Comparative Study on Various Unipolar PWM Strategies for Trinary DC source Multilevel Inverter

The need for high power apparatus in industry has increased in recent years. Multilevel inverters have developed as easy alternatives for such power requirements. Multilevel inverters consist of a group of semiconductor switches and a set of voltage source components like capacitors or independent sources. The basic concept of these inverters depends on using this series of switches and sources to synthesize a stepped or staircase output voltage waveform. Multilevel inverters play a significant role in enhancing the quality of high power distribution networks, power conditioning systems, variable speed drive systems etc because of the availability of higher number of voltage levels at the output. Aghdam et al [1] proposed multicarrier PWM methods for asymmetric multilevel inverter. Bensraj and Natarajan [2] developed multicarrier trapezoidal PWM strategies for a single phase five level cascaded inverter. Bahr Eldin et al [3] proposed new multicarrier based pwm for multilevel converter. Jing Zhao et al [4] developed a novel pwm control method for hybrid-clamped multilevel inverters. Liu and Luo [5, 6] developed Trinary hybrid multilevel inverter for motor drive with zero common mode voltage and used in STATCOM with unbalanced voltages. Mauricio Rotella et al [7] introduced pwm method to eliminate power sources in a non redundant 27-level inverter for machine drive applications. Reza et al [8] proposed harmonics elimination in a multilevel inverter with unequal dc sources using a genetic algorithm. Ramani and Krishnan [9] developed new hybrid 27 level ABSTRACT