Research On The Speed Sensorless Vector Control Of Three-phase Induction Motor

By eliminating the speed sensor,canceling the relevant encoder connection, reducing system maintenancecosts, improving system reliability, Speed sensorless vector control(SVC) Received extensive attention inrecent years. Then how to estimate the motor speed signal quickly and accurately becomes the focus ofdomestic and foreign scholars. At present, the more application speed identification methods commonly haveundesirable shortcomings,such as poor performance at low or near zero speed zone, dynamic performance isnot satisfactory when disturbanced by Load and motor parameters. Therefore, the speed estimator and thecorresponding high-precision motor parameter identification devices become a hot research..In this context,the induction motor (AC) as a control object, this paper researched speed sensorless vector control technologyboth in theoretical and experimental aspects, the main research contents are as follows:(1).Systematically analyzed the basic principles of induction motor vector control. Using the theory ofcoordinate transformation, Compared of induction motor's mathematical model on the three kinds ofcoordinates, analysised of the rotor flux-oriented vector control theory,the principle of space vector pulse widthmodulation (SVPWM) theory and implmentation.secondly, researched on two typical speed identificationmethods-calculating rotor synchronous angular velocity by rotor emf and constructing speed based onMRAS method. Analysised of the advantages and disadvantages of both, simulated under different conditions,they can be compared with identification method proposed in this article.(2). Based on the state equations of induction motor on two-phase synchronous rotating coordinate system,a speed estimation method with identification of stator resistance is proposed. On the base of estimating speedthrough the excitation current differential equation and torque current differential equation, identification ofstator resistance is proposed through equivalent relation, Stator resistance value is updated in real time toperfect the speed estimation project. The scheme has many advantages such as synchronous rotor speedestimation without the aid of the stator flux, rotor flux and rotor resistance, what is more, the impact of statorresistance has also been improved effectively in low-speed zone.(3). In Matlab/Simulink simulation environment, builded a simulation model for the proposed speedestimation scheme. Respectively, analysised error in two kinds of conditions_____constant and change from forward to reverse. Compared with structure speed by MRAS method closed-loop system,The results showthat the program has a high speed tracking accuracy, good robustness for motor parameter variation,and thesystem is stable.(4). Builded a hardware platform based on TMS320LF2407,including main power circuit, power-drivenplatforms and phase voltage, phase current sampling circuit,etc; Drawed a software flow chart, including themain program flow chart and flow chart of the interrupt subroutine. written the experimental software inCCS2.2development environment. Finally, showed experimental results and analysised the validity of theprogram.