- 學位論文
適用於低壓分散式能源之新型高升壓比轉換器建模及並聯控制
Modeling and Parallel Control of Novel High Step-Up Converters for Low-Voltage Distributed Energy Resources
摘要
近年來隨著油價高漲與環保議題受到關注，使得世界各國均積極推動替代能源分散式發電系統的開發。在小型分散式發電系統中，具有低電壓輸出特性的光伏電池與燃料電池，扮演著甚為重要的角色。本文之重點，即在針對此種低壓分散式能源提出具有高升壓比之高效率轉換器，以便將其提升至較高電壓以作為後級應用。本文首先針對高效率之目標，提出一新型多相升壓轉換器，其藉由順向式電路與倍壓電路的特性整合而得到低開關電壓應力、低導通週期、高升壓比與主動均流等優點。由於低開關電壓應力的電路特性，本文所提轉換器得以選用低額定電壓、低導通阻抗的功率元件以降低切換損失。而所提轉換器擁有的高升壓比能力則可避免開關工作週期過大、以有效地降低電路的導通損失、更有助於整體轉換效率的提升。基於相同的電路操作原理，所提新型轉換器的電路架構可拓展至三相、廣義n相以及另一種邱克型衍生電路。為了解本文所提新型轉換器的電路特性、本文除進行轉換器各工作模式的穩態電路分析之外，亦利用狀態空間平均技術推導得到直流、交流小訊號數學模型及其相對應的開路轉移函數，以供控制器補償與設計之用。再者，本文亦發展新型高升壓比轉換器的模組並聯系統，俾使所提轉換器更適用於具有低壓、大電流輸出特性的分散式能源。系統內各個高壓比轉換器模組除了保有原來的優良特性之外，整體系統的額定功率與可靠度亦能得到提升。針對此並聯系統，本文進一步提出並聯控制策略，以達到轉換器模組間負載電流之平均分擔、使系統在操作範圍內具有足夠的直流增益、增益交越頻率和相位餘裕。藉由所提轉換器本身優良的電路特性與並聯控制器的設計，本文所發展的高升壓比轉換器並聯系統能夠擁有較好的暫態響應及穩定性。最後，吾人依據理論分析的結果，實際製作一組規格為輸入電壓24V、輸出電壓200V、輸出功率400W的硬體電路用以驗證可行性。實測結果顯示所研製之轉換器並聯系統，其電能轉換效率於輕載至滿載的負載變化情況下皆保有93%以上，最高效率更能達到95.87%，而輸入電流漣波可降至50mA以下、模組間的平均電流誤差率低於5%。
並列摘要
With global energy shortage and strong environment movements, many countries are encouraging and promoting the development of distributed alternative energy sources. It is well-known that photovoltaic and fuel cells play an important role in the small-scale distributed generation systems. However, the output voltage of such new energies is rather low. For this reason, the main objective of this dissertation is therefore to develop a high efficiency high step-up converter as an interface for back-end applications. In this dissertation, a new multiphase converter by integrating a voltage-doubler and a forward-type circuit is first proposed for achieving high step-up and high efficiency objectives. Some topological extensions which include a particular three-phase, the generalized n-phase, and another Ćuk-type integrated circuit are also derived preserving the same advantages of the low switch voltage stress, lower duty ratio, and high voltage gain. Second, steady-state analyses are then made to show the merits of the proposed converter topologies. For further understanding the dynamic characteristic of the proposed forward-type integrated high step-up converter, steady-state and small-signal models of this converter are derived using state-space averaging technique. Open-loop transfer functions such as control-to-output voltage, audio susceptibility, output impedance and control-to-input current in the small-signal model are also derived to analyze the system performance in terms of DC gain, bandwidth, and stability. Third, for higher power applications, modules of high step-up converters are paralleled to further reduce the input and output ripples. Analysis and control of the interconnected converter are also made in the context. Finally, a 400W rating parallel converter prototype system is constructed for verifying the validity of the proposed converter. Experimental results show that the total input current ripple of the prototype system can be reduced to below 50mA, the differences among shared currents of the prototype system are within 5% of the averaged current over the load variation, and the highest efficiency of 95.87% can be achieved.