Firing angle optimization of seven-level cascaded H-bridge multilevel inverter with un-equal DC sources using GSA approach

This paper proposes a new approach to calculate optimal firing angles of a Seven-Level Cascaded H-bridge Multilevel Inverter(CHB-MLI) using Gravitational Search Algorithm(GSA). The presence of more levels in the output voltage waveform of MLI introduces large harmonic content which should be reduced. Selective Harmonic Elimination(SHE) method is the popular technique used for eliminating the desired harmonics in the output. The non linear transcendental equations involved in the calculation of SHE are solved by using Newton Raphson(NR) method. NR methods may not always converges when higher levels of voltages are considered. Hence a new population based search algorithm, GSA has been proposed in the present work to calculate the firing angles optimally. Un-equal DC voltage sources are considered for the input to the H-bridge cells and the obtained results using the proposed GSA algorithm are tabulated.