Optimal design and analysis simulation of an outer rotor hybrid excited generator for wind energy conversion systems

Selecting effective and applicatory generators for wind energy conversion systems (WECSs) undoubtedly plays a crucial role in the proficiency of wind energy exploitation. This paper demonstrates the feasibility of employing outer rotor hybrid excited generator (ORHEG) in WECSs. The main objective of this paper is to design and optimize an outer rotor generator with 24/16 doubly salient poles exciting with two different sources. While a permanent magnet, as the main excitation, is in charge of producing a magnetic field in the generator, a DC winding, as a supplementary excitation, has the duty of strengthening or weakening the flux in the air gap. Although using hybrid excitation can create somewhat difficulty for the generator implementation, this can make the output voltage be much more controllable in the wide range of speed variations. As a case study, for designing such a generator, output power and speed of 1 kW and 200 rpm are considered as the nominal generator values respectively. Besides of completely discussing of design requirements, the generator designing is optimized using Genetic Algorithm (GA) method. In this optimization, efficiency and power density are selected as the objective functions. This fitness function includes two variables whereby an increase in either of them leads to more improvement in one of the objective functions than in the other. Finally, the two dimensional Finite Element Method (2D-FEM) is employed for verifying the expected merits of designing and optimization.