Design Optimization of a Permanent-Magnet Flux-Switching Generator for Direct-Drive Wind Turbines

Abstract

Due to the increasing need for direct-drive wind turbines, a large number of papers are dedicated to the optimization of low-speed wind generators. A permanent-magnet flux-switching machine can be a valuable option to use in such applications. This paper describes the optimization procedure of a direct-drive flux-switching wind generator. The average losses, the required converter power, and the cost of permanents magnets were chosen as the optimization objectives. To reduce the calculation efforts during the optimization, a method to construct the substituting load profiles is proposed. Two-mode and three-mode substituting profiles were constructed on the basis of the nine-mode initial profile. The losses calculated under the two-mode, three-mode, and nine-mode profiles accurately coincided, which supported the use of the low-mode substituting profiles instead of the initial one. During the optimization, the average losses decreased by 30%, which corresponded to an increase in the average efficiency by almost 6%. The required converter power was decreased by 10%. The total active material mass, cogging torque, and torque ripple were also slightly decreased.

Optimal Design of Gearless Flux-Switching Generator with Ferrite Permanent Magnets

“…A novel approach has been proposed in Reference [7] to reduce the computational cost when optimizing AEP of the generator. It is suggested to use the equivalent load profiles consisting of a significantly reduced number of operating points (2 or 3) that substitute the initial load profile of the wind turbine.…”

“…The proposed approach of constructing the substituting load profiles making it possible to lower the computational cost was demonstrated using an example of an innovate type of wind generators with magnets on the stator [7]. The following criteria are used for its optimization: the average power losses in the generator, the cost of permanents magnets and the required AC-DC converter (active rectifier) power.…”

“…In Reference [7], design features of Flux-Switching Generator (FSG) with Nd-Fe-B magnets found out as a result of the optimization process are described. Among them there is the trapezoidal form of the stator teeth thinning near its base.…”

“…In this paper, the optimal design of the FSG with ferrite magnets based on the two-mode substituting load profile for a gearless wind generator is considered. It is shown that unlike FSG with rare-earth magnets [7], at making up the objective function to optimize FSG with ferrite magnets, the merit of the criterion of decreasing the reactive power must be significantly increased.…”

“…In Reference [7] the optimization of flux switching generator is considered with a reduced computational cost taking into account a large number of the operating points. However, features of the optimization process of FSG with ferrite magnets that are noticed in Reference [12] are not considered.…”