Adequacy assessment of generating systems containing wind power considering wind speed correlation

Wind power is an important renewable energy resource. Electrical power generation from wind energy behaves quite differently from that of conventional sources, and maintaining a reliable power supply is an important issue in power systems containing wind energy. In these systems, the wind speeds at different wind sites are correlated to some degree if the distances between the sites are not very large. Genetic algorithm methods are applied here to adjust autoregressive moving-average time series models in order to simulate correlated hourly wind speeds with specified wind speed cross-correlation coefficients of two wind sites. Multi-state wind energy conversion system models are used to incorporate the correlated wind farms in reliability studies of generating systems. A method to generate random numbers with specified correlation coefficients for application in a state-sampling Monte Carlo simulation technique is introduced. It is shown that the proposed method can be used in the adequacy assessment of a generating system incorporating partially dependent wind farms.     

储能设备对孤立风力发电系统的影响

采用序贯蒙特卡罗法对含有储能设备的风/柴孤立发电系统进行充裕度评估。针对样例系统,在发电系统强迫停运率、储能设备容量以及峰值负荷取值不同的情况下,计算发电系统的充裕度指标;研究储能设备对孤立发电系统充裕度的影响,并对产生影响的原因进行分析。结果表明,加入储能设备可改善发电系统的充裕度,提高系统的供电可靠性水平,减少风力发电机组输出功率波动对系统的影响。分析方法和结果可为储能设备在风力发电系统中的应用和储能设备容量的选择等方面提供参考。     

Considering load-carrying capability and wind speed correlation of WECS in generation adequacy assessment

Wind power is an intermittent energy source that behaves quite differently from conventional energy sources. The reliability impact of this highly variable energy source is an important aspect that needs to be assessed as wind power penetration becomes increasingly significant. Generation adequacy assessment including wind energy conversion systems (WECS) at multiple locations is described in this paper. Effective load-carrying capabilities (ELCC) obtained using the loss of load expectation (LOLE) and the loss of load frequency (LOLF) for a power system containing WECS are illustrated and compared. The results show that ELCC obtained using the LOLF and obtained using the LOLE for WECS can be considerably different, while they are similar for a conventional generating unit. The impact on the system reliability indices of wind speed correlation between two wind farms is also examined. The studies show that the degree of wind speed correlation between two wind farms has a considerable impact on the resulting reliability indices. The sequential Monte Carlo simulation approach is used as this methodology can facilitate a time series modeling of wind speeds, and also provides accurate frequency and duration assessments. An autoregressive moving average time series model is used in this study to simulate hourly wind speeds.     

A sequential simulation technique for adequacy evaluation ofgenerating systems including wind energy

A wind energy conversion system (WECS) has a different impact on the reliability performance of a generating system than does a conventional energy conversion system. This is due to the variation of wind speeds and the dependencies associated with the power output of each wind turbine generator (WTG) in a wind farm. In this paper, a sequential Monte Carlo simulation technique is proposed for adequacy evaluation of a generating system including WECS. The method is based on an hourly random simulation to mimic the operation of a generating system, taking into account the auto-correlation and fluctuating characteristics of wind speeds, the random failure of generating units and other recognized dependencies. The hourly wind speeds are simulated utilizing autoregressive and moving average time series models that are established based on the F-criterion. A small reliability test system designated as the RBTS is used to illustrate the proposed method     

Generating capacity adequacy associated with wind energy

The wind is a highly variable energy source and behaves far differently than conventional energy sources. This paper presents a methodology for capacity adequacy evaluation of power systems including wind energy. The results and discussions on two representative systems containing both conventional generation units and wind energy conversion systems (WECS) are presented. A Monte Carlo simulation approach is used to conduct the analysis. The hourly wind speeds are simulated using an autoregressive moving average time-series model. A wide range of studies were conducted on two different sized reliability test systems. The studies show that the contribution of a WECS to the reliability performance of a generation system can be quantified and is highly dependent on the wind site conditions. A WECS can make a significant reliability contribution given a reasonably high wind speed. Wind energy independence also has a significant positive impact on the reliability contribution of multiple WECS.     

