Design optimization and comparison of large direct-drive permanent magnet wind generator systems

The objective of this paper is to investigate the most cost-effective individual direct-drive permanent magnet (PM) wind generator systems by using the system design optimization method. Firstly, the analytical models of a three-phase radial-flux PM generator with a back to back power converter are presented. The design optimization is developed with a genetic algorithm for the minimum generator system cost. In order to demonstrate the electromagnetic designs and the optimization models, the design results of a 500-kW direct-drive PM generator are compared. Then, the optimal design approach is further employed for a range of power ratings from 750-kW up to 10-MW. The optimization results of the investigated generator systems are obtained. The criteria used for comparisons are considered, based on not only the generator design indexes, but also the annual energy production (AEP) per cost at the typical wind climates, respectively. Finally, the suitable ranges of the most cost-effective PM wind generator systems are also discussed.