Research On The Application Of Flux Observer And Speed Sensorless For AC Induction Motor

After the vector control technology, the direct torque control, as anew control method, eliminated the complex and frequent coordinatetransformation, had many characteristics such as simple structure, fastdynamic response, etal. However, it also had a large torque ripple andpoor low speed performance. This thesis analyzed an improved directtorque control method with a circular flux trajectory. To our knowledge,the installation of speed sensors will bring some negative effects, thus,more and more people are motivated to study software method which canbe used to replace the speed sensors. Recently, speed sensorlesstechnology is arousing an extensive attention. How to get accurate speedinformation of AC induction motor becomes an important issue to besolved. This thesis has researched on the proposed velocity estimationmothod.First，it is a general review of the existing AC drive control methods,which elaborates a variety of flux observers and the speed sensorlesstechnologies, analyzes of simple the various options. The performancesand theory of several flux observation methods are discussed with acomparison of their simulation experimental results. In this researchsystem, we choose the full-order flux observer as the flux estimationmethod.Second, from the perspective of mathematical model of the ACinduction motor, adopt the improved direct torque control method andanalyze the principle of the proposed method, simulation modeling iscreated for the improved direct torque control method in MATLABenvironment. A speed estimation method based on PI algorithm isintroduced. Furthermore, a single-neuron PI controller is added to thesystem to improve the dynamic speed estimation effect. The simulationresults of the two speed identification solutions show that the speedidentification of the full-order flux observer obtains desired recognitionresults, fast dynamic response, and high steady precision.Finally, the experimental platform of AC drives with TMS320F28-12of TI companies have been built, programming the software for the study system. Experimental results under different speeds are given todemonstrate the effectiveness, good dynamic and static performance ofthe control system.