Effect Of Wind Speed Variations Research Articles

Effect of wind speed variation on rainfed wheat production evaluated by the CERES-Wheat model.

Climate is one of the major factors affecting crop phenology and yield. In most previous studies, impacts of temperature (T) and rainfall (R) on crop development, growth, and yield were investigated, while the effect of wind speed (WS) has so far not been assessed. In this study, the influence of WS alteration on rainfed wheat production was evaluated in arid and semi-arid environments during a 25-year period in northeast Iran. In so doing, various climatic scenarios were defined using T, R, and WS changes, and then applied to the CERES-Wheat model included in DSSAT v4.7.5. The results showed that WS variation can alter total ET (planting to harvest) from -12.1 to +8.9%, aboveground biomass from -8.4 to +11.0%, water use efficiency from -13.4 to +19.7%, and grain yield from -11.2 to +15.3%. These changes were in many cases related to the climatic conditions. It was also revealed that in a greater amount of rainfall and shorter growing season (i.e., less drought stress), the WS variation had the stronger impact on total ET; while for aboveground biomass, water use efficiency, and grain yield, the greatest effect of WS variation was detected under the water scarcity conditions (i.e., low rainfall). The results demonstrate that wind speed needs to be better considered in climate change impact studies, in particular in water-scarce regions.

Experimental–numerical investigation of momentary discomfort in a high-speed train in varying wind speed conditions

Understanding the effect of wind speed variation on wind-induced momentary discomfort is the basis to improve the train vibration comfort. This study focuses on this challenge. Firstly, the momentary discomfort evaluation index Pw is developed and proved by the full-scale test. Then, setting Pw as the critical value, a multi-body nonlinear numerical investigation of the effect of the wind speed change rate, peak-wind speed duration, and wind speed variation amplitude on momentary discomfort in a train is conducted. Furthermore, the unfavourable wind speed variation condition for the wind-induced momentary discomfort in the train is obtained. Results indicate that the most intense condition for the train vibration momentary discomfort appears when the change rate of wind speed is faster and the duration of the peak wind drives the car-body rolling to the limit position. Consequently, critical wind speed for the wind-induced momentary discomfort in changing wind speed conditions is proposed, which provides a reference for an efficient train operation scheme to improve vibration comfort in a train under wind speed variation conditions.

Wavelet-Alienation Coefficient based Protection of Distribution System

Growth enhances the complexity in control of distribution networks which are progressing towards the vision of smart grids. Inclusion of non-conventional resource power generators affects in magnitude and flow directions of faults in the distribution system there by posing challenges towards protection of distribution system.. A wavelet and alienation coefficients based algorithm described in this paper for electrical distribution network protection which is also connected with wind farm. The algorithm takes the current samples at selected nodes of the wind farm connected distribution system. From the collected samples of the current signals approximation coefficients are extracted using wavelet technique. A moving half cycle window is used to obtain alienation coefficients of the current signals which were approximated by wavelet technique. Using the WT (Wavelet transform) decomposition on the currents measured at selected nodes approximation coefficients are computed, which are used for acquiring the alienation coefficients to fault classification and identification. MATLAB Simulink is used for simulation of modified IEEE 13 bus test feeder system.Effectiveness of proposed technique examine for all possible shunt faults at every bus of test feeder system. Also the effect of wind speed variations and location of wind farm connection conditions are tested to evaluate the reliability of the technique.

Impact of Correlation Between Wind Speed and Turbine Availability on Wind Farm Reliability

This paper proposes a new method to evaluate the reliability of a wind farm considering the correlation between wind turbine reliability and wind speed. With increasing integration of wind generation into the grid, the reliability and stability of the grid are increasingly impacted. Although there are obvious benefits from wind generation, the stochastic nature of wind speed causes several operational challenges. Recent research has shown that wind speeds also impact the failure rates of the turbines, thereby compounding the effect of wind speed variation. The objective of this paper is to evaluate the impact of wind speed on the reliability of a wind farm considering the correlation between wind speed and wind turbine failure rate. The method proposed in this paper is implemented using discrete convolution. The effectiveness of the proposed method is proved by comparing reliability indexes of the modified IEEE RTS-79 system with and without considering the impacts of the negative correlation between wind turbine reliability and wind speed.

