Research On Vector Inverter Of Direct Torque Control And Its Applications

For the reason of great energy saving effect and smooth speed control characteristic,vector-controlled inverter has attracted more and more attention. Also, as according with the government's energy saving policy, it has great potential in industry applications. In this paper the high performance vector inverter MFC710 is studied and the Direct torque control(DTC) algorithm the inverter applied is mainly focused with concern of the induction motor parameter calculation and finally an industry application example is given.The conventional DTC scheme based on switch table is firstly studied in this article, electromagnetic torque and stator flux is calculated in stationary reference frame,and Bang-Bang control is applied to control motor torque and flux. Then the essence of torque control is derived from the mathematical model of the induction motor. By detailed analysis of switch table control strategy, the vector selection table is obtained, the simulation results are reported to demonstrate its features.To improve the disadvantages as high torque ripple and variable switching frequency of conventional DTC, a DTC-SVM scheme with closed-loop torque and flux control which combines the virtue of DTC and FOC is studied in this paper. The appropriate parameters of PI controllers are obtained using root locus method. Also the simulation model is established in MATLAB to acquire a clearly comparition between this two scheme, an the siumulation result validate the effectivenesss of DTC-SVM scheme.In DTC-SVM scheme the information of feedback signals of flux, torque and speed is required. As the basic signal to calculate stator flux and motor torque, stator voltages are reconstucted from the switching signals with consideration of dead-time delay and dead-time compensation. Then some stator flux caculation algorithms are provided with the emphasize on voltage model with reference flux(VM-RF) and current model in rotor coordindte(CM-RC). Based on VM-RF, speed calculation algorithm using motor slip frequency is analyzed.Finally,the control structure and hardware configurition of high performance vector controlled inverter MFC710 is analyzed, utilizing the advantages, a tyre extruder system dirven by MFC710 is designed. The main extruder, tension control, and take-up part are mainly analyzed in this paper, and the crucial parameters of MFC710 in this driven system are given finally.