Research And Design Of Asynchronous Motor Vector Control Variable Frequency Speed Regulating System

This paper focuses on vector control variable frequency speed regulating system for asynchronous motor. Several key technologies about the vector control are studied, including:1. Importance of rotor flux observation in vector control is analyzed; the methods of observation are also discussed. Analysis and simulation shows the problems caused by pure integrator in voltage module flux observer. This study strongly emphasizes on the solution of low pass filter taking place of pure integrator and getting compensation from output feedback. An improved algorithm for flux observer is proposed, applied to variable flux occasions.2. Pulse width modulation modes commonly used in vector control are concluded, with an emphasis on the research of voltage space vector PWM. Realization of SVPWM in vector control includes three steps: determination of the sector, calculation of the basic space vectors duration and calculation of the PWM comparison threshold. Theoretical derivation of the algorithm is given in detail. The influence of DC bus voltage fluctuation on SVPWM in vector control is proposed and analyzed by simulation.3. Comparison between using actual values and per unit values in vector control calculation is analyzed. The method to get the per unit model of asynchronous motor, the selection of basic physical quantities and their base values, and the per unit model in MT coordinate are researched in detail, as the foundation of per unit vector control. Reference-frame transformation of per unit values is also discussed thoroughly.4. Transforming external voltage and current signals into per unit values is the primary process of per unit vector control, thus the hardware and software for realizing the transformation are researched.5. The hardware and software of the control variable frequency speed regulating system for asynchronous motor are both designed, and the vector control algorithm based on asynchronous motor per unit model is verified on experiment system. An improved method to record the dynamic curves of observed physical quantity is presented, simplifying and visualizing the research of system characteristics.