Method for operating a parallel hybrid drive train of a vehicle having a plurality of drive units

A method for operating a parallel hybrid drive train (1) of a vehicle having a plurality of drive units (2, 3) and with an output (5) described. In each case, at least one combustion engine (2) and an electric machine (3), wherein the at least one electric machine (3) is arranged in the power train between the output (5) and the at least one combustion engine (2). Between the combustion engine (2) and the electric machine (3) is arranged a frictional shift element, During between the electric machine (3) and the output (5), a hydrodynamic torque converter (8A) is provided. A at the output (5) to be applied target output torque is a function of a slip of between the electric machine (3) and the output (5) disposed hydrodynamic torque converter (8A). To illustrate the the output shaft (5) to be applied target output torque is a at least one of the drive units (2, 3) for generating the target drive torque as a function of the requested target output torque, an actual turbine speed of the hydrodynamic torque converter (8A) or an equivalent thereto speed size of the parallel hybrid power train (1 ) and the actual speed of the electrical machine (3) via an inverse converter identifier of hydrodymanischen torque converter (8A) is determined.