具功率控制與低電壓穿越之三相市電併聯換流器研製

Abstract

本文旨在研製一組具網路通訊實虛功控制與低電壓穿越功能之三相市電併聯換流器。利用三相三線式電壓源型換流器配合直交軸轉換控制，輸出三相交流電流進入市電，達到控制輸出實虛功之目的。並研製一組EIA-485網路通訊介面，讓使用者可以由電腦端之人機介面透過網路遠端，對市電併聯換流器下達實虛功命令。另外，為達成低電壓穿越功能，本論文提出一種不需透過相位鎖定迴路，即可精準且快速判別市電電壓量值的方法，達到極低電壓降之情境下，市電併聯換流器皆可達到持續與系統併接的低電壓穿越功能。並且於市電電壓回復時，能保持正確同步併網運作。最後，以實測波形來驗證本文所提出的具網路通訊實虛功控制與低電壓穿越功能之三相市電併聯換流器的特性與功能。 關鍵詞：網路通訊、虛功、低電壓穿越、市電併聯、三相換流器、EIA-485、電壓量值判別

A three-phase grid-connected inverter, which is capable of controlling real/reactive power via internet and achieving low-voltage ride through (LVRT) function, is proposed in this thesis. By adopting the strategy of direct quadrature transformation to control the three-phase current injected into the utility line, active/reactive power control can be achieved successfully by using the three-phase three-wire voltage source inverter. An EIA-485 communication interface is also developed for users to give the active/reactive power commend via internet. Besides, in order to achieve the LVRT function, a new method is proposed to calculate the accurate grid voltage without using the conventional phase-locked loop (PLL) so that the three-phase inverter can remain connecting to the utility line during the most severe voltage drop scenario. The proposed strategy also allows the three-phase inverter to maintain grid-connected operation during the voltage recovery period. Finally, experimental results measured from a prototype circuit are presented to verify the performances of the proposed three-phase grid-connected inverter with real/reactive power and LVRT capability.

Keywords：Communication through internet、Reactive power、LVRT(Low-Voltage Ride through)、Grid-connected、Three-phase inverter、EIA-485、Grid voltage calculation