具有高動態響應與雙向功率控制之單相直流-交流轉換器

A Single-phase DC-AC Converter with High Dynamic Response and Bi-directional Power Flow Control

葉昱廷(Yu-Ting Yeh)

指導教授 ： 黃明熙

國立臺北科技大學/電資學院/電機工程系研究所/碩士(2011年)

https://doi.org/10.6841/NTUT.2011.00271

摘要

本論文主要是研製具有雙方向功率流動之單相直流-交流轉換器，此轉換器為全橋架構並以雙極性脈寬調變方式，執行電網併網或對非線性負載提供暫態電流以降低電壓諧波成分。其中，對電網併網時其直流側連接具馬達與發電機雙重操作模式之電力轉換裝置，再依據直流鏈電壓進行直流與交流側之能量流動控制；當直流鏈電壓高於預設值時所連接之電力轉換裝置處於發電模式，因此將該電能轉換為交流與功率因數接近-1之方式將能量饋入電網；相對地，當直流鏈電壓低於預設值時，將交流電能轉換為固定電壓之直流對該電力轉換裝置供電並維持輸入之功率因數接近1。為有效提高輕載效率，本文研發具交流整數電流弦波併網之控制策略，當直流鏈功率較低時以直流鏈之電解電容作為儲能，停止全橋電路之功率晶體切換。
於高動態響應之應用時，可直接併接於交流電源供應器之輸出端或電網，經由已知的電壓波形命令與所偵測之實際電壓，在有限輸出電流下針對非線性負載所造成的電壓失真進行補償，可有效降低交流電源供應器之輸出電壓諧波成分以符合法規需求。
系統是以TI TMS320F28035作為控制核心，建構110V/1kW之全橋轉換器，所有控制策略皆由軟體撰寫以實現數位功率控制，並由所建平台驗證所提控制策略之有效性。

關鍵字

雙向直流-交流轉換器 ； 非線性負載 ； 功率因數修正

並列摘要

This paper is aimed to design a single-phase DC- AC converter with bi-directional power flow control. The converter is implemented by a full-bridge circuit with bipolar PWM control to act as grid-connected inverter or provide transient current to non-linear load to reduce AC voltage harmonics. A power device with both motoring and generating mode is connected to DC link and controls power flow between power device in DC-side and power grid in AC-side of the proposed DC-AC converter according to DC link voltage. The converter becomes DC-AC converter and sends the energy generated by the power device to electric grid when the DC-link voltage is higher than default voltage command. As the DC link voltage is less than default voltage command, the proposed converter withdraws power from electric grid to the power device. Meanwhile, the converter also provides near unity power factor control for electric grid in the bi-directional power flow control. In order to enhance light-load efficiency of the proposed converter when send the energy to electric grid, an integral-cycles injection of current is developed. When the generated power is less than a preset value, the energy will be stored in the electrolytic capacitance installed in the DC link and all the power switches of full-bridge circuit are turned off.
In the need of high dynamic response for AC power supply with line frequency transformer as isolated output, the AC-side of the proposed converter is connected to output of the line-frequency transformer. The converter co-works with the AC power supply and provides extra transient current, which is determined by the difference between AC voltage command and actual voltage of load, for the nonlinear loads to compensate the voltage distortion. Therefore, output voltage harmonics of the AC power supply can be reduced dramatically to meet the requirement of regulations.
A single-phase full-bridge DC-AC converter controlled by a DSP-TMS320F28035 with 110V/1 kW is constructed. To realize the digital power control, all the controlling strategies are written by software. Some experimental results are provided to show its efficiency.

並列關鍵字

Bidirectional DC-AC converter ； non-linear load ； single-phase power factor control

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