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International Journal of Engineering Trends and Technology (IJETT) – Volume-42 Number-3 - December 2016
Power Factor Improvement using Dual Boost
Converter
Miss. R. S. More, Prof .D.D.Ahire
1, 2
Electronics & Telecommunication
Matoshri College of Engineering & Research Center, Nashik, India
Abstract – The DC to DC converter are electronics
devices used whenever there is change in DC electrical
power efficiently from one voltage level to another. When
the supply voltage is too high or too low, the equipment
fails to operate at maximum efficiency. So, in some
application boost converter will used to change level of
voltage from low to high. There are two types of boost
converter. They are single boost and dual boost converter.
By applying same dc input voltage from bridge rectifier to
both boost converters, then different voltages for both boost
converters will obtained. But dual boost output voltage
should be greater than single boost output voltage and it
should be Vo>Vi. If a electrical device has a power factor
less than 1, that means more input current must be supplied
for a given output power dissipation and more powerful
source is required to deliver the required output power.
Hence, there is a continuous need for power factor
improvement and reduction of line current harmonics. The
aim of this paper is to develop a circuit for power factor
correction by implementing two boost converters arranged
in parallel to boost the input voltage, improve the power
factor device and current quality for reducing current
harmonics & switching losses.
Key words – Boost converter, Dual boost converter, power
factor correction (PFC), MATLAB.
I. INTRODUCTION
An ac to dc converter consisting of a diode
bridge rectifier with a large output filter capacitor is
cheap, but demands a harmonic rich ac line current.
As a result, the input power factor is poor [1].
Various power factor correction (PFC) techniques are
used to overcome these power quality problem [2].
The boost converter topology has been used in
various ac/dc and dc/dc applications. In fact, the ac/dc
power supplies with power factor correction (PFC) is
almost implemented with boost topology [4], [7], [8].
The use of power factor correction is necessary in
order to comply the recent international standards,
such as IEC-1000-3-2 and IEEE-519 [5]. This paper
introduces Dual boost PFC converter which provides
high boost factor and proper controlling [5]. Here
Average Current Control method is used for better
control. This paper initially involves simulation of
basic power electronic conventional rectifier circuits
and the analysis of the current and voltage
waveforms.
voltage and power factor is called as lagging. In
capacitive circuit, current leads the voltage and the
power factor is called as leading.
Fig1:Power Triangle
Power Factor =
A. Linear Systems
In a linear system, the load draws purely
sinusoidal current and voltage; hence power factor is
determined by the phase difference between voltage
and current.
B. Nonlinear Systems
In a nonlinear system like power electronics
system, due to the nonlinear behavior of the active
switching of power devices, the phase angle alone is
not valid. A nonlinear load draws distorted line
current from the line. For sinusoidal voltage and nonsinusoidal current the PF is given as follows :
Power Factor =
(2)
=
Power Factor =
=
(3)
,
← [0,1]
Where,
is the displacement factor of the voltage
and current.
is the purity or distortion factor.
Another important parameter that measures the
percentage of distortion is known as the current total
harmonic distortion (THDi). Which is given as
follows :
II. POWER FACTOR WITH LOADS
Power factor is defined as the cosine of the
angle between voltage and current in an ac circuit. If
the circuit is inductive, the current lags behind the
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=
(4)
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International Journal of Engineering Trends and Technology (IJETT) – Volume-42 Number-3 - December 2016
THDi =
(5)
All the types of switching converter produce
harmonics because of the nonlinear relationship
between voltage and current across the switching
device.
It creates harmonics and electromagnetic
interference (EMI).
It has poor power factor.
It produces high losses.
It requires over-dimensioning of parts.
It reduces maximum power capability from
the line.
III.RECTIFIERS
Rectifiers convert the AC supply into DC voltage for
either directly connecting to loads such as heater coils,
DC motors, etc. or for further conversion as in the
UPS system, variable frequency AC drives (VFD),
switched mode power supplies (SMPSs), induction
heating inverters etc. There are two types of rectifiers
called uncontrolled and controlled rectifiers.
A. Uncontrolled Rectifiers
Uncontrolled rectifier are used in SMPS, VFDs,
DC power supplies, and some UPSs. The cicuit
diagram of single phase uncontrolled rectifier is
shown in Fig2. It is directly connected to a DC
smoothing capacitor.
