controller takes input from the user and generates firing pulses for the TRIAC which controls the speed of the Induction motor. The total process is executed with ...
i
PID-HYSTERESIS VOLTAGE CONTROL TECHNIQUE FOR THREE PHASE INDUCTION MOTOR (MATLAB SIMULINK AND ARDUINO)
AMMAR HUSAINI BIN HUSSIAN
A project report submitted in partial fulfillment of the requirement for the award of the Degree of Master Of Electrical Engineering
Faculty of Electrical Engineering Universiti Tun Hussein Onn Malaysia
JANUARY 2014
iv
ABSTRACT
These phase induction motors are the most widely used electric motors in industry for converting electrical power into mechanical power. They are considered to be simple, rugged, robust, efficient and suitable for applications in harsh environment. However, their controllability remains a difficult task using conventional control method. The control difficulty is associated with high nonlinearity of the motor’s behavior, complexity of its analytical model and presence of interactive multivariable structures. Therefore, this project is proposed a design controller for three phase induction machines in high performance application. The PID Hysteresis controller is developed and simulates using MATLAB/Simulink software and downloads to Arduino where generates the PWM signal. The signals then send to gate driver of a three phase inverter to give a stable performance to the induction motor. The improvement of performance is by comparing the actual measured voltage of the motor with respect to their reference voltage. The difference is then corrected thus minimizing the voltage error. A simple hardware implementation of the PID Hysteresis voltage controller is designed and some simulation and experimental results are presented to demonstrate the validity of this approach.
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ABSTRAK
Projek ini menerangkan pengawal untuk motor aruhan tiga fasa. Motor aruhan adalah sebuah penggerak elektromekanikal yang digunakan secara meluas kerana kos penyelenggaraan yang rendah dan boleh dipercayai. Walau bagaimanapun, masalah kawalan motor aruhan adalah kompleks kerana tidak linear, gangguan tork beban dan parameter yang tidak menentu. Elemen yang dimasukkan dalam projek ini adalah kawalan voltan, yang mahu mengawal voltan dari inverter tiga fasa ke motor aruhan tiga fasa. Pengawal histeresis telah digunakan dalam projek ini untuk mengurangkan ralat voltan. Pengawal histeresis dilihat sebagai mundur fasa input–output. Pelaksanaan histeresis direka sebagai pengawal dilakukan dalam simulasi menggunakan MATLAB Simulink. Di samping itu, perkakasan disediakan dan eksperimen dijalankan untuk memerhati dan menganalisis model tersebut.
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CONTENTS
TITLE
i
DECLARATION
ii
ACKNOWLEDGEMENT
iii
ABSTRACT
iv
CONTENTS
vi
LIST OF FIGURE
ix
LIST OF TABLE
xii
LIST OF SYMBOLS AND ABBREVIATIONS
xiii
CHAPTER 1 INTRODUCTION
1
1.1 PROJECT BACKGROUND
1
1.2 PROBLEM STATEMENT
2
1.3 OBJECTIVE
3
1.4 SCOPE
3
CHAPTER 2 LITERATURE REVIEW
4
2.1 INDUCTION MOTOR
4
vii
2.1.1 THREE PHASE INDUCTION MOTOR 2.2 INVERTER DC TO AC 2.2.1 THREE PHASE INVERTER 2.3 ADAPTIVE CONTROLLER
4 6 6 7
2.3.1 PID CONTROLLER
8
2.3.2 FUZZY LOGIC CONTROLLER
9
2.4 PASSIVE CONTROLLER
10
2.4.1 HYSTERESIS
10
2.4.2 SLIDING MODE CONTROL
10
2.5 CONTROLLER 2.5.1 PROPOSED CONTROLLER 2.6 ARDUINO CHAPTER 3 METHODOLOGY
13 13 15 17
3.1 BLOCK DIAGRAM OF THE PROJECT
17
3.2 THE PROJECT FLOWCHART
18
3.3 WORKING FLOWCHART
19
3.4 INVERTER DESIGN
20
3.5 GATE DESIGN
21
3.6 CONTROLLER DESIGN
22
3.6.1 ADC
23
3.6.2 DAC
23
3.7 VOLTAGE SENSOR TECHNIQUE
26
viii
3.8 FILTER CHAPTER 4 DATA ANALYSIS AND RESULT
27 29
4.1 SIMULATION RESULT AND ANALYSIS
29
4.2 OPEN LOOP CONTROL ANALYSIS
33
4.3 CLOSED LOOP ANALYSIS FOR HARDWARE
37
4.3.1 THE WAVEFORM AT CURRENT SENSOR
38
4.3.2 THE WAVEFORM BEFORE TRANSFORMER
39
4.3.3 THE WAVEFORM AFTER TRANSFORMER
41
4.3.4 EFFECT ADD AN OFFSET
43
4.4 THE COMPARISON BETWEEN SIMULATION AND
45
HARDWARE CHAPTER 5 CONCLUSIONS
49
5.1 CONCLUSION
49
5.2 FUTURE WORKS
50
REFERENCES
51
APPENDIX A
55
APPENDIX B
57
APPENDIX C
60
APPENDIX D
61
APPENDIX E
64
ix
LIST OF FIGURE
2.1
Three phase induction motor.
