Variable-structure MRAS Speed Identification for Speed Sensorless Vector Control of Induction Motor

Variable structure control is robust to external disturbance and interior parameters perturbation while the uncertain factors such as parameters variation meet the “matching condition”, but it is somewhat difficult to find the bounds of uncertain parameters. Proposes a novel strategy of variable structure model reference adaptive system(VS-MRAS) observers for the speed identification of a sensorless vector controlled induction motor drive. This strategy combines MRAS with variable structure control to improve the veracity of flux observer and to improve the accuracy of speed identification making use of MRAS adaptive ability of the variation of system parameters to estimate variable boundary of uncertainty factorss in real time. The dynamic and static performance of the speed estimate is compared and analyzed for three cases that are the vector control system with encoder, the speed sensorless vector control system based on MRAS, and the VS-MRAS respectively. Simulation results verified that this strategy improves the veracity of fluxes observers and the dynamic and static performance of the speed estimation.