Analytical Approach to Maximum Power Tracking and Loss Minimization of a Doubly-Fed Induction Generator

本論文主要目的在研究雙饋式感應發電機的最大功率追蹤及損失之最小化，以達到發電機的最大功率輸出。在不忽略定子端電阻的前提下，本論文分別推導出兩種穩態等效電路(考慮鐵損及不考慮鐵損)電流控制命令的解析法。 首先，針對定子磁通導向控制進行分析，說明如何透過定子磁通導向達到解耦合控制，其次說明風機如何在不同風速的情況下達到最大功率追蹤，最後進行數學公式的推導，分別推導出考慮鐵損與否的情況下，讓風機運轉在最大功率追蹤點並達到損失之最小化的電流命令解析法。此外，進一步推導定子端功率、轉子端功率、銅損、鐵損及風機輸出功率的公式。最後，以一小型發電機為例，印證所推導的公式。 結果呈現方面，分成三個部分。第一部分在同時不考慮鐵損的情況下，本論文將推導出的解析法與先前文獻的搜尋法進行比較；第二部分則在皆為解析法的前提下，將考慮鐵損與否兩種情況下的解析法進行比較；第三部分則針對不同的定子端電壓，比較發電機運轉在次同步及超同步運轉點下實功與虛功輸出的差異。Maximum power tracking and loss minimization of a doubly-fed induction generator (DFIG) are studied in this thesis to yield maximum output power. Analytical solutions for rotor currents are derived for steady-state equivalent circuits with and without core loss. Stator resistance is considered in all the derivations. Stator-flux orientated control is first introduced to achieve decoupled real and reactive power control. Then the way to achieve maximum power tracking under different wind speeds is described. Finally, analytical solutions for rotor currents to achieve both maximum power tracking and minimum loss are derived. Furthermore, detailed expressions for stator power, rotor power, copper loss, core loss and generator output power are derived. Finally, with a small generator as an example, computational results are given to demonstrate the effectiveness of theoretical analysis. Results for a DFIG without core loss from the proposed analytical approach and those from exhaustic search method in a former study are first compared. Then the results from the analytical approach with and without considering core loss are compared. Finally, the real and reactive output powers under different stator voltage are presented