Onboard DC Power Systems for Hybrid Electric Ships: Simulation and Control
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- Institutt for marin teknikk 
The main contribution of this thesis is to build a complete model of the onboard DC power system for the simulation and control. The development motivation of the DC power system is for the better fuel economy to reduce the cost and the emission. In this master thesis, it begins with the design of the onboard DC power system for a shuttle tanker. First, the system topology is made after the study of the electrical devices that enables to transit the electrical power system from AC to DC. For the dimensioning of the design parameters, aninvestigation for the reference vessel is made to determine the power load and the available power. The modelling of the AC/DC rectifier, DC/DC converter, DC/AC inverter, protective devices, filters and energy storage systems (battery and supercapacitor) are found. AC/DC rectifier is connected with a LCL filter to reduce the ripple on the main DC voltage. For the DC/DC converter, there are several modelling methods are available, so the comparison between the state-space averaging method and generalized averaging method is carried out. However, the DC/AC inverter is excluded from the modelling, since the AC load is modelled as a constant power and constant impedance load which magnitudes are same in DC. For the control of the devices, DQ-decoupling control method for the AC/DC rectifier and sliding mode control for the DC/DC converter are studied. The battery is controlled based on the state of charge and the supercapacitor is regulated to be operated between the maximum and minimum voltage range. Lastly, the integrated simulation is carried out with the energy storage system both in charging mode and in discharging mode.