Dsp Based Induction Motor Variable Frequency Drive Control System

Speed adjustment of alternative current motors is a integrated subject, it refers to the knowledge of power electronics, automatic control, computer and motor. The basic idea of vector control is to divide the stator current vector into two parts according to rotor flux orientation via coordinate transformation, so the decouple control of the flux and the torque can be realized, and its control performance is better than direct current motor. The speed sensorless vector control of asynchronous motor brings the system simplicity and robustness, and it becomes the main developing direction of alternative current drive.This paper adopts the speed sensorless vector control method based on full order adaptive observer, and then designs the variable frequency speed adjustment control system on DSP. After the introduction of vector coordinates transformation and the basic principle of vector control, the paper studies the mathematic model of asynchronous motor in different coordinates, the space theory and scheme of vector pulse width modulation are narrated in detail. Through the narration of speed identification based on model reference adaptive theory, two speed identification methods are built, the one uses stator current and rotor flux as state variable, and another uses stator flux and rotor flux as state variable.Simulation model of vector control system is built in Matlab/Simulink, and the space vector pulse width modulation technology is simulated and analyzed. On the base of vector control platform, two adaptive observer models which are used to identify speed are constructed and then studied. The speed identification in low speed area which is the difficulty of speed sensorless control system is deeply studied, and the performance of two methods is compared.