A Two-State Linear Flux Weakening Strategy for an Operation Region Extension of the Variable-Flux Memory Machine

The variable-flux memory machine (VFMM) can perform flexible online PM flux adjustment by utilizing a magnetizing current pulse, effectively extending the machine operation range. However, the continuous flux adjustment (CFA) method generally suffers from sophisticated control effort due to frequent actions of the power converters. Thus, a new two-state magnetization state (TS-MS) manipulation method is developed to simplify the MS manipulation process, while maintaining almost the same operating envelope compared to the CFA method. In addition, for further extension of the operation region, this paper proposes a novel two-state linear FW (TS-LFW) strategy with simple implementation. In the TS-LFW strategy, piecewise linear approximations for FW are, respectively, planned at MS1 and MS2. Distinctively, the determination of the two working MS of all the two-state methods in this paper is discussed to avoid the unnecessary MS manipulations. Finally, the feasibility and effectiveness of the proposed TS-LFW strategy are verified through the experimental results on a hybrid magnetic circuit VFMM (HMC-VFMM) prototype.