台灣四面環海，東部海域經年有強大穩定之黑潮北上，西部海域亦有數個海流強勁之區域，攜帶巨大之能量，因此適於再生能源之海流發電，若能穩定供電，則可提供國內部分電力，解決目前所面臨之能源問題。然而海流流速並非全然穩定，因此在擷取海流能時，發電系統須具備調節或控制能力以達到高輸出效率，例如具有最大功率追蹤，穩定電壓、定功率等功能。
永磁發電機具高效率、高可靠度及高功率密度等優點，但也由於磁場來源為永久磁鐵之故，其發電機特性固定，例如其轉速與感應電壓之關係。因此，若欲達成最大功率追蹤，一般皆以發電機轉速控制加以達成。本論文藉由發電機可變繞組以改變之特性，探討可變發電機特性於發電系統之效能，結合流場環境、葉片特性及基本整流電路分析，藉由實作與實驗，驗證本論文之變結構發電機，可達成輸出特性如最大功率輸出、穩定功率等。

Taiwan, as an island, is surrounded by ocean and seas. In the sea area of the Pacific Ocean near Taiwan, the steady Kuroshio Current, carrying massive energy, flows toward north. In the west sea area, there are also a few sites that have strong currents. These areas are suitable for constructing renewable energy power systems that can effectively convert ocean or tidal current energy to electricity. This would provide great help in solving the more and more severe energy crisis. However, the flow rate of the currents is not always steady, and a regulable or controllable power conversion system should be considered to achieve high conversion rate when absorbing ocean energy. Therefore, the functions of maximum power tracking, steady voltage output or power, etc., can be accomplished.
Permanent-magnet (PM) generators have the advantages of high efficiency, reliability and power density. Due to the permanent magnets used, the characteristics of PM generators, such as the speed - induced voltage relationship is fixed. For peak power tracking, a speed controller is often applied to achieve the function. This thesis focuses on the characteristic regulation of permanent-magnet generators with winding changeover design to replace the speed controller. The turbine characteristic and a simple resistive load are considered to work with the designed regulable PM generator. Via experiments, the designed generator is capable of achieving the function of maximum power tracking, steady voltage output and steady power output.

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