DIGITAL SIMULATION OF WIND STAND-ALONE AND WIND-DIESEL ISOLATED POWER SYSTEMS
by
MOHSEN KALANTAR
CENTRE FOR ENERGY STUDIES
Thesis submitted
in fulfilment o f the requirements o f the Degree of
DOCTOR OF PHILOSOPHY
O
eiH' to the
INDIAN INSTITUTE OF TECHNOLOGY,DELHI
JULY, 1991
CERTIFICATE
This is to certify that the thesis entitled "DIGITAL SIMULATION OF WIND STAND-ALONE AND WIND-DIESEL ISOLATED POWER
SYSTEMS", being submitted by Mohsen Kalantar to the Indian Institute of Technology, Delhi, for the award of the degree of Doctor of Philosophy is a record of the bonafide research work carried out by him. He has worked under our guidance and supervision and has fulfilled the requirements, which to our knowledge, have reached the requisite standard for the submission of this thesis. The results contained in this thesis have not been submitted in part or full to any other University or
Institute for the award of any degree or diploma.
(■'Ljt _
Dr. S.C. Tripathy Professor and Head
Centre for Energy Studies
Indian Institute of Technology, New Delhi - 110 016, INDIA.
JZ
> a p , ^ ^ 1 ta-— _Dr. R. Balasubramanian Associate Professor
Centre for Energy Studies
Indian Institute of Technology, New Delhi - 110 016, INDIA.
to
my parents
Acknowledgments
I am very fortunate to have been associated with Prof. S.C.
Tripathy, who as my supervisor and head of the Centre for Energy Studies provided constant support, encouragement, enthusiasm and a peaceful environment to work in. No amount of words can really suffice in expressing my sincere thanks to him. His probing comments and insightful suggestions have helped me at every stage of this work.
I also express my deep sense of gratitude and indebtedness to my co-supervisor Dr. R. Balasubramanian for his useful suggestions throughout the course of this work. A good amount of work in this thesis evolved from simulating discussions with him and I am much grateful for his constant guidance and patience.
Thanks to my friends and colleagues for their help at various stages of the present work, particularly to mention the names P.S. Chandramohanan Nair, Hari Kumar, C.S. Sinha.
The technical staff of the power system laboratory at Centre for Energy Studies where this work was carried out, are thanked for their cooperation and hospitable attitude.
Finally I acknowledge my deep gratitude to my parents, my sisters, particularly to mention Nana and my brother who always gave moral support by way of "high expectations" and continuously encouraged my academic endeavor. The patient understanding and
cooperation extended throughout the work by my wife is greatly appreciated. My pursuit of higher technical education and research would not have been possible but for the readiness of my family to bear the economic cost of this pursuit and the physical separation it involved. For their sacrifices and their love, understanding and encouragement, I shall remain indebted.
Mohsen Kalantar
Abstract
Digital computer models of a wind stand-alone and a wind- diesel isolated power generation systems, including wind turbine generator pitch control and superconducting magnetic energy storage (SMES) unit are developed and presented in this thesis.
The dynamic performance of the isolated power system and its control are studied using the time domain solution approach.
For improvement in power frequency quality, the system incorporates a turbine blade angle pitch control scheme which monitors the wind turbine. This alters the pitch angle of the blades to control the wind turbine speed and shaft torque. It has been shown that the adopted control strategy results in significant dynamic performance improvement of the system.
The need to introduce a storage medium into the system arises due to the stochastic nature of the load demand and the available wind speed at any location. The reduction in wind speed may result in the shut down of the wind turbine generator.
Therefore, there must be some form of storage to cover the time required to start up the wind power again. For the wind-diesel power system, the diesel engine will take care of the increase in the load demand as well as wind turbine speed reduction by acting as a back up for wind power generation. Tfrfe problem of high numbers of diesel engine stop/start cycles can also be dealt with adequately by the addition of energy storage which can be reconverted into electricity. One of the serious problems faced
iv
by the isolated power generation system is the oscillation and instability following sudden changes in load or generation. This results in system frequency and power deviations. The introduction of a superconducting magnetic energy storage unit to the system for load leveling application and for the improvement of stability and system dynamic response is studied.
Based on a linear model of the system it is shown that changes in control system settings could be made to improve the power system performance. Optimization of the controller gain parameters and stability studies are done for the system with and without the SMES unit. A systematic method of choosing the gain parameter of the wind turbine generator pitch control for wind- diesel power system is adopted using the Lyapunov technique that guarantees stability. For wind stand-alone power system optimization is done by actual integration of the squared errors in the response and the stability with the optimal gain thus obtained is ensured by checking the dynamic response of the system.
Analysis of stability has further been explored using eigenvalue sensitivity technique. The eigenvalues of the system with and without SMES unit have been studied and effects of variation of SMES unit parameters on eigenvalue locations are
investigated. The system dynamic performance behavior under more realistic situations of continuous small deterministic as well as stochastic load perturbations has been studied. The power system
simulation under random load perturbations is performed on a digital computer using an appropriate time step to approximate the continuous process of the system.