Perspectives on condition monitoring techniques of wind turbines

The ever-increasing development of wind power plants has raised awareness that an appropriate condition monitoring system is required to achieve high reliability of wind turbines. In order to develop an efficient, accurate and reliable condition monitoring system, the operations of wind turbines need to be fully understood. This article focuses on the online condition monitoring of electrical, mechanical and structural components of a wind turbine to diminish downtime due to maintenance. Failure mechanisms of the most vulnerable parts of wind turbines and their root causes are discussed. State-of-the-art condition monitoring methods of the different parts of wind turbine such as generators, power converters, DC-links, bearings, gearboxes, brake systems and tower structure are reviewed. This article addresses the existing problems in some areas of condition monitoring systems and provides a novel method to overcome these problems. In this article, a comparison between existing condition monitoring techniques is carried out and recommendations on appropriate methods are provided. In the analysis of the technical literature, it is noted that the effect of wind speed variation is not considered for traditional condition monitoring schemes.

Modified virtual inertial controller for prudential participation of DFIG‐based wind turbines in power system frequency regulation

This study proposes a modified virtual inertial control (MVIC) scheme for doubly-fed induction generator (DFIG)-based wind turbines (WTs), which both improves the frequency response of these renewable resources and enhances the power system oscillation damping capabilities. It is shown that the proposed control structure enables the WT to participate prudentially in system frequency regulation, which means the amount of WT kinetic energy released to the grid and its participation in system frequency support is alleviated as its stored energy decreases. The proposed control strategy is introduced conceptually, and its performance is verified analytically. Effects of wind speed variations on the small-signal stability of DFIG WTs equipped with the proposed MVIC is investigated, as well. For these purposes, the system characteristic equation and its damping ratio, as well as the transfer function between the wind speed and the wind turbine rotor speed are derived and analysed. Eventually, time-domain simulation results and modal analysis verify the performance of the proposed method and demonstrate its superiority as compared to the conventional virtual inertial controllers.

Effect of wind speed variation on the dynamics of a high-speed train

ABSTRACTThe severe shaking due to wind speed variation in high-speed trains has a negative impact on driving safety and riding comfort. It is difficult to solve this problem by directly applying civil engineering technology because of the actual conditions. Therefore, set up a reasonable train operation plan considering the wind speed variation under strong winds is very important. In this study, a multi-body simulation model of a CRH2 high-speed rail vehicle is constructed, and the overturning coefficient is set as the safety limit, we established a crosswind model on the basis of measured wind speed curves and investigated the effect of the rate of wind speed changes, the duration of maximum wind speed and the variation of wind speed in different amplitude on the dynamics of the high-speed train. Considering the most critical wind speed variation conditions, the characteristic wind curve is obtained, which can be used as a reference to set up a reasonable train operation scheme considering the wind speed variation.

A computationally-efficient layout optimization method for real wind farms considering altitude variations

In this paper, a novel computationally-efficient optimization scheme is proposed to account for the effect of wind speed variations over non-flat terrain and irregular land plot boundary. In particular, typical analytical wake models are augmented with a wind multiplier (obtained from CFD simulations) to account for the effect of altitude variations, while irregular boundaries are addressed through novel constraint handling method in an unrestricted coordinate optimization formulation. In contrast to the optimization via CFD simulation alone, the augmented wake model provides acceptably accurate results with a reasonable computational burden. The new optimization approach is subsequently applied to two real wind farms with significant altitude variations: the Gokceada Island wind farm and the Grasmere and Albany wind farm. The optimized Gokceada wind farm layout exhibits a significant cost of energy (CoE) reduction when topography is considered (over conventional, flat-terrain optimization). However, the Grasmere and Albany wind farm shows a relatively small decrease in CoE over conventional optimization. This discrepancy can be attributed to the wind characteristics in each location: the Gokceada wind farm has a relatively consistent wind direction and the optimization can use topography to carefully avoid wake interactions. In contrast, the Grasmere and Albany wind farm with less-consistent wind directions leaves no clear method to avoid wakes using topography. These results indicate that the consideration of wind farm topography can yield significant benefits and the wake interactions can be greatly reduced through careful placement of wind turbines in the case where a narrow wind directions is dominant.

