International Journal of Engineering Trends and Technology (IJETT) – Volume 5 number 3 - Nov 2013
Implementation of Single Stage Three Level
Power Factor Correction AC-DC Converter
with Phase Shift Modulation
Ms.K.Swarnalatha#1, Mrs.R.Dheivanai#2, Mr.S.Sundar#3
#1
EEE Department, PG Scholar,
Vivekanandha Institute of Engineering and Technology for Women, Tiruchengode,Tamilnadu, India.
#2
EEE Department, Assistant Professor,
Vivekanandha Institute of Engineering and Technology for Women, Tiruchengode,Tamilnadu, India.
#3
EEE Department, Assistant Professor,
Bannari Amman Institute of Technology, Sathyamangalam, Tamil nadu, India.
Abstract—A new single stage Three level ac-dc
converter that can operate with standard phase shift
modulation is proposed in this paper. The converter
topology is very simple, and this method of control used
to achieve both power factor correction and ac-dc
conversion. Converter operation is explained and power
factor is improved in this paper. Finally the efficiency of
the new converter is compared with that of previously
proposed converter.
Keywords—PSM (Phase Shift Modulation), TL (Three
Level) converter, AC-DC converter, power factor
correction (PFC), single stage converter.
I. INTRODUCTION
Power-electronic inverters are becoming
popular for various industrial drives
applications. In recent years also high-power
and medium-voltage drive applications have
been installed. To overcome the limited
semiconductor voltage and current ratings,
some kind of series and/or parallel
connection will be necessary. Due to their
ability to synthesize waveforms with a better
harmonic spectrum and attain higher
voltages, multi-level inverters are receiving
increasing attention in the past few years.
THE ac–dc power supplies with transformer
isolation are typically implemented with
some sort of input power factor correction
(PFC) to comply with harmonic standards
such as IEC 1000-3-2 [1].
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With the rapid rise in the use of electrical
equipment in recent years, power converter
manufactures are being pressed by
regulatory to implement some form of PFC
intheir products. High power factor and low
input current harmonics are more and more
becoming mandatory performance criteria
for power converters. Although it is possible
to satisfy by adding passive filter elements
to the traditional passive diode rectifiers/LC
filter input combination. The result of this
converter is very bulky and heavy due to the
size of the low frequency inductors and
capacitors. Active power factor correction
techniques have been used in AC-DC
converter to improve power factor and
reduce the harmonics. Active power factor
correction can be classified into two stage
scheme. Two stage PFC contains two
independent power stages in cascade with
PFC stage and DC-DC regulator. The total
efficiency of the two stage is lower because
the total power has to be processed twice
with two cascade power stage. Cost of the
circuit is increase several schemes have
developed to combine stage into one stage
[13].
The voltage feed single stage PWM (Phase
Shift Modulation) full bridge converter have
disadvantages that have limited their use.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 5 number 3 - Nov 2013
These are following, 1) They are controlled
by single controller and the dc bus voltage is
left unregulated [12-15]. 2) They are
implemented with two level topologies that
subject the converter components to voltage
stresses[2],[15].The single stage AC-DC full
bridge converter is based on some sort of
voltage
fed
single
stage
PWM
converter[12]-[15].This converter have a
large energy storage capacitor connected
across their primary side dc bus.
They are operate with fixed switching
frequency and the bus capacitor prevents
voltage overshoots. The three level voltage
fed single stage PWM converter was
proposed in[15]. This converter does not
have disadvantage of previously proposed
single stage TL converter. This PWM
method is not standard PWM and is
therefore not found in commercially
available integrated circuit. A new single
stage TL AC-DC converter that can operate
with standard PWM is proposed in this
paper.
Fig.1. Single Stage TL ac-dc converter [15].
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Fig.2 Typical waveforms describing the
modes of operation.
II. PULSE WIDTH MODULATION (PWM)
The energy that a switching power converter
delivers to a motor is controlled by Pulse
Width Modulated (PWM) signals, applied to
the gates of the power transistors. PWM
signals are pulse trains with fixed frequency
and magnitude and variable pulse width.
There is one pulse of fixed magnitude in
every PWM period.However, the width of
the pulseschanges from period to period
according to a modulating signal.
When a PWM signal is applied to the gate of
a power transistor, it causes the turn on and
turns off intervals of the transistor to change
from one PWM period to another PWM
period according to the same modulating
signal. The frequency of a PWM signal must
be much higher than that of the modulating
signal, the fundamental frequency, such that
the energy delivered to the motor and its
load depends mostly on the modulating
signal.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 5 number 3 - Nov 2013
IV. CURRENT RATING OF MOSFETs AND
DIODES
Let the rms value of the line current
of the load be IL Therefore
IL =squre root of (2/3)*I
Irms MOSFET= Irms diode =
0.707 IL
Fig: two types of PWM signals
Above Figure, shows
two types of PWM signals, symmetric
and asymmetric edge-aligned. The
pulses of a symmetric PWM signal are
always symmetric with respect to the
center of each PWM period. The pulses
of an asymmetric edge-aligned PWM
signal always have the same side
aligned with one end of each PWM
period. Both types of PWM signals are
used in this application.
