Transactions on Engineering and Sciences
ISSN: 2347-1964 (Online) 2347-1875 (Print)
Special Issue on International Conference on Synergistic Evolutions in Engineering (ICSEE) – 2015.
Single Sensor Based PFC Using SEPIC Converter
Fed PMBLDC Motor Drive
T.Dimple Meenakshi1
1PG
K.Umarani2
Scholar , Dept. of EEE, Sasurie College of Engineering, Vijayamangalam.
Dept. of EEE , Sasurie College of Engineering, Vijayamangalam.
2Professor,
Abstract: This paper gives the power factor correction (PFC) of a single sensor based SEPIC converter fed BLDC
motor drive. This SEPIC converter fed BLDC motor used for cost effective, low power applications. The speed of the
BLDC motor is controlled by controlling the DC link voltage of the Voltage Source Inverter (VSI). By using
electronic commutation of the BLDC motor with fundamental switching frequency, switching losses of the VSI is
reduced. This proposed system of SEPIC Converter reduces the conduction losses. This system used for variable
speed application by varying voltage range. The performance of the proposed drive is simulated in the MATLAB /
Simulink environment, and the obtained results are validated experimentally on a development prototype of the
drive.
Index Terms: SEPIC Converter, Brushless Direct Current (BLDC) Motor, Discontinuous Inductor Current
Mode (DICM), Power Factor Correction (PFC), Power Quality.
I. INTRODUCTION
Efficiency and cost are the major problems in low and medium power applications [3] [4] using
household appliances like fans, water pumps, blowers and mixers. On the concept of high power
application cost are not taken as problematic. The features of the BLDC motors are high efficiency, high flux
density per unit volume, low electromagnetic interference and requires low maintenance. BLDC motors are
also used for medical appliances, motion control, HVAC and industrial tools [1] [2]. A BLDC motor has
three phase windings on the stator and permanent magnets on the rotor. In BLDC motor electronic
commutation is used instead of mechanical commutation to overcome the sparking and wear and tear of
brushes.
Power quality [8] [13] problems are the major problem in the power networks. Power quality problems
are followed by harmonics in the system. Total harmonic distortion of the supply current should be
maintained below 19% [9]. A BLDC motor with diode bridge rectifier will generate the THD of the system
above 65% and reduce the power factor below 0.8. Due to this reason the diode bridge rectifier is not used in
the converter circuit. Power factor Correction is also a major problem in the system to maintain the power
quality.
The choice of the operation of the conduction mode plays main role in the system. It will affect the cost
and rating of the components used in the power factor correction converter system. The continuous current
conduction mode and discontinuous current conduction mode are the two modes of operation. In CCM of
operation voltage across the intermediate capacitor and current in the inductor remains continuous, but it
requires sensing of two voltages and input side current foe PFC operation. In the DCM of operation only
single sensor required for sense the DC link voltage and PFC achieved at the AC mains.
The conventional scheme of buck-boost converter feeding a BLDC motor drive by constant DC link
voltage PWM-VSI for speed control which has high switching losses. A CCM operation of the Cuk convertor
has been used which needs 3 sensors and isn't inspired for low value and low power rating.
II. PROPOSED PFC SEPIC CONVERTER-FED BLDC MOTOR DRIVE:
In the proposed bridgeless SEPIC converter voltage step up and step down are achieved in a single
circuit with high efficiency and high reliability. The proposed system has SEPIC converter which has the
two inductors, three capacitors, one diode and a power switch.
Figure 1: Circuit Diagram of SEPIC converter
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Techscripts
Transactions on Engineering and Sciences
ISSN: 2347-1964 (Online) 2347-1875 (Print)
Special Issue on International Conference on Synergistic Evolutions in Engineering (ICSEE) – 2015.
A SEPIC is alleged to be in the continuous - conduction mode ("continuous mode") if the present
through the electrical device L1 ne'er falls to zero. Throughout a SEPIC's steady-state operation, the common
voltage across electrical condenser C1 (VC1) is adequate to the input voltage (Vin). As a result of electrical
condenser C1 blocks DC (DC), the common current across it (IC1) is zero, creating electrical device L2 the
sole supply of load current. Therefore, the common current through the electrical device L2 (IL2) is that the
same because the average load current and therefore freelance of the input voltage.
Looking at average voltages, the following can be written:
Figure 2: Circuit diagram of SEPIC Converter fed BLDC motor
=
+
+
Because the typical voltage of VC1 is up to VIN, VL1 = −VL2. For this reason, the 2 inductors will be
wound on an equivalent core. Since the voltages square measure an equivalent in magnitude, their effects of
the coefficient of mutual induction are zero, presumptuous the polarity of the windings is correct. Also,
since the voltages square measure an equivalent in magnitude, the ripple currents from the 2 inductors are
equal in magnitude.
