New generator structure with the doubly fed induction machine for better fault ride through properties

由于替代能源的扩张，与电网的相互作用，特别是故障时的相互作用，成为一个重要的课题。由于风电场装机容量越来越大，在故障期间必须保持与电网的连接，并对电网进行支撑。由于已知发电机结构的结构和工作原理，双馈感应发电机的电压骤降会导致发电机钳位处的电压和电流过大，从而损坏变流器并对电网造成压力。在本项目中，必须分析一种新的发电机结构，以减小电网故障对双馈感应电机的影响。这是通过在电网和发电机之间引入交流斩波器来实现的。由于直接矩阵转换器与转子绕组相连，交流斩波器的硬件工作量最小。这种新型发电机结构的控制是应用方案的主要部分。在适当控制交流斩波和矩阵变流器的情况下，在电网故障时必须将定子电压控制到参考值，而不受电网电压的影响。交流斩波器的换相策略也是本课题需要研究的一个突出课题。在理论工作的同时，还进行了仿真分析和变流器样机的搭建。最后，用新的发电机结构和变流器样机在试验台上进行了测量，验证了理论结果的正确性。

Due to the expansion of alternative energy the interactions with the grid especially during faults become an important topic. Caused by the growing installed power of wind plants, it is necessary to keep them connected with the grid during faults and support the grid. Attributable to the configuration and the function principle of the known generator structure with the doubly fed induction generator voltage dips cause excessive voltage and current increase at the generator clamps which may destroy the converter and stress the grid. In this project a new generator structure have to be analysed which reduces the impact of grid fault on the doubly fed induction machine. This is achieved by introducing an ac-chopper between grid and generator. With the direct matrix converter connected with the rotor windings the ac-chopper effects minimal hardware effort. The control of this new generator structure is the major part of the applied proposal. With an appropriate control of ac-chopper and matrix converter the stator voltage have to be controlled to the reference value during grid faults and should not be influenced by the grid voltage. Commutation strategies for the ac-chopper are also an outstanding subject which has to be treated in this project. The theoretical work is accompanied by simulative analyses and the construction of a converter prototype. Finally, the theoretical results haveto be approved by measurements at a machine test bench with the new generator structure and the converter prototype.