Possibility of using normally designed three phase squirrel cage induction motor as an autonomous self-excited induction generator for wind power generation is examined. Analytical technique to identify the steady state performance of the self
excited induction generator using the Newton-Raphson method is presented. Self excitation with capacitors at the stator terminals of the induction machines is well demonstrated experimentally on a DC motor driven induction generator set. The methods to overcome the problems of voltage and frequency control in self-excited induction generators have also been proposed in this thesis.
The state of the art of technology and present status of wind power generation system in the world is reviewed. Some aspects on design and cost considerations of autonomous energy systems are presented. Some practical aspects of the SMES unit installed for obtaining dynamic performance improvement of wind stand-alone and wind-diesel isolated power systems and its protection arrangements required are described.
Table of Contents
Acknowledgments ... i
A b s t r a c t... iii
Nomenclature ... xiii
List of Figures . . . xx
List of T a b l e s ... xxv
Chapter 1 Introduction 1.1 Introduction ... 1
1.2 Development of Windmills ... 2
1.3 Need for Wind Energy C o n v e r s i o n ... 3
1.4 Power from the Wind T u r b i n e ... 5
1.5 Wind Turbine Characteristics ... 7
1.6 Wind Turbine Control Configurations . . . . 9
1.7 System with Energy Storage Unit . . . 11
1.8 Superconducting Magnetic Energy Storage (SMES) . 14 Unit 1.9 System Parameter Optimization and Stability . 16 Studies 1.10 Self-Excited Induction Generator (SEIG) . . . 17
1.11 Literature Survey ... 19
1.12 Objective and Organization of the Thesis . . . 24
Chapter 2 Control and Dynamics of Wind Stand-alone and Wind-diesel Turbine Generators 2.1 Introduction . . . 30
2.2 Control Classification ... 31
2.3 Control Requirements ... 36 2.4 Wind Stand-alone System Configuration . . . . 37 2.4.1 Wind Stand-alone Power System Components . . 37 2.4.2 Digital Model of the Wind Stand-alone Power . 39
System
2.4.3 Wind Stand-alone System Parameters . 42 2.5 Transient Response of the Wind Stand-alone Power . 43
System
2.6 Wind-diesel System Configuration ... 45 2.6.1 Wind-diesel Power System Components . . . 4 5 2.6.2 Digital Model of the Wind-diesel Power . 47
System
2.6.3 Wind-diesel System Parameters . . . . 49 2.7 Transient Response of the Wind-diesel Power . 49
System
2.8 C o n c l u s i o n s ...53
Chapter 3 Digital Computer Model of the System with Superconducting Magnetic Energy Storage Unit
3.1 I n t r o d u c t i o n ... ....
3.2 SMES Unit Configuration in the Power System . . 56 3.3 Analysis of the SMES U n i t ... 58 3.4 SMES for Load-frequency C o n t r o l ... 60 3.5 Maximum and Minimum Excursions of Voltage and . 63
Current in the SMES Inductor
3.6 The Use of Inductor Current Deviation Feedback . . 66 3.7 SMES Unit Operation with Wind Stand-alone and 68
Wind-diesel Isolated Power Systems
3.8 Wind Stand-alone Power System Model with SMES . 69 Unit
vii
viii
3.9 Transient Response of the Wind Stand-alone Power System
3.10 Wind-diesel Power System Model with SMES Unit
3.11 Transient Response of the Wind-diesel Power System
3.12 Transient Response of the Wind Stand-alone Power System with SMES Unit Parameters Variation
3.12.1 Effect of the SMES Gain Variation
3.12.2 Effect of the SMES Inductor Current Set Point Variation
3.12.3 Effect of the SMES Inductance Variation . 3.13 Power Rating of the SMES Unit for Wind Stand
alone Power System
3.14 Transient Response of the Wind-diesel Power System with SMES Unit Parameters Variation
3.14.1 Effect of the SMES Gain Variation
3.14.2 Effect of the SMES Inductor Current Set Point Variation
3.14.3 Effect of the SMES Inductance Variation . 3.15 Power Rating of the SMES Unit for the Wind-diesel
Power System
72
75 77
82
82 83
86 89
92
92 96
96 103
3.16 Conclusions ... 103 Chapter 4 Controller Gain Parameter Optimization
4.1 I n t r o d u c t i o n ... 105 4.2 Performance Indices ... 106 4.3 Gain Parameter Optimization of the Wind Standi- . 108
alone Power System Using Integral Square Error Criterion
4.3.1 Performance Index of the Wind Stand-alone . 110 Power System
4.3.2 Transient Response of the Wind Stand-alone . 112
ix
Power System with Optimized Gain Parameter 4.4 Gain Parameter Optimization of the Wind-diesel
