微電網主要設計來確保電力供應的穩定性和品質，可靠的孤島轉換與隨後孤島微電網的運轉穩定性，將會是保證重要負載電力供應不中斷的關鍵。文獻中提出了現今孤島轉換的方案，使用區域內可快速響應的資源，如儲能設備等，建立安全的孤島轉換與孤島後的穩定運轉。然而，這些快速響應的設備較為昂貴，且歷史資料的分析顯示，在大多數情況下，這些孤島運轉的事件是可以預測的。利用這個特性，本論文提出一個最佳適應防衛機制來建立不依賴快速響應資源的安全孤島。
在隨後的孤島運轉中，太陽能與風電系統等可再生能源，可以提供動態頻率的支援，來保持微電網的穩定性。由於微電網中能使用的資源量有限，必須有適當的控制來最佳地利用這些資源的頻率支援能力。而一個最佳化的頻率支援服務，需要最小化頻率的變化，最大化最低頻率並快速抑制頻率震盪，使其符合設備的額定限制。因此，本文提出了太陽能和風電系統的新型控制器，以優化其頻率支援服務。並以模擬結果展示所提方法之性能。

Microgrids are designed to ensure reliability and quality of power supply. Reliable islanding transition and stable operation of the ensuing island microgrid are key to maintaining an uninterrupted supply of power to critical loads. Current islanding transition schemes proposed in the literature assume the availability of fast response from local energy resources, like battery storage system, to establish secure islanding transition and subsequent islanded operation; however, such fast response systems are often expensive. Analysis of historical events shows that the islanding event, at most instances, can be predicted; by exploiting this feature, this thesis proposes an adaptive optimal defense mechanism to establish secure islanding, without necessarily requiring fast response energy resources.
During the ensuing islanded operation, the renewable energy sources like solar PV and wind energy conversion system can provide dynamic frequency support to maintain the stability of the microgrid. Given the scarcity of resources in such islanded microgrids, suitable controls must be developed to optimally utilize these sources’ frequency support capability. An optimal frequency support service must minimize the magnitude of the rate of change of frequency, maximize the frequency nadir and quickly damp frequency oscillations to the nominal value subject to device level constraints. To this end, this thesis proposes new controllers for the solar PV and wind energy conversion systems to optimize their frequency support service. Simulation results are presented to demonstrate the performance of the proposed methods.

Acknowledgment ii
中文摘要 iii
Abstract iv
Table of Contents v
List of Figures vii
List of Tables xi
Nomenclature xii
Chapter 1 Introduction 1
1.1. Research Background and Objectives 1
1.2. Literature Review 5
1.2.1. Islanding Transition 5
1.2.2. Dynamic Frequency Support by Inverter Connected Energy Sources for Islanded Microgrids 10
1.2.3. Dynamic Frequency Support Capability of WECS and Resulting Torsional Oscillations 13
1.3. Research Contributions 17
1.4. Thesis Structure 18
Chapter 2 Adaptive Defense Plan Based Islanding Transition Scheme 20
2.1. Proposed Islanding Transition Scheme and Related Challenges 20
2.2. Problem Formulation and Solution Algorithm 26
2.2.1. Expected Cost of Arming and Executing the Defense Plan 28
2.2.2. Optimization Algorithm 29
2.2.3. Interaction of Optimization Engine and Simulator 30
2.3. Simulation Results 32
2.3.1. Application of the Proposed method 33
2.3.2. The sensitivity of the Expected Operation Cost to System Parameters 37
2.4. Summary 39
Chapter 3 Optimal Dynamic Frequency Support Service from Solar PV for Islanded Microgrid 42
3.1. Introduction 42
3.2. Problem formulation 45
3.2.1. Selection of VSM Parameters 46
3.2.2. Minimum De-loading of Solar PV Required to Avoid Frequency Instability in Islanded Microgrid 47
3.3. Performance evaluation 50
3.3.1. Simplified system and test results 50
3.3.2. Nonlinear dynamical model and test results 56
3.4. Optimal Switched Mode Control for VSM Based on State Feedback 61
3.5. Comparison of Solar PV De-loading Required to Avoid Frequency Instability 64
3.6. Summary 68
Chapter 4 Design of a Torsional Oscillation Damper to Minimize Fatigue Damage in WECS Providing Dynamic Frequency Support Service 70
4.1. Introduction 70
4.2. Type-4 Wind Energy Conversion System and Forced Torsional Oscillation 72
4.2.1. Wind Energy Conversion System Model 72
4.2.2. Torsional Oscillations Introduced by Droop Controller 75
4.3. Proposed Solution 80
4.4. Simulation Results and Comparison 85
4.5. Summary 91
Chapter 5 Conclusions and future work 92
5.1. Conclusions 92
5.2. Future work 95
References 97
Appendix A SQP Algorithm Implemented by Matlab® Adapted for Simulation Optimization 105
Appendix B Palmgren-Miner theory 107
Appendix C The S-N Curve of SAE 4130 Steel 108

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