Download High Performed Fuzzy Controlled Operation of Induction Motor Jithin

High Performed Fuzzy Controlled Operation of
Induction Motor
Jithin P1,Dr.T.Govindaraj2
M.E.PED Scholar,Head of the Department, EEE
Muthayammal Engineering College, India
[email protected]
Absract: This paper proposes fuzzy based current
control in the field weakening region of induction
motor. In this project it proposes an expert controller
before current regulators to process current command
and thus avoiding unreasonable fast tuning in the highspeed flux weakening region so as to keep current
command followed by actual current. The proposed
topology consist of a single phase ac input source,three
phase IGBT inverters ,fuzzy inference mechanism and
a capacitor filter is used. Thus proposed fuzzy inference
controller is to handle the current commands before
current regulator and this is based on the consideration
of the bandwidth decreasing and for the critical voltage
limitation.At the load one induction motor is connected ,
here current control of motor is done with the help of a
fuzzy controller.Simulation and experimental results
are provided to verify the stability of current control.
Index terms- Field weakening,
induction motor, fuzzy inference.
current
the extended high speed. Recently proved that in
,most of the research on the current control in the flux
weakening operation region is below 2 to 3 times of
the base speed. The most worse is that current
regulators are too unstable, and they even result in
damage to insulation gate bipolar transistors (IGBTs)
and drive equipment in some cases. In the view of
temperature variable, magnetic hysteresis and some
other reasons, parameters are mainly variable.
Mostly the existing research focuses on flux
weakening
control,
strategy
optimization
and
current
regulators design. In induction motor, the stator
winding
is
fed
from
3-phase
supply.
The
electromagnetic induction is the mechanism in the
I. INTRODUCTION
rotor winding. Generally the flux weakening strategy
In the fast running world the main problem is the
are of two types. They are robust and model based.
current global energy crisis. So the focus is on
The model based method uses motor parameters and
efficiency and delivering high performance, while
dc bus voltage to calculate current references.The
consuming less power for the electronic components.
ideal optimal current trajectory which consists of the
As a result of this crisis, various agencies around the
maximum torque per current trajectory at a specified
world have or are looking to increase their efficiency
speed is determined under the voltage and current
standards for numerous products in their respective
limitation due to the motor and inverter capacity. In
specifications. In general among the motors,the
the proposed flux weakening scheme realises the
induction motors (IM) are widely accepted as the
smooth transition between control modes and
most promising candidate for electric propulsion of
winding resistance is accounted for the speed range.
hybrid electric vehicles (HEVs) and electric vehicles
Although the model based control guarantees the
,due to their reliability, ruggedness, low maintenance,
stability and fast transient response, they are
low cost, and the ability to operate in fast mode for
extremely sensitive to the motor parameters and
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operating conditions.In the flux weakening region,
the current distribution (ids and iqs) is absolutely
important to the torque capability . There two major
flux weakening optimal strategies is to achieve
maximum torque capability. First, ids and iqsare
calculated by the IM parameters
Secondly, ids and
iqsare selected by utilizing voltage regulators and the
flux regulator .
Fig.1 Flux Weakening Strategy.
The current regulators forming the inner
This is critically limited as a result the differential
loop of the IFOC system are able to regulate the ac
term cannot be ignored. Thus the proposed fuzzy
current over a wide frequency range with high
bandwidth
and
zero
steady-state
error
inference controller to handle the current commands
by
before current regulator, it is based on the
proportional-integral (PI) regulators. Anyways, there
consideration of the bandwidth decreasing and the
will be cross coupling between ids and iqs that is
critical
proportional to the frequency of the fundamental
voltage
limitation
.This
also
avoids
unreasonable fast tuning of current concerning the
excitation. As a result of this , the performance of the
bandwidth of regulators and limit the current margin
current regulator has been shown to degrade as the
concerning the valid voltage.
excitation frequency increase. To eliminate the crosscoupling influence, the complex vector synchronous
frame the PI current regulator was introduced in. A
II. FLUX WEAKENING STRATEGY
similar solution was proposed in using an internal
model control formulation and by using the complex
In the flux weakening strategy analysis is in order to
vector current control approach generalized with a
produce the maximum current q axis component is
transfer function matrix. These schemes do not
proportional to current. .The basic strategy is that iqs
eliminate the ultimate influence of the interval delay
is inversely propotional to speed.. The fig 1 shows
caused by PWM and digital implementation .The
the advanced flux weakening strategy..The fig.1
stability of the current controller depends mainly on
shows the advanced flux weakening strategy in which
the bandwidth of the voltage that can be utilized. In
magnetizing current is inversely proportional to
the existing system approach the bandwidth of the
speed. This approach need to add just one regulator.
current regulators is decreased and voltage is
The method does not optimize maximum torque
critically limited in the high speed flux weakening
capability because it cannot modify iqs aacording to
region. In voltage model the direct and quadrature
our reqirement.Thus the commonly used flux
axis
of rotating synchronous coordination are
weakening strategies are constant voltage constant
computed to obtain mainly the synchronic angular
power control, constant current constant power and
speed, direct axis stator flux magnitude and
optimum current vector control.This figure explains
quadrature axis stator flux magnitude.
us the flux weakening strategy as a whole. The two
methods are explaind earlier in the context.
