Research On Cascade Inverter For Medium Frequency Application

With the development of aviation technology, the requirements of power density, efficiency, dynamic and static electrical performance for the air supply power system continuously is increasing. Compared with the standard full-bridge inverter, multilevel technology can use smaller output filter under the same output voltage harmonic to reduce the volume and weight for higher power density. In view of the high power density requirement for medium frequency inverter, this article has done researches on single-phase cascaded inverter circuits and the control technologies.Firstly, different topologies and modulation methods are introduced. Comparing their advantages and disadvantages, the cascaded inverter is chosen as the research object. Then, the operational principle, the characteristics of output voltage, and the parameters design of the output filter of unpolar carrier phase-shift full-bridge cascaded inverter are analyzed, and the corresponding simulation and experiments are carried out for the validation. The third chapter introduces the topology of hybrid cascaded inverter, and analyzes the principle of unipolar multi-carrier stacked modulation method. In order to compare the efficiency under the same power density and the same output harmonic content with the second chapter, the switching frequency is designed through the filter parameters design. Because of the bridge arm under unipolar multi-carrier stached modulation existing uneven fever, the optimization modulation method is put forward. The optimization modulation method does not change the harmonic content of output voltage and efficiency in the same filter, and the simulation and experiment are verified. In addition, in order to reduce the number of DCsource, the fourth chapter analyzes the hybrid cascaded multilevel inverter with capacitor instead of the low-voltage unit DC source. The stable condition is analyzed and the optimal parameters are chosen through the analysis of loss. Then, the control strategy is put forward, and the simulation and experiment are verified. Finally, the design of experimental verification platform based on DSP+FPGA is introduced, including hardware circuit design and software design.