IES: Equalising airgap radial forces in direct drive generators

用于直驱式风力发电机组的永磁发电机通常具有较大的重量以保持刚度，而较小的气隙则可获得较高的磁通密度。然而，由于电磁吸力、重力、转速、吊舱运动和不平衡磁拉力等因素的影响，气隙在运行过程中会发生偏转。小气隙的缺点之一是定子和转子之间存在巨大的吸引力。如此大的吸力与变化的气隙间隙相结合一直是发电机刚度的主要挑战，该项目旨在开发一种实时运行时气隙内径向吸力的均衡策略，以实现较小的气隙间隙并降低这些大型发电机的材料成本。其目的是通过控制具有可变弱磁和增强磁通能力的离散三相定子“模块”来均衡电机不同部分的径向力。该项目的子目标是改进静磁控制策略，并将其推广到旋转机械。通过有限元分析的验证和实际样机的测试，该项目将开发一个附加的多变流器系统来实现均衡。

Permanent magnet generators for direct-drive wind turbines normally have massive weight to hold the stiffness and small airgap for higher flux density. However, the airgap would deflect during operation due to the effects like electromagnetic attraction force, gravitational pull, rotational velocity, nacelle motion and unbalanced magnetic pull etc. One of the downsides of small airgap clearance is the tremendous attraction force between stator and rotor. Such large magnitude attraction force combined with varying airgap clearance has always been a major challenge to the generator stiffness.The project intends to develop an equalization strategy of the radial attraction forces within the airgap during real-time operation, enabling smaller airgap clearances and reducing the material cost of these large generators. The intention is to equalize the radial forces in different parts of the machine by controlling discrete three-phase stator "modules" with variable flux-weakening and flux-strengthening capability. The sub-objectives of the project are to improve the magneto-static control strategy and extend it to the rotating machine. With validation using Finite Element Analysis and testing on real prototype, the project would then develop an attached multi-converter system to realize the equalization.