Volume 6, Issue 5, September 2014
Index of content:
- REGULAR ARTICLES
6(2014); http://dx.doi.org/10.1063/1.4893571View Description Hide Description
Security risk assessment difficulties brought about by uncertainties can be solved by probabilistic power flow. A security risk assessment scheme of the power system using fast probabilistic power flow is proposed in this paper. The scheme applied probabilistic power flow on fast decoupled power flow model, considering multi-scenario of wind power and static characteristics of power systems, gaining the probabilistic distribution information of each desired variable by improved Von Mises method based on cumulants. Besides voltages and branch flows, the scheme can also obtain the distribution of frequency to assess the power system completely, which is not concerned in conventional probabilistic power flow calculation. The proposed algorithm was realized by programming based on Matpower 4.0. The examples executed on IEEE RTS-24 system demonstrate the rapidity, validity, and prospect for online application of the proposed scheme.
6(2014); http://dx.doi.org/10.1063/1.4895909View Description Hide Description
Occurrence of liquefaction in saturated sandy deposits under structure foundation can cause a wide range of structural damages from minor settlement to general failure because of bearing capacity loss. By comparing traditional foundations for offshore wind turbines, the soil inside and underneath the composite bucket foundation is subjected to the overburden pressure from the foundation self-weight and constrained by a half-closed bucket skirt. The objective of this paper is to clarify the effects of the soil-foundation interaction on the soil liquefaction resistance around the skirt and under the foundation. The dynamic response of the composite bucket foundation during earthquake, including coupled soil mode of porous media, is calculated using the ADINA finite-element program. A typical configuration of composite bucket foundation is used for the analysis, and two earthquake waves (peak ground accelerations of 0.035 g and 0.22 g) are applied as the base acceleration. The results show that the composite bucket foundation exhibited good resistance to seismic action by improving the anti-liquefaction capacity of the soil inside and under the foundation because of the overburden pressure of the self-weight and the constraint effect of the skirt.
6(2014); http://dx.doi.org/10.1063/1.4895919View Description Hide Description
This study presents a thorough methodology for wind park design and micro-siting. It encompasses all aspects of wind project development and prefeasibility analysis. This approach uses the long-term wind data taken from on site measurements. Collected data are analyzed statistically. Then, wind resources are estimated and a choice of the best fitted wind turbines is performed. An optimal layout for wind turbines is proposed using the Windstation and 3DEM software. The main contribution of this paper is to evaluate the amount of accuracy given by this methodology in terms of predicting the future annual energy production of wind projects. To achieve this objective, the methodology was applied to a specific site which already contains an installed wind park. The test case wind farm is located in the north-east of Tunisia. The evaluation is performed by comparing the estimated energy production with real-time operation database of the wind park. Finally, the paper discusses the prospects of wind farm upgrading in order to make better use of the local wind resource.
6(2014); http://dx.doi.org/10.1063/1.4896319View Description Hide Description
An offshore wind turbine in shallow water is installed by a self-elevated mobile unit that is usually referred to as a jack-up barge or jack-up vessel. The jack-up vessel consists of a buoyant platform together with independent legs that can position the vessel above the water, thereby reducing external loadings for a safe operation condition. The retrieval process for the jack-up legs can be very difficult due to the high extraction resistance caused by soft soil. In soft clay, high suction force can develop around the spudcan attached at the end of the jack-up legs. Therefore, a jetting system is required to break the suction in order to pull out the legs. It is important to design the jetting system with an optimized piping arrangement to allow the easy operation. Various factors must be considered in the design of the jetting piping system since the level of embedment, type of soil, and pipe sizes and locations can affect the performance of the system. In this paper, we present the characteristics of west coast geological features by subsea geological survey and the design of jetting system that was analyzed using pipe flow analysis program.