DIRECT TORQUE CONTROL OF SWITCHED RELUCTANCE MOTOR DRIVES
A Thesis submitted in partial fulfillment of the requirements for the degree of Master of Technology in Electrical Engineering (Power Control & Drives)
By
AMALENDU DASH
Roll No-210EE2225
Department of Electrical Engineering NATIONAL INSTITUTE OF TECHNOLOGY, ROURKELA PIN-769008 ODISHA, INDIA
DIRECT TORQUE CONTROL OF SWITCHED RELUCTANCE MOTOR DRIVES
A Thesis submitted in partial fulfillment of the requirements for the degree of Master of Technology in Electrical Engineering (Power Control & Drives)
By
AMALENDU DASH Roll No-210EE2225
Under the Supervision of Prof. Anup Kumar Panda Dept. of Electrical Engineering, NIT Rourkela & Co-Guidance of Er. Manoranjan Biswal Manager Maintenance Division, OHPC
Department of Electrical Engineering NATIONAL INSTITUTE OF TECHNOLOGY, ROURKELA PIN-769008 ODISHA, INDIA
Dedicated to my beloved parents and sisters
National Institute of Technology Rourkela
CERTIFICATE
This is to certify that the thesis entitled “DIRECT TORQUE CONTROL OF SWITCHED RELUCTANCE MOTOR DRIVES” submitted by AMALENDU DASH bearing Roll No.210EE2225 in partial fulfillment of the requirements for the award of the degree of “Master of Technology” in Electrical Engineering specializing in "Power Control and Drives" at the National Institute of Technology, Rourkela is an authentic work carried out by his under my supervision. To the best of my knowledge and belief, the matter embodied in the thesis has not been submitted to any other University / Institute for the award of any Degree or Diploma.
Prof. Anup Kumar Panda Date: Department of Electrical Engineering Place: National Institute of Technology Rourkela-769008
ACKNOWLEDGEMENT
With due regards and profound respect, I would like to express my deep sense of gratitude and indebtedness to my honorable, esteemed supervisor, Prof. Anup Kumar Panda, Electrical Engineering Department, NIT, Rourkela for his guidance, constructive criticism and constant support over the time he has introduced me to the academic world. His perspective on my work has inspired me to go on. I am glad to work with him. I would also like to express my deep regards to my co-supervisor, Er. Manoranjan Biswal, Manager, Maintenance Division, Odisha Hydro Power Corporation Limited, for his valuable support and inspiring guidance. I am grateful to Power Electronics Laboratory staff Mr. Rabindra Nayak, without him the work would have not progressed. I would like to thank all my friends of NIT, Rourkela and especially Susant Panigrahi , Sushree Sangita Patnaik, Subarni Pradhan, T. Ramesh kumar, for their endless encouragement and support in completing this project work. I cannot finish without thanking my lovely parents, elder sisters and my brother in laws on whose encouragement, support, love and noble devotion to my education. I would like to thank to all those who directly or indirectly supported me in carrying out this project work successfully. Last but not the least; I am sure this project work would not come to an end without remaining gratitude to God Almighty, the guide of all guides who has helped me a lot for completing this project work. I dedicate this thesis to my beloved parents, elder sisters Satyasmita, Debiprava, brother in laws Satyaballav, Suryanarayan and my two beautiful niece Sunu and Tweety.
Amalendu Dash
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CONTENTS
ACKNOWLEDGEMENT i TABLE OF CONTENTS ii LIST OF FIGURES iv LIST OF TABLES vii ABBREVIATIONS viii ABSTRACT ix
CHAPTER 1. Introduction 1 1.1 Overview 2 1.2 Advantage, Limitations and Applications of SRM 2 1.2.1 Advantages 2 1.2.2 Limitations of SRM 4 1.2.3 Applications of Switched Reluctance Motor 4 1.2.4 Direct Torque Control of Switched Reluctance Motor 4 1.3 Motivation 4 1.3.1 Switched Reluctance Motor 4 1.3.2 Direct Torque Control of Switched Reluctance Motor 5 1.4 Objectives 5 1.5 Thesis Outline 6
CHAPTER 2. Principle of Operation of the SRM 7 2.1 Introduction 8 2.2 Switched Reluctance Motor Configuration 8 2.3 Principle of Operation 10 2.4 Elementary Operation of Switched Reluctance Motor 12 2.5 The Relation Between Inductance and Rotor Position 14 2.6 Converters for Switched Reluctance Motor Drive 15 2.7 Asymmetric Bridge Converter 15 2.8 Stator Current Control by Modified Hysteresis Band Control 15
CHAPTER 3. Mathematical Modelling and Control of SRM 16
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3.1 Mathematical Modelling of SRM 17 3.2 PID Controller 18 3.3 Function of Proportional-Integral and Derivative Controller 19 3.3.1 Proportional Gain Constant 19 3.3.2 Integral Gain Constant 24 3.3.3 Derivative Gain Constant 24 3.4 Block Diagram Representation of Switched Reluctance Motor Drive 27
