Research On Multilevel Inverter For Medium-High Voltage

In recent years, multilevel converters have presented an important development toreach higher power with increasing voltage level. Lots of topologies of multilevel waspresented, such as diode clamped converter, flying capacitor converter, H-bridgeconverter, which are the most popular in practice. These topologies have manyadvantages, but all of them on using also have many disadvantages. After analyzingthe structures of the topologies on using, this paper extends the concept of basicmultilevel inverter units and presents a universal type of multilevel inverter topology.This universal topology use half H-bridge converter as basic unit. The basic unitsconnect in series at first,then connect in paralell. This topology is universal because itis the base of other topologies and presents self-voltage balancing without circuits inaddition.Firstly, several topologies and converters in using are introduced in the thesis.Secondly, the universal type of multilevel topology is constructed by basic multilevelinverter units.Then the concept and control strategy of the universal inverter areproposed in details. And the paper also presents the method to form inverter. Nextbased on power electronics'principles, mathematical model of five-level inverter hasbeen built. At last, with the help of MATLAB, the model has been realized in thecomputer and some simulating results have been showed. Afterwards, this paperanalyzes the harmonic components of multicarried PWM strategy with methods ofmathematics and simulation. Both of the means receive coincident results which aresatisfied .Finally, this research has something of significance for the further researchof the medium-high voltage converter.