Category Archives: Grid

Grid Connected Three-Level Converters


Remya Krishna – Uppsala University, Doctoral Dissertation, March 2014

Abstract

This thesis presents an electrical system analysis of a wave energy converter (WEC) for the objective of grid connection. To transfer the enormous amount of power from waves to the load centers, efficient power electronic systems are essential. This thesis includes the modeling of a buoy–translator dynamics and the modeling of a linear permanent magnet generator along with simulation and experimental validation. Continue reading

Advertisements

Leave a comment

Filed under Grid

HVDC Transmission for Offshore Wind Farms


Raymundo Enrique Torres Olguin, Alejandro Garces, Gilbert Bergna – Large Scale Renewable Power Generation, 2014

Abstract

Large-scale wind energy expansion is limited by factors such as the land use and the visual impact of facilities on land. Offshore wind energy can overcome the above-mentioned limitations. In addition, wind velocity is higher and more constant offshore than onshore. This chapter will present an overview of different topologies for grid integration of offshore wind farms. Special emphasis is made on the offshore grid topologies and types of power electronic converters.

Link

Leave a comment

Filed under Grid, Sector Overview

Integrating wave energy into the power grid: Simulation and forecasting


Gordon Reikard – Ocean Engineering, November 2013

Abstract

A major issue in integrating renewable energy into power grids is short-term forecasting. If some share of electric power is derived from renewable sources, gaps between demand and supply must be made up by other forms of generation. Because of the uniquely short-lived nature of electricity, utilities need to be able to forecast over horizons of a few hours. Up to now, studies of wave energy have relied primarily on the flux, due to the unavailability of data on power flows. This study analyzes the power output using simulations. Continue reading

Leave a comment

Filed under Grid, Modeling

Grid Connection of Wave Power Farm Using an N-Level Cascaded H-Bridge Multilevel Inverter


Rickard Ekström and Mats Leijon – Journal of Electrical and Computer Engineering, May 2013

Abstract

An N-level cascaded H-bridge multilevel inverter is proposed for grid connection of large wave power farms. The point-absorber wave energy converters are individually rectified and used as isolated DC-sources. The variable power characteristics of the wave energy converters are discussed, and a method of mitigating this issue is demonstrated. The complete power control system is given in detail and has been experimentally verified for a single-phase setup of the 9-level inverter. Theoretical expressions of the power sharing between multilevel cells are derived and show good correspondence with the experimental results.

Link

Leave a comment

Filed under Component Development, Grid


Elisabetta Tedeschi, Jonas Sjolte, Marta Molinas, and Maider Santos – Energies, May 2013

Abstract

The future success of wave energy in the renewable energy mix depends on the technical advancements of the specific components and systems, on the grid access availability and, ultimately, on the economical profitability of the investment. Small and remote islands represent an ideal framework for wave energy exploitation, due both to resource availability and to the current high cost of electricity that mostly relies on diesel generation. Energy storage can be the enabling technology to match the intermittent power generation from waves to the energy needs of the local community. In this paper real data from La Palma, in the Canary Islands, are used as a basis for the considered test case. As a first step the study quantifies the expected power production from Wave Energy Converter (WEC) arrays, based on data from the Lifesaver point absorber developed by Fred Olsen. Then, a stochastic optimization approach is applied to evaluate the convenience of energy storage introduction for reducing the final cost of energy and to define the corresponding optimal rating of the storage devices.

Link

Leave a comment

Filed under Economics, Grid

Optimal Constant DC Link Voltage Operation of a Wave Energy Converter


V. Kurupath, R. Ekströmemail, and M. Leijonemail – Energies, April, 2013

Abstract

This article proposes a simple and reliable damping strategy for wave power farm operation of small-scale point-absorber converters. The strategy is based on passive rectification onto a constant DC-link, making it very suitable for grid integration of the farm. A complete model of the system has been developed in Matlab Simulink, and uses real site data as input. The optimal constant DC-voltage is evaluated as a function of the significant wave height and energy period of the waves. The total energy output of the WEC is derived for one year of experimental site data. The energy output is compared for two cases, one where the optimal DC-voltage is determined and held constant at half-hour basis throughout the year, and one where a selected value of the DC-voltage is kept constant throughout the year regardless of sea state.

