Wind Farm Configurations Research Articles

DC-DC Chopper Excitation Control of WRSG for MPPT in Offshore Wind Farm

Abstract This paper gives an idea of different state of the art of offshore wind farm configurations. One of the configurations uses Wound Rotor Synchronous Generator (WRSG), which is connected to HVDC grid through diode bridge rectifier. Field excitation of the generator is controlled for achieving Maximum Power Point Tracking (MPPT) to have full utilization of wind power. The most important feature of the suggested prototype is its low cost and high efficiency. A working model of this configuration is implemented in hardware using DSPIC and the results are verified.

An investigation of in‐field blockage effects in closely spaced lateral wind farm configurations

AbstractA method of increasing the performance of wind farms has been established by limiting the lateral separation between neighbouring wind turbines. The close proximity of the wind turbines creates a beneficial in‐field blockage effect that results in a core of increased speed that is accelerated through the gap between the turbines. A preceding study indicated that the performance of three wind turbines can be increased by over 10% with tip‐to‐tip separation of 0.5 diameters (D) compared with the power output of the respective turbines in isolation. A corresponding flow‐mapping study has been completed in the current work using a single‐normal hot‐wire anemometer to characterize the increased flow speed through a narrow lateral gap, leading to the observation of a region of increased speed that occurs between 0D and 2.5D downstream of the gap between laterally spaced wind turbines. The experimental results were confirmed by conducting a series of computational simulations with the generalized unsteady vortex particle discrete vortex method code. The simulations were conducted with three rotors arranged in five different configurations, and the increase in power generated by the multi‐rotor configurations closely followed the observed experimental trends. The closely spaced lateral wind turbine configurations may have the ability to increase the annual capacity factor of wind farms while reducing wind farm land use requirements. Copyright © 2014 John Wiley & Sons, Ltd.

A Model-Free Approach for Maximizing Power Production of Wind Farm Using Multi-Resolution Simultaneous Perturbation Stochastic Approximation

This paper provides a model-free approach based on the Multi-Resolution Simultaneous Perturbation Stochastic Approximation (MR-SPSA) for maximizing power production of wind farms. The main advantage is that the method based on MR-SPSA can achieve fast controller tuning without any plant model by exploiting the information of the wind farm configuration such as turbines location and wind direction. In order to simulate the performance of the model-free scheme, a wind farm model with dynamic characterization of wake interaction between turbines is used and then the proposed method is applied to the Horns Rev wind farm. Simulation results illustrate that the method based on MR-SPSA achieves the maximum total power production with faster convergence compared with other existing model-free methods.

Some of the Design Considerations in Power Generation from Offshore Wind Farms

The global efforts to reduce carbon emissions from power generation have favoured renewable energy resources such as wind and solar in recent years. The generation of power from the renewable energy resources has become attractive because of various incentives provided by government policies supporting green power. Among the various available renewable energy resources, the power generation from wind has seen tremendous growth in the last decade. This article discusses various advantages of the upcoming offshore wind technology and associated considerations related to their construction. The conventional configuration of the offshore wind farm is based on the alternative current internal links. With the recent advances of improved commercialised converters, voltage source converters based high voltage direct current link for offshore wind farms is gaining popularity. The planning and construction phases of offshore wind farms, including related environmental issues, are discussed here.

A study of the performance benefits of closely-spaced lateral wind farm configurations

