Research On Direct Torque Control Strategy Based On Speed Sensorless

Direct Torque Control (DTC) is a high-performance control scheme in the modern ACdrive system. With the advantages of simple structure, easily control, good dynamic and staticperformance, it has become the focus of domestic and foreign scholars’ research. Althoughthe theoretical study and practical application of direct torque control had already made abreakthrough. There are still many disadvantages in this system. Such as huge torque ripplein low speed, round distortion of the stator flux, low and not fixed switching frequency, speedestimates inaccurate and so on. These shortcomings had become the important factors whichrestrict the system to improve its control performance.This paper analyzes the important and difficult control problems of the AC motor basedon DTC. Some solutions were proposed to improve the system performance after theadvantages and disadvantages of the existing control method were concluded. At first, thebasic principle of direct torque control was introduced which based on the dynamicmathematical model of asynchronous motor. Through understanding the torque and fluxcontrol method of traditional system, an improved SVM-DTC method was proposed in orderto overcome the lack of it. The simulation results verified that with the improved scheme thestator flux is more close to a circle, while it has effectively reducing the harmonic content andthe system error.DTC control system with speed sensorless technology can effectively simplify thesystem and reduce the economic costs. In this Chaos-Fruit Fly Algorithm(FOA) was used tooptimize BP neural network. Then it was applied it to design the speed identifierfor for theasynchronous motor which has the characteristics of non-linearity and parametertime-varying. This method can effectively improve the calculating speed of the system, andget a more accurate speed identification value.Finally, Build a simulation model in the Matlab/Simulink software platform. Thesimulation result shows that the improved speed sensorless direct torque control system caneffectively improved the low speed performance of the motor and the anti-jamming capabilityof the system.