Description
ABSTRACT
The speed control of separately excited dc motor is carried out by varying the armature voltage for below rated speed and by varying field flux to achieve speed above the rated speed. The Proportional Integral (PI) controller of A.C drives are commonly employed in industries and many other applications, because of its simplicity, but it does not give high degree of speed control of single phase induction motor. The intelligent control systems become a powerful tool for control nonlinear system in present time. This paper proposes the Proportional Integral (PI) controller designed based on fuzzy logic system as an intelligent speed controller of single phase induction motor. In addition, The mathematical modeling and simulation single phase induction motor capacitor run type as asymmetrical two phase induction motor is represented too Also, two phase four leg voltage source PWM inverter with Sinusoidal Pulse Width Modulation (SPWM) switching technique is demonstrated and simulated. The overall system for the proportional-integral (PI) controller designed based on fuzzy logic system is simulated using MATLAB/Simulink environment. The results shows high response of the controller to the change of load which make a wide range of speed variation and make the speed return to its reference value.
CHAPTER ONE
1.0 INTRODUCTION
1.1 BACKGROUND OF THE PROJECT
In modern industrialized countries, more than half the total electrical energy used is converted to mechanical energy through AC induction motors. Induction motors are extensively used in industrial and household appliances and consume more than 50% of the total generated electrical energy. Single-phase induction motors are widely used in home appliances and industrial control. During the last few years, the concept of speed and torque control of asynchronous motor drives has gained significant popularity. This way, it has been possible to combine the induction-motor structural robustness with the control simplicity and efficiency of a direct current motor. This evolution resulted to the replacement of the dc machines by induction motors in many applications in the last few years. Earlier only dc motors were employed for drives requiring variable speeds due to facilitate of their speed control methods [J. Zubek, 2010]. The conventional methods of speed control of an induction motor were either too extravagant or too inefficient thus limiting their application to only constant speed drives. They are used to drive pumps, fans, compressors, mixers, agitators, mills, conveyors, crushers, machine tools, cranes, etc. This type of electric motor is so popular due to its simplicity, reliability, less maintenance and low cost. Today, with advancements in power electronics, microcontrollers, and digital signal processors (DSPs), electric drive systems have improved drastically. Initially the principle of speed control was based on steady state consideration of the induction motor.
Induction motors like variable voltage, variable frequency, variable voltage variable frequency (v/f) [Mohan et al, 2015], changing stator poles, rotor resistance, doubly fed motor, Kramer circuits and etc[Mohan et al, 2015]. variable speed drive circuits employed different power electronics switches with various switching patterns to drive and control the speed of single phase induction motors [Bandhekar et al, 2013], one of these electronic drive circuits is the inverter which are vastly employed in industrial application, they are generally classified in to single and three phase inverters, in general the pulse width modulation switching technique are used to provide an AC output signal to these inverters [Kameswara et al, 2014], control the voltage as well as frequency to have an inverter AC output voltage as close as possible to sinusoidal waveform [Bandhekar et al, 2013]. There are various PWM techniques that can suit most industrial and other application such as sinusoidal PWM, space vector pulse width modulation which are widely used, the main subject of PWM is to control the output voltage and reduce the harmonics [Kameswara et al, 2014].
In recent years, intelligent control has emerged as one of the most active and fruitful areas of research and development (R&D) within the spectrum of engineering disciplines with a variety of industrial applications [Jamshidi et al, 2011], speed controllers of single phase induction motor employed some of the intelligent control techniques algorithm such as neural network, particle swarm optimization and etc.., they were suffering from several problems such as small range of controlled speed, but there are some techniques that are simple and can be employed in different process such as fuzzy logic controllers [Ahmad et al, 2011].
Software computing techniques such as fuzzy logic or fuzzy control (FC) provide a schematic method to incorporate human knowledge in the controller [Neema et al, 2011], it is a control algorithm depends on linguistic control strategy, which is proposed to employ the human experience knowledge to an automatic control strategy. While on the other hand, other control systems employed difficult arithmetic calculation to provide a model of the controlled plant, it only employs simple arithmetic calculation to model this experience. For The good performance of this control strategy, it can be or will be one of the best available answers for a broad class of challenging control problems [Anmol et al, 2011].
The work is organized as follows: chapter one discuses the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the methods applied which includes the simulation using MATLAB, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.
1.2 PROBLEM STATEMENT
Controlling the speed of a motor using traditional methods involve running the motor at full speed and then using mechanical means such as gears, hydraulic couplings or pulleys. This is not only expensive, but also consumes a lot of energy. There are many means of controlling induction motor speed, but the most popular problem discovered in them is that motor used to experience speed instability, the efficiency of the motor drops when the motor speed is varied and small rang of controlled speed.
Using Software computing techniques such as fuzzy logic or fuzzy control (FC) provide a schematic method to incorporate human knowledge in the controller [8], it is a control algorithm depends on linguistic control strategy, which is proposed to employ the human experience knowledge to an automatic control strategy which was introduced to overcome the above mentioned problem
1.3 AIM AND OBJECTIVE OF THE PROJECT
AIM
The main aim of this project is to control the speed of a single phase induction motor using Software computing techniques – fuzzy logic or fuzzy control.
OBJECTIVE
The objectives are:
- To develop a model for implementation of control scheme in a single phase induction motor.
- To enhance the efficiency of motor control techniques
- To increase the range of controlled speed
1.4 SCOPE OF THE STUDY
This work proposes the proportional integral (PI) controller designed based on fuzzy logic control system with optimized base rules and the output is the frequency which is applied to sinusoidal pulse width modulation technique employed to drive the two phase four leg inverter with (v/f) speed control technique to control the speed of single phase induction motor capacitor run type
1.5 SIGNIFICANCE OF THE STUDY
This research work will throw more light on the best techniques for controlling the speed of electric motor. This study will also be designed to be of immense benefit to all the users of electric motor most especially in industries.
It will also serve as a guide to whoever that wants to purchase speed controller for induction motor.
Finally, it will also serve as a useful piece of information for both producers and users of electric motor speed controller
1.6 MOTIVATION OF THE STUDY
Intelligent controlling the speed of an induction motor is necessary for both industrial and local applications in that it gives adjustable Speed Drives include energy savings, efficient motor starting, reversing, and speed and position control. The advantages of using this method of motor speed control is because it is cheap and efficient means of controlling the speed of an induction motor. However, advantages discussed above were points that motivate the carrying out of this research work.
