臺灣博碩士論文加值系統

在世界各國的鋼鐵產業中，電弧爐煉鋼廣為鋼鐵業者所採用，是為煉鋼之主要運轉設備。然而電弧爐於運作過程中因煉鋼材料與電極不斷發生短路與開路，造成電弧爐負載吸收低功因變動大電流並且導致無效功率劇烈且不規則變動，同時使得上游饋電線路產生嚴重之電壓閃爍問題。
本研究以嘉南供電區營運處之新營P/S轄區作為探討對象，由於該轄區內有多家營運之鋼鐵用戶，使得轄區內變壓器電壓調整用之有載分接頭切換設備(Onload Tap Changer, OLTC)長久以來因負載的驟變造成頻繁之切換，諸此現象不但影響設備本身壽命，同時也大大降低對下游用戶供電之品質與可靠度。
本研究將分析該轄區在擁有多家營運之鋼鐵廠用戶下，其劇變的負載變動特性對饋電線路所造成之電力品質衝擊與影響；同時利用模擬技術與準確的電力設備模型進行模擬測試，評估安裝靜態虛功補償器(Static Var Compensator, SVC)進行補償之效果，以佐證靜態虛功補償器實際安裝於現行轄區系統之可行性；並加入模糊控制，觀察靜態虛功補償器與有載分接頭變壓器之動作情形與協調效果；亦須探究有載分接頭變壓器動作與電壓閃爍之關連性，以釐清有載分接頭變壓器誤動作之因，並提供防範對策；最後對新營P/S進行整體性電力品質評估，了解電力供應者與用戶之用電狀況，以確保整體用電之穩定。

In this study, the goal is to investigate the power quality problems that occur in a Taipower’s primary substation system (P/S), where the P/S feeds electric power to several steel-making customers. Recently, due to the operations of these EAF loads, it is observed that serious voltage fluctuations occurred at the bus that connected to the P/S transformers. The on-load tap changers (OLTCs) of the transformers have thus frequently switched on and off, which deteriorate the transformer life and also affect the supply power quality.
This study analyzes the power quality impact of severely load variations on the feeder under the area where has several steel industry customers. It uses simulation techniques and accurate equipment models to test the simulation, and assess the effects of installing SVC to support the installation of SVC in the existing area. In order to improve the switching situation of OLTC, this study adopts the fuzzy control for OLTC and SVC coordination. And it explores the relation between the OLTC operation and the voltage flicker to clarify the result of OLTC malfunction. Finally, it assesses the power quality of a primary substation with large arc furnace loads.

Acknowledgments i
中文摘要 ii
ABSTRACT iii
TABLE OF CONTENTS v
LIST OF FIGURES viii
LIST OF TABLES xii
Chapter 1 Introduction 1
1.1 Motivation and Purpose 1
1.2 Research Contents and Methods 7
1.3 Summary of Chapters 7
Chapter 2 OLTC in P/S and SVC Installation 9
2.1 Introduction of OLTC 9
2.2 The Effect of Voltage Flicker to the OLTC Transformer 11
2.2.1 Electrical Characteristics of AC EAF 14
2.2.2 Electrical Characteristics of DC EAF 16
2.2.3 The Effect of Voltage Flicker to OLTC 17
2.3 Static Var Compensator (SVC) 17
Chapter 3 Effect of Steel Industry on Power Quality of a P/S Substation 22
3.1 Introduction of Power System 22
3.2 Introduction of OLTC AVR Control for the Primary Substation 25
Chapter 4 Voltage Flicker Improvement 29
4.1 Improvement on the Supply System Side 30
4.2 Improvement on the Load Side 30
4.3 Voltage Flicker Mitigation through Static Var Compensator 32
Chapter 5 Fuzzy Set Theory 35
5.1 Basic Definitions 35
5.2 Membership Function Formulation 37
5.3 Set-Theoretic Operations 38
5.4 Fuzzy Rules and Fuzzy Reasoning 39
5.4.1 Linguistic Variables 39
5.4.2 Fuzzy If-Then Rules 40
5.4.3 Fuzzy Reasoning 40
5.5 Fuzzy Inference System 42
5.5.1 Mamdani Fuzzy Models 43
Chapter 6 Case Study 45
6.1 Model Establishment 45
6.1.1 AVR Model Establishment 45
6.1.2 Dead Band of AVR Control 46
6.1.3 Integrator and Integrator Reset 47
6.1.4 OLTC Controller 49
6.1.5 OLTC Transformer Model Establishment 50
6.1.6 SVC Model 53
6.1.6 Fuzzy Control Design 55
6.2 System Model Establishment 60
6.2.1 Without SVC Installation 61
6.2.2 With SVC at the P/S Primary Side 69
6.2.3 With SVC at the D/S Primary Side 75
6.2.4 Fuzzy Control for SVC at the P/S Primary Side 81
6.2.5 Fuzzy Control for SVC at the D/S Primary Side 85
6.3 Compensation Comparisons 90
Chapter 7 Conclusions and Future Works 92
7.1 Conclusions 92
7.2 Future Works 92
REFERENCES 93

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