- 學位論文
基於阻抗分析之高效率奈米衛星電力次系統控制評估與性能研究
Controls Assessment and Performance Evaluation of a High-Efficiency Nanosatellite Electrical Power System Based on Impedance Analysis
摘要
小型衛星最初設計目的是為了系統工程教育，因低成本與小尺寸的優勢使它非常設合用於教育目的以外的衛星任務。近年來它也被用來執行科學探勘任務。雖然它體積較小，仍具備大型微星的子系統架構，例如姿態控制子系統、通訊子系統，以及小型電力系統。如何在小型體積內實現提供高效率及穩定的電力成為當今研究的一項課題。 在本次研究中是以一種使用四個降壓轉換器的電路拓樸結構為研究對象，該拓樸結構使用兩個太陽能板作為輸入以及一個可充電電池作為備用電源。雖然該結構能夠滿足太空運作電力需求，但在不同的轉換器設置下將可能導致系統的不穩定或是原本設計單級轉換器系統動態響應表現。本研究分析該電力系統中串級直流轉換器的阻抗，並基於Middlebrook 博士所提出的 Extra Element Theorem，針對各轉換器系統參數的影響進行分析。 本研究先針對兩級降壓轉換器架構進行各轉換器系統動態響應轉移函數進行探討，以及前級輸出阻抗與後級輸入阻抗的交疊如何影響系統，同時也驗證了用於輸入濾波器與轉換器上的準則也適用於兩級轉換器。 最後，也為奈米衛星的電力系統提供了簡潔的設計指南，此外為了方便和簡化阻抗分析的過程，也開發了一款MATLAB GUI工具，並透過模擬與實驗驗證結果，此研究結果將適用於未來小型多級直流轉換器的設計參考。
並列摘要
A CubeSat is a small satellite originally designed for systems engineering education. Due to its low cost and small size it is ideal for satellite missions related to educational purposes. In recent years, it has also become an observation platform for space science missions. Despite its small size, there are multiple subsystems inside such as an Attitude Determination Communication Subsystem (ADCS), Communications Subsystem, and other subsystems. One of the critical subsystems is the electrical power system (EPS). One challenge is how to maximize the power efficiency and deliver stable power within a small volume. In this research, a dc-dc converter topology using four buck converters is proposed to be used with an EPS with two solar panels as the input source along with a rechargeable battery. Even if the converters are design individually to meet the space mission requirements, mismatched impedance of each converter under different operation modes can potentially cause instabilities in the system. Both the source converter output impedance and load converter input impedance, which dictate the interaction of the converters, are analyzed in this research. The design of a two-stage buck converter system is discussed in this paper. A detailed analysis of how an improper design of the source converter can negatively affect the whole system performance is given. Middlebrook's extra element theorem is used to demonstrate how each standalone converter transfer functions are affected due to interaction factor or impedance overlap. It is shown that the Middlebrook's criteria can be used to minimize filter interaction of the converters in our system. The results of the two-stage converter system with a single load converter extend to the a two parallel load converters case. Finally, straight forward design guidelines are provided for the nanosatellite EPS design. In addition, to facilitate and the simplify impedance analysis process, a MATLAB GUI tool is developed and the results are verified by simulation and experimental results. The analysis provided in this thesis is also applicable to general subsystem interaction analysis of similar nanogrid systems.