A turbo-compound system having a crankshaft driven by an internal combustion engine; having an exhaust gas turbine arranged in the flow of exhaust gas of the internal combustion engine; having a hydrodynamic coupling, having a primary impeller and a secondary impeller, together forming a working chamber which may be filled or is filled with a working medium, which is arranged in a driven connection between the crankshaft and the exhaust gas turbine in such a way that, when the working chamber of the hydrodynamic coupling is filled, for the exhaust gas turbine driven by the exhaust-gas flow, drive power is transmitted from the exhaust gas turbine to the crankshaft.