IJERTV3IS20110.pdf

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IJERTV3IS20110.pdf

School
Lambton College*
*We are not endorsed by this school
Course
ELE 1001
Pages
11
Upload Date
Feb 10, 2024
Uploaded by BailiffHeronPerson1024 on coursehero.com
Bridgeless Cuk Converter Fed BLDC Motor with Power Factor Correction for Air Conditioning System Sinsha V 1 , E Thangam 2 1. PG Student (Power Electronics &Drives), Dept of EEE, Ranganathan Engineering College, Coimbatore, 2. Assistant Professor, Dept of EEE, Ranganathan Engineering College, Coimbatore, Tamilnadu. India. Abstract This paper deals with bridgeless cuk converter operating in discontinuous inductor current mode (DICM) for single-stage power factor correction converter for a permanent magnet brushless dc motor (PMBLDCM).A three-phase voltage-source inverter is used as an electronic commutator to operate the PMBLDCM driving an air-conditioning system. The speed control of PMBLDC motor achieved by controlling the voltage at DC bus using single voltage sensor. The bridgeless cuk converter topology is used for obtaining low switching losses and low size heat sink is used for switches. Keywords Bridgeless cuk converter Permanent magnet brushless DC motor (PMBLDCM),Discontinous inductor current mode(DICM),Power factor correction(PFC),Voltage source inverter(VSI). I. I NTRODUCTION The use of a permanent-magnet brushless dc motor (PMBLDCM) is used in low and medium power applications because of their high efficiency, wide speed range, high energy density ,high torque/inertia ratio, low maintenance and wide range of speed control. The BLDC motor has three phase distributed winding on stator and permanent magnet on the rotor. There is no brushes used for commutation. It is an electronically commutated motor. The hall sensors are used for rotor position sensing and it is used for commutation state of voltage source inverter switches. The problems associated with mechanical commutator such as sparking, electro-magnetic interference, wear and tear and noise problems in brush and commutator assembly are eliminated.BLDC motors are used household equipments like air conditioners, washing machines,refrigerators,fans etc and it is also used in medical equipments, industrial tools, heating ,ventilation and motion control systems. A BLDC motor has the developed torque proportional to its phase current and its back electromotive force (EMF), which is proportional to the speed [1] - [4]. 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 uses a reference voltage at dc link proportional to the desired speed of the permanent-magnet brushless direct current (PMBLDC) motor. The BLDC motor fed by a diode bridge rectifier (DBR) with a high value of DC-link capacitor results in highly distorted supply current and a poor factor [9]. Hence, a power factor corrected (PFC) converter is required for obtaining the improved PQ at the AC mains for a VSI-fed BLDC motor drive. Two stage PFC converters have been in normal practice in which one converter is used for the PFC operation which is typically a boost converter and other converter is used for the voltage control, selection of which depends upon the type of application [10]. This has more losses because of higher number of components and two switches. A single stage PFC converter has gained popularity because of single stage operation which has reduced number of components. A PFC and DC-link voltage control can be achieved in a single stage operation[11, 12]. Two basic modes of operation of a PFC converter, continuous conduction mode (CCM) and dis-continuous conduction mode (DCM) [11,12]. 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. The PFC converter operate in CCM, requires three sensors (two voltage, one current) while in DCM operation can be achieved by using a single voltage sensor [12]. The stresses on PFC converter switch operating in DCM are comparatively higher as compared with its operation in CCM. A PFC boost half-bridge-fed BLDC motor drive using a four switch VSI has been proposed by Madani et al. [13] which uses a constant DC-link voltage with PWM switching of VSI and have high switching losses. Ozturk et al. [14] have proposed a PFC boost converter feeding a direct torque controlled (DTC)-based BLDC motor drive which requires higher number of sensors for DTC operation, have higher switching losses in PWM-VSI and increased complexity of the control unit. A similar configuration using a front-end cascaded buck - boost converter-fed BLDC motor drive has been proposed by Wu and Tzou [15], which also confronts same difficulties. Gopalarathnam and Toliyat [16] have proposed an active PFC using a single ended primary inductance converter (SEPIC) for feeding a BLDC motor drive which again utilized a PWM-based VSI for speed control of BLDC motor which have switching losses corresponding to the switching frequency of PWM pulses. A PFC Cuk converter operating in CCM for feeding a BLDC motor drive has been proposed by Singh and Singh [17], but it requires three sensors for DC-link voltage control and PFC operation and hence this topology 199 International Journal of Engineering Research & Technology (IJERT) Vol. 3 Issue 2, February - 2014 ISSN: 2278-0181 www.ijert.org IJERTV3IS20110
