近年來微電網系統是電力產業研發的重點之一，集結再生能源端的直流微電網系統，往往需透過備載能源及儲能設備來解決再生能源的不穩定性。另一方面，併聯於直流微電網的交流電網亦是一種選擇。本文旨在探討當一直流微電網系統併聯交流電網時，藉由控制界接的電能轉換器使功率能雙向傳輸。當再生能源不足時，透過交流電網端來供給直流端的負載需求。另一方面，當再生能源供過於求，也可透過電能轉換器將電能饋入交流電網端。關於電路架構，本文首先探討具有可逆性的三相橋式電路，以正弦式脈波寬度調變來控制開關之導通率。再來探討利用同步軸鎖相迴路，使轉換器能與交流電網併聯。實驗證明當直流鏈電壓過高時，透過變流模式將多餘的能量傳送至交流電網端;在直流鏈電壓過低時，則透過整流模式讓交流電網對直流鏈充電，使得交流電網端與直流電網端達到供需平衡。

In recent years, micro-grid system is one of the key developing roadmap of electric power industry. To solve the unstable supply problem from renewable energy, the DC micro-grid used to be supplemented by several backup resources, like fuel cell and battery. If the DC micro-grid is interconnected with AC grid, the AC side can serve as another backup option. This thesis is to study the control of power flow between DC micro-grid and AC grid using a bidirectional power converter. As renewable energy shortage takes place at DC side, the deficit energy can be supplied from AC grid. On the other hand, as decreased DC loading or excessive renewable energy takes place at the DC side, the redundant energy can be transferred to AC grid. This thesis first describes a three-phase bridge topology controlled by Sinusoidal Pulse-width Modulation. Following that, a synchronous reference frame phase-lock loop method for AC grid connection is illustrated. The proposed three-phase power converter is operated between inverter mode and rectifier mode. As voltage of DC bus is higher than the preset threshold, the power converter effectively operates at inverter mode to transfer excess energy from DC grid to AC grid, and vice versa as the power converter is operating at rectifier mode. The experiment shows that power balance between DC micro-grid and AC grid is achieved by controlling bi-directional power flow.

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