Current derivative estimation by using AMR current sensor and its application in sensorless control of an IPMSM drive

Current derivative based sensorless control methods, which falls under saliency tracking technique, is a promising new sensorless control methods for AC machines over a wide speed range, including zero speed. This method requires accurate current derivative measurement under different applied PWM voltage vectors. The accuracy of current derivative is affected by the high frequency oscillations which are caused by parasitic effects when the switching devices change state. These current derivatives can be obtained directly from a dedicated di/dt sensor or estimated indirectly by using curve fitting algorithm from a standard current sensor. In this paper, high bandwidth anisotropic magneto-resistive (AMR) current sensors are used to estimate the current derivatives for a sensorless PMSM drive and the results are compared with simulation results. Experimental results on the performance of sensorless PMSM drive by using AMR based di/dt measurements over a few transient and steady-state operation conditions are presented.