臺灣博碩士論文加值系統

本論文提出一種應用於電流源型雙主動橋式直流轉換器之變頻式二次側超前關斷調變方法，目的在於解決轉換器輕載條件下產生的環流電流與責任周期丟失現象。傳統的二次側調變鉗位方法能在不外加鉗位電路或RCD緩衝器的情況下，使轉換器在低壓側和高壓側分別達成自然換向和零電壓導通，因此得到很多關注。然而，此方法會在輕載下分別造成很大的環流電流和占空比丟失現象。
為了避免上述所提到的缺點，本文首先提出一種固定頻率下的二次側超前關斷調變方法。與傳統的二次側調變鉗位方法相比，通過在低壓側與高壓側的驅動信號間產生一個時間差，此方法可以將環流電流降低到一半並且完全消除占空比丟失現象。
基於定頻操作的二次側超前關斷調變方法，本文又進一步提出一種變頻式二次側超前關斷調變方法，可以將輕載下的環流電流減小。除了解決傳統二次側調變鉗位方法中的主要缺陷，此方法也將傳統方法的優點全部保留。本論文將會詳細介紹並說明變頻式二次側超前關斷調變方法的操作原理與數學公式推導，並且將會藉由電腦模擬以及一台330W原型機的實驗結果來驗證此方法的可行性與表現。

This paper proposes a variable-frequency secondary leading-off-modulation (VF-SLOM) method for the current-fed dual active bridge (CF-DAB) converters to solve the high circulating current and duty loss issues at light load. Owing to the achievement of natural commutation without active clamp or RCD snubber circuits, the conventional secondary-modulation-based clamping (SMBC) method has received a lot of attention. However, two main drawbacks—high circulating current and duty loss phenomenon—were not expected.
In order to solve the aforementioned drawbacks in SMBC, a Secondary Leading-Off-Modulation (SLOM) method is first proposed. With a time gap between gate signals of the low voltage (LV) side and high voltage (HV) side, the SLOM method decreases the circulating current to half and eliminates the duty loss phenomenon in SMBC method.
Based on the SLOM method, the VF-SLOM method with variable switching frequency can further decrease the circulating current further. Besides solving the drawbacks in SMBC method, the proposed VF-SLOM method retains the advantages of SMBC such as natural commutation at all LV switches and zero voltage switching (ZVS) turn-on at all HV switches. Details of the operation principle and the mathematical derivations are provided in this thesis. The simulations and experimental results of a 330W prototype circuit are also presented to validate the performance of the proposed VF-SLOM method.

誌謝 i
中文摘要 ii
ABSTRACT iii
CONTENTS iv
LIST OF FIGURES vi
LIST OF TABLES viii
Chapter 1 Introduction 1
1.1 Background 1
1.2 Paper Review and Motive 2
1.3 Outline 4
Chapter 2 CF-DAB DC/DC Converter 6
2.1 Circuit Topology 6
2.2 Operation Mode of SMBC 7
2.3 Drawbacks of SMBC method 12
2.3.1 Duty Loss 13
2.3.2 Peak Current and Circulating Current 14
Chapter 3 SLOM Method 15
3.1 Operation Principle 15
3.2 Mathematical Derivation 17
3.3 Comparison between SMBC and SLOM 19
3.3.1 Duty Loss 19
3.3.2 Peak Current and Circulating Current 20
3.3.3 RMS Current 22
Chapter 4 VF-SLOM Method 25
4.1 Derivation of Switching Frequency 25
4.2 Operation Principle of VF-SLOM 27
4.3 Improvements over SLOM 29
4.3.1 Peak and Circulating Current 29
4.3.2 RMS Current 30
Chapter 5 Computer Simulation 32
5.1 Specification of CF-DAB 32
5.2 Simulation Scenarios 33
5.3 Simulation Results 34
5.3.1 Full Load (k=1) 35
5.3.2 Half Load (k=0.5) 36
5.3.3 Light Load (k=0.2) 40
Chapter 6 Experimental Results 45
6.1 Circuit Diagram and Prototype 45
6.2 Boost Mode Operation 46
6.2.1 Full Load 47
6.2.2 Half Load 48
6.2.3 Transient Results 52
6.2.4 Efficiency 53
6.3 Buck Mode Operation 54
Chapter 7 Conclusion and Future Research 56
7.1 Summary and Major Contributions 56
7.2 Suggestions for Future Research 57
REFERENCES 58

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