A two-level fuzzy based DTC using PLLC to improve the induction motor performance

This paper presents proportional integral direct torque control (PIDTC) and fuzzy direct torque control (FDTC) of induction motor (IM) using bus clamped space vector modulation (BCSVM), in which BCSVM always clamps any phase of the inverter for given switching period. Conventionally, the total cost of control scheme significantly increases in real time applications as it needs to sense three voltages, three currents, and speed of the IM. The proposed control scheme (PIDTC/FDTC) uses only single voltage and single current sensors are enough to estimate all voltages, currents, and speed of the IM using the phase locked loop control (PLLC) and the transport delay. The PLLC estimates frequency and amplitude of respective voltage/current waveform of the IM. The other two voltages/currents are estimated by providing proper delay using transport delay. In addition, the IM speed is estimated from the frequency command of PLLC. The PIDTC provides considerable distortion in current, flux, torque, and speed due to poor performance of PI-controllers. In order to improve the dynamic performance of IM drive the FDTC is used. In FDTC, the fuzzy controller estimates the control variable very close to practical values using Mamdani and Centroid methods. Also, the switching duty ratios of the inverter are independent of the switching period with FDTC.