本文主要研製一高效率微型逆變器，其係一種併網型隔離式太陽能系統，可獨立將單片太陽能面板能量轉換至市電電網，解決傳統太陽能板模組之間的局部陰影遮蔽問題。系統主要針對雙級式電路架構進行研究，前級採用本文所提出之諧振式主動箝位順向/返馳式電路架構，負責轉換太陽能板能量至高壓，以提供後級逆變器足夠的電壓調節空間，其電路工作模式結合了順向式與返馳式轉換器之概念，提高了傳統返馳式轉換器在變壓器上的利用率，並且在其電路元件參數的設計上加入了額外的諧振概念，可有效提升電路開關之零電壓切換之範圍、次級側二極體有零電流截止的優點，只需更改元件的參數即可達成定頻脈波關渡調變操作，有著高效率且容易實現的電路特性。後級採用全橋式逆變器電路架構，配合單臂切換技術在正弦脈波寬度調變的優化，可減少在全橋式逆變器開關的切換損失，提升電路效率。本文以數位信號處理器為控制核心來實現太陽能最大功率追蹤與鎖相迴路控制，並達成電路性能改善與優化目的。
最後研製了一台250W微型逆變器來驗證本文所提架構的可行性，並且針對不同的負載應用，設計了獨立運轉與市電併聯兩種操作模式。經實驗測試，微型逆變器在不同的日照條件下，都能準確地追到最大功率點，並且前級諧振式主動箝位順向/返馳式轉換器最高效率可達97.2%，後級全橋式逆變器最高效率也有97.5%以上，整機系統效率在美國加州能源委員會規範下可達94.2%。

This dissertation presents a highly efficient micro-inverter, which is a grid-tied isolated micro-inverter for photovoltaic (PV) system that can individually extract the maximum solar power from each PV panel for transfer to the AC utility network and solve the problem of shadowing effects between conventional PV panels. This study focuses on the two-stage topology. The active-clamp forward/flyback converter topology is adopted for the front-end of the system, which converts energy from the PV panel to a higher voltage for the post-stage inverter, while providing enough room for modulation. Moreover, the topology combines the new design concepts with forward and flyback converters to increase the utilization of the flyback transformer, at the same time the resonant mechanism is added to the converter unit design, thus bringing the benefit of extending the MOSFET’s zero-voltage-switching (ZVS) region and having the secondary diodes achieve zero-current-switching (ZCS). Furthermore, the fixed frequency pulse-width modulation (PWM) can be achieved to control the converter by only changing the component value. It retains the advantages of high efficiency and easy to control. With the single-arm switching technique, the inverter efficiency can be increased dramatically due to the switching loss of particular switching arm is eliminated. The improvements and optimizations, along with maximum power point tracking (MPPT) and the phase-locked loop control are implemented with a digital signal processor (DSP).
Finally, a prototype system of the 250W micro-inverter system is implemented to verify the feasibility of the proposed scheme. Furthermore, standalone and grid-tied modes are designed for different applications. The experimental results show that the system is able to track the maximum power point in different irradiation conditions, also the peak efficiency of the active clamp forward/flyback and full bridge inverter can achieve 97.2% and 97.5% respectively, and the system total efficiency can reach 94.2% under the standard proposed by California energy commission (CEC).

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