Patent ID: 8553432

Claim:
An apparatus configured to transmit power between a first electricity network and a second electricity network, the first electricity network being either a single-phase DC-network or a polyphase AC-network, and the second electricity network being either a polyphase AC-network or a polyphase electric machine, the apparatus comprising: a plurality of low-voltage power cells arranged to connect the first electricity network to the second electricity network, wherein each low-voltage power cell of the plurality of low-voltage power cells includes a single-phase input connection (IN) and a single-phase output connection (OUT), wherein the plurality of low-voltage power cells are arranged into one or more groups, wherein each group of the one or more groups includes at least one low-voltage power cell per each phase of the first electricity network, at least one low-voltage power cell per each phase of the second electricity network, controllable semiconductor switches connected to the input connections (IN) of each of the low-voltage power cells of the group, and a group-specific transformer, wherein, inside each group of the one or more groups, a single-phase input connection (IN) of a first low-voltage power cell is connected to a first winding of the group-specific transformer, the first winding being galvanically isolated from other windings of the group-specific transformer that are connected to single-phase input connections (IN) of other low-voltage power cells of the corresponding group, and wherein, inside each group of the one or more groups, the controllable semiconductor switches are configured to be controlled so that voltage waveforms of all input connections (IN) of the corresponding group are cophasal with a 50% pulse ratio.