WPT using High Frequency Rotary Transformer for Separately Excited Synchronous Generator

This paper proposes a novel high frequency rotary transformer (HFRT) structure for a separately excited synchronous generator (SESG) used in offshore wind turbines. The SESG can eliminate and reduce rare earth permanent magnet (REPM) usage and provide a better performance in offshore wind turbine systems. However, the major drawback of such SESG is the necessity of brushes and slip rings to supply the field current, which increases the maintenance cost and operation reliability. To overcome these problems, an HFRT integrated with SiC Schottky diodes can be used to replace brushes and slip rings in the SESG. In contrast to conventional low-frequency rotary transformers, the HFRT working at over 100kHz operating frequency exhibits excellent performance of Wireless Power Transfer (WPT) efficiency and significant size reduction. The proposed HFRT features a high frequency magnetic ferrite for both the stationary part as the transformer primary and the rotating part as the transformer secondary and a large air gap, allowing safe operation at high rotational speeds. Hence, this novel rotary transformer can enable the adoption of a wound rotor synchronous generator.