Fig 3: Single phase controlled rectifier
V.PURPOSE OF PFC
Fig2 :Phase uncontrolled rectifier
B. Controlled Rectifiers
Controlled rectifiers are used in variable speed
DC drives, DC power plants, induction heating and
welding furnace control, etc. Fig3 shows the circuit
diagram of single phase fully controlled rectifier. And
it is normally connected to a smoothing inductor on
the DC side. Thus output current of controlled rectifier
could be considered as constant. Voltage distortions
takes place due to two factors namely, commutation
notches and voltage clamping.
IV.NEED FOR IMPROVEMENT OF POWER
FACTOR
Conventional AC rectification is a inefficient process,
resulting in waveform distortion of the current drawn
from the mains. This produces large harmonics signals
that may interfere with other equipment. At higher
power level severe interference with other electronics
equipment may become apparent due to these
harmonics sent into the power utility line.
Conventional AC rectification has following main
disadvantages:
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Low power factor means poor electrical efficiency, the
higher the apparent power drawn from the distribution
network. When an electric load has a PF lower than 1,
the apparent power delivered to the load is greater
than the real power which the load consumes. Only
real power capable of doing work, but apparent power
determines the amount of power that flows into the
load. In power system, wasted energy capacity also
known as poor power factor. It can result in poor
reliability, safety problems and higher energy costs.
The lower power factor means the less economically
the system operates. So for this reason, power factor
correction is necessary [5].
Power factor correction circuit is to minimize
the input current waveform distortion and make it in
phase with the voltage one.
A. Active PFC
It is the most effective way to correct power
factor of electronics supplies. In this approach place
different Active PFC converters between the bridge
rectifier and the load. The converter tries to maintain a
constant DC output voltage and draws a current that is
in phase with and at the same frequency as the line
voltage.
Active PFC has following main Advantages:
Active wave shaping of the input current.
Filtering of the high frequency switching.
Feedback sensing of the source current for
waveform control.
Feedback control to regulate output voltage.
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International Journal of Engineering Trends and Technology (IJETT) – Volume-42 Number-3 - December 2016
VI.BOOST CONVERTER
The principle that drives the boost converter is the
tendency of the inductor to resist the changes in the
current. When being charged it acts as a load and
absorbs energy like resistor [8], [9]. When being
discharged it acts as an energy source like a battery.
The voltage produced during discharge phase is
related to the rate of change of current, and not to the
original charging
voltage, thus allowing different input and output
voltages. The Fig 4 shows boost converter.
current is employed in the feedback loop of the switch
mode power converters. It has given new avenues of
analysis and at same time introduced complexities in
terms of multiple loops.
VII. SIMULATION AND RESULTS
This paper involves simulation of basic power
electronic circuits and the analysis of the current and
voltage waveforms. It starts with simple circuits with
a gradual increase in complexity by inclusion of new
components and their subsequent effect on the current
and voltage waveforms. It will focus on the objective
of improving the input current waveforms i.e. making
it sinusoidal by tuning the circuits. All the simulation
work is done in MATLAB simulink.
Fig 4:Boost converter
A. Dual boost converters
Boost converters are used as active power factor
correctors.
However, a recently PFC is to use dual boost
converter (Fig.5) i.e. two boost converters connected
in parallel. Where choke Lb1 and switch Tb1 are for
main PFC while Lb2 and Tb2 are for active filtering,
the filtering circuit serves two purposes i.e improves
quality of line currents and reduces the PFC total
switching loss. The reduction in switching losses
occurs due to different values of switching frequency
and current amplitude for the two switches. It involves
phase shifting of two or more boost converters
connected in parallel and operating at the same
switching frequency. This converter provides
regulated dc output voltage. The control of output
voltage should be performed in closed loop manner
using principle of negative feedback. There are two
technique of closed loop PWM dc-dc converter
namely voltage mode control and current mode
control.
Fig 6: Current control mode
A. Simulation and results for Conventional converter
Fig 7 shows that this circuit consist of two groups of
diodes: top group with diodes 1 and 3 and bottom
groups with diodes 2 and 4. It is easy to see the
operation of each group of diodes with Ls=0. The
current id flows continuously through one diode of the
top group and one diode in the bottom group. The
circuit is simulated using Simulink and input current
with respect to input voltage waveforms are plotted in
graph as shown in the Fig 8 and output waveforms are
plotted in graph as shown in Fig 9. The input current
waveform consists of Total Harmonics Distortion. The
Fig 7 shows THD of input current and THD
percentage is 97.54. This problem will effect at the
supply side equipments.
