Automated bi-objective design optimization of multi-MW direct-drive PM machines using CE-FEA and differential evolution

Design optimization of a multi-MW direct-drive PMAC machine based on computationally efficient-FEA (CE-FEA) and multi-objective differential evolution (DE) algorithm is presented in this paper. The CE-FEA based models allow ultra-fast analysis and design of synchronous electric machinery. In this work, a DE algorithm is used to vary a large number of stator and rotor parameters to optimize multiple objectives, such as average torque, efficiency, the cogging and the ripple torques that are evaluated using CE-FEA. The method is demonstrated on a motor for a direct-drive rated at 20 MW and 150 r/min. The following four case-study machines are optimized: 1) fractional-slot embedded surface-PM, 2) fractional-slot interior-PM, 3) integer-slot embedded surface-PM, and 4) integer-slot interior-PM. Design optimization of interior-PM machines includes an additional search for an optimum operating torque angle corresponding to the maximum torque per ampere (MTPA) condition.