An adaptive neuro-fuzzy inertia controller for variable-speed wind turbines

A Variable-Speed Wind Turbine (VSWT) can serve as a good reservoir of Kinetic Energy (KE) for few seconds owing to wide operating rotor speed. Based on this fact, several approaches have been proposed to introduce synthetic inertial response in VSWT. Usually, this is accomplished by introducing an additional control loop at the outer most level of the control hierarchy. However, several key issues including the selection of control parameters and the effects of wind speed variations on the synthetic inertial support are not addressed. As a result, the KE reserve is severely under utilized. To address these concerns, in this work, a simple approach is proposed to control parameter selection which ensures the optimal use of available KE reserve. Further, to tackle the variable KE reserve, a comprehensive inertia controller using intelligent learning paradigm is designed. The proposed inertia controller can adapt to wind speed variations while providing optimum inertial response. Efficacy of the proposed approach is evaluated over the entire operating range of the VSWT. For further evaluation, wind speed data from NREL western wind integration is utilized. The results indicate that the proposed system is quite effective and can maintain an adequate performance over the entire operating range.

Dynamic characteristics of an isolated self-excited synchronous reluctance generator driven by a wind turbine

This paper studies the dynamic characteristics of an isolated three-phase self-excited synchronous reluctance generator (SESRG) driven by a variable-speed wind turbine under different operating conditions. Self-excitation is achieved via capacitors connected across the generator terminals. A detailed mathematical modeling of the proposed self-excited wind generation system is presented. The proposed analysis is based on the dynamic qd-axis model of the SESRG. Magnetic saturation is taken into account and is assumed to be confined to the direct axis and is accounted for as a variable direct-axis magnetizing reactance. Effect of wind-speed variation, excitation-capacitance variation, and loading-conditions variation on the generated output voltage and frequency are presented and discussed. The presented results show the effectiveness of the proposed wind-generation system. A close agreement between experimental and simulated results has been observed, which supports the validity of the proposed analysis.

Wind Speed Variation Impact on Transmission Loss Reduction in Electricity Market

Abstract In this paper, effect of wind speed variation on its output has been obtained and analysis has been carried out for transmission loss minimization. Mixed integer nonlinear programming (MINLP) approach has been utilized for determining optimal location and number of DFIG as distributed generators considering minimization of transmission loss. The impact of wind speed variation has also been incorporated in the optimization model for obtaining the impact of DFIG output on the transmission loss. The capability curves of DFIG have been modeled in an optimization model and impact of wind speed variation for 24 hrs has been considered to obtain the impact on DFIG output and thereby on the transmission loss. The total real and reactive power loss, optimal DG location, 24 hr optimal schedule of conventional generators and DG output has been obtained. The effect wind variation is determined on the location and output of DG. The proposed MINLP based optimization approach has been applied for IEEE 24 bus reliability test system.

Effect of turbine wake on optimal generation schedule and transmission losses in wind integrated power system

The aim of this paper is to study the effect of turbine wake on economic load dispatch (ED) of power system having substantial wind power capacity. The loss of power due to wind turbine wake is included in the proposed model. The ED problem is solved by Gbest guided artificial bee colony algorithm (GABC) to determine the optimum generation schedule of thermal units. The simulation results for 20 unit test system without considering wind power are presented to prove the superiority of the GABC-algorithm over previously reported methods. Finally the effect of wind speed variations, wind shade area and turbine spacing on fuel cost and transmission losses is analyzed considering modified 20 unit test system.

Factors affecting the performance of triangular pyramid solar still

This work presents a few important factors that affect the performance of a triangular pyramid solar still. An experimental work has been conducted to find the effect of water depth on the performance of the triangular pyramid solar still. From the present study, it is concluded that the convective and evaporative heat transfer coefficients are important for designing solar distillation systems and the effect of temperature difference between the evaporative and condensing surfaces is also important to optimize the operating temperature range. The condensing area of the solar still is more than that of evaporating area. Thus the experimental results showed that the effect of depth of water in the solar still affects the fresh water production. Nevertheless, outdoor experimental tests were conducted to study the effect of wind speed variations to cool down the glass cover. It was found that increasing the wind speed from 1.5 to 3m/s and to 4.5m/s has the effect of increasing the still productivity by 8 and 15.5% respectively.

