Variable Frequency Phase-Disposition Pulse Width Modulation Technique for Multilevel Inverter

Abstract

The Multilevel Inverters (MLI) are used to obtain the desired output AC voltage from the DC voltage source. This paper implement a variable frequency pulse width modulation (PWM) technique to improve the output voltage of the MLI which is the cascaded H-bridge multilevel inverter (CHMI) by using SIMULINK/MATLAB. Some of the conventional PWM technique still causes extra losses of power due to high frequency switching. In order to overcome this problem, a variable frequency of Phase Disposition (PD) PWM is implemented in minimizing the distortion by injecting variable frequency of the carrier wave into the CHMI. It is confirmed that the variable frequency method offers lower switching losses. Furthermore, Variable Frequency Phase Disposition (VF-PD) PWM gives better total harmonic distortion (THD) for the multilevel output voltage compared to its conventional PD PWM. The results showed VF-PD PWM gives 33.45% of THD better than PD PWM. The THD performance comparison for each PWM technique is presented for five, seven and nine levels of CHMI.