is suited for high-power applications. This main objective of this paper is the development of cost effective motor drive which requires minimum sensors and has reduced switching losses in the VSI. Moreover, the proposed drive operates for improved PQ operation at AC mains over a wide range of speed control. II. P ROPOSED B RIDGELESS C UK C ONVERTER -F ED BLCD M OTOR D RIVE Fig. 1 shows the bridgeless Cuk converter-fed BLDC motor driving an air conditioning compressor. The bridgeless Cuk converter is used to control the DC-link voltage (Vdc) of the VSI and to achieve a unity power factor at AC mains. To eliminate a DBR in the front end, a bridgeless converter topology is used which has an advantage of low conduction losses and thermal stress on the devices. A new approach of speed control by controlling the voltage at the DC link is used which utilizes a fundamental frequency switching of VSI (i.e. electronic commutation of BLDC motor) hence offers reduced switching losses. A voltage follower approach is used for the control of bridgeless Cuk converter operating in discontinuous inductor current mode (DICM) in which a single voltage sensor is required for the sensing of DC-link voltage (Vdc). The proposed drive is designed to operate over a wide range of speed control with improved PQ at AC mains. III. O PERATION O F B RIDGELESS C UK C ONVERTER To eliminate the requirement of a DBR such that its conduction losses are reduced, a bridgeless converter topology is used [18 - 20]. The converter is designed to operate in DICM, in which the current in output inductor Lo1 and Lo2 remains discontinuous while the current in input inductors (Li1 and Li2) and voltage across the intermediate capacitors (VC1 and VC2) remain continuous to achieve a PFC at the AC mains. Figs. 2a and b show the operation of the converter for a positive and negative half cycles of the AC supply, respectively. As shown in Fig. 2a, for the positive half cycle of the supply voltage, switch Sw1 is in conduction through Li1 and Dp. The energy is transferred through the energy transferring capacitor C1 through Lo1 and D1. Similarly, for negative half cycle of supply voltage, switch Sw2 is conducting through Li2 and Dn as shown in Fig. 2b. A common DC-link capacitor Cd is used for both the positive and negative half cycle of operation. The voltage across this DC-link capacitor Cd is controlled to achieve the speed control of the BLDC motor. Figs. 2c - e show the operation of bridgeless Cuk converter for a complete switching cycle during the positive half cycle of supply voltages. Different modes of operation are described below. Fig. 1 Bridgeless Cuk converter-fed BLDC motor drive Mode I: When switch Sw1 is turned on, an energy is stored in the input inductor L i1 via diode D p , hence the inductor current i Li1 increases as shown in Fig. 2c. Moreover the energy stored in intermediate capacitor C 1 is discharged to the DC-link capacitor C d and the output inductor L o1 . Therefore the current i L01 and DC-link voltage V dc are increased and the voltage across the intermediate capacitor V c1 reduces in this mode of operation. Mode II: When switch Sw1 is turned off, the inductor L i1 discharges through intermediate capacitor C 1 via diode D 1 and D p . Moreover, inductor L o1 also transfers its stored energy to DC-link capacitor C d as shown in Fig. 2d. Hence, in this mode of operation, the current in inductors i Li1 and i Lo1 continues to decrease while the voltage across DC-link capacitor C d and intermediate capacitor C 1 increases. Mode III: Fig. 2e shows the DCM of operation. In this mode, none of the energy is left in the output inductor L o1 , 200 International Journal of Engineering Research & Technology (IJERT) Vol. 3 Issue 2, February - 2014 ISSN: 2278-0181 www.ijert.org IJERTV3IS20110
that is, i Lo1 = 0. The voltage across intermediate capacitor C 1 and current in input inductor i Li1 increases, while the DC- link capacitor C d supplies the required energy to the load, hence V dc reduces in this mode of operation . This operation continues till the switch Sw1 is again turned 'on'. 201 International Journal of Engineering Research & Technology (IJERT) Vol. 3 Issue 2, February - 2014 ISSN: 2278-0181 www.ijert.org IJERTV3IS20110
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