Fig 5: Dual boost converter
B. Current mode control
In this mode of control as shown in Fig 6 signals in
current waveform has advantage over voltage over
voltage signals. Voltage being an accumulation of
flux, which is slow in time as far as control
mechanism, is concerned. This led to the development
of a new area in switch mode power supply design
using Current mode control. Here, the average or peak
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Fig 7: Conventional Rectifier
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International Journal of Engineering Trends and Technology (IJETT) – Volume-42 Number-3 - December 2016
It is clear from Fig 10 that the power factor is
0.90 which is very low and it needs to be improve by
using proceeding methods.
The circuit is simulated using Simulink and input
current with respect to input votage waveform are
potted in graph as shown in the Fig12 and output
waveforms are plotted in graph as shown in the fig
13.
(a)
Fig 10: Power factor
(b)
Fig 8: (a) Input voltage and (b) Input current waveforms
Fig11:THD of Conventional Rectifier
Fig 9: Output voltage waveforms as function of time
B. Simulation and results for rectifiers circuit with
PFC Boost Converter
Boost converter is a DC-DC Converter which
provides output voltage is grater than input voltage.
Here, the inductor responds to changes in current by
inducing its own voltage to the change in current, and
this voltage adds to the source voltage while the
switch is open. If a diode and capacitor combination
is placed in parallel to the switch, the peak voltage
can be stored in the capacitor, and the capacitor can
be used as a DC source with an output voltage greater
than the dc voltage driving the circuit. This boost
converter acts like a step- up transformer for DC
signals is shown in Fig 12.
Fig 12: Boost converter
(a)
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International Journal of Engineering Trends and Technology (IJETT) – Volume-42 Number-3 - December 2016
(b)
Fig 13 : (a) Input voltage and (b) Input current
C. Simulation and results for Dual boost converter
Fig 17 shows inductors L1 and L2 have the same
values, the diodes D5-D6 are the same type and the
same assumption was for the MOSFET( M1 & M2).
Each inductor has its own switch and thus is similar
with the paralleling of two single converters.
When the MOSFETS M1 and M2 are in ON
state, the proposed topology transfers energy from the
dc source (Vb) into the inductors L1 and L2. Here, the
current divides and equal current are flowing through
inductor L1 and inductor L2. The output current
flowing through load RL and C where C is the
smoothing capacitor.
Fig17 : Dual boost converter
Fig 14 : Output voltage waveform as a function of time
The Fig 15 shows that the power factor is 0.989 which
is improved from previous model. The boost converter
could not provide high boost factor. The power factor
can be improved nearly unity by using dual boost
converter
Input current with respect to input voltage waveform
are plotted in graph as shown in the Fig 18 and output
waveforms are plotted in graph as shown in the Fig 19
. here, the input current waveform is nearly sinusoidal.
The power factor increased from 0.989 to 0.9926 as
shown in fig 20. It is made nearly equal to unity using
dual boost converter.
(a)
Fig 15 : Power Factor
Fig 18 : (a) Input voltage and (b) Input current
Fig16:THD of Boost Converter
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International Journal of Engineering Trends and Technology (IJETT) – Volume-42 Number-3 - December 2016
VIII: CONCLUSION
The power factor correction with different
converters are simulated with MATLAB simulink. In
this paper conventional converter, boost converter and
dual boost converter using current mode control are
discussed. It is noticed that the power factor is better
for dual boost converter circuit. And it is noticed that
THD is less for dual boost converter. This can be
further improved by using PI and Fuzzy controllers.
REFERENCES
Fig 19 :output voltage as a function of time
Sr
no
Circuit
topolologies
1
Conventional
rectifier
Boost
converter
Dual boost
converter
2
3
[1]
Input
power
factor
0.90
THD
Output
voltage
94.77
16
0.989
36.89
310
0.9926
3.40
360
[2]
[3]
[4]
Table 1: Analysis of PF and THD
[5]
[6]
[7]
[8]
[9]
Fig 20 : Power factor
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Fig21:THD of Dual Boost Converter
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