Loss comparison of the 3 level topologies for four-leg voltage converters

This paper is to compare the loss of the each 3 level topologies for four-leg voltage converters. In case of the power conditioning system connected to the grid without a transformer, 4 leg topology is essential to cover the unbalanced three phase loads. Using simulations with real loss data table of the power switches, loss analysis of the each 3 level topology with 4 legs according to the different PWM methods is carried out at the normal state and at the stand-alone operation with various kinds of load conditions. From the simulation and experimental results, it is shown that T-type with the MLPWM is the most efficient combination regardless of whether the loads are balanced or not.