CHAPTER 4. Modelling and Simulation of SRM Drive 31 4.1 Switched Reluctance Motor Specification 32 4.2 Modelling of Three Phase Switched Reluctance Motor Drive 33 4.2.1 Simulation Results for Three Phase SRM 33 4.3 Modelling of Four Phase Switched Reluctance Motor Drive 34 4.3.1 Simulation Results for Four Phase SRM 34 4.4 Modelling of Five Phase Switched Reluctance Motor Drive 34 4.4.1 Simulation of Five Phase SRM 34
CHAPTER 5. Direct Torque Control of Switched Reluctance Motor Drive 43 5.1 Introduction 44 5.2 Direct Torque and Flux Control 44 5.2.1 Mathematical Model of Switched Reluctance Motor Drive 44 5.2.2 Voltage Source Inverter 44 5.2.3 Direct Torque Control Techniques and Its Objectives (A) Flux Hysteresis Control Loop 44 (B) Torque Hysteresis Control Loop 5.2.4 Voltage Vector Switching Selection 45 5.3 Simulation Results 46 5.4 Summary 59
CHAPTER 6. Conclusion & Scope for Future Work 60 6.1 Conclusion 61 6.2 Scope for Future Work 62 REFERENCES 63
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LIST OF FIGURES
Figure No Page No 2.1 6/4 Switched Reluctance Motor Configuration 6 2.2 Operation of SRM(a) phase ‘c’ aligned (b) phase ‘a’ aligned 7 2.3 Basic Rotor Position in A Two Pole SRM 8 2.4 Inductance Profile for Switched Reluctance Motor 9 2.5 Asymmetric H-Bridge Drive Circuit for SRM 12 2.6 (a) Positive voltage Mode 13 2.6 (b) Negative Voltage Mode 14 2.6 (c) Return Current Mode 14 3.1 Single Phase Equivalent Circuit for Switched Reluctance Motor 16 3.2 Structure of PID Controller 18 3.3 Block Diagram of Traditional Feedback Control 20 4.1 Voltage v/s Time Characteristics of Three Phase SRM 22 4.2 Torque v/s Time Characteristics of Three Phase SRM 22 4.3 Flux Linkage v/s Time Characteristics of Three Phase SRM 23 4.4 Current v/s Time Characteristics of Three phase SRM 23 4.5 Speed v/s Time Characteristics of Three Phase SRM 24 4.6 Inductance v/s Time Characteristics of Three Phase SRM 24 4.7 Voltage v/s Time Characteristics of Four Phase SRM 25 4.8 Torque v/s Time Characteristics of Four Phase SRM 25 4.9 Flux Linkage v/s Time Characteristics of Four Phase SRM 26 4.10 Current v/s Time Characteristics of Four Phase SRM 26 4.11 Speed v/s Time Characteristics of Four Phase SRM 27 4.12 Inductance v/s Time Characteristics of Four Phase SRM 27 4.13 Voltage v/s Time Characteristics of Five Phase SRM 28 4.14 Torque v/s Time Characteristics of Five Phase SRM 29 4.15 Flux Linkage v/s Time Characteristics of Five Phase SRM 29 4.16 Current v/s Time Characteristics of Five Phase SRM 30 4.17 Speed v/s Time Characteristics of Five Phase SRM 30
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4.18 Inductance v/s Time Characteristics of Five Phase SRM 31 5.1 Direct Torque and Flux Control of SRM 34 5.2 Two-Level Voltage Source Inverter 36 5.3 Two-Level Hysteresis Controller for Controlling the Flux Error 37 5.4 Three-Level Hysteresis Controller for Controlling the Torque Error 38 5.5 α-β axis for motor voltage 39 5.6 Sectors and voltage vectors 41 5.7 Voltage v/s Time Characteristics for Three Phase SRM with DTC 43 5.8 Torque v/s Time Characteristics for Three Phase SRM with DTC 43 5.9 Speed v/s Time Characteristics for Three Phase SRM with DTC 44 5.10 Flux v/s Time Characteristics for Three Phase SRM with DTC 45 5.11 Trajectory of Stator Flux Vector 45
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LIST OF TABLES
Table No Page No
3.1 Effects of Kp , Kd , Ki on a Closed Loop System 20 5.1 Switching Logic for Flux error 38 5.2 Switching Logic for Torque Error 38 5.3 Switching Table of Inverter Voltage Vectors 26 5.4 Flux and Torque Variation Due to application of Voltage Vectors 42
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ACRONYMS
NS No. Of Stator Pole
Nr No. Of Rotor Pole m No. Of Phases
La Aligned Inductance
Lu Un-aligned Inductance
βs Stator Pole Arc
βr Rotor Pole Arc
Pr No. Of Rotor Pole ψ Flux linkage per phase e Induced emf
Kb Emf constant
Pi Instantaneous power input
Pa Air gap power
Te Electromagnetic torque kp Proportionality Gain kd Derivative Gain ki Integral Gain
Vαs α- axis Stator Voltage
Vβs β- axis Stator Voltage
Vαr α- axis Rotor Voltage
Vβr β- axis Rotor Voltage iαs α- axis Stator Current iβs β- axis Stator Current iαr α- axis Rotor Current iβr β- axis Rotor Current
Ls stator inductance
Lr Rotor inductance
Lm Mutual inductance
RS Stator Resistance
Rr Rotor inductance
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ψαs α- axis Stator Flux Linkage
ψβs β- axis Stator Flux Linkage
ψαr α- axis Rotor Flux Linkage
ψβr β- axis Stator Flux Linkage