DC converter for connecting high-voltage DC networks (59, 67) with different voltages, with - a converter series circuit formed of sub-converters (21, 22, 23, 24) connected in series that is arranged between a positive and a negative connection terminal of a first DC connection, - wherein at least two sub-converters of the converter series circuit are arranged as positive pole sub-converters (21, 22) in series between a central connection terminal and the positive connection terminal of the first DC connection and - the positive pole sub-converters (21, 22) are connected together through positive pole power exchanging means, so that the exchange of electrical power between the positive pole sub-converters (21, 22) is enabled, - wherein the potential node between the positive pole sub-converters (21, 22) forms a positive connection terminal of a second DC connection, - wherein at least two sub-converters of the converter series circuit are arranged as negative pole sub-converters (23, 24) in series between the central connection terminal and the negative connection terminal of the first DC connection and - the negative pole sub-converters (23, 24) are connected together through negative pole power exchanging means, so that the exchange of electrical power between the negative pole sub-converters (23, 24) is enabled, - wherein the potential node between the negative pole sub-converters (23, 24) forms a negative connection terminal of the second DC connection, - wherein additional power exchanging means are provided that are connected to the positive pole sub-converters (21, 22) and the negative pole sub-converters (23, 24) in such a way that an exchange of power between the positive pole sub-converters (21, 22) and the negative pole sub-converters (23, 24) through the additional power exchanging means is enabled, and - the positive pole power exchanging means comprise a positive pole transformer and the negative pole power exchanging means comprise a negative pole transformer, characterized in that - the additional power exchanging means comprise a tertiary winding in the negative pole transformer and a tertiary winding in the positive pole transformer and the tertiary winding of the positive pole transformer is galvanically connected to the tertiary winding of the negative pole transformer, - each sub-converter (21, 22, 23, 24) comprises at least two phase modules, wherein each phase module comprises a series circuit of two-pole sub-modules, and - each sub-module comprises an energy store and a power semiconductor circuit, wherein a half-bridge or full-bridge circuit, or a double module, is formed. - a converter series circuit formed of sub-converters (21, 22, 23, 24) connected in series that is arranged between a positive and a negative connection terminal of a first DC connection, - wherein at least two sub-converters of the converter series circuit are arranged as positive pole sub-converters (21, 22) in series between a central connection terminal and the positive connection terminal of the first DC connection and - the positive pole sub-converters (21, 22) are connected together through positive pole power exchanging means, so that the exchange of electrical power between the positive pole sub-converters (21, 22) is enabled, - wherein the potential node between the positive pole sub-converters (21, 22) forms a positive connection terminal of a second DC connection, - wherein at least two sub-converters of the converter series circuit are arranged as negative pole sub-converters (23, 24) in series between the central connection terminal and the negative connection terminal of the first DC connection and - the negative pole sub-converters (23, 24) are connected together through negative pole power exchanging means, so that the exchange of electrical power between the negative pole sub-converters (23, 24) is enabled, - wherein the potential node between the negative pole sub-converters (23, 24) forms a negative connection terminal of the second DC connection, - wherein additional power exchanging means are provided that are connected to the positive pole sub-converters (21, 22) and the negative pole sub-converters (23, 24) in such a way that an exchange of power between the positive pole sub-converters (21, 22) and the negative pole sub-converters (23, 24) through the additional power exchanging means is enabled, and - the positive pole power exchanging means comprise a positive pole transformer and the negative pole power exchanging means comprise a negative pole transformer, - the additional power exchanging means comprise a tertiary winding in the negative pole transformer and a tertiary winding in the positive pole transformer and the tertiary winding of the positive pole transformer is galvanically connected to the tertiary winding of the negative pole transformer, - each sub-converter (21, 22, 23, 24) comprises at least two phase modules, wherein each phase module comprises a series circuit of two-pole sub-modules, and - each sub-module comprises an energy store and a power semiconductor circuit, wherein a half-bridge or full-bridge circuit, or a double module, is formed.