基于动态重构混合互联变压器技术的双馈感应发电机风电系统故障穿越能力提升

The abnormal grid voltages, such as sags, swells, and harmonics caused by grid faults, seriously threaten the safe operation of a doubly-fed induction generator (DFIG)-based wind energy conversion system (WECS). To enhance the fault ride-through (FRT) capability of DFIG and improve the converter capacity utilization, this paper proposes a novel DFIG-based WECS using a dynamic reconfiguration hybrid interlinking transformer (DR-HIT) technique for performance improvement under grid faults. Multiple operating modes and flexible switching strategies were developed based on the analysis of the proposed topology and principles. The proposed DR-HIT approach smooths the DFIG ’s output power fluctuations through the cooperative control of the multifunctional converter (MFC) and grid-side converter (GSC) in shunt mode when the grid voltage is stable. Upon the occurrence of a grid voltage fault, the DR-HIT flexibly switches from shunt mode to series mode, maintaining the terminal voltage at a constant value. Additionally, once grid voltage recovers, the DR-HIT reverts flexibly to its shunt mode. Finally, simulations and experimental results demonstrate that the proposed scheme can achieve accurate control of the system and flexible switching between different modes.