A Hybrid Genetic Algorithm for Selective Harmonic Elimination Control of a Multilevel Inverter with Non-Equal DC Sources

The paper presents an optimal solution for eliminating pre-specified order of harmonics from a stepped waveform of a multilevel cascaded inverter topology with non-equal dc sources. The main challenge of solving the associated nonlinear equations, which are transcendental in nature and therefore have multiple solutions, is the convergence of the relevant algorithms and therefore an initial point selected considerably close to the exact solution is required. The paper discusses an efficient hybrid real coded genetic algorithm (HRCGA) that reduces significantly the computational burden resulting in fast convergence. An objective function describing a measure of effectiveness of eliminating selected order of harmonics while controlling the fundamental component is derived. Different cases including seven- and nine-level inverters with different values of modulation indices are reported. The theoretical findings are validated through simulation studies