New Hybrid Multilevel Inverters for High-Current Applications

In the paper two new DC/AC hybrid multilevel bidirectional switching cells are proposed. First cell has three voltage levels (3L) and is called 3L-Bidirectional-Vienna (3L-BV). It contains semiconductor devices that work at different switching frequencies. The second switching cell has five voltage levels (5L), is named 5L-Parallel-BV (PBV), and is based on parallel connection of two groups of stacked HF switching cells (according to 3L-BV concept) by means of two coupled-inductors (CIs) and a basic switching cell. An interesting property of the 5L-PBV cell is the use of two CIs. These CIs work alternatively only on a half-cycle and the currents in inductor windings of CIs are naturally set to zero after each cycle. In this way, any difference between the currents in windings is cancelled periodically. The proposed switching cells are used to develop new single-and three-phase multilevel inverters. The operation principle of the two multilevel switching cells is verified by numerical simulations both for single-and for three-phase inverters topologies.