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III. BLOCK DIAGRAM DESCRIPTION
AC
SUPPLY
AC-DC
RECTIFIER
THREE
PHASE
INVERTER
12V DC
SUPPLY
DRIVER
UNIT
5V DC
SUPPLY
FUZZY BASED
PIC
CONTROLLER
INDUCTION
MOTOR
Fig. 2. Block diagram for proposed fuzzy controlled induction motor.
In the fig.2 the induction motor is controlled by the
three phase inverter .The block diagram consist of
input supply, driver unit and a fuzzy based PIC
controller.
energy source 230V-50Hz and stepping down
transformer, rectifier, filter and voltage regulator.
Rectifier Unit :In the power supply unit,
rectification is normally achieved using a solid state
Input Source :As we know for the circuit given we
are giving a ac supply to the ac-dc rectifier . A dc
supply is given to the driver unit and to the control
algorithm. The ac output is given to the induction
motor after rectification. As we know any invention
of latest technology cannot be activated without the
source power. So in this fast moving world wide
liberately need proper power source which will be apt
for a particular requirement. All the electronic
components starting from diode to Intel IC’s work
with DC supply ranging from +5v to +12v.We are
utilizing the same cheapest and commonly available
diode. Diode has the property that will let the
electron flow easily in one direction at proper biasing
condition. An AC is applied to the diode, electrons
only flow when the anode and cathode is negative.
Reversing the polarity of voltage will not permit
electron flow. A commonly used circuit for supplying
large amounts of DC power is the bridge rectifier. A
bridge rectifier of four diodes (4*IN4007) are used to
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achieve full wave rectification. Two diodes conduct
simple, rugged, low-priced, easy to maintain and can
during negative half cycle and the other two during
be manufactured with characteristics to suit most
positive half cycle. The DC voltage appearing across
industrial requirements. Like any electric motor, a 3-
the output terminals of the bridge rectifier will be
phase induction motor has a stator and a rotor. The
somewhat less than 90% of the applied RMS value.
stator carries a 3-phase winding (called stator
Normally one alteration of the input voltage will
winding) while the rotor carries a short-circuited
reverse
the
winding (called rotor winding). Only the stator
transformer will therefore always be 180 degree out
winding is fed from 3-phase supply. The rotor
of phase with each other. For a positive cycle, two
winding derives its voltage and power from the
diodes are connected to the positive voltage at the top
externally
winding and only one diode conducts. At the same
electromagnetic induction and hence the name. The
time one of the other two diodes conducts for the
induction motor may be considered to be a
negative voltage that is applied from the bottom
transformer with a rotating secondary and it can,
winding due to the forward bias for that diode In this
therefore, be described as a “transformer-type” ac.
circuit due to positive half cycle D1 and D2 will
machine in which electrical energy is converted into
conduct to give 10.8V pulsating DC. The DC output
mechanical energy.
the
polarities.
Opposite
ends
of
energized
stator
winding
through
has a ripple frequency of 100Hz.Since each alteration
Advantages of Induction motor:
produces resulting output pulse, frequency=2*50Hz.
The output obtained is not
pure DC and therefore
It has simple and rugged construction.
filtration has to be done.
It is relatively cheap.
Bridge Rectifier :Here bridge rectifier is coming as a
It requires little maintenance.
part of resonant converter .The ac voltage coming
It has high efficiency and reasonably good power
after resonant inverter is the input to this bridge
factor.
rectifier. Here the rectifier is in uncontrolled manner
It has self starting torque.
with diode switches. It is very cheap and simple. This
rectifier converts ac to dc output and fed to capacitor
Three Phase Inverters :Three-phase inverters are
filter to reduce the ripples in the output voltage. Then
used for variable-frequency drive applications and for
the output dc is fed to induction motor.
high power applications such as HVDC power
transmission. A basic three-phase inverter consists of
Induction Motor : The three-phase induction motors
three single-phase inverter switches each connected
are the most widely used electric motors in industry.
to one of the three load terminals. For the most basic
They run at essentially constant speed from no-load
control scheme, the operation of the three switches is
to full-load. However, the speed is frequency
coordinated so that one switch operates at each 60
dependent and consequently these motors are not
degree point of the fundamental output wave
easily adapted to speed control. We usually prefer dc.
motors when large speed variations are required.
