ABSTRACT:
In order to implement the
vector control technique, the motor speed information is required.
Tachogenerators, resolvers or incremental encoders are used to detect the
speed. These sensors require careful mounting and alignment and special
attention is required with electrical noises. Speed sensor needs additional
space for mounting and maintenance and hence increases the cost and the size of
the drive system .These problems are eliminated by speed sensorless vector
control by using model reference adaptive system. Model reference adaptive
system is a speed estimation method having two models namely reference and adaptive
model .The error between two models estimates induction motor speed. This
project proposes a Model Reference Adaptive System (MRAS) for estimation of
speed of induction motor. An Induction motor is developed in stationary
reference frame and Space Vector Pulse Width Modulation (SVPWM) is used for inverter
design. PI controllers are designed controlling purpose. It has good tracking
and attains steady state response very quickly which is shown in simulation
results by using MATLAB/SIMULINK.
KEYWORDS:
1.
Sensorless vector control
2.
Model Reference Adaptive System
(MRAS)
3.
Induction motor
4.
stationary reference frame
5.
Speed estimation
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig 2: block diagram of MRAS
EXPECTED SIMULATION RESULTS:
Fig 3: 3-f currents, Speed, and Torque for no-load reference speed of 100
rad/sec
Fig 4:3-f currents, Speed, and Torque for no-load reference speed of 100
rad/sec
Fig 5: 3 -f
currents, Speed, and Torque for step
signal
CONCLUSION:
In this thesis, Sensorless control of
induction motor using Model Reference Adaptive System (MRAS) technique has been
proposed. Sensorless control gives the benefits of Vector control without using
any shaft encoder. In this thesis the principle of vector control and
Sensorless control of induction motor are given elaborately. Simulation results
of Vector Control and Sensorless Control of induction motor using MRAS
technique were carried out by using Matlab/Simulink. From the simulation
results, the following observations are made.
i) The transient response of the drive
is fast, i.e. we are attaining steady state very quickly.
ii) By using MRAS we are estimating the
speed, which is same as that of actual speed of induction motor.
Thus by using sensor less control we can
get the same results as that of vector control without shaft encoder. Hence by using
this proposed technique, we can reduce the cost of drive i.e. shaft encoder’s
cost, we can also increase the ruggedness of the motor as well as fast dynamic
response can be achieved.
REFERENCES:
[1] Abbondanti, A. and Brennen, M.B.
(1975). “Variable speed induction motor drives use electronic slip calculator
based on motor voltages and currents”. IEEE Transactions on Industrial
Applications, vol. IA-11, no. 5: pp. 483-488.
[2] Nabae, A. (1982). “Inverter fed
induction motor drive system with and instantaneous slip estimation circuit”.
Int. Power Electronics Conf., pp. 322-327.
[3] Jotten, R. and Maeder, G. (1983).
“Control methods for good dynamic performance induction motor drives based on
current and voltages as measured quantities”. IEEE Transactions on Industrial
Applications, vol. IA-19, no. 3: pp. 356-363.
[4] Amstrong, G. J., Atkinson, D. J. and
Acarnley, P. P. (1997). “A comparison of estimation techniques for sensorless
vector controller induction motor drives”. Proc. Of IEEE-PEDS.
[5] Wang yaonan,lu jintao,haung
shoudao(2007).”speed sensorless vector control of induction motor based on MRAS
theory”.
