Design of 20 MW direct-drive permanent magnet synchronous generators for wind turbines based on constrained many-objective optimization

This study introduces a constrained many-objective optimization approach for the optimal design of 20 MW direct drive (DD) permanent magnet synchronous generators (PMSGs). Designing a high-performance, competitive DD-PMSG requires considering the generator's performance as well as its weight and material cost. Therefore, we focus on four main characteristics as our design objectives: (1) specific power (power per weight), (2) power-per-cost, (3) efficiency, and (4) power factor. To achieve this, we apply an advanced constrained nondominated sorting genetic algorithm III (NSGA-III), a many-objective optimization method utilizing evolutionary computation, capable of optimizing four or more objectives with constraints. Additionally, the electromagnetic finite element method is employed to evaluate the generator's characteristics. Through our proposed design process, we optimize three distinct 20 MW DD-PMSG configurations: a 320-pole/300-slot, a 350-pole/300-slot, and a 350-pole/336-slot topology. Following this optimization, we perform additional multiphysics simulations (covering electromagnetic, structural, overload, and thermal aspects) and control response simulations on four selected models from the Pareto-optimal solutions to validate their effectiveness as preliminary DD-PMSG designs. Finally, we conduct a comprehensive analysis of all simulation results.