A novel concept of extreme fine tuning in harmonic profile improvement in multilevel inverter for electrical drives

This article proposes a novel concept of improving the harmonic profile in multilevel inverter (MLI) using the ratio rule method. THD minimisation in MLI using selective harmonic elimination (SHE) approach using various optimisation techniques is covered in several literatures followed by further THD reduction using alterable DC sources. The methods discussed in various literature use rigorous derivations of constants that are used for further reduction of THD profile. This article introduces the ratio rule method for further reduction of the THD in multilevel inverter, after optimisation process using various algorithms. The proposed study is conducted using the SHE approach for THD reduction using genetic algorithm followed by further THD reduction using ratio rule. A three-phase seven-level cascaded H-bridge inverter is simulated in MATLAB as well as its hardware is implemented for deriving the proof of proposed concept. It is found that the proposed method is faster, easier and produces a maximum of 12.60% reduction in THD profile.