Nevertheless, the 3-phase induction motors are
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IV. CIRCUIT DIAGRAM DESCRIPTION
Fig.3. Circuit diagram for proposed fuzzy controlled induction motor drive
Here Fig 2 shows the proposed circuit diagram of
applied to the diode, electrons only flow when the
the ac to dc converter using fuzzy controller for an
anode and cathode is negative. Reversing the polarity
induction motor is shown above. Here the driver
of voltage will not permit electron flow. As we know
circuit is the key part, output from inverter is
any invention of latest technology cannot be activated
effectively utilized for driving a induction motor, and
without the source power. So in this fast moving
motor controlling is done with the help of a fuzzy
world we deliberately need proper power source
controller. In the circuit consists of an ac supply at
which will be apt for a particular requirement. All the
the input , this given to the rectifier for conversion
electronic components starting from diode to Intel
between the rectifier and three phase inverter. . Here
IC’s work with DC supply ranging from +5v to +12v.
the induction motor is connected at the ouput
We are utilizing the same cheapest and commonly
side..thus the proposed system includes appropriately
available energy source 230V-50Hz and stepping
sized power supply unit, rectifier and voltage source
down transformer, rectifier, filter and voltage
inverter to energize the Induction motor. along with
regulator. Filter circuits which are usually capacitors
this auxiliary power supply unit also considered to
acting as a surge arrester always follow the rectifier
energize the control equipments. The rectification is
unit. The capacitor is also as a decoupling capacitor
normally achieved using a solid state diode. Diode
or a bypassing capacitor, is used not only to ‘short’
has the property that will let the electron flow easily
the ripple with frequency .
in one direction at proper biasing condition. As AC is
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performance than the conventional PI control. The
fuzzy algorithm is based on the human intuition and
experience and can be regarded as a set of heuristic
decision rules. It is possible to obtain very good
performance in the presence of varying load
conditions and changes of mechanical parameters and
inaccuracy in the process modeling .Comparing the
traditional current control in IFOC, an expert
controller is added to preprocess current commands
before the current regulators. The expert controller
based on the fuzzy inference consists of the following
Fig.4 Fuzzy Controller Block
components. They are knowledge database, the fuzzy
inference
V. PRICIPLE OF OPERATION
mechanism
and
the
characteristics
recognition. The feature recognition records the
waveform features of idsfed, iqsfed, vds, and vqs.
The operation of the induction motor in this
When a period of the tuning ends, it calculates
paper is by implementing the new expert controller
mainly the properties of the current control, such as
so as to improve the performance .This is done using
the rise time, the ratio of attenuation and the
the fuzzy controller. The fuzzy control is explained in
oscillation period. The characteristic recognition
detail.
provides
references
for
the
fuzzy
inference
FUZZY LOGIC CONTROLLER :
mechanism . Fuzzy logic (FL) is one of the main
INTRODUCTION
artificial intelligent techniques. Fuzzy logic apart
In the recent years the fuzzy logic has
from Boolean logic, deals with problems that have
become popular in many applications of electrical
fuzziness or vagueness. The classical set theory is
drives and control, where classical PI controllers
based on Boolean logic, where the particular object
were used. Several design techniques exist to tune
or variable is either a member of a given set (logic 1),
the classical PI controller parameters, but they can be
or it is not (logic 0). On the other hand, in fuzzy set
time consuming and moreover fixed controller
theory is based on the fuzzy logic, where in a
settings cannot usually provide good dynamic
particular object has a degree of membership in a
performance over the whole operating speed range of
given set that may be anywhere in the range of 0
the drive. Varying load conditions, changes of
(completely not in the set) to 1 (completely in the
mechanical parameters and process non linearity and
set). For this reason, FL is often defined as multi-
inaccuracy in the process modeling can cause
valued logic, compared to bi-valued Boolean logic by
degradation of the performance. Fuzzy control
B.K. Bose, in 1986. The self-tuning mechanism
technique does not need accurate system modeling. It
consists of a performance model, an evaluation block
employs the strategy adopted by human operator to
and a fuzzy logic control (FLC) block. This
control
reference
complex
process
and
gives
superior
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model defines the desired dynamic
performance of the motor drive. It is selected based
depends on the bandwidth of current regulators and
on the maximum performance of the drive and to
the voltage that can be utilized in the mechanism.. As
avoid the excessive control action. For the IFOC of
previously mentioned , the bandwidth of current
the induction motor, the reference model can be
regulators is decreased and voltage is critically
approximated by a second order system. Mainly the
limited in high-speed flux weakening region. The
second order model is obtained from the procedure
differential items are always ignored by considering
used in and the constants a and b are adjusted to
the stable condition. However, it is unreasonable
meet the specific requirements of the induction
when a motor is in dynamic process because the
motor.
