Robust Maximum Torque-per-Ampere Control by applying Virtual Inductance against Parameter Errors for Direct Torque Control of Permanent Magnet Synchronous Motors

Abstract

This paper proposes a method for robust control of a drive against parameter errors of permanent magnet synchronous motors (PMSMs). Direct torque control (DTC) of PMSM drive systems aims to realize maximum torque-per-ampere (MTPA) control by providing an optimal target magnetic flux. However, MTPA control by this approach cannot be realized owing to the following reasons. Command voltages and armature resistance are used in the estimation of the stator magnetic flux. Moreover, q-axis inductance and rotor magnetic flux are used in the calculation of the target magnetic flux. This paper proposes armature reaction flux control which can realize MTPA control in systems involving the above-mentioned error components. The proposed method compensates for these error components on the basis of the phase information of the current vector and the rotor flux vector in the maximum torque control (MTC) frame. By using the concept of the MTC frame, the proposed method is available to all PMSMs regardless of magnetic saliency. Finally, the effectiveness of the proposed method is confirmed experimentally.