Simulation of the dynamic behaviour of a CODLAG propulsion plant

The paper presents a comprehensive approach to simulate the propulsion system behaviour of a ship during transients and off design conditions. The behaviour of the ship systems is simulated by means of a numerical model, developed by the authors, which includes the ship dynamics (3 D.O.F. model), the propulsion plant dynamics and the control system dynamics. The presented approach was successfully used for the design of the Italian Aircraft Carrier ‘Cavour’. The application presented in this paper concerns the design of the propulsion control system of the new Italian Frigates FREMM. This class of ships has a new propulsion plant concept : the COmbined Diesel eLectric And Gas (CODLAG) type, with single gear and two shaft lines. With respect to the previous applications, the new model is able to capture the unbalance of the shaft lines during a turning manoeuvre. This feature is used to develop a control system able to limit the undesirable consequences of this effect on the shaft line components.