Ac Induction Motor Direct Torque Control System Research And Practice

Direct Torque Control (DTC) of induction motor, which follows the field-oriented control, is a new control method for motor drive. It doesn's need complicated coordinate transformation, has simple control structure and relies on less AC motor parameter. Especially with the rapid development of artificial intelligence technique and electronics technique, DTC is further developed. In this paper, in order to improve system performance, fuzzy control technique and Voltage Space Vector Modulation(VSVM) technique were applied to DTC.In this paper, DTC of induction motor was introduced based on analyzing AC motor mathematic model, then two techniques were applied to DTC. Firstly, Fuzzy Control technique was applied to DTC to improve torque response during the startup and during a step change. Secondly, in order to weaken steady torque ripples which usually overstep the limit due to the delay of digital system, Voltage Space Vector Modulation (VSVM) was used in Fuzzy DTC. Simulation experiment proved its validity. Finally, experiment was done in the motor experiment system whose control center is digital signal processor (TMS320LF2407), experiment validated DTC's main algorithm.Experiment results show that Fuzzy DTC has quicker torque response during the startup and during a step change; VSVM technique applied to fuzzy DTC can effectively weaken the torque ripple without increasing system sampling frequency, consequently, heightening precision of speed control. In the actual motor control system, DTC suits greatly digital control system because of its simple algorithm and direct control. In conclusion, DTC is a promising AC drive scheme.