The increasing participation of wind turbines based on doubly fed induction generator (DFIG) in the power system around the world is motivating the investigation of novel strategies to enhance the reliability of DFIG and power system connection. This paper proposes the use of a new hybrid multilevel back-to-back converter on DFIG wind turbine to improve its fault ride-through capability and power system transient stability. The proposed topology is built adding single-phase full-bridge inverters in series with each phase of traditional three-phase inverter. This converter is able to generate higher voltages in rotor circuit whenever it is required, which can effectively protect power converter and at the same time contribute with grid transient performance. Simulation results, using PSCAD ® , are presented for a 2 MW DFIG machine submitted to symmetrical faults in single machine—infinite bus and three-bus system. Results show that the proposal is effective as a protection and works well as an alternative to traditional solutions, limiting currents and maintaining power control during voltage dips. It is also effective in contribution with the improvement of transient stability margin by the possibility of reactive power injection.

中文翻译：

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一种新型混合多电平转换器，用于基于 DFIG 的风力涡轮机故障穿越和瞬态稳定性增强

基于双馈感应发电机 (DFIG) 的风力涡轮机越来越多地参与到世界各地的电力系统中，这推动了对新策略的研究，以提高双馈感应发电机和电力系统连接的可靠性。本文提出在双馈风力发电机上使用一种新型混合多电平背靠背变流器来提高其故障穿越能力和电力系统暂态稳定性。所提出的拓扑结构是在传统三相逆变器的每一相上添加单相全桥逆变器。该转换器能够在需要时在转子电路中产生更高的电压，可以有效保护功率转换器，同时有助于电网瞬态性能。仿真结果，使用 PSCAD®，为 2 MW 双馈电机提交单机对称故障 - 无限母线和三母线系统。结果表明，该提议作为一种有效的保护措施，可以很好地替代传统解决方案，在电压骤降期间限制电流并保持功率控制。通过注入无功功率的可能性，它还有助于提高暂态稳定裕度。