The Optimal Layout of Electrical Interconnection and Transmission Systems of Offshore Wind Farms

Off-shore Wind Farm (OWF) is the largest renewable energy resource. The cost of electrical interconnection and transmission systems of OWFs is a considerable fraction of the overall design cost of the farm. In order to minimize the investment and operational costs, this thesis proposes an optimization formulation to find the optimal electrical interconnection configuration of Wind Turbines (WTs) and the optimal size of cables cross section (cable sizing) simultaneously, while the transmission system and other relevant components are optimized as well (e.g. the offshore platforms, offshore substation transformers, switchgears). This simultaneous minimization of total trenching length and cable cross sections creates a complex optimization problem that is solved by the Harmony Search (HS) algorithm. The optimization performance of HS has been compared with the genetic algorithm. The proposed simulations can be applied to a symmetric or asymmetric topology of OWF, which are applied in two case studies. In the first case study, two distinct methods of full and partial optimal cable sizing have been considered to comprehensively assess the optimal interconnection layout of OWFs. Furthermore, various shipping and burying costs as well as various WTs power rating have been considered to investigate their impact on the layout of optimal electrical interconnection system. In the second case study, the optimal layout of electrical interconnection, transmission system and other relevant components of a real OWF have been found simultaneously. In order to demonstrate higher performance of the proposed optimization method and formulation, the results have been compared with another study, where a real OWF has identically been assumed to have a fair comparison, under identical conditions and constraints. The comparison results reveal that, our proposed optimal interconnection system reduces the interconnection cost, cable length and power loss of OWF. Keywords: Off-shore Wind Farm (OWF), optimal interconnection configuration, cables cross section, transmission system, Harmony Search (HS) algorithm, and simultaneous optimization.