Research On Motor Speed Modulation System Based On Asymmetric Hybrid 6-level Inverter

Nowadays, kinds of asymmetric topologies just like asymmetric topologies of 5-level and 9-level shows up with the development of inverter technique which breaks down the constraint from the traditional symmetric stuctures. A single-phase asymmetric hybrid 6-level inverter is researched in this paper in view of the 0 level output of the asymmetric 5-level and the complicated structure of asymmetric 9-level inverter, In this type of asymmetric hybrid inverter a 3-level half-bridge unit and a half-bridge unit are cascaded to form an inverter phase leg. This kind of construction can make the mid-point voltage balance without any other special circuit and complicated control methods. Meanwhile, 6-lever will be put out at the end of the circuit. The EPWM method control is proposed considering for the construction of the inverter.This kind of topology combined with the EPWM is used in the speed control system Firstly, the single-phase and three-phase voltage waveforms under defferent frequency and proportion of power voltage are output through MATLAB/Simulink and the waveforms seem well. Then, the design of the motor's speed control system is achieved. Based on the achievement of the simulation ahead, the experiment on the asymmetric 6-level inverter for motor's speed control is carried out through DSP platform with defferent load at last.The experiment contains four kinds of frequency, and the results contain the variation curves of speed and torque with the time changing.The results show the ideal single-phase voltage waveforms, and the amplitude of the voltage change proportionality with the frequency changes. Meanwhile, the speed and torque will change when the load changes, and as a result they will come to a stable value. And the speed will recover to the original stable value. The results of the experiment indicate the feasibility of the construction and the reasonable of the EPWM method.