Comparison of Active Torque Damping Methods for a Power Unit in Relation to Implementation Complexity

A power unit is used if a grid failure occurs or an off-grid operation is necessary. The energy conversion is possible with the coupling of an internal combustion engine (ICE) and an electric machine. A torque ripple, caused by the pressure in the cylinder, occurs during the compression and expansion stroke of the ICE. This torque ripple has a great influence to the acoustic noise, vibrations and the lifetime of the power unit. The main task for a smooth operation is to reduce the torque ripple. For this purpose the electric machine can be used as actuator to compensate the torque ripple in addition to its main use of converting the electric energy. This is possible by using it in the compression stroke as an electric motor and in the expansion stroke as an electric generator. The challenge of this approach is to estimate accurately enough the produced torque of the ICE. The estimation is possible by using different technology efforts. The quality of the torque ripple compensation depends of the available sensors and the controlling effort. Consequential the main task results for this paper: It has to compare different compensation methods with the implementation complexity to estimate the achievable maximum torque damping.