Power loss benchmark of nine-switch converters in three-phase online-UPS application

Three-phase online-UPS is an appropriate application for the nine-switch converter, where its high voltage stress of the power device caused by the reduced switch feature can be relieved significantly. Its power loss and loss distribution still have the flexibility from the control point of view due to its asymmetrical structure, which are critical indicators for efficiency and reliability. They are therefore analyzed mathematically in this paper, in terms of conduction loss and switching loss. Moreover, various modulation strategies that fit for the nine-switch converter as well as parameters like modulation index and phase angle of the load are taken into account. The benchmark of power loss will become a guidance for the users to make best use of the advantages and bypass the disadvantages of nine-switch converters. The results are finally verified on a 1.5 kW prototype.