Loss Comparison and Thermal Performance of Modular Multilevel Converters under Discontinuous Pulse Width Modulation

摘要

Discontinuous modulation of the modular multilevel converter can be used for reduction of submodule capacitor voltages and switching losses by clamping one of the arms to its corresponding dc-rail. In this paper, the impact of discontinuous modulation in the losses as well as the expected thermal performance of the devices in the submodules of the converter are evaluated by a direct comparison with a normal modulation strategy. Three loss estimation methods are also reviewed in order to identify the impact that the choice of a loss calculation method might have in the loss value as well as the temperature estimations of the converter. The extended simulation results provided demonstrate loss reduction in the MMC as a result of discontinuous modulation together with variations in maximum temperatures across the devices of a submodule.