9): 4153-4160. 12. Ismail, E.H., 2009. "Bridgeless SEPIC rectifier with unity power factor and reduced conduction losses", IEEETrans. Ind. Electron., 56(4): 1147-1157. 13. Vlatkovic, V., D. Borojevic and F.C. Lee, 1996. Input filter design for power factor correction circuits, IEEE Trans. Power Electron., 11(1): 199-205. 14. SPRS174R-TMS320F28xx Digital Signal Processors-DataManual, 2010. TexasInstruments, Dallas, TX, USA. 15. Alaeinovin, P. and J. Jatskevich, 2012. Filtering of Hall-sensor signals for improved operation of brushless dc motors, IEEE Trans. Energy Convers., 27(2): 547-549. 16. Kuo, B.C., 2010. Automatic Control Systems. New Delhi, India: PHI Learning.