本研究針對20 kVA三相三線高低頻互補換流器進行深入探討，旨在降低開關元件選擇成本和難度，並解決三相之間的耦合問題。我們提出「解耦合直接數位控制」方法和漣波補償技術，有效減少低頻漣波對電網的影響。
根據研究結果顯示，在低頻換流器的切換頻率為6 kHz，功率分配為16 kVA，以及高頻換流器的切換頻率為48 kHz，功率分配為4 kVA的設定下，我們成功證明漣波補償技術對輸出電流的總諧波失真率有效控制。根據IEEE STD 519-2014的要求，我們的研究結果顯示總諧波失真率小於5％。同時，通過調整實功和虛功的輸出功率，成功實現了對輸出電流的有效控制，確保其符合電網功率因數為1的要求。
這一技術的應用潛力廣泛，尤其適用於太陽能發電系統併入電網的場景。我們的研究成果具有重要意義，能夠實現高性能且低成本的多功能轉換器。同時，我們的研究為未來龐大的能源需求，提供了解決方案，對於實現高功率轉換器，降低成本和提高效能具有重要價值。
總體來說，我們的研究成果對於推動電力轉換技術發展、促進可再生能源的可持續利用具有重要意義。未來研究和應用領域可以參考我們提出的「解耦合直接數位控制」方法和漣波補償技術。
本研究主要貢獻為：(1) 實作一部20 kVA三相三線高低頻互補併網型換流器；(2) 推導漣波補償公式，驗證漣波補償法之理論可行性；(3) 在高低頻互補換流器，實現實功和虛功的調整。

This research focuses on a 20 kVA three-phase three-wire hybrid frequency inverter, reducing the cost and difficulty associated with component selection, as well as addressing coupling issues among the three phases. We propose a decoupling direct digital control method with a division-summation process and ripple compensation techniques to effectively mitigate the impact of low-frequency ripple on the power grid.
The research results show that with a switching frequency of 6 kHz for the low-frequency inverter of 16 kVA, and a switching frequency of 48 kHz for the high-frequency inverter of 4 kVA, we successfully demonstrate the effective control of total harmonic distortion in the output current through ripple compensation techniques. According to the requirements of IEEE STD 519-2014, our research results illustrate that the total harmonic distortion is less than 5%, complying with the regulation. Furthermore, by adjusting the output real and reactive power, we successfully achieve effective control of the output current, ensuring the compliance with a power factor of unity.
This technology has wide-range applications, especially in the scenarios where solar power generation systems are connected to the grid. Our research findings are highly significant as they enable the realization of high-performance and cost-effective multifunctional inverters. Moreover, our research provides a solution for future high-power conversion requirements, with the important value in terms of cost reduction and efficiency improvement.
In summary, our research findings are of great significance in promoting the development of power conversion technology and facilitating the sustainable utilization of renewable energy. Future research and applications can refer to the proposed decoupling direct digital control method with a division-summation process and ripple compensation techniques.
The main contributions of this research are as follows: (1) implementation of a 20 kVA three-phase three-wire hybrid frequency grid-connected inverter; (2) derivation of ripple compensation formulas to verify the feasibility of ripple compensation methods; (3) realization of adjustment for real power and reactive power in the hybrid frequency inverter.

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