Optimized Switching Angle Control Using Newton-Raphson Method for THD Reduction in Cascaded H-Bridge Multilevel Inverters

A power electronics multilevel inverter (MLI) can take numerous lower level DC voltages as input and use them to produce the desired alternating voltage level at the output. There are various varieties of multilevel inverters. A cascaded multilevel inverter is the most efficient type among its various variations. Compared to diode clamped and flying capacitor inverters, it uses switches and capacitors and requires fewer components at each stage. Such inverters produce stepped staircase waveforms as their output, indicating the presence of additional harmonic components in addition to the basic component. The primary requirement is to lower the total harmonic distortion (THD), and several optimization strategies are used for selective harmonic elimination. Based on the Newton-Raphson approach for solving the nonlinear equations, which are transcendental in nature and have many solutions, this paper suggests an extended way to compute the switching angles. The expected formula for determining the initial angle values is used to calculate the switching angels. Using MATLAB/SIMULINK software, this work gives solutions for 3, 5, 7, and 9 multilevel inverters under various modulation index values. The outcomes show that the switching angles that remove certain lower order harmonics from the MLI output voltage and lessen the overall harmonic distortion may be computed using the Newton-Raphson approach. The effectiveness of the suggested approach was demonstrated by the simulated outcomes. In this paper Newton Raphson Technique is used to find the optimized firing angle values.