Current Issue : October - December Volume : 2020 Issue Number : 4 Articles : 5 Articles
By the increase of the penetration of power-electronic-based (PE-based) units, such as\nwind turbines and PV systems, many features of those power systems, such as stability, security,\nand protection, have been changed. In this paper, the security of electrical grids with high wind\nturbines penetration is discussed. To do so, first, an overview of the power systemsâ?? security\nassessment is presented. Based on that, stability and security challenges introduced by increasing\nthe penetration of wind turbines in power systems are studied, and a new guideline for the security\nassessment of the PE-based power systems is proposed. Simulation results for the IEEE 39-bus test\nsystem show that the proposed security guideline is necessary for PE-based power systems, as the\nconventional security assessments may not be able to indicate its security status properly....
This paper presents an experimental investigation of stayed cable vibrations in dry-wind and rain-wind coupling hazards. To\nmitigate large vibrations of the cable, the use of spiral wires wrapped around the cable is proposed. By testing two cable models in a\nwind tunnel in dry and rain conditions for different yaw angles and wind speeds, the effectiveness of using the spiral wires to\nmitigate large vibrations is clarified. Finally, the paper provides a further understanding of the complex mechanism of windinduced\nand rain-wind-induced vibrations. It is found that the low-frequency vortex flows in the wake play a significant role in the\nexcitation of large responses of the cable in high wind speeds. The spiral wires dismiss these low-frequency flows and then reduce\nthe large vibrations....
Four-dimensional (4D) trajectory is considered to be one of the effective means to reduce the environmental impact of aviation\nwhile increasing capacity and safety. This paper proposes an approach to optimize cruise speed profile subject to wind uncertainty,\naiming to reduce the fuel burn complying with the Required Time of Arrival (RTA) constraints. The approach is based on a\nprobabilistic framework, and the uncertainty propagation is analyzed using a Probability Transformation Method, and the\nprobability distributions of arrival time and fuel consumption are determined. In addition, from an airborne operation perspective,\ntransition profiles need to be considered in the reference speed optimization problem, aiming to improve the rationale of\nthe reference trajectory. Numerical simulations are presented, and the results demonstrate that the speed profiles optimized by this\nmethod are able to meet the RTA constraints in the presence of wind uncertainty, with an average reduction of 7.04% in fuel\nconsumption compared with that of the flight data....
Voltage source converter-high-voltage direct current (VSC-HVDC) is the mainstream technology of the offshore wind power\ntransmission, which has been rapidly developed in recent years. The small-signal stability problem is closely related to offshore wind\npower grid-connected safety, but the present study is relatively small. This paper established a mathematical model of the doubly fed\ninduction generator (DFIG) integrated into the IEEE9 system via VSC-HVDC in detail, and small-signal stability analysis of offshore\nwind farm (OWF) grid connection is specially studied under different positions and capacities. By selecting two load nodes and two\ngenerator nodes in the system for experiments, the optimal location and capacity of offshore wind power connection are obtained by\ncomparing the four schemes. In order to improve the weak damping of the power system, this paper presents a method to determine the\nparameters of the power system stabilizer (PSS) based on the particle swarm optimization (PSO) algorithm combined with different\ninertia weight functions. The optimal position of the controller connected to the grid is obtained from the analysis of modal control\ntheory. The results show that, after joining the PSS control, the system damping ratio significantly increases. Finally, the proposed\nmeasures are verified by MATLAB/Simulink simulation. The results show that the system oscillation can be significantly reduced by\nadding PSS, and the small-signal stability of offshore wind power grid connection can be improved....
Small Darrieus vertical-axis wind turbines (VAWTs) have recently been proposed as a\npossible solution for adoption in the built environment as their performance degrades less in complex\nand highly-turbulent flows. Some recent analyses have even shown an increase of the power coefficient\nfor the large turbulence intensities and length scales typical of such environments. Starting from these\ninsights, this study presents a combined numerical and experimental analysis aimed at assessing the\nphysical phenomena that take place during the operation of a Darrieus VAWT in turbulent flows.\nWind tunnel experiments provided a quantification of the performance variation of a two-blade VAWT\nrotor for different levels of turbulence intensity and length scale. Furthermore, detailed experiments\non an individual airfoil provided an estimation of the aerodynamics at high turbulence levels and\nlow Reynolds numbers. Computational fluid dynamics (CFD) simulations were used to extend the\nexperimental results and to quantify the variation in the energy content of turbulent wind. Finally,\nthe numerical and experimental inputs were synthetized into an engineering simulation tool, which\ncan nicely predict the performance of a VAWT rotor under turbulent conditions....
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