5
2.2
Standard three-phase inverter
6
2.3
Basic configuration for an adaptive control system
7
2.4
PID controller block diagram
8
2.5
Basic hysteresis controller
11
2.6
Boundary layer
12
2.7
Hysteresis voltage control operation waveform
14
2.8
The Arduino microcontroller
16
3.1
Block diagram of the project
17
3.2
The project flowchart
18
3.3
Working flowchart
19
3.4
Schematic circuit of three phase inverter
20
3.5
The three phase inverter of hardware
20
3.6
Schematic diagram of gate driver for inverter
21
3.7
The hardware of gate driver for three phase inverter
21
3.8
PID Hysteresis controller
22
3.9
Analog-digital-converter.
23
x
3.10
Digital-analog converter
23
3.11
Function block parameter of PID
24
3.12
LED blinking likes PWM (pre-testing)
25
3.13
The expectation for PWM produces from Arduino
25
3.14
The sketching for signal after add an offset
26
3.15
The hardware for voltage sensor technique
27
3.16
The circuit for the filter
27
4.1
PID Hysteresis controller using MATLAB simulation
29
4.2
The function block parameter of discrete 2nd order filter
30
4.3
ADC output and DAC output
31
4.4
Simulation of error in controller
31
4.5
Result simulation of PWM signals
32
4.6
The result simulation after through the transformer
32
4.7
The result simulation after filtering with discrete 2nd order
33
4.8
Open loop simulation using MATLAB simulink
33
4.9
The overall of model hardware for this project
34
4.10
The waveform result of the hardware at sensor current
35
4.11
The waveform result hardware after inverter before through
35
the transformer 4.12
The waveform result hardware after transformer
36
4.13
The result waveform after add an offset
36
xi
4.14
Simulink models for closed loop PID hysteresis controller
37
4.15
The waveform at current sensor injected 10Vdc
38
4.16
The waveform at current sensor injected 20Vdc
38
4.17
The waveform at current sensor injected 30Vdc
38
4.18
The waveform before Transformer injected 10Vdc
39
4.19
The waveform before Transformer injected 20Vdc
39
4.20
The waveform before Transformer injected 30Vdc
40
4.21
The waveform after transformer with injected 10Vdc
41
4.22
The waveform after transformer with injected 20Vdc
41
4.23
The waveform after transformer with injected 30Vdc
42
4.24
The waveform after add an offset with injected 10Vdc
43
4.25
The waveform after add an offset with injected 20Vdc
43
4.26
The waveform after add an offset with injected 30Vdc
44
4.27
The simulation result after inverter
45
4.28
The hardware result after inverter
45
4.29
The simulation result after transformer
46
4.30
The hardware result after transformer
46
4.31
The simulation result add offset
47
4.32
The hardware result add offset
47
xii
LIST OF TABLE
2.1
Specifications of Arduino
15
4.1
The value of voltage at open loop condition for the hardware
36
4.2
The gain calculated by using DAC equation
38
4.3
The comparison between variable voltage supply and the
39
current Irms 4.4
The comparison between injected voltage and Vrms after
40
three phase inverter
4.5
The scale down of voltage after transformer
42
xiii
LIST OF SYMBOLS AND ABBREVIATIONS
V
-
Voltage
DC
-
Direct current
AC
-
Alternating current
Vac
-
Alternating current voltage
VSI
-
Voltage source inverter
CSI
-
Current source inverter
PID
-
Proportional integral derivative
PWM -
Pulse width modulation
DSP
Digital signal processing
-
r.m.f. -
Rotating magnetic field
DFO
-
Direct field-oriented
FFT
-
Fast fourier transform
IC
-
Integrated circuit
SMC -
Sliding mode controller
DTC
-
Direct torque ratio
USB
-
Universal serial bus
ADC -
Analog to digital converter
DAC -
Digital to analog converter
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IPM
-
ICSP- -
Interior permanent magnet In circuit serial programming
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CHAPTER 1
INTRODUCTION
1.1 Project Background One of the most common electrical motor used in most applications which is known as Induction Motor. This motor is also called as asynchronous motor because it runs at a speed less than synchronous speed. Induction motor is widely used in industry because of its reliability and low cost, either single phase or three phases. However, three phases induction is the most interesting and has attracted the attention of many researchers because of induction motor is strongly nonlinear [1]. The function of three phase inverter to Induction motor is produced the 6 pulse PWM signals where the three phase induction motor based on three phase with different shifting time. Many controllers have been