09-02-2013, 10:52 AM
Implementation of PMBLDC motor using Cuk PFC converter
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Abstract:
This paper aims at an improve speed quality employing
Cuk DC-DC converter is used as a power factor correction (PFC)
converter for feeding a voltage source inverter (VSI) based
permanent magnet brushless DC motor (PMBLDCM) driven air
condition. This PFC converter is front end diode bridge rectifier
(DBR) fed from single-phase AC mains and connected to a three
phase voltage source (VSI) feeding the permanent magnet
brushless DC motor (PMBLDCM). The PMBLDC Motor is used
to drive a compressor load of an air conditioner through a
three-phase VSI fed from a controlled DC link voltage. The speed
of the compressor is controlled to achieve energy conservation
using a concept of the voltage control at DC link proportional to
the desired speed of the PMBLDC Motor. Therefore the VSI is
operated only as an electronic commutator of the PMBLDCM. The
stator current of the PMBLDCM during step change of reference
speed is controlled by a rate limiter for the reference voltage at DC
link. The proposed PMBLDCM drive with voltage control based
PFC converter is designed, modeled and its performance is
simulated in Matlab-Simulink environment for an air conditioner
compressor driven PMBLDC motor.
INTRODUCTION
PMBLDCM is used to drive the air conditioner compressor, speed
of which is controlled effectively by controlling the DC link
voltage [1]–[4]. Permanent Magnet Brushless Direct Current
(PMBLDC) motors are one of the motor types rapidly gaining
popularity. Permanent Magnet Brushless Direct Current
(PMBLDC) is Air conditioning systems are typically the largest
consumers of electrical energy in homes and office buildings. The
most common type of air conditioning that we see is technically
referred to as direct expansion, mechanical, vapor-compression
refrigeration system. BLDC motors are used in industries such as
Appliances, Automotive, Aerospace, Consumer, Medical,
Industrial Automation Equipment and Instrumentation. The
compressor load is considered as a constant torque load equal to
rated torque with the speed control required by air conditioning
system. A 1.5 kW rating A few of these are: Better speed versus
torque characteristics, High dynamic response, High efficiency,
Long operating life, Noiseless operation, Higher speed ranges.
PROPOSED SPEED CONTROL OFPMBLDC MOTOR FOR AIR CONDITIONER USING CUK PFC CONVERTER
Figure 2 shows details diagram of the proposed speed control reference voltage at DC link as an equivalent reference speed, there by replaces the conventional control of the motor speed and a stator current involving various sensors for voltage and current signals. It has two control loops namely speed control loop and voltage control loop. Moreover, the rotor position signals acquired by Hall-effect sensors are used to generate the switching sequence for the voltage source inverter as an electronic commutator (switching sequence generator) of the Permanent Magnet Brushless Direct Current (PMBLDC) motor [1]–[4]. The Cuk dc–dc converter controls the dc link voltage using capacitive energy transfer which results in non-pulsating input and output currents [8]. The proposed PFC converter is operated at a high switching frequency for fast and effective control with additional advantage of a small size filter. For high-frequency operation, a metal–oxide–semiconductor field-effect transistor (MOSFET) is used in the proposed PFC converter, whereas insulated gate bipolar transistors (IGBTs) are used in the VSI bridge feeding the PMBLDCM because of its operation at lower frequency compared to the PFC converter.
PERFORMANCE EVALUATION OF PMBLDCMD
The proposed PMBLDCMD is modeled in Matlab–Simulink environment, and its performance is evaluated for an Air-Con compressor load. The compressor load is considered as a constant torque load equal to the rated torque with variable speed as required by an Air-Con system. A 0.816-kW rating PMBLDCM is used to drive the air-conditioner, the speed of which is controlled effectively by controlling the dc link voltage. The detailed data of the motor are given in the Appendix. The performance of the proposed PFC drive is evaluated on the basis of various parameters such as THD and CF of the ac mains current and displacement power factor (DPF) and PF at different speeds of the motor as well as variable input ac voltage. For the performance evaluation of the proposed drive under input ac voltage variation, the dc link voltage is kept constant at 298 V.
CONCLUSION
A new speed control strategy for a PMBLDCMD using the reference speed as an equivalent voltage at dc link has been simulated for an air-conditioner employing a Cuk PFC converter and experimentally validated on a developed controller. The speed of PMBLDCM 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 a 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 has ensured near unity PF in a wide range of the speed and the input ac voltage. Moreover, PQ indices of the proposed PFC drive are in conformity to the International Standard IEC 61000-3-2 [7]. The proposed PMBLDCMD has been found as a promising variable speed drive for the Air-Con system. Moreover, it may also be used in the fans with PMBLDC motor drives on the trains recently introduced in Indian Railways.