Scaled wind turbine experiments were conducted in order to evaluate the beneficial effect of closely-spaced lateral wind turbine configurations on the performance of a wind farm. Two outer wind turbines were spaced apart with a particular gap distance and the longitudinal setback of a central rotor was varied at each gap width. The turbine placement resulted in tip-to-tip separation distances that ranged from 1 diameter (D) to 0.25D. Additionally, the performance of a wind farm layout in rough and smooth boundary layers, designed to mimic onshore and offshore conditions, respectively, was evaluated. It was observed that a narrow gap between several laterally-aligned rotors creates an in-field blockage effect that results in beneficial flow acceleration through the gap. This increase in speed increases the power output of the central turbine when its longitudinal setback is between 0D and 2.5D. A cumulative increase in power output of 17% was observed when 3 rotors were aligned in a lateral plane with a blade tip separation of 0.5D or 0.25D, compared to the same number of rotors in isolation. While the benefits of closely-spaced wind turbines were observed in both of the tested boundary layers, the performance benefits with a smooth boundary layer were smaller than with a rough boundary layer. These results may lead to new wind farm design methodologies for certain topology- and wind distribution-specific sites and suggest that wind turbines can be closely-spaced in the lateral direction in order to obtain substantial increases in power.

A Multivariate and Multimodal Wind Distribution model

This paper presents a new methodology to accurately characterize and predict the annual variation of wind conditions. The estimate of the distribution of wind conditions is necessary to quantify the available energy (power density) at a site, and to design optimal wind farm configurations. A smooth multivariate wind distribution model is developed to capture the coupled variation of wind speed, wind direction, and air density. The wind distribution model developed in this paper avoids the limiting assumption of unimodality of the distribution. This method, which we call the Multivariate and Multimodal Wind Distribution (MMWD) model, is an evolution from existing wind distribution modeling techniques. Multivariate kernel density estimation, a standard non-parametric approach to estimate the probability density function of random variables, is adopted for this purpose. The MMWD technique is successfully applied to model (i) the distribution of wind speed (univariate); (ii) the joint distribution of wind speed and wind direction (bivariate); and (iii) the joint distribution of wind speed, wind direction, and air density (multivariate). The latter is a novel contribution of this paper, while the former offers opportunities for validation. Both onshore and offshore wind distributions are estimated using the MMWD model. Recorded wind data, obtained from the North Dakota Agricultural Weather Network (NDAWN) and the National Data Buoy Center (NDBC), is used in this paper. The coupled distribution was found to be multimodal. A strong correlation among the wind condition parameters was also observed.

Reactive Power Compensation and Configuration of Wind Farm

Wind turbine absorbs reactive power while generating active power. Seriously, it causes voltage drop or even voltage collapse. It is needed to compensate reactive power. In this paper, a combination of capacitor bank and SVC is used in wind farm. Equivalent circuit of two kinds of wind turbine is described firstly. Then, equation of reactive power and active power is derived. Then an optimization method is used to calculate capacity of capacitor bank and SVC. Finally, load flow of IEEE14 system with a wind farm connected to it is calculated to verify the effect of reactive power compensation.

Optimization of Wind Farm Turbine Layout Including Decision Making Under Risk

This paper presents a new contribution to optimal wind farm design, including the main risk management aspects. The objective of the algorithm is to optimize the expected profits of the wind farm by taking into account that the wind data used to design the wind farm involves some degree of uncertainty that affects the final return of the project. Net present value (NPV) will be used as a figure of the profitability in the proposed method. The maximization of the NPV means the maximization of the cumulative net cash flows (by maximizing the generation of net energy) and minimization of the investment. Both terms mainly depend on the number and type of wind turbines, tower height, and geographical position, among other factors. Therefore, the tool developed in this paper is intended to determine the wind farm configuration most suitable in the presence of risk due to uncertainty in the wind data.

Calculating annualized sound levels for a wind farm.

Modeling done for wind farms usually focuses on calculating a worst‐case short term average sound level. However, the impact to homes is not simply defined by a single meteorological condition. Rather, a more complete picture of the impacts is given by calculating sound levels under various meteorological conditions that occur during the year. The actual sound level at a receiver will depend on variations in atmospheric stability, wind speed, wind direction, and other parameters that change hourly. This paper will describe a method to calculate hourly sound pressure levels for individual receivers over the course of an 8760 h year and give examples of different wind farm configurations and how they affect annualized sound levels.

