AUTOMATIC REACTIVE POWER CONTROL OF AUTONOMOUS HYBRID POWER SYSTEMS

Transcription

1 AUTOMATIC REACTIVE POWER CONTROL OF AUTONOMOUS HYBRID POWER SYSTEMS by RAMESH CHAND BANSAL Centre for Energy Studies Submitted in fulfillment of the requirements of the degree of Doctor of Philosophy to the Indian Institute of Technology, Delhi India December 2002

2 Indian Institute of Technology, New Delhi, 2002

3 fp c.c-t'' FT -

4 Dedicated to My spiritual guru

5 CERTIFICATE This is to certify that the thesis entitled AUTOMATIC REACTIVE POWER CONTROL OF AUTONOMOUS HYBRID POWER SYSTEMS being submitted by Shri RAMESH CHAND BANSAL to the Indian Institute of Technology, New Delhi (India) for the award of the degree of Doctor of Philosophy in Centre for Energy Studies is a bonalide research work carried out by him under our supervision and guidance. The research reports and the results presented in this thesis have not been submitted in parts or in full to any other University or Institute for the award of any degree or diploma. gct 1. S. Bhatt P. S. 0. Centre for Energy Studies Indian Institute of Technology New Delhi (P k-/i4' D. P. Kothair- Professor Centre for Energy Studies Indian Institute of Technology New Delhi

6 DECLARATION This is to certify that the thesis entitled AUTOMATIC REACTIVE POWER CONTROL OF AUTONOMOUS HYBRID POWER SYSTEMS being submitted to the Indian Institute of Technology, New Delhi (India) for the award of the degree of Doctor of Philosophy in Centre for Energy Studies is a bonafide research work carried out by me under supervision and guidance of Dr. T.S. "Matti and Prof. D.P. Kothari. The research reports and the results presented in this thesis have not been submitted in parts or in full to any other University or Institute for the award of any degree or diploma. Work reported in the thesis includes automatic reactive power control of autonomous hybrid power system modelling based on power equations. The modelling can be easily extendable to an autonomous hybrid power system having more machines. To test the proposed reactive power control system, state space models of wind-diesel, wind-multi-diesel, multi-wind-diesel, and winddiesel-micro-hydro using the three different types of SVC models have been developed on the basis of small signal analysis. Simulation studies have been carried out on the different examples of hybrid power systems for deterministic and realistic disturbances in load and/or input wind power. Optimum gain settings of the controllers have been obtained for step disturbances in input wind and/or in reactive power load. Discussion has been made on the number of observations obtained from the responses of the system considered under optimum gain settings. ANN models have been developed for different autonomous hybrid power system configurations for tuning the proportional-integral controller of SVC for optimum performance. (RAMESH AND BANSAL) 11

7 ACKNOWLEDGEMENTS I have a great pleasure in expressing my deep sense of gratitude, indebtness and thankfulness to my supervisors Dr. T.S. Bhatti and Prof. D.P. Kothari for their invaluable guidance, constant encouragement and support throughout this work. No amount of words can really suffice in expressing my sincere thanks to them. Without their constant encouragement and unremitting support, this thesis work would have never been complete. I am also very grateful to Prof. A. Chandra, the Head of the Department and to the other faculties and staff members of the Centre for Energy Studies, who guided me through my presentations and also encouraged me in various other ways. I am thankful to my fellow research scholars Sunil Bhatt, Ashish, Ramnarayan, Shikha, Himani, and Anshu for extending their help. I am also thankful to Mr. Rana and Prit for their help. I would also like to thank the Birla Institute of Technology and Sciences authorities and staff members who have been very generous and very helpful towards me in maintaining a suitable atmosphere and in extending all the facilities required for carrying out research work. 1 would like to express my thanks and sincere regards to all of my family members, my mother, uncle Shri. G.N. Bansal, aunt Smt. Anita Rani, brothers Naresh, Dinesh, Mohit, and Rohit, bhabhis Reena and Ranjana, who had been waiting patiently for completion of my Ph D work, I would also like to express my love to kids Lakshya, Nikita and Sakshi and my newly born son. The patience, understanding, cooperation and bearing with the worst of my moods by my wife, Neetu is greatly appreciated. RAMESH CHAND I3ANSAL UI

