Research On Control System Of AC-DC-AC Power Converter

With uninterrupted development of the electric power electron technology and the control technique,its application already goes deep into to the commercial run and the social life.As the non-linear nature of the traditional transformer,the input line currents have significant harmonics and high total harmonic distortion (THD).At the high power applications,the multi-pulse rectifier has been used to eliminate the certain harmonics,shape the input current,and reduce the harmonics pollution to the utility.Research and application on mufti-level inverter is one of the newest developments of modern power electronic.In comparison to two-level inverter,it has some advantages as following:Multilevel inverter reduce the di/dt and the dv/dt on switches;At a same frequency,a multilevel inverter's output has a better waveform than that of a two-level one;Multilevel inverter can have higher voltage with the increasing of the number of its levels.The article analyze the shift-phase principle of the multi shift-phase rectify transformer.The relationship between the number of the rectifier pulse and the order of the harmonics is conclude.And the paper designs the 12 pulse waves rectifier and the filter circuit.The selection of the main circuit components are also discussed detailedly.Then the theory of SVPWM is discussed in detail.And the thesis researches the work principle of two levels inverters and the voltage vector modulating technique in detail.At the same time,the basic principle of SVPWM of three-level inverter is studied.At last we simulate the SVPWM modulating means of two-level inverters and three-level inverters by MATLAB.And in order to get the high quality output voltage we establish the closed-loop control system based on MATLAB,and prove the correction of modulating means.