Maximum Efficiency per Torque Control for IPMSM with DC-Current-Injection-Based Torque Observer and Online Searching

Recent years, the maximum efficiency per torque (MEPT) control approach has gained significant attention due to its ability to minimize both iron and copper losses in interior permanent magnet synchronous machines (IPMSMs). In order to deal with the unexpected deviations of IPMSM characteristics and their impact on the MEPT current, online-searching control strategies are generally preferred for their lower computational burden. However, the torque fluctuations during the searching process could be substantial, owing to the accuracy constraints of existing torque observers that neglect iron-loss variations. To address such problems, this paper proposes an online-searching MEPT control strategy with an improved torque observer. This observer uses dc current signal injection to generate a full-rank inactive power matrix, thereby bypassing the defects of iron loss on torque observation accuracy and computational burden. The proposed approaches have been experimentally validated.