8 ABSTRACT The optimum utilization of resources for providing power to community at large, has resulted in large interconnected power systems. The demand to provide power to all by large interconnected system in India remains unfulfilled due to non-availability of sufficient funds, constraints on right-of-way for additional transmission lines and rapid growth in load with developments, but on the other hand the gap between supply and demand increases day-by-day. Not only to reduce the gap between generation and load, but because of limited life of conventional sources with high pollution rate, more exploration has been carried out on alternative sources of energy during the last three decades. During this period the assessment of potential of the sustainable ecofriendly alternative sources and refinement in technology has taken place to a stage so that economical and reliable power can be produced. Different renewable sources are available at different geographical locations close to loads, therefore, the latest trend is to have distributed or dispersed power system. Examples of such systems are wind-diesel, wind-diesel-micro-hydrosystem with or without multiplicity of generation to meet the load demand. These systems are known as autonomous hybrid power systems. A detailed literature survey shows that there is a great need to improve the reactive power control strategy of autonomous hybrid system to maintain the voltage within specified limits. Work in this thesis deals with the reactive power control of different configurations of autonomous hybrid power systems. The mathematical modelling for automatic load-voltage control of autonomous hybrid power systems has been developed using power balance equations. State-space equations have been derived for wind-diesel systems operating at constant speed/slip or at variable speed/slip and for wind-die 1-micro-hydro systems. To have automatic reactive load voltage control three iv

9 types of SVC (static VAR compensator) models have been considered in the mathematical modelling, which are frequently used in conventional power systems studies. Dynamic performances of wind-diesel, multi-wind-diesel and wind-multi-diesel system have been analyzed with optimum gain settings of SVCs. The optimum gain settings have been obtained using ISE (integral square error) criterion. The load is located at the hybrid power system generation terminals, therefore, it is designed that for the same input error signal AV, the AVR with the synchronous generator performs the function of maintaining constant voltage profile, whereas the SVC eliminates the reactive power mismatch in the system. The SVC regulator gain depends upon the size of the wind power generation and its value increases with the decrease in the size of wind power generation. The deviations in various variables also directly depend upon the size of wind power generation in the system but settling time remains unchanged. There is a considerable effect of the incorporation of speed/slip in the system model (variable slip model) on the system performance. Ignoring variable slip condition may result in fixed capacitors, which can cause variation in the system load voltage. The settling time of the system with and without multiplicity of generation remains almost same for different disturbances but the magnitude of first peak depends upon the size of the disturbance. It is observed that the performance of both SVC types II and III is better than SVC type-i. The Simulink, which is an interactive environment for modelling, analyzing and simulating a variety of dynamic systems, has been used to study the dynamical performance of different configurations of autonomous hybrid power systems. ANNs models have been developed for different autonomous hybrid power system configurations for tuning the proportional-integral controller for SVC. Transient responses of

10 different autonomous configurations show that SVC controller with its gained tuned by the ANNs provide optimum system performance for a variety of loads. Finally, it is recommended that a variable source of reactive power is required by an autonomous hybrid power system having induction and synchronous generators as electromechanical devices to maintain balance in the reactive power generation and absorption in the system, otherwise large voltage fluctuations may occur. The tuning of SVC controller parameters using ANN is very much necessary for achieving optimum performance of the system under varying load and input wind power conditions. vi

11 TABLE OF CONTENTS Page No. CERTIFICATE DECLARATION ACKNOWLEDGEMENTS ABSTRACT TABLE OF CONTENTS LIST OF FIGURES LIST OF TABLES NOMENCLATURE I ii iii iv vii x xx xxii CHAPTER -1 INTRODUCTION INTRoDucrIoN REACTIVE POWER CONTROL PROBLEM OF AUTONOMOUS HYBRID POWER SYSTEM ORGANIZATION OF THE THESIS CONCLUSIONS 10 CHAPTER -2 LITERATURE REVIEW INTRODUCTION INDUCTION GENERATORS Steady State and Performance Analysis of SEIGs Transient Analysis of SEIGs Modelling D-q reference model Impedance-based model ,3 Admittance-based model ,3.4 Operational circuit-based model Voltage Control Aspects of SEIGs Parallel Operation of SEIGs SYNCHRONOUS GENERATORS ELECTRIC LOADS REACTIVE POWER CONTROL OF HYBRID SYSTEMS SYSTEM OPTIONS Multiple-Wind-Single Diesel System Multiple-Diesel-Single Wind Systems 27 2,6.3 Multiple Diesel-Multiple-Wind Systems Wind-Diesel-Micro-Hydro System CONTROL AND SIMULATION TECHNIQUES Proportional Controllers Proportional Controllers Matlab/Simulink 29 vii

