It is presented a power system (3) for dynamic positioning of a vessel. The power system disclosed herein reduces the specific fuel consumption, reduces carbon buildup deposits and the risk of cylinder bore glazing while in combustion engine driven generators and provides an adequate protection against blackouts for several dynamic positioning classes. The power system (3) comprises a first combustion engine driven generator (G1), a second combustion engine driven generator (G2), a battery unit (11), and a converter unit (9) arranged to provide power to the vessel from the battery unit (11), wherein in a first operational state of the power system (3) only the first combustion engine driven generator (G1) is arranged to deliver power to the vessel, and wherein in a second operational state, in which the first combustion engine driven generator (G1) is subject to a fault, the second combustion engine driven generator (G2) is arranged to deliver power to the vessel, and wherein the converter unit (9) is arranged to deliver power to the vessel during transition from the first to the second operational state. It is also presented a sectionalised power system (2) which is a system comprising several power systems (3) as defined hereabove.