Flux Observer Influence The Output Character Of Asynchronous Motor Feed By Three-Level Inverter

Direct torque control is another high performance control technique after flux oriented control of AC motor, it adapt the oriention of space vector of stator voltage, directly control stator flux and torque. It has the advantage of rapid torque response and less relying on stator parameters, however, it has the disadvantage of bigger torque ripple. Three-level inverter is one of the current research focus, with the advantages of small output voltage harmonic, low switching frequency, small dv/dt,di/dt.The research is based on the DTC equipment of three-level induction motor in this paper.Analysis shows that the accuracy of the flux plays a vital role in improving torque performance. In this paper, the mathematical model of induction motor, direct torque control principle and the three-level topology are analyzed and the effects of different flux observer for the motor output torque, speed and current, which is based on the establishment of u-i model, i-n model, u-n model, flux observer base on flux linkage amplitude and phase compensation and full-order flux observer. The simulation model of Three-level induction motor DTC system is built in MATLAB/SIMULINK. The five kinds of flux method are respectively studied by simulation, with comparative analysis of the effects of various flux method in the context of different speeds on the output characteristics.Finally, comparative experiment is made about the pure integral u-i model flux observer and full-order flux observer method for 1.1 kW induction motor by assembly language program on the three-level direct torque control platform based on TMS320LF2407A DSP. The experimental results show that the observed results of full-order flux observer can be better at low speeds. Meanwhile, experimental results testify that full-order observer has excellent performance, which is consistent with the simulation analysis.