Real-Time Selective Harmonic Minimization in Cascaded Multilevel Inverters with Varying DC Sources

A new approach for selective harmonic elimination in a 7-level cascaded multilevel inverter with separate DC sources will be presented. As opposed to previous research in this area, the DC sources feeding the multilevel inverter are considered to be varying in time. This method uses genetic algorithms to obtain switching angles offline for different DC source values and uses neural networks to determine the switching angles that correspond to the real-time values of the DC sources. This implies that each one of the DC sources of this topology can have different values at any time but the output fundamental voltage will stay constant and the harmonic will still meet the specifications. The paper gives details on the approach used, together with simulation and experimental results.