Direct drive generators applied to large wind turbines present some problems, such as very heavy and expensive price. The use of magnetic bearings has a possibility to reduce the weight of the direct drive generator. The control system for such magnetic bearings is considered.
In the beginning, the thesis discusses the problems of direct drive generators in large wind turbines, introduces a hybrid concept of active magnetic bearings, gives a demonstrator of magnetic bearings used in this project, and presents a basic control system of active magnetic bearings.
For the purpose of support such magnetic bearings in wind turbines, this thesis gives a complete control system. This control system includes electrical circuits and decentralized control method. The implementation of the electrical circuits is distributed into two PCBs. The decentralized control method is designed with six PID controllers.
Finally, in order to improve the stability of the system, the H-infinity control method is suggested to magnetic bearing system in wind turbine applications.