Self-Commissioning Algorithm for Inverter Nonlinearity Compensation in Sensorless Induction Motor Drives

Abstract

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.

Online Estimation of the Rotor Flux Linkage and Voltage-Source Inverter Nonlinearity in Permanent Magnet Synchronous Machine Drives

“…The technology for the online estimation/compensation of the distorted voltage due to VSI nonlinearity has been widely reported [22]- [30], [34]- [36], [41]- [43]. However, most methods need accurate PMSM parameter values [22]- [27], [35], [42], or zero rotor speed [8].…”

Robust Control of High-Speed Synchronous Reluctance Machines

“…During all tests, inverter non-linearities have been compensated by adding proper voltage correction terms, which have been experimentally evaluated by means of the specific test procedure reported in [17].…”

“…In order to further improve the control system performance, the effects of inverter dead-times and resistive voltage drops need to be accurately identified and compensated [17]. The effects of the inverter non-linear behavior are more evident during phase currents zero crossing, therefore they are even more critical when the fundamental frequency grows with rotational speed.…”

Identification of rotor resistance and transient inductance of induction motors using frequency selection criterion

“…3. Feedforward compensation of the inverter nonlinearity is implemented [14]. Since the actual current does not totally track the reference one, the measured d-axis motor current is used instead of the reference one.…”