Minimisation of total harmonic distortion in a cascaded multilevel inverter by regulating voltages of dc sources

Recently, a switching strategy based on minimisation of total harmonic distortion (MTHD) has been proposed. Normally, in multilevel flexible AC transmission systems, DC voltages of capacitors are changed. It is proposed to regulate this value on a predefined value. Thus, desired value is employed for optimising THD value. Results show effectiveness of the proposed method in minimising THD, when it is compared with the case of a multilevel inverter with constant DC sources. Genetic algorithm as a powerful tool is used to minimise THD as well as satisfy fundamental component. To verify theory and simulation results, a seven-level cascaded inverter-based hardware prototype is built.