The Research And The Design Of Medium-voltage Five-level Module Cascade Inverter

With the development of the society, the research and application of the Medium-voltage high power converter has been a new direction for research in the field of Power electronics. Multi-level converter has lots of unique advantages in the field of high power converters, The cascaded multilevel inverter is the greatest hopeful type of the Multi-level converter, which are always combined with three-level module. The project of this thesis is supported by "the integrated and optimized ecological research about the motor-converter system" of the program "863", the new five-level module cascaded inverter, which is the goal of this project, has much less module than the traditional converter, the qualification of output waveform is better than that.The main circuit topology of five-level module cascaded inverter and the phase-shift rectifier technology given in details in the thesis, the Math Model in space of the system of cascaded inverter and motor are induced and analysed with coordinate alternating. The phase shifting and cascading PWM has been selected as the control arithmetic of the converter after the comparison and research about several arithmetic of PWM. The thesis also gives the switch strategy of IGBT of five-level module, and the new way for the problem of module balance control. Synchronously, the application of vector control in the field of the cascaded medium converter has been researched in the thesis.In the design of the system, the design of software and hardware is completed, The key technology like the identification of the fault on line,the bypass protect system, DSP/CPLD control system etc. are researched, the new cascaded inverter and the five level modules is also produced successfully. the thesis has constructed and simulated the motor asynchronous system of the PWM control and vector cotroll with the software "MATLAB", at the same time, the rated experiments of the system with different load and in the different condition is underway, the result implements that the five-level module cascaded inverter has stable output and good dynamic reaction, the satisfied anticipated impression is gotten. At last, the conclusion is drawn for the research in the thesis, and some another problem that will be solved of the next stage is implied.