MSPWM & MTPWM techniques for asymmetric H-bridge multilevel inverter

Multilevel inverter is a new breed of power converter which is suited for high power applications. The various topologies of multilevel inverter are diode - clamped, capacitor clamped and cascaded H-bridge inverter. It is an effective solution for increasing the number of levels in output waveform with reduced dc sources and switching elements, thereby dramatically reduces harmonics without increasing the switching frequency and decreasing power output. It has emerged as an important alternative in the area of high power and medium voltage energy control. This paper focuses on cascaded H-bridge multilevel inverter using two unequal dc sources in order to produce a seven level output and this is implemented to produce a three- phase seven level output waveform. Various modulation methods are available for multilevel inverter, but this paper emphasis on Multiple Trapezoidal PWM (MTPWM) and Multiple Sinusoidal PWM (MSPWM) technique with triangular as carrier. The performance evaluation of the proposed PWM strategies for single-phase multilevel inverter is done using MATLAB and Total Harmonic Distortion (THD) is determined.