developed, that can be divided into two classifications, passive and adaptive power controller. The example for passive power controller is hysteresis, relay and sliding mode control and for adaptive power controller is Proportional Integral Derivatives (PID), fuzzy, and P-resonant controller. Each of them has their advantages, such as simple structure and low maintenance cost [2]. Inverters that use PWM switching techniques have a DC input voltage that is usually constant in magnitude. The inverters job is to take this input voltage and output ac where the magnitude and frequency can be controlled. Many applications that require an inverter use three phase power. The example is an ac motor drive. One option for a three phase inverter is to use three separate single phase inverters but vary their
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output by 120° [3]. The three phase inverter setup consists of three legs, one for each phase. In three phase inverters PWM is used in the same way as it is before except that it much be used with each of the three phases. When generating power to three different phases one must make sure that each phase is equal, meaning that it is balanced. Nowadays, an embedded system such as Arduino is rapidly developed in many applications. This is because the Arduino is the low cost other than else and it also an open source [3]. Furthermore the Arduino also can be directly interfaced to the MATLAB Simulink. In many applications of the induction motor, high performance voltage control is one of the fundamental issues [4]. However, induction motors are difficult to control because of their dynamics are intrinsically nonlinear and multivariable and for feedback, it has a critical parameter such as load torque, stator and rotor resistances which may considerably vary during operations [5]. That’s the point why a strong controller like PID-Hysteresis control was chosen.
1.2 Problem Statement The recent advances in the area of field-oriented control (FOC) bring the rapid development and cost reduction of power electronics devices for three phase induction motor give more economical for many industrial applications. However, the control problem of the induction motor is complex due to the nonlinearities. It has several parameters such as load torque, stator and rotor resistances which may considerably vary during operations. There are exists of control strategies such as even adaptive schemes tend to be sensitive but poor in the flux and torque estimation especially during low speed operation. So the proposed here is to implement a design PID-Hysteresis control modeling using MATLAB Simulink by injecting a corrected voltage to the three phase inverter. The challenge in induction motor is to run at the desired speed the voltage generated in the motor is the same as the applied operating voltage. The processes that drive the induction motor are hard because it has electric magnets in both side, the stator and in the rotor. The rotor windings are shorted and act like the secondary windings of a transformer. The magnetic field rotating in the stator induces a current in the shorted rotor windings, which then generates its own magnetic field [10].
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1.3 Objective The objectives of this project are listed as follows: 1. To develop the PID Hysteresis controller approach for motor control. 2. To implement hardware of induction motor drives that is voltage control using PID Hysteresis Controller carried by Arduino embedded devices. 3. To simulate and design the PID Hysteresis control model by using MATLAB Simulink. 4. To analyze the PID Hysteresis Controller.
1.4 Scope In this project the scope of work will be undertaken in the following three developmental stages: 1. Study of the control system of induction motor for voltage control based on PID Hysteresis control. 2. Perform simulation of PID Hysteresis control. This simulation will be carried out on MATLAB platform with Simulink as it user interface. 3. Development of the target MATLAB Simulink model to Arduino and implements the hardware of voltage control of induction motor for PID Hysteresis Controller.
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CHAPTER 2
LITERATURE REVIEW
2.1 Induction motor The principles of motor is when a current-carrying conductor is located in an external magnetic field perpendicular to the conductor, the conductor experiences a force perpendicular to itself and to the external magnetic field.
