Research On The Modular Multilevel Converter(MMC)

The modular multilevel converter (Modular Multilevel Converter, MMC) with its the modular design, flexible control, easy to expand and easy to achieve high output characteristics, so it’s widely used in high voltage and high power applications. The research on MMC has become a hot research.There is pragmatic value in improving the power quality that the application of MMC in STATCOM. This paper gives a brief description to the origin of the multilevel inverter and several kinds of topology circuit of multilevel converter briefly. The circuit and operation principle of MMC topology structure are analyzed. It derives the relationship between the output voltage and current and the voltage and current of bridge arm. According to the voltage current relationship, constructs the equivalent circuit model of MMC topology. There is a simple introduction of the module capacitor voltage unbalance, and voltage control scheme is given. The cause and the influence to output voltage of the circulation of MMC in three-phase circuit are analysis and simulation.The multilevel inverter PWM control methods are introduced. And is compares the advantages and disadvantages of various methods. The application of MMC in STATCOM is studied. And it analyses the structure and the working principle of STATCOM. The feed-forward decoupling is used to control STATCOM.M-STATCOM system simulation model is built to simulate, the record of the simulation of M-STATCOM compensation device in the dynamic load conditions indicate that the M-STATCOM adapts to different load requirements. It has the advantages of fast speed, good compensation, etc.The hardware circuit and software flow diagram of the master-slave mode of DSP and FPGA are designed.