Speed Control of Single and Three Phase Induction Motor Using Full Bridge Cycloconverter
Speed Control of Single and Three Phase Induction Motor Using Full Bridge Cycloconverter
Speed Control of Single and Three Phase Induction Motor Using Full Bridge Cycloconverter
ABSTRACT -This project proposes a full bridge cyclo- period for each MOSFET. However, control of induction
converter for three and single-phase induction motor speed motor is challenging task, many authors have suggested
control. The speed control of Induction Motor is simple and different techniques for speed control of induction of
can be made efficient by using various methods to control the induction motor. These includes sliding mode control,
action of Cyclo-converter which will control the motor
fuzzy logic control and model predictive control and cyclo-
performance. There are two ways to control the speed of the
motor, one method is by changing the frequency and the converters etc. The advancement of standard field-oriented
second method is by changing the number of poles. The speed control could be viewed as a control methodology. It
control by the second method is uneconomical because under involves2 control loops, i.e. the speed control and the rotor
running conditions the number of poles can’t be varied and the flux loops, intended using the active control method, using
machine size becomes bulkier, but the problems can be disturbance rejection with the aim to cope with both
overcome by the first method. In this scheme, the motor supply endogenous and exogenous disturbances, which are
frequency can be varied in running conditions, so it will not projected by means of two extendedlinear state observers
change the motor size. In this scheme, the Cyclo-converter is a and then remunerated. Additionally, with the aim of total
frequency changing device. It is a power electronic device used
robustness.Uncertainties and disturbance estimation errors
to convert constant frequency constant voltage AC power to
adjustable frequency adjustable voltage. AC power is used and in the knowledge of the control gains, for which the
without a DC link. Among all the schemes the frequency sliding mode-based control is designed. The Fuzzy
method is reliable, simple and economical. By using Cyclo controller algorithm is designed and carried out by fuzzy
converter the various speed of induction motor is obtained. set theory inMATLAB/Simulink 2013a using T-S model
The merits of proposed bridge type cyclo converter for speed (Takagi-Sugeno model). The output of both the controllers
control of single and three phase induction motor is verified by are examined by simulation and the results are compared.
simulations in MATLAB/Simulink environment. By the simulation result T-S model gives the better
Key words - Cyclo converter, AC-AC frequency converter performance to control the speed of the motor with respect
1.INTRODUCTION to load variations and control delay, when compared to the
With the ever-increasing demand of power requirement in PI controller. The overall post and pre-analysis proves the
the present world, efficient energy conversion is the top proposed controller robustness with respect to all
priority. These high efficiency converter units are the disturbances. The T-S model controller replaces the
power converters, where power electronics comes into conventional PI controller in terms of dynamic performance
action. Among the various converters, an AC-AC of non-linear system. In some conditions such as
frequency converter is a single step converter. Speed interruption of power, the motor may be continuously
control of Induction motor plays Important role in rotating before the motor is powered by the inverter. Initial
industries, there are various ways to control speed of motor direction of rotation and speed is unknown for the speed
but considering its efficiency, this paper proposed acyclo- less operation, so it will not achieve the smooth and fast
convertor technique by thyristors to control the single- resume of normal operation if the starting scheme is not
phaseand three-phase induction motor speed in three steps. well designed. In this methodology an adaptive full order
AC Induction motors have the great benefits of being very observer (AFO) is designed to address the problems.
reliable and relatively inexpensive. Induction motors are Without a proper feedback gain matrix, the estimated speed
very robust in many domestic appliances such as vacuum cannot converge to the actual speed, if the speed is lower
cleaners, washing machines, water pumps, and also used in than the actual speed. By transfer function analysis of stator
very large industries. It is also known as a constant-speed current error, the speed estimation is assumed. For
machine, one of its main disadvantagesis that the speed of improved restarting performance a feedback gain matrix
the motor is difficult to vary and also it is very cost condition is used for normal operation. The variable
effective. Cyclo-converter have several important features, frequency has important usage in the industrial world. The
cyclo-converter frequency can be varied by conduction electricity produced from the generating station are
978-1-5386-3817-0/18/$31.00 2018
c IEEE 318
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normally 50Hz and these frequency is not applicable for modulation technique has been done and comparison has
most of the application. The Speed Control of Induction been made among different PWM techniques. The various
Motor by Using Cyclo-converter. Some electrical devices methods of implementation of frequency converters are
which need variable frequency than the fixed supply also available in various literature.
frequency. The induction motors are one of the best
example for variable frequency drives. The induction 2. Block Diagram
motors are used in traction system, mobile power supplies
etc. The variable frequency drive has the great demand in
industrial applications. The cyclo-converter is such a device 1p Full Bridge 1 ph
which generates variable frequency. This project proposes
the Cyclo-converter for induction motor application with h Cyclo I.M
neuro fuzzy controller. In this paper AC supply frequency
cannot be changed, so this paper proposed a use of Cyclo-
converter using thyristor which enables the speed control in
steps for an induction motor. The controller used in this
project is from PIC (Programmable interface Controller)
family, a couple of switches is provided to select the set
speed (F/3, F/2 and F) of the induction motor. These
PWM
switches are implemented to the microcontroller. The
switch status enables the microcontroller once it enabled
the pulses and it will trigger the SCR’s in a dual bridge.
Thus, the speed control can be achieved in three steps i.e.