III. PULSE WIDTH MODULATION
TECHNIQUES
The control of output voltage is done using
pulse width modulation. The commonly
used techniques are
1.
2.
3.
4.
Single pulse width modulation.
Multiple pulse width modulation.
Sinusoidal pulse width modulation.
Modified sinusoidal pulse width
modulation.
5. Phase displacement control.
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It is easily seen that the peak
forward blocking as well as the peak reverse
voltage on the MOSFET is equal to the
maximum capacitor voltage. Hence the
voltage rating of the thyristor is equal to Vco.
V. VOLTAGE RATING OF DIODES
The peak reverse voltage across a
diode occurs just before the switch in the
same leg is fired and is given by (Vco-IR/3).
This could be taken as Vco itself for a safe
design.
VI. PSM TECHNIQUE FOR TL SINGLE-STAGE
CONVERTERS
The proposed converter, shown in Fig. 3,
integrates an ac–dc boost PFC into a TL
dc/dc converter. It is almost the same as the
converter proposed in [15] and with a flying
capacitor between two clamping diodes. The
PFC is performed by using an auxiliary
winding taken from the main transformer
that acts like a switch that turns on and off in
an appropriate manner.
Typical converter waveforms are shown in
Fig. 4, and equivalent circuit diagrams that
show the converter’s modes of operation
with phase-shift modulation (PSM) are
shown in Fig. 5. The diode rectifier bridge
output is replaced by a rectified sinusoidal
source, and the thick lines represent the
paths of current conduction.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 5 number 3 - Nov 2013
discharges through Cf until Cs4, the output
capacitance of S4, clamps to zero. The
energy stored in the input inductor during
the previous mode starts to be transferred
into the dc-link capacitors. This mode ends
when S4 turns on with zero-voltage
switching (ZVS).
Fig3: Proposed single stage TL converter.
Fig4: typical
converter.
waveform
of
3) Mode 3 (t2 < t < t3) [Fig. 5(c)]: In Mode
3, S1 is OFF and S2 remains ON. The
energy stored in the input inductor during
Mode 1 is completely transferred into the
dc-link capacitors. The amount of stored
energy in the input inductor depends upon
the rectified supply voltage. This mode ends
when the input inductor current reaches
zero. Also, during this mode, the load
inductor current freewheels in the secondary
of the transformer.
proposed
The converter has the following modes of
operation.
1) Mode 1 (t0 < t < t1) [Fig. 5(a)]:During
this mode, switches S1 and S2 are ON, and
energy from dc bus capacitor C1 is
transferred to the output load. Since the
auxiliary winding generates a voltage
(Naux/N1 =2) that is equal to the total dclink capacitor voltage (sum of C1 and C2),
the voltage across the input inductor is the
rectified supply voltage, and thus, the input
inductor current starts rising.
2) Mode 2 (t1 < t < t2) [Fig. 5(b)]: In this
mode, S1 is OFF and S2 remains ON.
Capacitor Cs1 charges and capacitor Cs4
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International Journal of Engineering Trends and Technology (IJETT) – Volume 5 number 3 - Nov 2013
5)
Mode 5 (t4 < t < t5) [Fig. 5(e)]: In this
mode, S1 and S2 are OFF, and the current in
the transformer primary charges capacitor
C2 through the body diode of S3 and switch
S4. This mode ends when switches S3 and
S4 are switched on and a symmetrical period
begins.
4) Mode 4 (t3 < t < t4) [Fig. 5(d)]: In this
mode, S1 is OFF, the primary current of the
main transformer circulates through diode
D1 and S2, and the load inductor current
freewheels in the secondary of the
transformer.
VII. SIMULATION DIAGRAM FOR THREE LEVEL AC-DC CONVERTER
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International Journal of Engineering Trends and Technology (IJETT) – Volume 5 number 3 - Nov 2013
VIII. RESULT AND DISSCUSION
can always be used to ensure that at least
two switches can turn on with ZVS.
REFERENCES
New TL Output Waveform
1.
2.
3.
4.
5.
DC Output Waveform
6.
7.
8.
9.
10.
IX. CONCLUSION
A new TL single-stage converter
has been proposed in this letter. In this
paper, the operation of the converter was
explained, and its feasibility was confirmed
with experimental results obtained from a
prototype converter. The efficiency of the
new converter was compared to that of a
previously proposed converter of the same
type. It was shown that the new converter
had a better efficiency, and power factor is
improved for particularly under light-load
conditions, and it was explained that this
was because energy from the input inductor
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