A full sliding mode sensorless control of three-level inverter-fed induction motors

Abstract

A speed sensorless induction motor drive fed by a 3-level neutral point clamped (NPC) inverter is presented, which combines the principle of sliding mode controller (SMC), sliding mode observer (SMO), direct field oriented control (DFOC) and space vector modulation (SVM). PI is widely used in field oriented control for speed, flux and current regulation whereas the performance of drive is usually affected by the invariant parameters of PI. In this paper, SMC is introduced in stead of conventional PI to produce fast and accurate response and reject the external disturbance and motor parameters variation. Moreover, SMO is introduced to observe rotor speed and flux for the implementation of DFOC. The induction motor is driven by a 3-level NPC inverter, which provides more smooth and accurate response than conventional 2-level inverter, and the neutral point potential is well controlled using hysteresis control. By introducing sliding mode theory in both controller and observer, the system demonstrates excellent dynamic and steady-state performance, robustness to motor parameter variations and wide speed range operation, which is confirmed by simulation and experimental results.