本研究研製一部適用於快速充/放電系統之三相四線半橋式轉換器，包含市電併聯、整流模式及穩壓功能，在市電併聯模式中，將直流電轉換成交流電饋入市電電網；在整流模式中，將市電轉換成直流電供給直流負載；在穩壓功能中，可以根據負載的需求，將直流鏈多餘的能量饋入市電或是提供給直流負載，反之，直流鏈欠缺的能量，則可以透過整流模式維持住直流鏈的電壓。控制級採用微處理器RX62T做為數位控制核心，實現所推導出的開關責任比率。
本論文會先說明元件的選擇，包括使用的功率模組、電感的設計。接著推導此架構在分切合整數位控制(D- 數位控制)下的控制法則、動作原理，並且模擬在此控制法下的市電併聯、整流模式；由於此架構使用的直流鏈為雙電容架構，所以也會確切地提出中性點電容平衡機制，並且驗證此機制的可行性，最後實作一台三相四線半橋式轉換器，以實測波形驗證模擬的結果、操作理論與可行性。
本研究的主要貢獻條例如下:第一點是使用了分切合整數位控制(D- 數位控制)，將交流電壓、電感感值納入考慮，因此可精準計算出當週期的工作責任比率，避免因為電感值的衰減，造成輸出電流的失真。第二點則是當此轉換器連接太陽能板時，不會有共模電壓的問題，因為此系統的第四線為接地迴路，準確地將下電容準位箝位在一半的直流鏈電壓。第三點為符合一機多功能的特性，不僅節省成本、體積，更能依照不同的需求執行不同的模式。

This thesis presents a high power bi-directional three-phase four-wire half bridge converter for charger/discharger systems, including grid-connection mode, rectification mode and dc-bus voltage regulation mode. In grid-connection mode, power is transferred from DC to AC and injected into the utility grid. In rectification mode, the utility power is transformed to DC with power factor correction. In dc-bus voltage regulation mode, the converter can inject power into the utility grid or supply DC loads when the bus voltage is higher than the setpoint. On the contrary, it will regulate the voltage by operating at rectification mode. A single-chip microcontroller Renesas RX62T is adopted to realize the control algorithm.
In the thesis, component selection, including IGBT modules and design of inductors is first presented. Next, control law and operation principle of the converter with division-summation (D- ) digital control are addressed. Additionally, the converter in grid-connection mode and rectification mode with the D- digital control is simulated. Due to the DC bus constructed with capacitors in series, capacitor voltage balancing algorithm is also proposed. Finally, the converter has been implemented and tested so as simulated and measured results can verify the control scheme and feasibility.
The major contributions of this research can be summarized as follows: First, the derived control law can accommodate grid voltage and inductance variations. The microcontroller RX62T is adopted to calculate the duty ratio exactly which can avoid output current distortion when inductance varies over a wide range. Secondly, the proposed operation does not yield high frequency common mode voltage so as it can be applied to PV inverter system. Thirdly, the converter has a property of multi-functions which can not only reduce production cost and volume, but can execute different operation modes according to load demands.

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