Simulation based approach for Fixing Optimum number of Stages for a MMC

摘要

Modular multi level converters (MMC) are gaining importance day by day due to their inherent advantages of bidirectional capability, reduced switching loss. MMCs have become one of the best choices for electric vehicles (EV) and storage based electric vehicles as these converters have the ability of conduction in both the directions with bidirectional switches. One of the major issues of concern of an EV is that the storage of energy, as these vehicles battery storage with large capacity and these batteries required to be charged continuously. This feature of EV makes usage of MMCs as an attractive solution. The output available across a MMC is stepped sine wave. As the number of steps increases nearness of output voltage with a sine wave is increased, but this is not true. The authors feel that it is not true in case of a Sinusoidal Pulse Width Modulated Inverter. As the number of levels are increased the Total Harmonic Distortion (THD) in a voltage waveform decreases to a minimum value and then increases. MMC configuration proposed in [1] taken into consideration and simulation studies are conducted using Sinusoidal Pulse Width Modulation control scheme with the help of MATLAB / SIMULINK. The THD levels in the phase voltages and load currents are presented. With the help of simulation studies the optimum number of an inverter are identified.