(F/3, F/2 and F). The speed control of asynchronous motor
(AM) or induction motor (IM) can be varied by varying the Fig1: Single phase Cyclo-Converter
slip ‘S’ or number of poles ‘p’ or frequency fof the supply.
The ability of varying any one of the above three quantities
will provide methods of speed control of an induction R-phase
motor. Constant V/F method is commonly used for constant Rph
and variable speed control of induction motor. The different AC Full Bridge
methods of speed control of IM can be broadly classified
into scalar and vector control methods. In this paper, scalar
control methods are used. This transforms input AC power Y-phase
at one particular frequency into output AC at a completely Yph
different frequency avoiding a multiple step conversion AC Full Bridge 3 ph
thus reducing losses. These converters may be a step-up
converter (cyclo-inverter) or a step-down converter (cyclo-
converter) as per the requirement of the application. They
are widely used in variable speed constant frequency Bph B-phase
systems (VSCF), large AC motor drives, arc welding, high
AC
frequency induction heating, plasma generation, industrial Full Bridge
laser drives, power factor correction and so on. The output
of these conventional converters is very rich in harmonics
resulting in poor efficiency of the entire process. The
normally used conventional technique of filtering can’t be
used in this case as it has problems related to design as well Fig 2: Three phase Cyclo-Converter
as in economic aspects when it is applied to a variable
frequency system. In addition to this, use of tuned filters is
not at all feasible to eliminate each of the harmonic
component as the nature of the output frequency of the
converter is varying. Hence the only way out of the
problem is to use modulation techniques as they are
feasible compared to use of tuned filters. Some of the
modulation techniques that are in use are delta A. Single phase Cyclo-Converter Circuit Diagram
modulation,sinusoidal PWM,890 space vector PWM and
staircase modulation. Some work on trapezoidal
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always keep the non-conducting thyristor bank off,
otherwise the mains would have been shorted via the two
thyristor banks, resulting in possible device failure and
waveform distortion from the shorting current. A cyclo-
convertor has the major control problem is to swap between
the banks in the shortest period of time to avoid distortion
and also ensure that the two banks does not conduct at the
same period of time. To overcome this problem center
tapped inductor called a circulating current inductor
between the outputs of the two banks in addition to the
power circuit that removes the requirement of one bank off.
Now the both banks can conduct together without short
Fig3: Single phase Cyclo-Converter Circuit Diagram circuit in the mains. Also, the inductor keeps the circulating
current in both banks operates at all the time, and this will
B. phase Cyclo -Converter Circuit Diagram improve the result of output waveforms. But this technique
is not used often, because of the circulating current passed
through the inductor tends to be bulky and expensive and
this reduces the power factor of the input.
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that here the output frequency is 1/2 times the supply characteristics. A Cyclo-converter can supply unity, lagging,
frequency. or leading power factor loads while its input is always
lagging in nature. This operation characteristic matches the
A. Types of Cyclo-converter Cyclo-converter to any synchronous machine. The Cyclo-
Based on the type of input ac supply applied to the circuit. converter does not have an edge compared to other
The Cyclo-converter are divided into 3 types converters in this aspect for running as an induction
• Single ĭ to Single ĭ Cyclo-converter machine, on the other hand, induction machines can only
• Three ĭ to Three ĭ Cyclo-converter draw lagging current, so cyclo-converters used for speed
• Single ĭ to Three ĭ Cyclo-converter control purposes are used in Scherbius drives driving wound
rotor induction motors. Equations (1) and (2) give the value
B. Single-phase to Single-phase (1 ĭ-1 ĭ) of rotor and stator flux of induction motor.
Cycloconverter
The single-phase to single-phase Cyclo-converter consists (1)
of back-to-back connection of 2 full-wave rectifier circuits.
The frequency vs AC voltage as shown in the simulation
(2)
result. Assume that all the thyristors are fired at Į=0°firing
angle, for the understanding purpose i.e. thyristors act like a
Electro-magnetic torque developed by 3-phase induction
diode. Note that the firing angles are named as ĮN for the
motor is given by equation-3
Negative converter and ĮP for the Positive converter.
Contemplate the operation of Cyclo-converter to get 1/4thof
the input frequency at the output of the motor. For the first 2 (3)
cycles, the load current is supplied by the positive converter
and it rectifies the input. In the next two cycles, the load Where (4)
current supplied in the reverse direction by the negative
converter. The waveforms of the current are not shown in
(5)
the figure because the voltage and current waveform will
have the same resistive load current but only scaled by the
resistance. Note that the other one is disabled when one of
the converters operates, because there is no current 5. Simulation Results
circulating between the 2 rectifiers.
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Fig 6: Input Voltage
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Fig 9: Phase Current Fig 12: Phase Current
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Fig 14: Output Voltage Mutual Inductance Lm 0.06931 H
Inertia J 0.0089
Pole pairs 2
A. Mode 1 Fo=Fin
Fig 16: Simulink for Three Phase Cyclo-converter Fig 18: Speed Response
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Fig 19: Torque Response
Fig 22: Speed Response
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Fig 28: Output Voltage
Fig 25: Per Phase Voltage
C. Mode 3 Fo=Fin/2.5
7. CONCLUSION
Fig 26: Speed Response The single and three phase full bridge cyclo-converter
circuit has been intended for speed control of induction
motor with adjustable frequency. Single phase Cyclo-
converter used to change the speed of induction motor with
different desired frequency is obtained to equalize the
desired speed. This different frequency of cyclo-converter is
obtained in the manner of adjustable speed to F, F/2 & F/3.
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