Patent ID: 7558087

Claim:
A multilevel AC/DC converter for converting a single-phase, line-frequency AC supply voltage of an AC supply line to a DC link voltage (U DC ) of a DC link in railway traction applications, comprising a traction transformer for establishing a galvanic isolation between the AC supply line and the DC link, wherein the traction transformer is operable at a transformer nominal frequency (f TR ) above the AC line frequency, multiple primary converters connectable to the AC supply line, wherein inputs of the primary converters are connected in series and wherein an output of each primary converter is connected to a primary winding of the traction transformer, and at least two secondary converters, a secondary converter being connectable to the DC link, wherein an input of the respective secondary converter is connected to a respective secondary winding of the traction transformer, wherein outputs of the at least two secondary converters are connected in parallel, wherein the primary converters are cycloconverters, and wherein the nominal frequency of the traction transformer(f TR ) is less than 3 kHz.