Realization of Signal-Injection Sensorless Control of SMPMSM With Saturation-Induced Saliency by Modification of Current Trajectory

Abstract

This article discusses the feasibility of signal-injec- tion sensorless control (SISC) in low saliency surface-mounted permanent-magnet synchronous motors (SMPMSMs). At first, dynamic inductances of a target SMPMSM according to rotor position and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> -axes currents are measured from an experiment. The current response induced by the injected voltage is theoretically calculated based on the inductances. The induced current signal in every operable point on <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dq</i> current plane is evaluated with a newly defined index variable. An optimal current trajectory for the SISC is proposed after the evaluation. By adopting optimal trajectory control instead of maximum torque per ampere control, the performance of the SISC in the SMPMSM can be conspicuously improved at the cost of slightly increased electrical loss. The proposed method is verified with experimental results.