本篇文章提供一個在分散式系統(DGS)中的實功控制方法來解決傳統上的垂
降控制(droop control)所造成的穩定度問題。垂降控制已經廣泛的被使用在分散式不斷電系統中，為分散式系統提供了適當的功率分配法則且無須任何通訊系統來連結各個電能轉換器，但是其快速地暫態響應對系統的穩定度會造成威脅。為了改善此問題，本篇文章提出一個虛擬同步機(VSM)的實功控制方法。這個方法可以讓電能轉換器模擬真實同步機運轉時的動態響應，而同步機的轉動慣量可以改善穩定度的問題。文章內包含詳細的理論描述和實驗驗證來證實此方法的有效性。

This dissertation presents an active power control method for distribute generation system(DGS) to resolve the stability problem of conventional P−f droop control. P−f droop control has been widely discussed in the application of distributed uninterrupted power supplies (UPS) systems. It can make appropriate power sharing of DGS without any communication. But the fast transient response of the control method causes some stability problem. To improve the problem, the virtual synchronous machine-based power control is presented in these paper. These method can make converters to emulate the dynamic response of synchronous machine(SM). The inertia of SM would improve stability of power system. Many detailed description and experiment are presented in the dissertation to confirm the effectiveness of proposed method.

1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.3 Dissertation organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
2 Literature review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
2.1 Autonomous power sharing control . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.2 P − ! droop control and Q − V droop control . . . . . . . . . . . . . . . . . . . . 4
2.3 Power sharing design of P − f droop control . . . . . . . . . . . . . . . . . . . . 6
2.4 Frequency restoration of P − f droop control . . . . . . . . . . . . . . . . . . . . 7
2.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3 Virtual Synchronous Machine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.2 Virtual Synchronous Machine-based power control . . . . . . . . . . . . . . . . . 10
3.2.1 Small signal model of swing equation . . . . . . . . . . . . . . . . . . . . 12
3.2.2 Normalization of swing equation . . . . . . . . . . . . . . . . . . . . . . . 15
3.2.3 SM v.s. VSM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3 The relation between P − f droop and VSM-based power control . . . . . . . . . 20
4 Experiment Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.1 Implement virtual synchronous machine in a 2-level converter . . . . . . . . . . . 23
4.2 Control block diagram of main controller . . . . . . . . . . . . . . . . . . . . . . 23
4.3 P − f power droop control v.s. VSM-based power control . . . . . . . . . . . . . 27
4.3.1 Case 1 : P − f power droop control . . . . . . . . . . . . . . . . . . . . . 27
4.3.2 Case 2 : VSM-based power droop control . . . . . . . . . . . . . . . . . . 27
4.3.3 Case 3 : P − f power droop control with low pass filter . . . . . . . . . . 28
4.3.4 VSM : The inertia and damping factor test . . . . . . . . . . . . . . . . . 29
4.4 Parallel connection and power sharing issue . . . . . . . . . . . . . . . . . . . . . 30
4.4.1 Case 1 : P − f power droop control is used in these two converters . . . . 31
4.4.2 Case 2 : VSM-based power droop control is used in these two converters . 32
4.4.3 Case 3 : different control methods are used in these two converters . . . . . 34
4.4.4 Case 4 : Different power rating test . . . . . . . . . . . . . . . . . . . . . 35
4.5 Frequency Restoration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
4.5.1 Case 1 : The same power sharing test . . . . . . . . . . . . . . . . . . . . 37
4.5.2 Case 2 : Different power sharing test . . . . . . . . . . . . . . . . . . . . . 38
5 Conclusion and future work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
5.1 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
5.2 Future work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
APPENDICES
REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

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