POWER CONTROL UNIT

A power control unit (1) for a propulsion system (100) of a marine vessel comprising an internal combustion engine (4) and a shaft (2) with a shaft generator (5) is configured to provide a fuel command to the internal combustion engine (4) based on a slow component of a speed error of the shaft (2), i.e. the slow component of a deviation of the shaft speed from a speed setpoint. A generator power command is provided to the shaft generator (5) based on a fast component of the speed error of the shaft (2) as well as on an electrical grid state of an electrical grid that is electrically connected to the shaft generator (5). An energy buffer (7) is used for storing and releasing electrical power from and to the shaft generator (5) and to the electrical grid (8). Thus, a more stable engine control regime and the avoidance of an engine overload is easier to achieve.