本研究主要在於研製由分切合整數位控制法所實現的三相三線模組化多階層雙向轉換器，並利用此轉換器參與直流微電網整合系統研究，與再生能源發電、儲能、電力品質提升以及保護協調等子系統共同整合測試，實現直流微電網的能源轉換系統。
分切合整數位控制法的特點，在於可以將電感值隨著電流大小變化的特性納入參數考量，在相同的電流下與傳統控制法相比，分切合整控制法可以得到較小的電感體積。藉由此控制法，微控制器可以精準的算出相應的責任比率，再經由交錯式脈衝寬度調變方法，以達到降低電流漣波的效果。本文的整合型研究，其目標在於先以低額定功率的系統驗證所開發的核心技術，再與各子系統進行整合測試，最後提出改善方案，建立開發平台，為下個階段的中壓、大功率電網系統佈局。
本研究的主要貢獻包含以下幾點。第一點為採用分切合整數位控制法，不僅可以將電感值變化納入考量，也可以藉由此控制法得到模組電容電壓表示式，再藉由此表示式計算出可以有效抑制電容電壓漣波的諧波補償電流。第二點為採用多階層架構實現高壓直流傳輸，利用模組串接，可以有效的提高直流鏈電壓，如此一來在遠距離的直流微電網傳輸過程中，可以選擇較細的傳輸導線。第三點為將模組化多階層轉換器、充放電系統、電子斷路器系統以及靜態同步補償系統整合為一個直流微電網能源轉換系統，在市電、太陽能源以及電池儲能系統三種電能之間完成穩定且有效率的能源配置。

This research designs and implements three-phase three-wire modular multilevel converter (MMC) based on division-summation (D-Σ) digital control law. This converter is integrated into a grid-connected high-power system. The integrated system includes renewable power generation, energy storage, power quality improvement and protection mechanism, achieving a DC-microgrid converter system.
The D-Σ digital control law can take into account inductance variation with its current. Compared with traditional control approaches, the D-Σ digital control method can adopt a smaller core under the same current value. The used microcontroller (RX63T) can precisely achieve current tracking control which through interleaved PWM can reduce current ripples. The integrated research is to design and implement scale-down power modules, and then focus on integration test. Finally, it is prepared for a test with medium-voltage and high-power rating.
There are several major contributions in this research. The first one is to use D-Σ digital control law. It can not only consider inductance variation in current tracking, but also derive cell voltage expression from the control law. We can use the voltage expression to calculate the compensation current which can reduce cell voltage ripple. Secondly, we adopt a MMC to improve high voltage transmission. Thinner wires can be selected for long-distance transmission. Thirdly, MMC, Charger/Discharger, MPPT, Electronic Breaker and STATCOM are integrated to the DC-microgrid conversion system, achieving a stable and efficient energy distribution among grid, solar and battery storage systems.

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