Speed Sensorless Stator Flux Oriented Control of Three-Level Inverter-Fed Induction Motor Drive Based on Fuzzy Logic and Sliding Mode Control

A novel simplified stator flux oriented control (SFOC) for three-level inverter-fed induction motor drive is proposed to achieve high performance torque control in both steady state and transient conditions. Sliding mode control (SMC) is designed, in stead of conventional PI controller, to obtain the continuous commanding voltage vectors. The speed accuracy and dynamic tracking performance, as well as robustness to external disturbance, are improved by using fuzzy logic control (FLC). A speed adaptive flux observer with novel gain and load torque observation is introduced to improve the dynamic performance of speed estimation. The issue of large starting current in SFOC is addressed, and a strategy with pre-excitation and ramp function of commanding stator flux is proposed to solve this problem. By utilizing the redundant states of small vectors, the neutral point voltage fluctuation of three-level inverter is kept within a certain range. Experimental results prove that the sensorless three-level inverter-fed IM drive exhibits excellent dynamic performance and steady-state accuracy over a wide speed range.