DSP全數位快速響應單相功率因數修正器之研製

Abstract

本論文研製一個以單晶片數位信號處理器(DSP)為基礎的全數位單相功率因數修正器，本文所提出的控制架構，在保持單一功率因數的情況下，仍然具有快速的動態響應與零誤差的穩態響應，能夠避免輸出漣波電壓所造成的電流失真。控制架構採用多迴路控制方式，包含電流內迴路及電壓外迴路。在電流迴路方面，藉由預測電感電流之變化，產生所需要之PWM控制信號。此外，提出了一個輔助的前饋補償控制器，以提高內迴路頻寬。在電壓迴路方面，以線電壓頻率的雙倍頻取樣頻率，避免因輸出電壓雙倍頻漣波所造成的誤差；當輸出電壓回授不再含有雙倍頻電壓漣波時，將可提高電壓迴路的頻寬而不致造成電流失真。傳統的類比式控制方法，則難以解決此一問題。這種控制方法，具有簡單易於實現的優點，與傳統類比控制比較，不僅在動態響應方面得到顯著的改善，在其他非線性動態負載的控制效果、穩態響應、乃至於線電壓鎖相同步控制均可達到良好的控制效果。本文採用PSIM進行所提出的PFC數位控制方法的電腦模擬，並以單晶片DSP (TMS320F240)實現所提出的控制法則，最後並以一個2kVA的升壓型PFC功率級完成系統整合測試，模擬與實驗均一致的顯示本文所提出控制方法的效果與優越性。本文所研製的數位式單相功因修正器具有高功率因數、快速動態響應、零穩態誤差、高效率(可以較低的開關頻率達到相同的功率因數)、寬廣的線電壓(30%)與頻率(5%)波動控制範圍、自動鎖相同步控制等優點。

This thesis presents the design and implementation of a DSP-based fully digital-controlled single-phase power-factor converter with fast dynamic response. The proposed control scheme can provide a fast dynamic response under large line and load variations at the same time maintains a unit power factor, lower current harmonic distortion, and high efficiency. The proposed fast PFC controller consists of an inner current-loop controller and an outer voltage-loop controller. The current-loop controller adopts predicted current control with an auxiliary feed-forward controller. The voltage-loop controller employs a double line frequency sampler to remove the line frequency ripples from the measured output voltage. By using the synchronized sampling scheme, the output voltage feedback contains no ripple components and we can improve the voltage loop bandwidth compared with the conventional approaches. The control algorithm, which is simple and fast, provides a significant improvement in system dynamic responses compared to conventional analog control techniques. The proposed control scheme has been verified by using computer simulation with PSIM and implemented using a single-chip DSP (TMS320F240) from Texas Instruments. Experimental verification has been carried out on a 2 kVA PFC converter using DSP controller. Experimental results show the feasibility and superiority of the proposed digital fast response PFC control scheme.