2.1.1 Three phase induction motor Induction motor also called asynchronous motor in motor. All the rotor's energy is produced from the magnetic field of the stator winding to electromagnetic induction . An induction motor not requires mechanical commutation for all or part of the energy transferred from stator to rotor. An induction motor's rotor can be both wound and the type. Three squirrel-cage induction motors are widely used in industrial drives because they are rugged, reliable and economical. Single-phase induction motors are used extensively for smaller loads, such as household appliances like fans. One of the advantages of an induction motor is its mechanical simplicity. This leads to not only to inherent reliability, but also to simpler design for shock requirements. Through careful motor and system design, it has been possible reduce structure borne noise signatures to levels that permit hard mounting of the motor to the hull of a surface combatant [5].It also easy to program for its various uses and low maintenance cost. The Hence for fine speed control applications dc motors are used in place of induction motors. Disadvantage is that speed control of induction motors is difficult.
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In paper [6] had presented novel field-weakening scheme for the induction machine. The proposed algorithm, based on the voltage control strategy, ensures the maximum torque operation over the entire field-weakening region without using the machine parameters. Also, they had introduced the direct field-oriented (DFO) control, which is insensitive to the variation of machine parameters in the field-weakening region, the drive system can obtain robustness to parameter variations. Lastly, they founded Experimental results for the laboratory induction motor drive system confirms the validity of the proposed control algorithm.
In paper [7] had presented hysteresis control method for three-phase current controlled voltage-source PWM inverters. It minimizes interference among phases, thus allowing phase-locked loop (PLL) control of the modulation frequency of inverter switches. Then they had discussed about control theory, and described the controller implementation. Design criteria are also given. The results of experimental tests show excellent static and dynamic performance.
The advantages of the three phase induction motor are it has simple and rugged construction, it is relatively cheap, requires little maintenance, it also has high efficiency and reasonably good power factor. Lastly it has self starting torque. The disadvantages are it is essentially a constant speed motor and its speed cannot be changed easily. Its starting torque is inferior to DC shunt motor. The Figure 2.1 shows the three phase induction motor.
Figure 2.1: three-phase induction motor
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2.2 Inverter DC to AC An electrical power converter which is changes direct current DC to alternating current AC is called power inverter. It can be any required of voltage and frequency usually used in transformer , switching and control circuit. It also used from small switching power supplies to large high-voltage electric equipments applications that transport bulk power and solid-state inverters have no moving parts. Commonly inverter is used to supply solar panels or batteries and it perform the opposite function of a rectifier. The electrical inverter is high-power electronic oscillator because generally AC to DC converter was made to work in reverse and thus was inverted which is to convert DC to AC. 2.2.1 Three-phase inverter Three-phase inverter circuit works at line-frequency, which the main output power. The switches work at line frequency, so the switching loss is small and the efficiency of output syetem is high [6].The three-phase inverter the main output power; three single-phase full-bridge inverters are used to improve the system dynamic performance. Compared with the traditional inverter circuit, the circuit can achieve high efficiency and low harmonics at the same time, and it can also reduce the voltage stress of the power switches. This is a new way for the combination of the inverters. The circuit can be controlled easily, so it was easy to be modularized. High frequency inverter used PWM modulation and line-frequency inverters worked.
Figure 2.2. : standard three-phase inverter
7
The standard three-phase inverter shown in Figure 2.2. has six switches the switching of which depends on the modulation scheme. The input dc is usually obtained from a single-phase or three phase utility power supply through a diode-bridge rectifier and LC or C filter.The PWM inverter A has most applications such as unintermptible power systems (UPS'S), active filters, high power factor converters, and adjustable frequency drives.Almost all applications of PWM inverters with a current minor loop, and performance of the inverter system largely depends on the quality of the current minor loop. Therefore current control of PWM inverter is one of the most important subject of power electronics [7]. 2.3 Adaptive controller Basically controller devide into two categories which is adaptive and passive controller. The example of adaptive controller is PID, Fuzzy and Neural Network. Adaptive Control covers a set of techniques which provide a systematic approach for automatic adjustment of controllers in real time, in order to achieve or to maintain a desired level of control system performance when the parameters of the plant dynamic model are unknown and/or change in time [8]. The Figure 2.3 below shown the basic configuration for adaptive system.
Figure 2.3 : Basic configuration for an adaptive control system The advantages of Adaptive Control is convenience controller so that it can continuously adapt itself to the current behavior of the process and outperformed their fixed parameter counterparts in terms of efficiency. It also can eliminate the error faster and with fewer fluctuations. Allow the process to operate closer to its constraints where profitability is highest but the disadvantage is much more complex.
