本研究提出一個以分切合整數位控制為基礎的三相四線式電壓型換流器，此三相四線式換流器可達成再生能源交流供電系統，將直流電源轉換為相電壓127 Vrms 的三相交流弦波，供給不同種類的負載使用。研究中所提出之調變方式是以分切合整數位控制為基礎，克服傳統控制法所採用的abc至d-q座標轉換之限制，而穩壓策略則利用回授電壓、電流來估測負載電流，計算下一週期的開關責任比率，並提高對電壓進行補償的頻率，使電壓於切載後迅速回復至穩態；同時使用重複控制以準確地追蹤交流三相弦波電壓訊號，且能在三相不平衡負載或非線性負載之狀況下仍可穩定輸出三相交流弦波。
此換流器可分為電力級與控制級，電力級採用三相四線式架構，而控制級則採用微控制器Renesas RX62T 做為數位控制核心，實現每週期所推導出之開關責任比率，可避免使用到過多的類比電路，降低電路體積、重量及成本，並可提升可靠度與自由度。
本論文主要貢獻為採用分切合整控制法，重新推導控制法則，改善因區間轉換導致的電壓諧波失真，並將電感值變化納入控制法則推導，使換流器可允許寬廣的電感值變化，有效減少電感鐵芯的損失與尺寸，以及降低輸出電流漣波。另外，藉由估測負載電流及電壓的快速響應，使換流器能迅速反應負載變化，使波形迅速回到穩態。
最後，本研究模擬並實作一部3 kW單相換流器及一部10 kW三相四線式換流器，來證實本研究所提出之換流器其理論與控制策略的正確性及可行性。

This thsis presents a division-summation (D-Σ) digital control based three-phase four-wire inverter with capacitor-current compensation, and fast outer voltage loops. The inverter is adopted to uninterruptible power supply applications and can supply unbalanced, linear and rectified loads. With the proposed capacitor-current compensation scheme, the D-Σ digital control which was originally developed for current tracking can be adopted to generate sinusoidal voltage output. The adopted D-Σ digital control can accommodate wide filter inductance variation and achieve fast tracking response when including the fast outer voltage loops.
In the thsis, the control laws for the inverter are derived in detail first. In the design and implementation, the inverter inductances corresponding to various inductor currents are stored in a single-chip microcontroller for scheduling loop gain cycle by cycle, but the capacitor currents are estimated online to determine control laws (duty ratio) which are accompanied with fast outer voltage loops to improve voltage tracking accuracy.
The major contributions of this research can be summarized as follows. One is deriving the control law based on D-Σ digital control. It can take care of inductance variations, so that the inverter allows a wide inductance value change, effectively reduce the size and losses of the inductor core. The other one is estimating load current and using the fast outer voltage loop to achieve fast tracking action to load changes.
Simulated and experimental results measured from a 10 kW inverter have verified the analysis and discussion.

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