The Vector Control Variable-Frequency Drive System Of Asynchronous Motor Based On Cascaded Inverter

During recent years, multi-level inverter has been widely researched in high power level application with high voltage output. Power energy with characteristic of high capacity and high quality can be achieved by this type of inverter, in which relatively small - capability and low-voltage switches are adopted. Cascaded inverter as one kind of multilevel inverters is widely applied to high and medium power conversion. Based on comparing and summarizing the merit, topology and control method of cascaded inverter, a new control method called Pulse Step Modulation is presented, which is the combination of the Pulse Width Modulation and the Step Modulation. It is an important technology which is used in high-voltage high-power switching power supply systems.The asynchronous motor is widely used because it is suit for the direction of high voltage, high speed and large capacity. Vector control is its ideal speed modulation method. On the base of analyzing asynchronous motor model, the paper studies the principle of vector control, adopting current model of rotor flux observer and speed and torque double closed loop. Cascaded inverter is convenient to realize high sinusoidal voltage output. The maximum voltage strength which each electric component bears is small, and it is easy for cascaded inverter to realize large capacity. The research on the asynchronous motor vector control based on the cascaded inverter is a novel work.This paper fully takes advantages of the powerful functions of MATLAB/SIMULINK to set up the simulation model. This construction is very explicit. The simulation results verify the inverter voltage output is correct, the rotor flux is steady, the asynchronous motor's dynamic and steady state performances and speed modulation are excellent.