Performance Improvement Study Of Direct Torque Control In Induction Motor

Direct Torque Control is a new type of high-performance AC drive technology, it getrid of the traditional exchanges governor control decoupling idea, by direct control themotor stator flux and the electromagnetic torque. The control idea is fresh and controlstructure is simple, nowadays have a good static performance and dynamic response.In this paper, we introduced the mathematical model of asynchronous motor at first,detail analysis the principle of the Direct Torque Control and study two kinds of directtorque control scheme: hexagonal flux trajectory control and nearly circular flux trajectorycontrol, compare the two kinds of characteristics of the control scheme, and a detailedanalysis in the shortcomings of the two programs, namely the low-speed performance is notsatisfactory, the adverse effects of motor parameters in the system.In order to improve the performance deficiencies of the traditional direct torque control,direct torque control scheme based on vector modulation method is proposed. We addingthe expected ideological to get the expected voltage vector, make the stator flux along theideal circular trajectory to improve low-speed state make up the sub-flux distortion statorcurrent harmonic electromagnetic torque ripple shortcomings; reduce motor parameterchanges, especially the adverse effects of the stator resistance variation, the establishment ofa full-order adaptive state observer the motor speed and stator resistance can be observedsimultaneously, no speed sensor technology is achieved, effectively inhibit the adverseeffects of the stator resistance variation.Finally, the establishment of a simulation model of the traditional direct torquecontrol method for the two control schemes, from the simulation results proves thetheoretical and practical anatomizes. Vector modulation method and the full-order adaptivestate observer-based direct torque control simulation model, the simulation results provethat the program can effectively improve the low-speed direct torque control performanceand reduce motor parameters, especially the stator resistance change impact.