Peak-shaving Control of Loads on Diesel-Generators in Hybrid Electric Ships

Electric propulsion is quite common on dynamic positioned (DP) vessels, due to benefits with regards to operational availability, safety, cost effectiveness and flexibility. Thrusters, auxiliary equipment and other electric consumers gives a complex and fluctuating power demand. In this thesis the use of energy storage devices, such as batteries and capacitors, to assist the diesel-generators in a beneficial manner is studied. Several ways of enhancing the power plant dynamics by using energy storage devices is given. Peak-shaving is studied in detail and is the focus in this thesis. The idea of peak-shaving is to reduce the load variation on the diesel-generator such that they only supply a value close to the mean value. A hybrid marine power plant simulator is established and executed in real-time, as well as a human-machine interface for controlling and monitoring of the power plant. The simulator is interfaced with a real power plant located at Marintek at Tyholt in Trondheim. Several simulations are carried out and the achieved performance with respect to transient performance, fuel consumption and emissions is studied.