Optimization of wind farm turbines layout using an evolutive algorithm

The optimum wind farm configuration problem is discussed in this paper and an evolutive algorithm to optimize the wind farm layout is proposed. The algorithm's optimization process is based on a global wind farm cost model using the initial investment and the present value of the yearly net cash flow during the entire wind-farm life span. The proposed algorithm calculates the yearly income due to the sale of the net generated energy taking into account the individual wind turbine loss of production due to wake decay effects and it can deal with areas or terrains with non-uniform load-bearing capacity soil and different roughness length for every wind direction or restrictions such as forbidden areas or limitations in the number of wind turbines or the investment. The results are first favorably compared with those previously published and a second collection of test cases is used to proof the performance and suitability of the proposed evolutive algorithm to find the optimum wind farm configuration.

Simulation of wind turbine wake interaction using the vorticity transport model

AbstractThe aerodynamic interactions that can occur within a wind farm can result in the constituent turbines generating a lower power output than would be possible if each of the turbines were operated in isolation. Tightening of the constraints on the siting of wind farms is likely to increase the scale of the problem in the future. The aerodynamic performance of turbine rotors and the mechanisms that couple the fluid dynamics of multiple rotors can be most readily understood by simplifying the problem and considering the interaction between only two rotors. The aerodynamic interaction between two rotors in both co‐axial and offset configurations has been simulated using the Vorticity Transport Model. The aerodynamic interaction is a function of the tip speed ratio, and both the streamwise and crosswind separation between the rotors. The simulations show that the momentum deficit at a turbine operating within the wake developed by the rotor of a second turbine is governed by the development of instabilities within the wake of the upwind rotor, and the ensuing structure of the wake as it impinges on the downwind rotor. If the wind farm configuration or wind conditions are such that a turbine rotor is subject to partial impingement by the wake produced by an upstream turbine, then significant unsteadiness in the aerodynamic loading on the rotor blades of the downwind turbine can result, and this unsteadiness can have considerable implications for the fatigue life of the blade structure and rotor hub. Copyright © 2009 John Wiley & Sons, Ltd.

Load flow analysis for variable speed offshore wind farms

A serial AC–DC integrated load flow algorithm for variable speed offshore wind farms is proposed. It divides the electrical system of a wind farm into several local networks, and different load flow methods are used for these local networks sequentially. This method is fast, more accurate, and many factors such as the different wind farm configurations, the control of wind turbines and the power losses of pulse width modulation converters are considered. The DC/DC converter model is proposed and integrated into load flow algorithm by modifying the Jacobian matrix. Two iterative methods are proposed and integrated into the load flow algorithm: one takes into account the control strategy of converters and the other considers the power losses of converters. In addition, different types of variable speed wind turbine systems with different control methods are investigated. Finally, the method is demonstrated using an 80-MW offshore wind farm.

3D-simulation of the turbulent wake behind a wind turbine

The paper relates to the simulation of the airflow around a wind turbine (WT) of the type ENERCON E66 with emphasis on the turbulent wake. The simulations were undertaken with the Computational Fluid Dynamics (CFD) software ANSYS FLUENT 6.3 using the LES technique for turbulence modeling. It is the aim of the work to capture the full three-dimensional turbulent flow behind a WT in a sufficient spatial and temporal resolution to generate information for wind loads of WTs in wind farm configuration. This information shall help to optimize wind farm layouts in the future. Using an incoming wind field that matches the requirements of the IEC-61400 for wind fields used in load calculations it was possible to simulate a full meandering turbulent wake. The turbulent features of the WT wake could be reproduced with numerical methods not using further assumptions but solely based on the WT geometry and the solution of the governing physical equations. The project is supported by ENERCON GmbH, Germany.

The economics of wind farm siting in Holland

The economic feasibility of wind farms dos not only depend on the turbine costs and the local wind resource. The turbine costs take 50 to 75 percent of the investments. The non-turbine costs are: • - cable works, connection to the local grid • - foundation and road constructions • - purchase costs of ground • - engineering costs These costs will be discussed and methods will be presented to select low cost locations and to make optimal use of these locations. These methods will result in an optimal wind farm configuration of single lines.