Fler-niveau resonans konverter / Multilevel resonant converter

An Uninterruptible Power Supply (UPS) is often used in computer environments. The UPS converts energy from a storage facility, such as a battery to a standard ac line voltage. In the case of a line voltage drop, the computers are disconnected from the regular line and the UPS DC/AC converter supplies the computers. The transition from normal line operation to UPS operation is transparent, as seen from the omputers. The DC/AC converter used in the uninterruptible power supply is always active, the load current may be close to zero but the converter switches are operating and the UPS tracks the line voltage. The UPS is always ready to take the full load current. Because the UPS is active continuously, there is a standby power loss. A high efficiency is therefore a significant parameter. An especiallly high efficiency converter is the soft switching converter, where the switch losses are significantly reduced. This project is to improve the efficiency relative to state-of-the-art converters available today. Known problems with stability, controllability and output voltage quality are dealt with in this project. Several papers and patents held by the university project members are involved. Two patens are: Patent Application No.553/2000 Resonant converter issued April 2000 and Patent Application No. WO9853550 A method and a circuit for resonance inversion, issued May 1998. The Danish Technological Institute supports both patents technically and economically. (Stig Munk-Nielsen, Michael Møller Bech; Remus Teodorescu; APC Denmark A/S)