differential items take an important part in the valid
The actual speed of the motor ωr is
voltage. Particularly, when a motor is in high-speed
compared with the output from reference model ω’r ,
flux weakening region, the valid voltage except
to generate the speed signal e’r , which is the
CEMF is mostly critically limited. As a result of this,
difference between ωr and ω’r . The error signal is
the differential items cannot be ignored any more.
given as an input to the evaluation block. The
For improving the current control stability in high-
evaluation block is designed in such a way that, if the
speed flux weakening region, a fuzzy inference
error signal is within + 1 rad/sec, the self-tuning
expert controller is proposed to handle current
mechanism will not operate perfectly . If the error e’r
commands before current regulators. This is based on
exceeds the specific range of ±1 rad/sec, the
the consideration of the bandwidth decreasing and the
evaluation block generates the tuning error e ω which
critical voltage limitation. The controller performes
is given as an the input to the fuzzy logic control
mainly has two purposes. Firstly, it can avoid
(FLC) block. The first input is error ‘e’ and second is
unreasonable fast tuning of current concerning the
the change in error ‘ce’ at the sampling time ‘ts,. The
bandwidth of regulators. Secondly, it can limit the
two input variables are calculated e(ts) and ce(ts) at
current margin concerning the .valid voltage.
every sampling time as e(ts) = ωr*(ts) – ωr(ts) ce(ts)
Comparing with the traditional current control in
= e(ts) - e(ts-1) Where ‘ce’ denotes the change of
IFOC, an expert controller is added to preprocess
error ‘e’, ωr*(ts) is the reference rotor speed , ωr(ts)
current commands before the current regulators. The
is the actual speed, e(ts-1)is the value of error at
expert controller based on the fuzzy inference
previous sampling time. The output variable is the
consists of the following parts , knowledge database,
change in torque ΔT which is integrated to get the
the
reference torque as shown in the equation T*(ts) =
characteristics recognition. The feature recognition
T*(ts-1) + ΔT .
records the waveform features of idsfed, iqsfed, vds,
fuzzy
inference
mechanism
and
the
and vqs. When a period of the tuning ends,it
The fuzzy logic controller has four functional
calculates the properties of the current control, the
blocks. They are the Fuzzification, Interference
rise time, the ratio of attenuation and oscillation
mechanism, knowledge the fuzzy inference.base and
period. These are the main properties of fuzzy
Defuzzification. The stability of a current control
inference.
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.
Fig..5 Main Simulation Circuit.
Fig..6 Simulation of Three phase inverter circuit.
VI. EXPERIMENTAL RESULTS
Fig.7 Sub System Circuit
The proposed circuit is developed and analyzed with
MATLAB simulation circuit diagram, resultant
MATLAB software. for analysis of the current
waveforms for converter output voltage, current and
controlling for the field weakening operation and
motor speed is given below.
output voltage is fed to an induction motor.
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current commands.This is done in order to avoid the
Resultant Waveforms :
unreasonable variation of current commands. The
extensive simulation have been performed and the
results verify that the performance of current control
has been improved. Thus it is proved tha the scheme
proposed is very much effective.
REFERENCES
[1] H. Liu, Z. Q. Zhu,Y. Fu, and X. Qi, “Fluxweakening control of nonsalient pole PMSM having
Fig 8 .Inverter Output voltage
large winding inductance, accounting resistive
voltage drop and inverter nonlinearities,” IEEE Trans
Power Electron., vol. 27, no. 2, pp. 942–952, Feb.
2012.
[2] M. Mengoni, L. Zarri, A. Tani, G. Serra, and D.
Casadei, “A comparion of four robust control
schemes for field-weakening operation of induction
motors,” IEEE Trans. Power Electron., vol. 27, no. 1,
pp. 307–320, Jan.2012.
Fig. 9 Motorcurrent, speed and torque
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and D. Boroyevich, “Improved asymmetric space
vector modulation for voltage source converters with
low carrier ratio,” IEEE Trans. Power Electron., vol.
27, no. 3, pp. 1130–1140, Mar. 2012.
VII. CONCLUSION
In this new proposed paper
a simplified flux
[4] GovindarajThangavel,” Finite Element Analysis
of the Direct Drive PMLOM” In book: Finite
Element Analysis - New Trends and Developments,
Chapter: 6, InTech online Publisher,10 Oct 2012 .
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