Speed Sensorless Vector Control System Of Induction Motor Research

As a new and promising research orientation, speed-sensorless vectorcontrol of technology can eliminate speed sensor, at the same time, maintaininggood performance of vector control. It’s an effective way for realizing ACfrequency control with low cost and high performance, and it’s the major trendsin advanced frequency conversion control system.In this paper, the induction motor, which are most commonly used inindustry was taken as a research objective, and a deeply research on speed-sensorless vector control system of induction motor was performed. AnExtended Luenberger Observer was designed to estimate rotor speed ofinduction motor. In order to have an effective control and regulation on theperformance of control system, the system controller was designed, and theSVPWM algorithm program was write to control the inverter.Firstly, based on the reference frame theory, parameters of induction motorunder three-phase reference coordinate were transformed to an arbitrary rotatingtwo-phase coordinate. And control models of induction motor under two-phasestationary reference coordinate and two-phase synchronous rotating referencecoordinate were built respectively. Through rotor flux orientation, an originallyhigh order, nonlinear and time varying induction motor model turns to be asystem with only four-order. As a result, the induction motor control modelswere simplified and the influences caused by time-varying parameters wereeliminated.Afterward, the space vector pulse width modulation (SVPWM) algorithmof induction motor was studied. Firstly, the power circuit topological structure of three-phase voltage source inverter was analyzed, and mathematical model ofthree-phase voltage source inverter was built through DC bus voltage along withswitches states of inverter. The space distribution of basic voltage vectors thatproduced by inverter were analyzed, based on which, the desired referencevoltage vectors were synthesized, and the operating time of two adjacent basicvoltage vectors on each sector were calculated, the optimum design of inverterswitches on-off sequences were also given.Then, the speed-sensorless vector control system of induction motor wasdesigned. Based on modular thought, the whole control system was dividedinto speed estimation module, controller module, SVPWM algorithm model,inverter module, induction motor module and some coordinate transformationmodule, and the speed estimation module along with controller module wereemphasized, among which, an Extended Luenberger Observer was adopted forspeed estimation. To ensure the observer system processing a faster dynamicresponse under the prerequisite of stability, the poles of the observer weredesigned to place on proportional to the ones of induction motor, and the speedadaptive law was designed based on a suitable lyapunov stability theorem. Inorder to perform an effective adjustment and control on the control system, thespeed regulator, flux regulator and current regulator of induction motor weredesigned.In order to analyze the dynamic performance of the whole control system,on the basis of mastering the overall design of control system, the simulationmodels of component modules of the whole system were built on the platform ofMATLAB/Simulink, and simulation analyses were performed. The SVPWMalgorithm was write on a programmatic way and applied to the invertersimulation model, the simulation results showed the correctness of componentsmodels and the validity of SVPWM algorithm. Lastly, the simulation model ofthe whole control system was built, and the simulation result showed that thisobserver system could track the actual output rotor speed effectively within certain limits with a good dynamic performance, accordingly, showing that thiscontrol system was reasonable and valid.