The average currents can be summed as follows:
=
−
Figure 3: SEPIC component voltages during CCM
III. Duty cycle
Assuming 100% efficiency, the duty cycle, D, for a SEPIC converter operating in CCM is given by
=
+
+
+
Figure 4: SEPIC components current during CCM
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Techscripts
Transactions on Engineering and Sciences
ISSN: 2347-1964 (Online) 2347-1875 (Print)
Special Issue on International Conference on Synergistic Evolutions in Engineering (ICSEE) – 2015.
Where VFWD is the forward voltage drop of the Schottky diode. This can be rewritten as
1−
=
+
=
D(max) occurs at VIN(min), and D(min) occurs at VIN(max).
IV. THE PWM SWITCH MODEL IN THE SEPIC DEVICE:
The best thanks to analyze each the AC and DC characteristics of the SEPIC converter are by
victimization the PWM switch model, developed by Dr. Vatché Vorpérian in 1986. Some minor circuit
manipulations are 1st required to reveal the location of the switch model. First, capacitance C1 is rapt to the
bottom branch of the device. Then, inductor L2 is force over to the left, keeping its ends connected to
constant nodes of the circuit. This reveals the PWM switch model of the device, with its active, passive, and
common.
In this proposed system PWM generation is achieved by the hall-effect sensor feedback. In this
system closed loop operation is achieved by taking the speed of the Brushless DC motor as feedback to the
controllers. Here Hall Effect decoder is used to control the switching to the Voltage Source Inverter (VSI).
Gates are also used for control action, it is connected with a Hall effect decoder. It generates the pulse
pattern to the switches. Control of the BLDC motor is achieved by changing the pulse pattern of the
switches. Each and every change in the pulse changes the pattern speed of the motor.
Figure 5: Pulse pattern to the switches of VSI
Figure 6: Three phase output of the voltage source inverter
Figure 7: Single phase output voltage of the Voltage Source Inverter
Figure 8: Input voltage of the system
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Techscripts
Transactions on Engineering and Sciences
ISSN: 2347-1964 (Online) 2347-1875 (Print)
Special Issue on International Conference on Synergistic Evolutions in Engineering (ICSEE) – 2015.
Figure 9: Comparative analysis of (a) losses and (b) the efficiency of the conventional and the proposed
conFigureuration.
Figure 10: Comparative analysis of (a) THD of supply current at ac mains and (b) power factor variation
with output power for the conventional and the proposed conFigureuration.
Table 1: Comparative Analysis Of Proposed Configureuration With Conventional Schemes
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Techscripts
Transactions on Engineering and Sciences
ISSN: 2347-1964 (Online) 2347-1875 (Print)
Special Issue on International Conference on Synergistic Evolutions in Engineering (ICSEE) – 2015.
V. POWER FACTOR CORRECTION:
The issue of power issue arises as a result of for a system mistreatment electrical energy, AC power, the
voltage and current might not forever be in a section. If the load is solely resistive, then the present and the
voltage is in the section.
Figure 11: Voltage and Current in Phase - Power Factor = 1
Figure 12: Simulation used in the PFC circuit
Table 2: Switching States For Achieving Electronic Commutation Of Bldc Motor Based On Hall-Effect
Position Signals
Figure 13: Steady-state performance of the proposed BLDC motor drive at rated conditions.
Power Factor Correction calculation is based on the input AC side voltage and current. If the input
current and voltage are in phase, the power factor will be 1. The good quality system contains 0.8-1 power
factor.
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Transactions on Engineering and Sciences
ISSN: 2347-1964 (Online) 2347-1875 (Print)
Special Issue on International Conference on Synergistic Evolutions in Engineering (ICSEE) – 2015.
VI.
BENEFITS OF POWER FACTOR CORRECTION:
An improvement in power issue can cut back the I2R losses of transformers and distribution
instrumentality for a given consumption measured in watts.
Power issue correction[18] will result in a discount within the heat in cables, switchgear, transformers,
etc. as a result of this level is reduced for a given power level measured in watts.
An improved power issue can lead to a lower current being consumed for a given electric power
consumption. As a result fall in cables is reduced. This could have enabled smaller cables to be employed in
some instances.
VII. CONCLUSION
The Power Factor Correction (PFC) SEPIC converter based Voltage Source Inverter (VSI) fed BLDC
motor drives mainly used for low and medium power applications. A new type of speed control is achieved
at the dc link side of VSI. Here electronic commutation of the BLDC motor is used at fundamental frequency
for reduce the switching losses at the VSI. The front end SEPIC converter operates at DICM mode of
operation used to get the power factor correction at the AC mains. The speed control action is achieved for
our requirement at the BLDC motor side.
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