An Optimum nearest Level Modulation Technique...

An Optimum nearest Level Modulation Technique to Modular Multilevel Inverter

Author Name : N. Karthikeyan, Dr. Sujatha Balaraman

ABSTRACT

The modular multi-level inverter (MMI) is one of the advanced topologies in high voltage, high power in the recent decade. The key advantage of this method is any number of levels can be achieved with single DC source. However, the balancing of sub-module capacitor voltagesof the inverter and the minimization of circulating current are the challenging one to achieve. The performance of MLI depends on the PWM schemes and Nearest Level Modulation (NLM) is the most prevalent one for multi-level inverters. The key advantages of NLM includes PWM generation with fundamental switching frequency and ease of implementation owing to large number of sub-modules. In this paper, the optimum nearest level modulation control strategy is used for generating the gating pulses to a nine-level inverter and their performance is analyzed in Matlab/Simulink. The improved output voltage waveformwith reasonable Total Harmonic Distortion (THD) value is achieved with capacitor voltage balancing across the sub-modules.

Key Words: Modular Multilevel Inverter, Nearest level modulation control, capacitor balancing, Total Harmonic Distortion (THD).