12 2.7.4 Artificial Neural Networks 2.8 PARAMETER OPTIMIZATION 2.9 CONCLUSIONS CHAPTER -3 MATHEMATICAL MODELLING OF AN ISOLATED HYBRID POWER SYSTEM FOR AUTOMATIC REACTIVE POWER CONTROL INTRODUCTION 3.2 THE MAVAR LOAD VOLTAGE CONTROL PROBLEM Excitation Control Systel The Flux Linkage Equation Incremental Reactive Power Balance Analysis MATHEMATICAL MODEL OF INDUCTION GENERATOR MODELLING OF STATIC VAR COMPENSATORS (SVCs) SYSTEM STATE SPACE MODELLING Wind-Diesel System State space model with constant slip for type-i SVC model State space model with constant slip for type-ii SVC model State space model with constant slip for type-iii SVC model State space model with variable slip for type-i SVC model State space model with variable slip for type-ii SVC model State space model with variable slip for type-iii SVC model Multi-Wind-Diesel System State space model of 2-wind-diesel system with type-1 SVC model State space model of 2-wind-diesel system with type-ii SVC model State space model of 2-wind-diesel system with type-iii SVC model Wind/Multi-Diesel System State space model of wind-2-diesel system with type-i SVC model State space model of wind-- 2-diesel system with type-ii SVC model State space model of wind- 2-diesel system with type-iii SVC model Wind-Diesel-Micro-Hydro System State space model of wind-diesel-micro-hydro system with type-i SVC model State space model of wind-diesel-micro-hydro system with type-ii SVC model State space model of -wind-diesel-micro-hydro system with type-iii SVC model CONCLUSIONS 70 CHAPTER -4 PARAMETER OPTIMIZATION AND DYNAMIC PERFORMANCE STUDY OF AUTONOMOUS HYBRID POWER SYSTEMS INTRODUCTION PARAMETER OPTIMIZATION OF HYBRID POWER SYSTEMS TRANSIENT RESPONSES OF THE WIND DIESEL SYSTEMS WIND-DIESEL AUTONOMOUS HYBRID POWER SYSTEMS (CONSTANT SLIP MODEL) 74 viii

13 4.32 WIND-DIESEL (VARIABLE SLIP MODEL) MULTI-WIND-DIESEL SYSTEMS WIND- MULTI-DIESEL SYSTEMS 4.4 CONCLUSIONS CHAPTER -5 SIMULATION OF AUTONOMOUS HYBRID POWER SYSTEMS USING MATLAB/SIMULINK FOR REALISTIC LOAD DISTURBANCES INTRODUCTION TRANSIENT RESPONSES OF THE AUTONOMOUS HYBRID POWER SYSTEMS Wind-Diesel Autonomous Hybrid Power Systems (Constant Speed/Slip Model) Wind-Diesel Systems Multi-Wind-Diesel Systems Wind-Multi-Diesel Systems Wind-Diesel-Micro-Hydro Systems CONCLUSIONS 183 CHAPTER -6 OPTIMUM SELECTION OF SVC CONTROLLER GAINS USING ARTIFICIAL NEURAL NETWORKS INTRODUCTION TRAINING OF ANN PARAMETERS TRANSIENT RESPONSES OF THE AUTONOMOUS HYBRID POWER SYSTEMS Wind-Diesel Autonomous Hybrid Power Systems (Variable Slip Model) Multi-Wind-Diesel Autonomous Hybrid Power Systems Wind-Multi-Diesel Autonomous Hybrid Power Systems ,4 Wind-Diesel-Micro-Hydro Autonomous Hybrid Power Systems CONCLUSIONS CIIAPTER -7 CONCLUSIONS AND SCOPE OF FUTURE WORK 7.1 INTRODUCTION 7.2 CONCLUSIONS 7.3 SCOPE FOR FUTURE WORK REFERENCES APPENDIX-I APPENDIX-11 APPENDIX-Ill 1310-BATA ix