3-Φ AC LOAD CONTROL
BY PWM TECHNIQUE
Abhishek H. Jadav & R.N. Rathod
Power Electronics Engineering Department
L.E.College, Morbi, Gujarat, India-363642
Email: abhishekjadav22@gmail.com, rathod_45@yahoo.com
Abstract - Induction motors are being used in greater numbers
throughout a wide variety of industrial and commercial
applications because it provides many benefits and reliable
device to convert the electrical energy into mechanical motion.
In some applications, it’s desired to control the speed of the
induction motor. Because of the physics of the induction motor
the preferred method of controlling its speed is to vary the
frequency of the AC voltage driving the motor. In recent years,
with the microcontroller incorporated into an appliance, it
becomes possible to use it to generate the variable frequency
AC voltage to control the speed of the induction motor. This
study investigates the variable frequency power inverter. The
variable frequency pulse width modulation (PWM) signal that
controls the applied voltage on the gate drive, which provides
the required PWM frequency with less harmonics at the output
of the power inverter. The fully controlled bridge voltage
source inverter has been implemented with semiconductors
power devices isolated gate bipolar transistor (IGBT), and the
PWM technique has been employed in this inverter to supply
the motor with AC voltage. The proposed drive system for
three & single phase power inverter is simulated using
Matlab/Simulink. The Matlab simulation results of the
proposed system were achieved with different PWM. From the
result, a stable variable frequency inverter over wide range has
been obtained and a good agreement has been found between
the simulation and hardware of a microcontroller based single
phase inverter.
Figure 1 Block diagram.
Also in electric vehicle, variable speed equipments, and
AC variable frequency power source used in the
laboratory, where there are many experiments require
the use of different AC sources in terms of the voltage
amplitude and frequency. Thus, it can be very useful in
the laboratory for testing appliances, products, and
equipment. It may also be helpful in an automated
production line for checking the Device Under Test
(DUT) in a specified operating range of voltage and
frequency.the variable frequency inverter have been
presented as low-cost, high-performance, such as:
microelectronics, allowing the use of software instead of
hardware to solve complex control problems for an
affordable price; power semiconductors technology,
providing powerful, fast and easy to drive switches;
control algorithms, which control the inverter output and
reduce the harmonic. With the increasing demands for
high-quality power sources, and reduction of harmonic
distortion, a PWM inverter has been used as a key
element for a high-performance power conversion
system. Recently, microcontrollers
are used as
advanced control techniques. Many researchers
developed the software for the control system, which
confirmed the high quality of the control based on
microcontroller techniques and to provide additional
real time processing through put in an inverter
operation, microcontrollers and DSP features minimize
the CPU's overhead in an interrupt intensive application
Index Terms —Microcontroller, Induction motor, three and
single phase power inverter, PWM technique.
I.
INTRODUCTION
The variable frequency inverters are used in wide
applications. three phase induction motor drive traction
and it is popular in many high power industrial
applications, such as speed and torque control. Single
phase induction motor, which has a common using in
residential applications domestic such as dishwashers,
cloths dryers, fans, pumps, etc. ,when the SPIMs are
preferred due to the greater availability of single phase
power supply.
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[4]. Motorola MC68HC11 microcontroller has been
chosen for this implementation because it is easy to
develop, instantly response, high performance, high
speed, and low-power chip with multiplexed capable of
running at up to 2 MHZ. Traditionally, variable speed
operation of a single phase induction motor suffers from
large harmonic and limited speed, therefore the system
has been built using voltage control method with
semiconductors power devices IGBT and PWM
techniques have been implemented to avoid the large
harmonics. Simulation of a single phase and three phase
variable frequency inverter, which has been constructed
on matlab software to check its capability to achieve
sinusoidal waveform with variable frequency to use as
single phase and three phase variable frequency power
supply.
The Matlab simulation results achieved with
different PWM frequencies. this system can be
considered as high power variable frequency voltage
source inverter.
