Harmonic Distortion Optimization of Multilevel H-bridge Inverter with Delta-Connected

In full-bridge cascaded multi-level inverters with delta connection, the presence of odd harmonics multiple of three voltages and rotating currents in the delta ring causes additional losses. In this paper, a low frequency optimization method is proposed to reduce odd harmonics multiple of three voltages in full bridge cascaded multilevel inverter with delta connection. With this method, in addition to reducing these harmonics, the amount of Total Harmonic Distortion (THD) is also maintained at the optimal level and the requirements of standards such as EN50160 WG36-05 and IEC61000-3-6 are also met. In this method, by using the Optimal Minimization of Total Harmonic Distortion (OMTHD) keying method, the optimal values of keying angles and DC sources have been obtained by using the particle Swarm Optimization (PSO) algorithm. The simulation results show the effectiveness of the proposed method in reducing odd harmonics multiples of three voltages and rotating current along with maintaining the THD value at the optimal level.