Reduction of Voltage Dynamics in Isolated Wind-Diesel Units Susceptible to Gusting

The characteristic low mechanical inertia of isolated (grid-independent) wind-diesel generating units makes them significantly susceptible to time-varying components of wind speed, such as gusting and periodic ramping. With the electrical frequency maintained nearly constant by the diesel/alternator part, wind dynamics are typically reflected in terminal voltage magnitude of the overall configuration. This paper shows that a simple static excitation system, if suitably designed for a diesel/alternator setup, can reduce terminal voltage oscillations to negligible levels. The experiments reported use a laboratory wind-diesel emulator that includes a commercial diesel/alternator set, together with a wind-turbine/induction-generator emulation realized by LabVIEW-RT control of a dc drive. Output characteristics as well as real-time waveform recordings establish effectiveness of the static exciter in overcoming the adverse effect of wind speed variations.

A multiprocessor coupled ice‐ocean model for the Baltic Sea: Application to salt inflow

Within the Swedish Regional Climate Modeling Program, SWECLIM, a three‐dimensional (3‐D) coupled ice‐ocean model for the Baltic Sea has been developed to simulate physical processes on timescales of hours to decades. The code has been developed based on the massively parallel version of the Ocean Circulation Climate Advanced Modeling (OCCAM) project of the Bryan‐Cox‐Semtner model. An elastic‐viscous‐plastic ice rheology is employed, resulting in a fully explicit numerical scheme that improves computational efficiency. An improved two‐equation turbulence model has been embedded to simulate the seasonal cycle of surface mixed layer depths as well as deepwater mixing on decadal timescale. The model has open boundaries in the northern Kattegat and is forced with realistic atmospheric fields and river runoff. Optimized computational performance and advanced algorithms to calculate processor maps make the code fast and suitable for multi‐year, high‐resolution simulations. As test cases, the major salt water inflow event in January 1993 and the stagnation period 1980–1992, have been selected. The agreement between model results and observations is regarded as good. Especially, the time evolution of the halocline in the Baltic proper is realistically simulated also for the longer period without flux correction, data assimilation, or reinitialization. However, in particular, smaller salt water inflows into the Bornholm Basin are underestimated, independent of the horizontal model resolution used. It is suggested that the mixing parameterization still needs improvements. In addition, a series of process studies of the inflow period 1992/1993 have been performed to show the impact of river runoff, wind speed, and sea level in Kattegat. Natural interannual runoff variations control salt water inflows into the Bornholm Basin effectively. The effect of wind speed variation on the salt water flux from the Arkona Basin to the Bornholm Basin is minor.

Shallow soil CO2 flow along the San Andreas and Calaveras Faults, California

We evaluate a comprehensive soil CO2 survey along the San Andreas fault (SAF) in Parkfield, and the Calaveras fault (CF) in Hollister, California, in the context of spatial and temporal variability, origin, and transport of CO2 in fractured terrain. CO2 efflux was measured within grids with portable instrumentation and continuously with meteorological parameters at a fixed station, in both faulted and unfaulted areas. Spatial and temporal variability of surface CO2 effluxes was observed to be higher at faulted SAF and CF sites, relative to comparable background areas. However, δ13C (−23.3 to −16.4‰) and Δ14C (75.5 to 94.4‰) values of soil CO2 in both faulted and unfaulted areas are indicative of biogenic CO2, even though CO2 effluxes in faulted areas reached values as high as 428 g m−2 d−1. Profiles of soil CO2 concentration as a function of depth were measured at multiple sites within SAF and CF grids and repeatedly at two locations at the SAF grid. Many of these profiles suggest a surprisingly high component of advective CO2 flow. Spectral and correlation analysis of SAF CO2 efflux and meteorological parameter time series indicates that effects of wind speed variations on atmospheric air flow though fractures modulate surface efflux of biogenic CO2. The resulting areal patterns in CO2 effluxes could be erroneously attributed to a deep gas source in the absence of isotopic data, a problem that must be addressed in fault zone soil gas studies.