A method including:



mechanically driving a generator with an internal combustion engine, creating a generator rotary speed corresponding to a generator frequency,
control of the internal combustion engine such that the generator frequency is in a tolerance range, wherein a grid frequency is within the tolerance range,
detecting a phase angle difference between a current and/or a voltage generated by the generator and a grid current and/or a grid voltage,
synchronizing the voltage and/or the current with the grid voltage and/or the grid current to reduce as phase angle difference (Δφ), and
electrically connecting the generator to a power supply grid,
wherein at least one temporary change in an ignition timing of at least one cylinder unit of the internal combustion engine is performed to reduce the phase angle difference (Δφ).