Power System Using Lyapunov Technique
4.4.1 Algorithm for Solution of Lyapunov Equation 4.4.2 Performance Index of the Wind-diesel Power
System
4.4.3 Transient Response of the Wind-diesel Power System with Optimized Gain Parameter
4.5 Conclusions ...
Chapter 5 System Stability Analysis Using the Eigenvalue Sensitivity Technique
5.1 Introduction ...
5.2 Eigenvalue Sensitivity ...
5.3 Eigenvalue Analysis of the Wind Stand-alone Power System
5.3.1 Effect of the SMES Unit on Eigenvalue Locations
5.3.2 Effect of the SMES Gain Variation on Eigenvalue Locations
5.3.3 Effect of the SMES Inductor Current Set Point Variation on Eigenvalue Locations
5.3.4 Effect of the SMES Inductor Current Deviation Feedback Gain Variation on Eigenvalue Locations
5.3.5 Effect of the Simultaneous Variation in the SMES Unit Parameters on Eigenvalue Locations
5.4 Eigenvalue Analysis of the Wind-diesel Power System
5.4.1 Effect of the SMES Unit on Eigenvalue Locations
5.4.2 Effect of the SMES Gain Variation on Eigenvalue Locations
. 117
. 120
. 121
.
122. 132
. 133 . 135 . 136
. 136
. 139
. 141
. 142
. 144
. 144
. 146
. 149
5.4.3 Effect of the SMES Inductor Current Set . 151 Point Variation on Eigenvalue Locations
5.4.4 Effect of the SMES Inductor Current . 152 Deviation Feedback Gain Variation on
Eigenvalue Locations
5.4.5 Effect of the Simultaneous Variation in . 152 the SMES Unit Parameters on Eigenvalue
Locations
5.5 Conclusions . . . -,KC:
• • • • • • • • 1DD
Chapter 6 System Performance Under Random Load Disturbances
6 . 1 I n t r o d u c t i o n ... ..
6 . 2 Power System Realistic Load Disturbance Models . . 157 6.3 Random Component Modeling of the Load . . . . 158 6.4 Wind Stand-alone Power System Transient Response . 159 6.5 Wind-diesel Power System Transient Response . . 165 6.6 C o n c l u s i o n s ... ..
Chapter 7 wind Turbine Driven Self-excited induction Generator
7.1 I n t r o d u c t i o n ...
7.2 System Configuration ... 174 7.3 Analytical Techniques ... 175 7.4 Measurement of the Equivalent Circuit Parameters . 181 7.4.1 DC Resistance Measurement . . . 181 7.4.2 Blocked Rotor T e s t ... 1 8i 7.4.3 Synchronous Speed T e s t ... ..
7.5 Experimental Setup and Machine Parameters . . . 186 7.6 Controller Concept ... I87
7.6.1 Voltage Control Using Saturable Core Reactor
7.6.2 Voltage Control Using Series Capacicor 7.6.3 Frequency Control Using SMES Unit,
7.7 Performance of the SEIG on Load with DC Motor 7.7.1 Variation of Shunt Capacitance with Load 7.7.2 Variation of Voltage with Load
7.7.3 Effect of Speed Variation
7.7.4 Effect of Saturable Core Reactor . 7.7.5 Effect of Series Capacitor
7.8 Conclusions . . . .
Chapter 8 Economic and Practical Considerations of the Wind Stand-alone and Wind-diesel Isolated Power Systems
8.1 Introduction ...
8.2 Present Status of Wind Energy Conversion 8.3 Wind Energy Conversion Expediences in India
8.4 Wind-diesel Power Generation System with Energy Storage
8.5 Factors Affecting Diesel Fuel Consumption of a Wind-diesel Power System
8.6 Economics of Wind Turbine Control . . . . 8.7 Economic Aspects of Self-excited Induction
Generator
8.8 Some Aspects of SMES Unit Design . . . . 8.9 Economic Aspects of the SMES Unit . . . . 8.10 Protection Requirements of the SMES Unit
8.11 Conclusions ...
109 191 191 191 192 194 194 198 202
XI
188
. 205 . 207 . 215 . 216
. 217
. 219
. 221
. 222
. 224 . 225 . 228
xii Chapter 9 Conclusions and Scope for Future Work
9.1 Objective of the Thesis . 9.2 Summary of Principal Results
9.3 Scope for Future Work ...
System
Appendix B
Appendix C
References Bio-data
. 231 . 232 . 236 Appendix A
(I) Mathematical Modeling of the Wind Stand-alone . 238 Power System
(II) Mathematical Modeling of the Wind-diesel Power 240 Svstpm
(I) Mathematical Modeling of the Wind Stand-alone . 243 Power System with SMES Unit
(II) Mathematical Modeling of the Wind-diesel Power 244 System with SMES Unit
(I) Mathematical Modeling of the Wind-diesel Power . 247 System in Autonomous Form
(II) Mathematical Modeling of the Wind-diesel Power . 248 System with SMES Unit in Autonomous Form
. 251 . 258
