Wave farm collection grid analysis and design

Report, 2013

In this report, the collection grid of a wave farm is designed and analysed, the system under consideration goes from the connection point at each power converter (included in each wave energy unit) up to the point of common connection with the main grid. Time series that have been provided by Ocean Harvesting Technologies (OHT), being obtained from their simulation models for a scaled prototype and include data for mild, medium and strong sea states. The simulation models have been validated against small scale tank testing of a prime mover, a wave rider buoy, and scaled testing of the power take-off in a land based test-rig. Wave data is taken from EMEC, Scotland [7]. The design of the collection grid aims to optimize its size by minimizing its cost while maximizing the power output. For the economical assessment three layouts are taken into account and several scenarios for different energy prices and interest rates are presented. A life-cycle analysis is also done where the entire life span of the collection grid is considered showing that around 30Euro/MWh will be the share of the electricity price required to install and operate the collection grid. The power quality of the resultant layout and its compliance with the grid code of the UK are analysed as well. This analysis includes power factor and voltage fluctuation estimation, line-fault ride-through assessment and flicker contribution analysis. Given the pulsating nature of the wave power systems special emphasis in the study of flicker emissions is done concluding that the proposed wave park is within the grid code limitations and even a reduction of a 66% in the flicker coefficients is reported when considering the aggregation of several units in one model.