A Magnetization State Initialization Control Scheme for Variable Flux Memory Machines Without Requiring Position Sensor Information

Variable flux memory machines (VFMMs) normally suffer from excessively low initial magnetization state (MS), which will cause a large starting current or even startup failure. This article proposes an MS initialization control scheme for VFMMs equipped with incremental encoders, in which the required rotor position is estimated by injecting high-frequency square-wave voltage. Based on the estimated initial rotor position, the MS initialization can be accurately and smoothly achieved by applying a d-axis current pulse. The general framework of the proposed scheme is demonstrated first. The voltage pulse magnitude determination of the bipolar injection method is then particularly discussed to realize the polarity detection within a full flux regulation range. The implementation of the d-axis current pulse injection method for the MS initialization based on the estimated rotor position is subsequently introduced. Finally, the feasibility and effectiveness of the proposed MS initialization control scheme are experimentally verified on a manufactured VFMM prototype.