Total Harmonic Distortion Optimization of Delta-Connected H-Bridge Multilevel Inverters

Presence of triplen voltage harmonics and circuiting current in a delta-connected cascaded H-Bridge multi-level inverter causes extra power losses. In this paper, a low frequency optimization method is proposed to reduce triplen voltage harmonics in delta-connected cascade H-Bridge multilevel inverters. Using this method, in addition to reducing these harmonics, the total harmonic distortion (THD) is also maintained at optimum level and the requirements of standards such as EN50160, WG36-05 and IEC61000-3-6 are also satisfied.  In this method, using optimal minimization of total harmonic distortion (OMTHD), the optimal values of the switching angles and DC sources are obtained using the Particle Swarm Optimization (PSO) algorithm. The simulation and experimental results show the effectiveness of the proposed method in reducing triplen voltage harmonics and circuiting currents while keeping the THD at optimal levels.