Loss Estimation of Brushless Doubly-Fed Generator With Hybrid Rotor Considering Multiple Influence Factors

The brushless doubly fed generator (BDFG) has been a research focus of wind power generation due to its inherent promising features. Although it is important to consider the effect of losses on the design and analysis of the BDFG, there are a few related comprehensive studies. Moreover, a hybrid rotor is studied to improve the performance of BDFG, which brings greater challenges to the loss calculation. The aim of this paper is to propose the accuracy calculation methods of core loss and copper loss for the studied BDFG with hybrid rotor. The core loss calculation model which taken the influence of harmonics, alternating magnetization, rotating magnetization and two-dimensional magnetic property of material into account is proposed based on the analysis of the magnetic field characteristics. In order to calculate the copper loss considering the skin effect, the inductive current of the assisted cage bars which is difficult to obtain directly is calculated. The accuracy and correctness of the proposed approaches and models are validated by experimental results from a 25kW prototype BDFG with hybrid rotor. In addition, the proposed loss calculation method, especially the core loss calculation model, is also applicable to BDFG with other rotor structure which is operated by the magnetic field modulation mechanism.