Figure 3 180 Degree conduction
In three phase inverter of fig.2&3,each IGBT
conducts 180 degree of a cycle.IGBT pair in each arm,
i.e.S1,s4;s3,s6 and s5,s2 are turned on with a time
interval of 180 degree.s1 conducts for 180 and s4 for
next 180 of cycle.IGBT in upper group,i.e.s1,s3,s5
conduct at an interval of 120 Degree.it means that s1 is
fired at wt=0,and s3must be at wt=120and s5 at
wt=240.same procedure for s4,s6,s2 lower group of
IGBTs. The fig.3 shows that s5,s6,s1 shoud be gated for
step1;s6,s1,s2 for step2;s1,s2,s3 for step 3;s2,s3,s4 for
step4 and so on. From this procedure every step of 60
degree duration,only three IGBTs are conducting.One
from upper group and two from the lower group or two
from the upper group and one from lower group.
II. CIRCUIT OPERATION
Figure2 3phase Inverter ckt
The ckt operation is shown in the fig. three
phase inverter input is rectifier. As shown in fig
there are six IGBT based inverter the output is not
pure Ac,so we connect LC filter at output of
inverter. So we can get sinusoidal waveform. In
three phase inverter three phase line connected to
the ckt so high power supply passes from the ckt.
Three phase inverter has two conduction mode:
120 Degree and 180 Degree. The IGBT triggered
as per delay time. The triggering wave form of the
both conduction mode is as shown in figure.
Figure 4 120 conduction mode
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ITSI Transactions on Electrical and Electronics Engineering (ITSI-TEEE)
In three phase inverter of fig.2&4,each IGBT conducts
120 degree of a cycle.IGBT.from the first row shows
that s1 conducts 120degreeand for next 60
degree,neither s1 and s4 conducts.s4 is turn o at 180
degree and further conduct as 120 to180,series
connected IGBTs s1,s4 do not conduct.At wt=360,s4 is
turned off,then 60 interval elapses before s1 is turned on
again wt=360degree.in second row s3 is conducts for
120,then 60 interval elapses during which neither s3 nor
s6 conducts.at wt=300degree ,s6 is on,it conducts for
120 and then 60 interval elapses after which s3 is turned
on again.thired row is also complete similarly.s6,s1on
for step1;s1,s2 for step2;s2,s3 for step 3and so on.the
sequence of firing six IGBTs are same as for 180 degree
mode inverter. During each step,only two IGBTs
conducts for this inverter.one from upper group and one
from lower group.
Figure 6 3 phase inverter ckt.
III. EXPERIMENTAL SETUP.
In this study, the full bridge rectifier has been used
to convert the AC supply to a DC voltage. A capacitor
and an inductor are connected to form a smoothing
filter. The output of the rectifier is the input to the
inverter, which receives the smooth DC voltage and
converts it to AC power to get the variable frequency
power source. The microcontroller-based control system
hardware has been programmed to vary the frequency of
the PWM signal that controls the frequency of the power
inverter. The PWM module gets two inputs ―duty cycle
and frequency‖ the duty cycle can be ranged from 0%
to 100%. In order to use the output compare function as
PWM generator, the frequency is converted from Hz to
counts according to the following equation.
Figure 7 rectifier output.
FREQHZ
FREQCNT =
05
Where, 0.5μs is the one cycle period of microcontroller.
The PWM signals of the MCU are applied to the gate of
Figure 8.Gate pulse of inverter.
IGBT through gate drive; the gate driver provides
isolation, low impedance and high current supply to
drive the IGBT’s.
IV. RESULT ANALYSIS
Simulation
is
carried
out
in
the
MATLAB/SIMULINK environment as shown in. Load
is assumed resistive. Voltage 230v to rectifier and 330v
to inverter, switching frequency is set 50 KHz
Figure 9 180degree conduction mode
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Figure 13 Phase voltage
Figure 10.inverter output with filter.
