A Closed-loop Magnetization State Controller for Variable-Flux IPMSMs

Variable-flux interior permanent magnet synchronous machines (VF-IPMSMs) have an additional degree of freedom, which is the magnetization state (MS) of the low-coercive permanent magnets. Thus, good flux controllability. While a prior focus was on magnetization sate (MS) estimation and operating envelopes determination of the VF-IPMSMs, this paper proposes a closed-loop MS controller for variable-flux machines using a pseudo-derivative feedback control algorithm. The estimated magnetization state signal is used as an actual signal in the proposed closed-loop controller. The nonlinearity of the plant is first highlighted and the inability of the conventional linear proportional-integral compensator to control the system is shown. The controller is designed in the dq synchronous reference frame and shows a good performance in tracking the magnetization state reference without the use of lookup tables.