Abstract
The problem of elimination of harmonics and the need of a large number of switches in multilevel inverters (MLIs) have been a hot topic of research over the last decades. In this paper, a new variant swarm optimization (SO) based selective harmonic elimination (SHE) technique is described to minimize harmonics in MLIs, which is a complex optimization problem involving non-linear transcendental equation. Optimum switching angles are calculated by the proposed algorithms considering minimum total harmonic distortion (THD) and the best results are taken for controlling the operation of MLIs. The performance of the proposed algorithm is compared with the genetic algorithm (GA). Conventional MLIs have some disadvantages such as the requirement of a large number of circuit components, complex control, and voltage balancing problems. A novel seven-level reduced switch multilevel inverter (RS MLI) is proposed in this paper to recoup the need of a large number of switches. Matlab/Simulink software is used for the simulation of two symmetrical topologies, i.e., a seven-level cascaded H-bridge multilevel inverter (CHB MLI) and a seven-level (RS MLI). Simulation results are validated by developing a prototype of both MLIs. The enhancement of the output voltage waveform confirms the effectiveness of the proposed SO SHE approach.
Highlights
Nowadays many industrial drives require high or medium power for their operation and some require high power with medium voltage
This paper reports the development of a reduced switch seven-level multilevel inverters (MLIs) (RS MLI) topology which uses 7 switches and requires less number of driver circuits
For the proposed reduced switch multilevel inverter (RS MLI), a total number of (Nl+3)/2 switches including discrete diodes are in the current path at any time whereas (Nl-1) switches are in the current path for the cascaded H-bridge multilevel inverter (CHB MLI)
Summary
Nowadays many industrial drives require high or medium power for their operation and some require high power with medium voltage. This paper presents the design of a single phase seven-level cascaded Hbridge MLI using 12 switches aiming to reduce lower order harmonics which produce staircase voltage output waveform. SHE or programmed PWM technique [17] approach is used to eliminate specific order harmonics by calculating optimal switching angles. All three voltage levels are taken equal, i.e. Vdc1=Vdc2=Vdc3=Vdc. In Figure 1(b), 1 , 2 , and 3 are three switching angles needed to be calculated by solving non-linear equations to minimize THD. To construct the same output obtained as in a seven-level CHB MLI, a new circuit topology has been developed with a reduced number of switches without increasing the number of H-bridges.
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