Figure 14 Load voltage
Figure 11 Load current and Voltage
Figure 15 SPWM Technique
V. CONCLUSION
The single phase and three phase variable frequency
inverter is simulated using Matlab/Simulink software.
The
stable AC power source with variable amplitude
and variable frequency over wide range has been
obtained. The M68HC11E-9 microcontroller based
single phase variable frequency power inverter has been
introduced and it can be successfully achieved. Results
of the experiment have been obtained for the
microcontroller, which offers reliable and low-cost
Figure 12 Carrier and Reference signals
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ITSI Transactions on Electrical and Electronics Engineering (ITSI-TEEE)
solutions for single phase variable frequency inverter
and good agreement was found between simulation and
hardware results. In general, the AC-DC-AC conversion
was successful, on the other side, some overshoot were
found due to suspected causes such as the control
algorithm used in the microcontroller and harmonic
content at the inverter output. However, good results
confirming the initial intention for design.
[7]
Kondapalli Siva Rama Rao and Lee Teng
Hong)Department of Electrical and Electronics
Engineering, University Teknologi PETRONAS,
Tronoh 31750, Malaysia. Published: April 30,
2012.
[8]
EXPERIMENTAL IMPLEMENTATION OF
SINGLE-PHASE,
THREE-LEVEL,
SINUSOIDAL PULSEWIDTH MODULATION
(SPWM) VOLTAGE SOURCE INVERTER
(VSI) WITH R-L LOAD(C.I. Odeh, D.B.N.
Nnadi), Department of Electrical Engineering,
University of Nigeria, Nsukka, Nigeria. Vol. 31,
No. 1, March, 2012.
[9]
Mr. R.Senthilkumar ―DESIGN OF SINGLE
PHASE INVERTER USING dsPIC30F4013‖,
Associate Professor/EEE,
[10]
Saveetha
Engneering
Chennai- 602105, India.
[11]
Dr. Adel Gastli ―ADVANCED POWER
ELECTRONNICS PWM INVERTERS.‖
[12]
Anuradha Tomar Electrical & Electronics
Department Northern India Engineering College,
NewDelhi, India.‖ Literature Survey on Variable
Frequency drive‖
[13]
P.S. Bhimra by ―Power electronics.‖
[14]
M.H. Rashid by ―Power electronics Circuits,
Devices and Applications.‖
[15]
Khanchandani by ―Power electronics‖
VI. REFERENCES
[1]
khaled A. Madi Ali and Mohammad E. Salem
Abozaed ―Microcontroller Based Variable
Frequency Power Inverter‖.
[2]
SIMULATION AND COMPARISON OF
SPWM AND SVPWM CONTROL FOR THREE
PHASE INVERTER.‖( K. Vinoth Kumar, Prawin
Angel Michael, Joseph P. John and Dr. S. Suresh
Kumar) VOL. 5, NO. 7, JULY 2010.
[3]
[4]
dsPIC based SPWM controlled Three Phase
Inverter Fed Induction Motor Drive‖ ( Sandip A.
Waskar, U.L.Bombale,PhD.,Tanaji B. Sonawane,
Department of ElectronicsTechnology, Shivaji
University Kolhapur.) International Journal of
Computer Applications (0975 – 888)Volume 47–
No.16, June 2012.
Kapil Jain, Pradyumn Chaturvedi,”Matlab -based
Simulation & Analysis of Three -level SPWM
Inverter‖. International Journal of Soft
Computing and Engineering (IJSCE) ISSN:
2231-2307, Volume-2, Issue-1, March 2012
[5]
Pankaj H Zope1, Pravin G.Bhangale‖
[6]
Design and
Implementation of carrier
basedSinusoidal PWM Inverter, International
Journal of Advanced Research in Electrical,
Electronics and Instrumentation Engineering
Vol. 1, Issue 4, October 2012
College,Thandalam,
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