Circuit assembly for linking different electrical voltage levels, as well as control method

A method for controlling a converter connected between a DC voltage (U1) of a first voltage level and a DC voltage (U2) of a second voltage level, which has an electric machine (1) having induction coils (2) arranged in a star point circuit, with a first switching unit (4) associated with the electrical machine (1) and a second switching unit (6) for a bidirectional flow of energy between the DC voltage (U1) of the first voltage level and the DC voltage (U2) of the second voltage level,

• wherein the DC voltage (U2) of the second voltage level is provided in an additional switching branch (7),
• wherein the DC voltage (U2) of the second voltage level is provided in a first branch part (12) of the additional switching branch (7) having a first switching element (8′) or in a second branch part (13) of the additional switching branch (7) having a second switching element (8″)
• the method comprising controlling the switching elements (8, 8′, 8″) of the second switching unit (6) in such a way that a star point current (iSt) of the electric machine (1) flows in a predetermined direction with a predetermined magnitude corresponding to the predetermined energy flow from the DC voltage (U1) of the first voltage level to the DC voltage (U2) of the second voltage level or from the DC voltage (U2) of the second voltage level to the DC voltage (U1) of the first voltage level.