Research On Modulation Strategy Of Modular Multilevel Matrix Converter

With the development of power semiconductor and microcontroller,power converter become much more popular in power system.While the capacity and voltage level are increasing,the high voltage and large capacity power converters is a must.Modular multilevel matrix converter(M3C)not only succeeds the topology and benefits of matrix converter,but also has modular design which makes it easy for expansion.M3 C has some unique characterists especially in variable voltage,variable frequency and high efficiency power conversion.The thesis first analyzes the structure and operational principle of M3 C.Then based on three-phase to three-phase M3 C,the bipartie graph tree constrain model of M3 C is provided.Similar to traditional space vector modulation of voltage source converter,a potential matrix for space vector modulation is also provided.Based on bipartie graph tree and potential matrix,a matrix mask modulation is presented.After all,the feasibility of modulation strategy is tested by simulation.Secondly,after constructing M3C's mathematical model,power fluctuation of capacitor is investigated.Then a capacitor voltage control strategy based on bipartie graph tree is presented.Simultion is also implemented for testing the feasibility of control strategy.With offshore wind turbine as the target application,the design process for M3 C parameters is provide.In the mean time,operations such as variable voltage,variable frequency and power flow control are tested in simulation.At last,a M3 C physical model is built for testing the modulation and voltage control strategy.The result shows that the aforementioned modulation and voltage control strategy are valid and applicable.