Shipboard electrification : emission reduction and energy control

Phd ThesisThe application of green technology to marine transport is high on the sector’s agenda, both for environmental reasons, as well as the potential to positively impact on ship operator running costs. In this thesis, electrical technologies and systems as enablers of green vessels were examined for reducing emissions and fuel consumption in a number of case studies, using computer based models and simulations, coupled with real operational data. Bidirectional auxiliary drives were analysed while providing propulsion during low speed manoeuvring, coupling an electrical machine with power electronic converter and feeding power to the propulsion system from the auxiliary generators. Models were built to enable quantification of losses in various topologies and machine setups, showing how permanent magnet machines compared to induction machines, as well as examining different losses in different topologies. Another examination of topologies was performed for onshore power supply systems, where a number of different network configurations were modelled and examined based on the visiting profile for a particular port. A Particle Swarm Optimisation algorithm was developed to identify optimal configurations considering both capital costs as well as operational efficiency. This was additionally coupled with the consideration of shore-based LNG generation giving a hybrid onshore power supply configuration. Hybrid systems on vessels are more complex in terms of energy management, particularly with on-board energy storage. Particle Swarm Optimisation was applied to a model of a hybrid shipboard power system, optimising continuously for the greenest configuration during the ship’s voyage. This was developed into a generic and scalable Energy Management System, with the objective of minimising fuel consumption, and applied to a case study

Multiobjective design optimization of IGBT power modules considering power cycling and thermal cycling

Insulated-gate bipolar transistor (IGBT) power modules find widespread use in numerous power conversion applications where their reliability is of significant concern. Standard IGBT modules are fabricated for general-purpose applications while little has been designed for bespoke applications. However, conventional design of IGBTs can be improved by the multiobjective optimization technique. This paper proposes a novel design method to consider die-attachment solder failures induced by short power cycling and baseplate solder fatigue induced by the thermal cycling which are among major failure mechanisms of IGBTs. Thermal resistance is calculated analytically and the plastic work design is obtained with a high-fidelity finite-element model, which has been validated experimentally. The objective of minimizing the plastic work and constrain functions is formulated by the surrogate model. The nondominated sorting genetic algorithm-II is used to search for the Pareto-optimal solutions and the best design. The result of this combination generates an effective approach to optimize the physical structure of power electronic modules, taking account of historical environmental and operational conditions in the field

System-level design optimization of a hybrid tug

\u3cp\u3eDesigning a new vessel is a complex multi-objective design process. It involves knowledge from different fields, like naval architecture and mechanical engineering. Assessment of an optimal design for more complex topologies than a conventional Diesel powertrain becomes more difficult due to the increased number of powertrain components and feasible combinations. The purpose of this work is to present a system-level design methodology, which speeds up the component sizing and control for a powertrain topology. This system-level design problem is formulated into the minimization of a cost function. The cost function consists of the costs of the different powertrain components together with the operational costs over a specified operational profile. For the sizing of the battery and control parameters, the use of a convex optimization algorithm ensures a global optimum is found very quickly in the search space at relatively low-computational effort. For the ON/OFF switching of the Diesel engine and the Diesel generator set, an iterative scheme using convex and mixed-integer optimization is proposed. Here, without loss of generality, the optimization case study is presented for a hybrid tug.\u3c/p\u3