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2.3.1 PID Controller (Proportional Intergral and Derivative) Proportional-integral-derivative(PID) controllers have been the most popular and the most commonly used industrial controllers in the past years [9]. The popularity and widespread use of PID controllers are at tributed primarily to their simplicity and performance characteristics.Although linear fixed-gain PID controllers are often adequate for controlling a nominal physical process, the requirements for highperformance control with changes in operating conditions or environmental parameters are often beyond the capabilities of simple PID controllers [10][11]. The Figure 2.4 shows the PID controller block diagram.
P
Kp e(t)
disturbance t setpoint error
1
Ki e(t2)dt2
1
PROCESS
output
8
I
measured
D
Kd
de(t) dt
SENSOR
Figure 2.4 : PID controller Block Diagram ( )
( )
( )
∫
( )
( )
= proportional gain, a tuning parameter. = integral gain, a tuning parameter. = derivative gain, a tuning parameter. = error. = time or instantaneous time
(2.1)
9
In Proportional Derivative Integral mode, the controller make the following:
-
Multiplies the Error by the Proportional Gain (Kp), Added to the Derivative error multiplied by Kd and Added to the Integral error multiplied by Ki, to get the controller output.
The advantages of PID controller is using both integral and derivative control (PID) has removed steady-state error and decreased system settling times while maintaining a reasonable transient response.
2.3.2 Fuzzy logic controller
Fuzzy logic control is one of the most interesting fields where fuzzy theory can be effectively applied. Fuzzy logic techniques attempt to imitate human thought processes in technical environments. Fuzzy control also supports nonlinear design techniques that are now being exploited in motor control applications. Initially fuzzy control was found particularly useful to solve nonlinear control problems or when the plant model is unknown or difficult to build. The present work includes application of fuzzy techniques to control the speed of an induction motor. Fuzzy rules can be obtained through machine learning techniques, where the knowledge of the process is automatically extracted or induced from sample cases or examples. Many machine learning methods developed for building classical crisp logic systems can be extended to learn fuzzy rules [12]. The adaptive fuzzy control can compensate for any under estimation of the bounds of the uncertainties [13]. However, the performance may still be unsatisfactory when the machine parameters vary too much. The basic reason for the unsatisfactory performance is that the control algorithms lack the ability to learn how to deal with the system complexity. Results of comprehensive computer simulation show that fuzzy model reference leaning control (FMRLC) has potential to improve the close-loop control performance [14][15].Limitations Of Fuzzy Logic Controller is hard to develop a model from a fuzzy system and require more fine tuning and simulation before operational.
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2.4 Passive controller
Normally controller divides into two groups, they are adaptive and passive. The example the passive controller is consists of hysteresis, relay and sliding mode control. Passivity is a property of engineering systems, used in a variety of engineering disciplines, but most commonly found in analog electronics and control systems. A passive component, depending on field, may be either a component that consumes but does not produce energy thermodynamic passivity, or a component that is incapable of power gain (incremental passivity). 2.4.1 Hysteresis The hysteresis is the dependence of a system not only on its current environment but also on its past environment. Some significant advantages of hysteresis controllers overother types of controllers designed with linear or nonlinear control techniques are as follows: • switching behavior of the power inverter can be directlytaken into account at the design level. • robustness to load parameters’ variation can be proved. • almost static response is achieved (the dynamics are obviously bounded by the dclink voltage and by the actual switching frequency). • simple hardware implementation, based on logical devices, is possible according to the Boolean nature of controller input/output variables. However, conventional type of hysteresis controllers (with independent comparator for each phase of the load) suffers from some well known drawbacks, e.g., limit cycle oscillations, overshoot in current errors, generation of sub harmonic components in the current and random (non-optimum) switching[16]. The figure below shown the basic hyteresis controller. The Figure 2.5 shows the basic hysteresis controller.
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Figure 2.5 : basic hysteresis controller. Hysteresis occurs in ferromagnetic materials and ferroelectric materials, as well as in the deformation of some materials (such as rubber bands and shape-memory alloys) in response to a varying force. In natural systems hysteresis is often associated with irreversible thermodynamic change. Many artificial systems are designed to have hysteresis: for example, in thermostats and Schmitt triggers, hysteresis is produced by positive feedback to avoid unwanted rapid switching. Based on the electrical engineering, Hysteresis can be used to filter signals so that the output reacts slowly by taking recent history into account. A three-level inverter-fed induction motor drive operating under Direct Torque Control (DTC) is presented. A triangular wave is used as dither signal of minute amplitude (for torque hysteresis band and flux hysteresis band respectively) in the error block. This method minimizes flux and torque ripple in a three-level inverter fed induction motor drive while the dynamic performance is not affected. The optimal value of dither frequency and magnitude is found out under free running condition. The technique can reduces torque ripple by 60% (peak to peak) compared to the case without dither injection, results in low acoustic noise and increases the switching frequency of the inverter [17]. 2.4.2 Sliding mode control (SMC) The major advantage of a sliding-mode controller is its insensitivity to parainetcr variations and external load disturbance once on the switching surface.The SMC is found to be attractive in terms of robustness of the drive response but suffers from the problem of chattering,apart from being slightly difficult to realize [1]. The Figure 2.6 shows the baundary layer for SMC.
