IEEE Power Engineering Review

France appears to have the second largest wind energy potential in Europe, after the United Kingdom. According to certain estimates the potential annual production is evaluated at 70 TWh on the land and more than 90 TWh for offshore sites located in an area along the coast, with a maximum width of 10 km and where the sea depth is less than 10 m. This potential production of more than 160 TWh represents approximately 33% of the present electricity generation in France. However, the wind energy potential that will actually be exploitable will be noticeably lower. This paper describes the EOLE 2005 Program, a French national program for the promotion of wind power, launched in February 1996. The targets and incentive measures for wind power development are discussed. The grid connection of wind farms and offshore wind energy are also discussed.     

Synthesis by a soft chemistry route and characterization of LixNi1 ? xO (0 < x < 0.5) compounds: Behavior in molten carbonates

Li_xNi_{1 – x}O powders and Li_xNi_{1 – x}O/Au with 0 < x < 0.5 are synthesized by a soft chemistry route. Analysis of Li_xNi_{1 – x}O by XRD shows an evolution from NiO (0 < x < 0.3) to LiNiO₂ (0.3 < x < 0.5) structures. The stability of Li_xNi_{1 – x}O/Au (0 < x 0.5) compounds synthesized by soft chemistry is studied in molten (Li_0.52Na_0.48)₂CO₃ eutectic at 650°C, under the cathode atmosphere used in molten carbonate fuel cells (air/CO₂: 70/30). After a 48 h immersion, analysis by XRD of the lithiated nickel oxide shows that lithium ions diffuse from the oxide to the bulk of the melt. The major oxide detected at the surface of the sample has a composition very close to that of NiO formed in situ at the surface of a nickel foil. Hence, highly lithiated nickel oxides are not stable in the melt. Li_xNi_{1 – x}O is rapidly transformed confirming the very high stability of Ni(II) in the working conditions.     

A composite electromechanical distance approach to transientstability

To offset the heavy computations involved in power system transient stability studies, the authors decompose the system into internal and external areas and reduce the latter. The identification of these areas relies upon a composite electromechanical distance, designed to assess propagation of transient phenomena relating to a given contingency. To encompass a set of contingencies, a combined composite distance is devised on the basis of the concept of correlation between composite distances. Also, to encompass a set of operating conditions, a similar technique is proposed. A composite distance handling both sets of contingencies and of operating conditions is developed. Overall, the approach attempts to comply with any method of transient stability assessment and to provide a tool for online applications. This network deals with its fundamentals. Essential features such as flexibility, efficiency and reliability are tested and illustrated by means of numerous simulations performed on a 31-machine system     

Extended equal area criterion revisited [EHV power systems]

A study was conducted on the extra high voltage (EHV) French power system in order to explore the extended equal-area criterion and test its suitability as a fast transient stability indicator. The assumptions underlying the method are reexamined, causes liable to invalidate them are identified, and indices are devised to automatically circumvent them. The selection of candidate critical machines is also reconsidered, and an augmented criterion is proposed. The various improvements were developed and tested on about 1000 stability scenarios, covering the entire 400 kV system. The severity of the scenarios, resulting from the combination of weakened pre and post-fault configurations, subjected the method to particularly stringent conditions. The simulation results are summarized     

Contribution to frequency control through wind turbine inertial energy storage

An innovative way for wind energy to participate in some sort of frequency control using kinetic energy stored in the rotor for a fast power reserve that could be delivered in a short period (from several seconds up to a few tens of seconds) is presented. This kinetic-energy-based fast reserve is ensured despite wind speed variations - a disoptimisation of the power coefficient through the modification of the rotor speed set point or through the pitch control. In case of a frequency drop, the power coefficient could then be increased to produce more energy. This approach could help to reduce the dynamics and the depth of the frequency drops and therefore allow wind farms to participate in frequency control. Basic economic aspects of the provision of fast power reserve by wind turbines as a function of the amount of reserve considered are also discussed.     

Power system reduction techniques for direct transient stabilitymethods

To speed up transient stability assessment using direct methods the authors use power system reduction techniques, combining the composite electromechanical distance (CED) approach, to identify and ultimately aggregate machines (almost) irrelevant to the transient phenomena with node reduction, to eliminate irrelevant nodes while possibly taking advantage of other techniques, such as sparsity preserving and connectivity based ones. The resulting approach is illustrated for the French EHV power system. It uses direct methods of the extended equal area criterion type, together with a CED appropriately tailored to the system specifics and various node reduction techniques. Many variants so devised are compared. It is found that the CED approach significantly speeds up the direct methods while fully preserving accuracy