具高功因與高頻隔離之單級三相交流／直流轉換器研究

Designing a Single-Stage High Frequency Isolated Three-Phase AC/DC Rectifier with High Power Fact Correction Function

在工業製造過程中，常需使用到具電源隔離功能的高的直流電流量，傳統的方法為了提高直流電流量，通常都採用三相電源系統再加上低頻變壓器隔離，而低頻變壓器二次側則用三相全橋式整流電路。此種方式雖具有低成本及控制簡單，可用於大功率之優點，但缺點為輸出直流電壓漣波大，且輸入三相電流諧波成分大，因此降低整體電路的效率。本文主要為研製具高功因特性之三相單級高頻隔離型交流–直流轉換器，此架構與同一控制方式下之單相交流–直流器相較，則三相架構可提高轉換功率、降低直流輸出電壓漣波等優點，更適合運用於低壓大電流。藉由市電三相四線式Y 接輸入，每相皆為獨立高頻隔離變壓器，一次側開關為全橋式切換，二次側為三相全橋式整流，再經由L-C 濾波電路以得到直流電壓源。在本研究中，一個簡單的相移PWM 方法被提出，由於這種方法只使用一個載波，載波實施方式容易，故非常容易以類比電路件或微控制器實現。本研究以12 脈波整流系統，輸出為直流24 V/1 kW的實驗結果來證明所提出之架構與切換方式之可行性。

A high capacity of a direct current source is essential in manyindustrial processes; however, a conventional diode or SCR phase controlrectifier applied to power system often results in high harmonic currentsand low power factor, thus it will not meet the quality requirements of a modern power system. This paper presents a simpler topology of highfrequency AC-DC converter especially for low voltage high currentindustrial applications. In the proposed topology, a rectifier module and lowfrequency L-C filter in the primary stage is replaced by a high-frequencyinsulated based AC-DC converter, which dramatically reduces bulky andheavy low-frequency transformers. The proposed control algorithm is basedon phase shift control, which employs constant switching frequency phaseshift modulation. It may be implemented by analog circuit, where the costis further reduced. The proposed idea is supported by experimentalresults from a three-phase 12-pulse rectifier of 24 V, about 1 kW rating.The important features observed in the proposed converter include highinput power factor, simple control scheme using an analog control, and lowvoltage ripple output.