12 sm(x)=0
Boundary layer State trajectory Manifold s(x)=0
s(x)=0
Figure 2.6: Boundary layer There is definition of terms in sliding mode control:
State Space – An n-dimensional space whose coordinate axis consist of the x1 axis, x2 axis until xn axis.
State trajectory- A graph of x(t) verses t through a state space.
State variables – The state variables of a system consist of a minimum set of parameters that completely summarize the system’s status.
Disturbance – Completely or partially unknown system inputs which cannot be manipulated by the system designer.
Sliding Surface – A line or hyperplane in state-space which is designed to accommodate a sliding motion.
Sliding Mode – The behavior of a dynamical system while confined to the sliding surface.
Reaching phase – The initial phase of the closed loop behavior of the state variables as they are being driven towards the surface.
The sliding mode control approach for induction motor drives is based on the model of an induction motor in a frame rotating synchronously with the stator current vector. As with the indirect vector control of induction motor, the method allows rotor flux and torque to be controlled by two independent control variables. Since the control law is represented in a set of inequalities instead of equalities, as the motor parameters change, the stability of the sliding mode and the feature of independent control of the flux and torque will not be destroyed as long as the corresponding inequalities hold stated in paper C.C.Chan, H.Q. Wang [18].
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The SMC does not need accurate mathematical model but requires knowledge of parameter variation range to ensure stability and satisfy reaching conditions. As the power converters are highly variable structured, sliding mode control offers several advantages, such as stability even for large supply and load variations, robustness, good dynamic response and simple implementation. 2.5 Controller In three phase induction motor, there are two technique for controller which is voltage source control technique and the current source technique. Both of the control technique quite same in terms of comprising an internal voltage/current feedback loop and correct the error occurs using the adaptive or adaptive controller to make the correction in terms to control the performance of the induction motor.Error in the current controller degrades the drive's performance in the same way as de-tuning the field orientation control.Another current control technique involves de-coupling of the motor emf voltage to improve the performance of the current regulation [19]. 2.5.1 Proposed controller Adaptive-Passive controller is a main controller for this project. Voltage source control technique for PID Hysteresis mode controller will propose to be a controller. It is because PID control is the gold standard for most moving machines, and quite adequate in most applications that require closed-loop control. However, it's vulnerable to disturbances, and tuning can be tedious. For these reasons, some industrial drives go beyond traditional PID structures and servo algorithms for position control with sliding mode that increase stability over a wider range of conditions, to make tuning easier for design engineers. PID control is limited, as it depends on a plant model, so is sensitive to real-world parameter variations and disturbances such as motor and load inertia changes. In contrast, Hysteresis controller has a much simpler control structure. Unlike other advanced servo algorithms, Hysteresis control structure is simpler. Its performance and ease of use are comparable to that of competitive technologies. Another
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advantage of Hysteresis control is that the majority of applications need only manipulate one parameter to achieve optimal performance making it easier to use. In this project also, a voltage source control technique is a part of the controller to control the voltage that supply to the induction motor. The voltage source control technique operate by comparing the voltage line to line (to three induction motor) with a voltage reference(as a reference voltage) and the error will send to PID Hysteresis to minimize the error. The PID Hysteresis will minimize the error by sending a Pulse Width Modulation (PWM) to a three phase inverter .
Figure2.7: Hysteresis voltage control operation waveform.
The voltage controllers of the three phases are designed to operate independently. Each voltage controller determines the switching signals to the inverter. The switching logic for phase A is formulated as below:
If Va < (Varef -HB) upper switch (G1) is OFF and lower switch (G4) is ON If Va < (Varef +HB) upper switch (G1) is ON and lower switch (G4) is OFF In the same action, the switching of phase B and C are derived but in different phase shift that is phase B in 120° shift and phase C in 240° shift.
