Performance Evaluation of Multilevel Inverter Based on Total Harmonic Distortion (thd)

In general Pulse width modulation (PWM) techniques of a voltage source inverter (VSI) need a sinusoidal reference signal and triangular carrier signal to generate the required modulating signals for the desired output. Modifications in modulating techniques can be considered in two ways, namely modified reference and modified carrier. The existing multilevel carrier based pulse width modulation (PWM) strategies have no special provisions to offer good quality output, besides lower order harmonics are introduced in the spectrum, especially at low switching frequencies. In this paper a pulse width modulation (PWM) scheme for multilevel inverters is proposed. The proposed PWM scheme generates the inverter leg switching times using only the sampled amplitudes of reference phase voltages. The proposed PWM technique does not involve any sector identification and considerably reduces the computation time when compared to the conventional space vector PWM technique. The proposed PWM signal generation scheme can be used for any multilevel inverter configuration. The main objective of this work is the most relevant control and modulation methods by a new reference/carrier based PWM scheme for a Diode clamped and Cascaded multilevel inverters are proposed for 5level inverters. The performance indexes used in this comparison is total harmonic distortion (THD).