Implementation of Seven Level Cascaded Multilevel Inverter in Closed Loop For Different Modulation Index

This paper explains a control strategy SHE-PWM and a closed loop control of the cascaded multilevel inverter based on the modulation index. The modulation index is taken as the feedback to the cascaded multilevel inverter, the proposed system reduces the total harmonic distortion by optimizing the angles of the inverter and the DC voltage sources applied to the cascaded inverter. The specific lower order harmonics are eliminated by using SHE-PWM method. The optimized angles for the cascaded inverter are obtained by using the particle swarm optimization (PSO) algorithm for the various modulation indexes. The objective function is used to reduce the lower order harmonics in the output voltage. The simulation results of various modulation indexes and equal, unequal DC voltage sources for seven level cascaded multilevel inverter are carried out. Index terms –Cascaded H Bridge (CHB), Modulation Index (MI), Particle Optimization Technique (PSO), Selective Harmonic Elimination (SHE), Total Harmonic Distortion (THD).