Link

Leave a comment

Filed under Grid, Modeling, System Development

Network Security Assessments for Integrating Large-Scale Tidal Current and Ocean Wave Resources Into Future Electrical Grids


J. Khan, D. Leon, A. Moshref, S. Arabi, and G. Bhuyan – Proceedings of the IEEE, April, 2013
Abstract
Marine energy, especially tidal current and ocean wave resources, bear immense potential for generating renewable power toward meeting global electricity needs. A number of conversion technologies have been successfully demonstrated worldwide and precommercial/commercial deployments are expected to appear in the near future. While electric power utilities foresee renewable technologies as a viable alternative to fossil fuels, marine energy technologies are generally excluded in their energy planning processes. Lack of technological preparedness and unavailability of device information are two major obstacles in that regard. This article provides an insight on how such novel schemes of power generation can be analyzed under conventional network planning exercises using generic information. Continue reading

Leave a comment

Filed under Grid, Modeling

The current status of wind and tidal in-stream electric energy resources


H.H.H. Aly and M.E. El-Hawary – American Journal of Electrical Power and Energy Systems, March, 2013

Abstract

Renewable energy is an effective and clean source of supplying electrical loads especially in remote and rural areas. In this paper we discuss offshore wind and tidal in-stream energy as they rely on similar technologies for generating electricity at offshore sites. In particular, we survey the impacts of offshore wind and tidal current integration into the grid, various types of generators and their dynamic modeling, fault ride-through techniques used to improve generator and grid integration performance, the aggregated wind turbines modeling and finally put the light on the stability and control problems.

Link

Leave a comment

Filed under Grid

Influence of tidal parameters on SeaGen flicker performance


J. MacEnri, M. Reed and T. Thiringer – Phil. Trans. R. Soc. A, 2013

Abstract

This paper presents the analysis of the study of the flicker emitted from the 1.2 MW tidal energy converter (TEC), SeaGen, against varying tidal parameters. This paper outlines the main elements of the TEC itself, the environment it is located in and the measurement set up. In this paper, the flicker emitted by the TEC is compared with the different tidal parameters, including flood and ebb tides, tidal speed, water depth and turbulence strength and intensity. Flicker emissions have been calculated from measured data in over 90 measurement (10 min) periods, and all of the tidal parameters vary significantly over that testing period. This allows for a detailed statistical and graphical analysis of the variation of flicker with the variation of the tidal parameters outlined above. It is found, with the exception of tidal speed, that there is no strong relationship between flicker emissions and any other tidal parameter. As SeaGen is an asymmetrical TEC with full blade pitching for flood and ebb generation, it was also found that the expected difference of flicker emissions owing to the effect of the submersed crossbeam was not significant. The TEC harmonic performance versus tidal speed is also presented.

Link

Leave a comment

Filed under Grid

A review of energy storage technologies for marine current energy systems


Z. Zhou, M. Benbouzid, J.F. Charpentier, F. Scuiller, and T. Tang – Renewable and Sustainable Energy Reviews, February, 2013

Abstract

Increasing concerns about the depletion of fossil resources and the issue of environment lead to a global need for producing more clean energy from renewable sources. Ocean is appreciated as a vast source of renewable energies. Considering marine renewable energies, it can be noticed that significant electrical power can be extracted from marine tidal currents. However, the power harnessed from marine tidal currents is highly fluctuant due to the swell effect and the periodicity of the tidal phenomenon. To improve the power quality and make the marine generation system more reliable, energy storage systems can play a crucial role. In this paper, an overview and the state of art of energy storage technologies are presented. Characteristics of various energy storage technologies are analyzed and compared for this particular application. The comparison shows that high-energy batteries like sodium–sulphur battery and flow battery are favorable for smoothing the long-period power fluctuation due to the tide phenomenon while supercapacitor and flywheel are more suitable for eliminating short-period power disturbances due to swell or turbulence phenomena. This means that hybrid storage technologies are needed for achieving optimal results in tidal marine current energy applications.

Link

Leave a comment

Filed under Grid