[Article] Self-Commissioning Algorithm for Inverter Non-Linearity Compensation in Sensorless Induction Motor Drives

In many Sensorless Field Oriented Control schemes for Induction Motor (IM) drives the flux is estimated by means of the measured motor currents and the control reference voltages. In most of cases, the flux estimation is based on the integral of the back-EMF voltages. The inverter nonlinear errors (dead-time and on-state voltage drops) introduce a distortion in the estimated voltage that reduces the accuracy of the flux estimation, particularly at low speed. In the literature, most of the compensation techniques of such errors require the off-line identification of the inverter model and off-line postprocessing. The paper presents a simple and accurate method for the identification of the inverter parameters at the drive start-up. The method is integrated into the control code of the IM drive and it is based on the informations contained in the feedback signal of the flux observer. The procedure applies, more in general, to all those sensorless AC drives where the flux is estimated using the back-EMF integration, not only for IM drives but also permanent magnet synchronous motor drives (SMPM, IPM). The self-commissioning algorithm is presented and tested for the sensorless control of an induction motor drive, implemented on a fixed-point DSP. The feasibility and effectiveness of the method are demonstrated by experimental results.