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2.6 Arduino In 2005, Massimo Banzi and David Cuartielles was made of one embedded system named as Arduino which are less expensive than other prototyping systems available at the time. They began producing boards in a small factory located in Ivrea, a town in the Province of Turin in the Piedmont region of northwestern Italy.Arduino is a single-board microcontroller designed to make the process of using electronics in multidisciplinary projects more accessible. The hardware consists of a simple open source hardware board designed around an 8-bit Atmel AVR microcontroller, though a new model has been designed around a 32-bit Atmel ARM. The software consists of a standard programming language compiler and a boot loader that executes on the microcontroller [16]. Micro- controllers are also attracted to Arduino because of its agile developement capabilities and its facility for quick implementation of ideas.The Arduino is a microcontroller board based on the ATmega328 (datasheet). It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz ceramic resonator, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started. The Uno differs from all preceding boards in that it does not use the FTDI USB-to-serial driver chip. Instead, it features the Atmega16U2 (Atmega8U2 up to version R2) programmed as a USB-to-serial converter [16].There are specifications of Adruino: Table 2.1: Specifications of Arduino Microcontroller
Atmega328
Operating Voltage
5V
Input Voltage (recommended)
7-12V
Input Voltage (limits)
6-20V
Digital I/O Pins
14 (of which 6 provide PWM output)
Analog Input Pins
6
DC Current per I/O Pin
40 mA
DC Current for 3.3V Pin
50 mA
Flash Memory
32 KB (Atmega328) of which 0.5 KB used by
16 bootloader SRAM
2 KB (Atmega328)
EEPROM
1 KB (Atmega328)
Clock Speed
16 MHz
The advantages of the Arduino are stated below:
Inexpensive - Arduino embedded devices are inexpensive compared to other microcontroller embedded devices.
Cross-platform - Most microcontroller systems are limited to Windows. Different with Arduino, it can runs on Windows, Macintosh OSX, and Linux operating systems.
Simple, clear programming environment - The Arduino programming environment is easy to use for beginners.
Open source - The Arduino software is published as open source tools, so the user easy to get the information experienced programmers.
The applications of the embedded system like the Arduino rapidly growth due to the advantages it. According to the paper [17], a novel Open loop phase control method is developed by coding a program using ARDUINO software in which ARDUINO controller takes input from the user and generates firing pulses for the TRIAC which controls the speed of the Induction motor. The total process is executed with the help of an ARDUINO controller kit where ARDUINO and Tera-Term softwares are used for micro controller and for serial monitor. The Figure 2.8 shows the Arduino microcontroller,
Figure 2.8: The Arduino microcontroller
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CHAPTER 3
METHODOLOGY
3.1 Block diagram
Three-phase induction motor
Three-phase inverter
DC
PWM
PID HYSTERISIS CONTROLLER
V ref
Figure 3.1: Block diagram of the project The Figure 3.1 above shows the block diagram of the project. For this project its consists of four mains parts which is the DC source as the input, the three phase inverter, the three phase induction motor as a load and the controller to give the system to a robustness performance. The first part is the input. The input for this project is the DC voltage that fed to a three phase inverter. As the input it will give the power to whole system. Second part is the three phase inverter. The general function of the inverter is to convert the DC voltage to the AC voltage. But for this
18
system, the three phase inverter will be used because it will depend on the outputs that are used. The six switch of switching inverter will be used because the PWM will be fed from the controller. The load that is used is the three phase induction motor. So the performance of the motor will be observed in terms of motor current and the speed. The three phase induction motor is well known of its non linear characteristics and for that reason the controller is needed to improve the performance of the induction motor. The important part is the controller of the system which is the voltage source control technique and PIDH will act as a controller to the system. The controller will compare the motor current with the reference current and if there is an error, the controller will generate the pulse width modulation to feed into the three phase inverter. By fed the PWM to the inverter the inverter will rescale the output to power up the load. By adding the controller to the system it can give high level of performance of the induction motor. 3.2 Project flowchart The flowchart below will explained how the system will operate from the starting to end process. The Figure 3.2 of the project flowchart:
START
DC SUPPLY TO INVERTER
THREE PHASE INVERT DC TO AC
POWER UP THE THREE PHASE INDUCTION MOTOR
CONTROLLER GENERATE THE PWM
NO
MOTOR VOLTAGE = REFERENCE VOLTAGE
YES END
Figure 3.2: The project flowchart
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3.3 Working flowchart The Figure 3.3 shows the flow chart of work for this project from the beginning until the ending. The challenging part is the controller part which is consists several parameters that must be considered to accomplish this project successfully.
