A wave-to-wire model for grid integration studies of oscillating-body wave energy converters

Wave energy converters (WECs) are still at an earlier stage of development when compared to variable renewable energy systems based on wind or solar power. Indeed, only a few WECs have exported power to electric grids until recently. Thus, the development of mathematical models able to represent essential aspects of the system and its connection to the grid becomes fundamental to assess the impact of integrating wave power to grids. This work develops a fully integrated wave-to-wire model, where the electrical model has re-configurable dynamic models of rotary and linear generators (with controllers) to accommodate different types of oscillating-body systems. Such an electrical model is interfaced with the WEC hydrodynamic and mechanical models. A complete wave-to-grid model is presented by integrating the generator system model, an electrical grid interface unit and a network equivalent for the receiving grid in a unified simulation environment with the WEC-Sim, an open-source tool for simulating the dynamic behaviour of WECs. Numerical simulation studies are presented considering different operating conditions for the grid integration of a floating body that is connected to either an hydraulic power take-off system or a direct-drive system.A wave-to-wire model for grid integration studies of oscillating-body wave energy convertersacceptedVersio

Grid Integration of offshore wind farms using a Hybrid HVDC composed by an MMC with an LCC-based transmission system

This paper presents a hybrid HVDC-transmission system composed by a Full-Bridge Modular Multilevel Converter (FB-MMC) and a Line-commutated Converter (LCC) from the grid integration of offshore wind farms. The operational characteristics of a three-terminal hybrid-HVDC system, e.i. two LCC stations plus one MMC station, are investigated using PSCAD/EMTDC. This paper mainly focuses on the performance of the system under ac faults at the LCC inverter. This condition is critical for the entire system because LCC is prone to commutation failure, which can be translated into dc faults on the hybrid system. Numerical results show that FB-MMC can help to alleviate ac faults conditions in the LCC, and the system is able to restart after clearance of the fault.publishedVersio

Technology perspectives of the North Sea Offshore and storage Network (NSON)

-This report contains an overview over the most relevant technologies for realising an offshore power system in the North Sea. Also electric energy storage technologies are being considered, as these may be built offshore and integrated into the offshore power system. Special focus is given on the future perspectives and potentials of the technologies. The technologies are regarded both on component and system level. This technology assessment is concluded with a gap analysis and recommendations for the ways forward toward the realisation of the North Sea Super Grid

Investigation on Fault-ride through Methods for VSC-HVDC Connected Offshore Wind Farms

-This paper proposes a novel fault-ride through method for offshore wind farms connected to grid through a voltage source converter (VSC)-based high voltage direct current (HVDC) transmission. The proposed method introduces a controlled voltage drop at offshore grid when an onshore fault occurs. The idea behind is to achieve a fast power reduction. Additionally in the proposed idea, every individual wind turbine detects the voltage drop of offshore grid almost simultaneously, then its controller decreases the power set-point to reduce the power output from each wind turbine. The effectiveness of this method is verified by numerical simulations performed in PSCAD

Grid Integration of offshore wind farms using a Hybrid HVDC composed by an MMC with an LCC-based transmission system

This paper presents a hybrid HVDC-transmission system composed by a Full-Bridge Modular Multilevel Converter (FB-MMC) and a Line-commutated Converter (LCC) from the grid integration of offshore wind farms. The operational characteristics of a three-terminal hybrid-HVDC system, e.i. two LCC stations plus one MMC station, are investigated using PSCAD/EMTDC. This paper mainly focuses on the performance of the system under ac faults at the LCC inverter. This condition is critical for the entire system because LCC is prone to commutation failure, which can be translated into dc faults on the hybrid system. Numerical results show that FB-MMC can help to alleviate ac faults conditions in the LCC, and the system is able to restart after clearance of the fault