The Research On A Stator-Flux-Oriented Speed Sensor-less Vector Control System For Induction Motor Drive

The induction motor stator-flux-oriented (SFO) vector control scheme not only reduces the big dependence of its performances on the rotor parameters, such as in the rotor-flux-oriented vector control, but also eliminates the torque ripple produced by Bang-Bang control in Direct Torque Control. So the SFO vector control is a high-performance and robust induction motor control scheme. In this paper a new speed sensor-less vector control system based on stator-flux-oriented is researched and analyzed.Firstly, according to an induction motor model under SFO vector control, the characteristic of the SFO control scheme is analyzed. There is a great cross coupling in the dynamic motor model. So the current decoupling control will greatly complex the structure of the control system. Furthermore, the variety of the stator resistance influences the control system greatly. Secondly, the advantages and disadvantages of some popular used indirect stator flux linkage observation methods are investigated. On the basis of an observation formula which does not contain any resistance parameters of the motor, the stator flux linkage peak value is maintained constant at the order value under a self-adaptive control strategy by means of fully compensating the stator resistant voltage drop. Because there is no need of currents coupling control, the system structure is greatly simplified. So this stator flux control strategy supplies a precondition and a foundation for the research of the speed sensor-less control system.Adding a speed observer, a slip frequency calculator and a torque current component limiter to the SFO vector control system, a speed sensor-less vector control system based on stator flux orientation is formed. In the speed observer, the difference between the measured value of the torque current component and its speed regulator output value is adopted. The equivalent model of the proposed scheme in the d-q axis reference frame is built up. The simulation is finished by use of the SIMULINK toolbox of MATLAB software. The simulation results show that, the good dynamic characteristics and wide range of speed regulation of the proposed system as well as a smooth torque are achieved. The set valve error of moment inertia parameter has no effect on the speed observation. The error of slip frequency calculating is also analyzed briefly.At last a implementation scheme of the proposed system is discussed presumably,...