start
Hardware part
Software part [MATLAB simulink]
Study threephase inverter
Study the structure of three-phase induction motor
Study the threephase induction motor
Derive mathematical modeling of threephase induction motor
Hardware setup
PID Hysteresis control design
no Time response meet requirement yes Upload to Adriano
Observe performance of controller
Write thesis
end
Figure 3.3: Working flowchart
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3.4 Inverter Design The circuit of three phase inverter design by using Proteus software. In this circuit, the MOSFET (SPP11N60C3) is used with voltage rating till 600V which accommodate the three phase inverter PWM. This inverter is connected from gate driver to control the 6 switching PWM before it transfer to the Induction Motor. This Figure 3.4 shows the schematic circuit for three phase inverter:
Figure 3.4: schematic circuit of three phase inverter
The capacitor with value 470uF is used to storage the energy with voltage rating up to 400V. The hardware of three phase inverter is showing in Figure 3.5. The 2 port at the left hand side below the capacitor is the Vdc input, the six positive and negative (red and black wire) is the PWM switching signal and the three ports at right hand side is the output phase A, B and C in Vac that will fed to induction motor.
Figure 3.5: the three phase inverter of hardware
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3.5 Gate Design
Figure 3.6: schematic diagram for gate driver for inverter The Figure 3.6 above shows the schematic diagram for gate driver inverter by using PROTEUS software. From the Arduino, three signals were sent to the gate driver inverter. It had change to six pulse signal after trough IC7414 (NOT gates) which is one signal same likes original and one signal is invert from original. Then, IC4081 (quad two core or AND gate) as a function to double up the amplitude. The function HCPL3120 is as a driver for power of MOSFET. The IL0515S supply to HCPL3120 with 15V to operate. The minimum of voltage to power up the MOSFET at three phase inverter is 12V.Figure 3.7 shows the hardware of gate driver for three phase inverter.
Figure 3.7: the hardware gate driver for three phase inverter
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3.6 Controller Design
Figure 3.8.: PID Hysteresis controller
Figure 3.8 shows the MATLAB simulink of PID Hysteresis voltage controller .The input voltage with amplitude 18V is injected to the controller before it compared with the voltage reference. The functional of ADC and DAC are used to make likes Arduino system where the Arduino are accepted the digital signal from the Induction Motor waveform and then convert it to analog again. Electronic equipment is frequently used in different fields such as communication, transportation, entertainment, etc. Analog to Digital Converter (ADC) and Digital to Analog Converter (DAC) are very important components in electronic equipment. Since most real world signals are analog, these two converting interfaces are necessary to allow digital electronic equipments to process the analog signals. An Analog to Digital Converter (ADC) is a device for converting an analog signal (current, voltage etc.) to a digital code, usually binary. In the real world, most of the signals sensed and processed by humans are analog signals. Analog-to-Digital conversion is the primary means by which analog signal are converted into digital data that can be processed by computers for various purposes. Digital to Analog Converter (DAC) is an inverse function of ADC. In order to get back the signal that can be processed or sensed by humans or equipment.
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3.6.1 ADC
Figure 3.9: Analog-digital-converter Figure 3.9 shows the diagram to convert analog signal to digital signal. The value of analog signal is 20Vac with convert 10 bits, 1023. From here the equation will calculated to generate the ADC equation. (3.1) (
)
For(20,1023); (
)(
)
So the ADC equation is;
3.6.2 DAC
Figure 3.10: digital-analog converter
24
Figure 3.10 shows the diagram of digital to analog converter. Same with ADC, the DAC equation must be calculated as follows:
(
)
)(
)
For(1023,20); (
So the DAC equation is;
The signal after the converters are compared via voltage reference with the amplitude is 20 and then correcting the error feedback from the induction motor. The error will filtering with PID controller first which is the PID must be setup with Kp=1(proportional), Ki=0.1 (integral) and Kp=0 (Derivative).The figure 3.11 below shown the function block parameter of PID controller:
Figure 3.11: function block parameter of PID
The signal after PID will be filtering again by Hysteresis controller to produce the constant PWM. The constant values 0.2 is used to cutoff the waveform from PID and then make the different shifting between phase. The Figure 3.12 shows the connection between MATLAB software with Arduino with the LED signal acting likes the PWM signals before injected to the gate driver of three phase inverter. The
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