Improved MTPA Control for Variable-Flux Memory Machine With Operating Envelope Prediction-Based MS Manipulation

This article proposes an improved maximum torque per ampere (MTPA) control method for variable-flux memory machine (VFMM) with operating envelop prediction-based magnetization state (MS) manipulation. The proposed method can achieve the MTPA control under the voltage limitation and simplify the MS adjustment process for expanding the operating region. The mathematical model of the studied VFMM is established to calculate the reference current for MTPA control online as well as to predict the operating envelop at each MS. According to the calculated operating envelop, the proposed MS manipulation method can separate the magnetization and demagnetization processes by setting two MS manipulation boundaries correspondingly, which is easily implementable and can avoid frequent MS manipulation processes. Besides, the inductance characteristics of the machine are measured to improve the model accuracy and control performance. Experiments are carried out on a VFMM prototype to validate the feasibility and effectiveness of the proposed method.