Performance calculation and improved model research of direct-drive permanent magnet generator based on FEM

In some control strategies of the direct-rive permanent magnet generator (DDPMG), the mathematics model is excessively simplified and some complex nonlinear characteristics, such as core saturation and cross-saturation, are generally neglected. To solve this problem, this paper utilizes the frozen element permeability method to compute the armature self- and mutual-inductance, permanent magnet d- and q-axis flux varying with d-axis and q-axis current, then an improved model is presented in which the core saturation and cross-saturation between d-axis and q-axis are considered effectively. Based on this model, the method for computing the performance of the generators is also proposed. Taking a 1.5-MW DDPMG as an example, the time-stepping finite element method (T-S FEM) is adopted to analyze the performance with no-load and loaded conditions, the results show a good agreement with the ones obtained by the improved model. Compared with the simplified model, it is demonstrated that the presented model has the high efficiency and reliability and can provide a good reference for optimization design of DDPMG and other PM motors.