Wind energy for the 1990s and beyond

Electrical power must be available to the consumer in any amount upon demand. Conventional methods of power generation, such as the burning of fossil fuels, hydroelectric plants, and nuclear power plants, have considerable shortcomings. Governmental regulations have increased in quantity and have raised the already rigid standards of producing electric power without further damage to the environment. Electrical power produced by wind energy conversion systems are undergoing extensive research and revitalization as a viable solution to clean air power generation. The basic challenge to scientists and engineers is to develop wind energy conversion systems that produce adequate amounts of power, but at a cost comparable to present conventional methods. This article discusses the background and impact of the modern wind energy conversion system on future power generation.     

A review on reliability assessment for wind power

The application of wind energy in electric power systems is growing rapidly due to enhanced public concerns to adverse environmental impacts and escalation in energy costs associated with the use of conventional energy sources. Electric power from wind energy is quite different from that of conventional resources. The fundamental difference is that the wind power is intermittent and uncertain. Therefore, it affects the reliability of power system in a different manner from that of the conventional generators. This paper, from available literatures, presents the model of wind farms and the methods of wind speed parameters assessment. Two main categories of methods for evaluating the wind power reliability contribution, i.e., the analytical method and the Monte Carlo simulation method have been reviewed. This paper also summarizes factors affecting the reliability of wind power system, such as wake effect, correlation of output power for different windturbines, effect of windturbine parameters, penetration and environment. An example has been used to illustrate how these factors affect the reliability of wind power system. Finally, mainstream reliability indices for evaluating reliability are introduced. Among these reliability indices, some are recently developed, such as wind generation interrupted energy benefit (WGIEB), wind generation interruption cost benefit (WGICB), Equivalent Capacity Rate (ECR), load carrying capacity benefit ratio (LCCBR).     

风电场风功率实时预测效果综合评价方法

超短期风电功率预测对含大规模风电的电力系统安全经济运行有着重要意义。但目前对预测结果的评价均停留在常规统计学指标上,缺乏合理的评价体系来评价某特定风电场所选取预测模型的优劣。简述了目前风电功率预测结果评价指标的不足,提出一种基于预测误差评价和预报考核等指标的风电场输出功率实时预测效果评估方法,为不同地区风电场根据其风电输出功率变化的特点,选择预测模型以及风电场输出功率预测效果的工程检验提供依据。最后,利用吉林省某风电场实测数据,采用该评估方法对不同预测模型的实时预测结果进行分析评价,实现了该风电场不同预测模型间的择优,验证了该评价方法的指导价值。     

Wind farm modelling for reliability assessment

Increasing exploitation of wind energy requires the development of adequate models and techniques for reliability assessment of wind farms (WFs) and of electric power systems including wind energy conversion systems. A novel approach to WF modelling is investigated for reliability assessment, which is based on the universal generating functions. Such an approach combines the use of the z-transform and composition operators, allowing to account for all the factors affecting the WF performance. The results, both theoretical and numerical, of the case study, give evidence of the effectiveness of the proposed approach in terms of accuracy as well as of flexibility and efficiency of the solving algorithm.     

Dynamic participation of doubly fed induction generator in automatic generation control

Increasing levels of wind generation have resulted in an urgent need for the assessment of their impact on frequency control of power systems. The displacement of conventional generation with wind generation will result in erosion of system frequency. The paper analyzed the dynamic participation of doubly fed induction generator (DFIG) to system frequency responses of two-area interconnected power system having variety of conventional generating units. Frequency control support function responding proportionally to frequency deviation is proposed to take out the kinetic energy of turbine blades in order to improve the frequency response of the system. Impacts of different wind penetrations in the system and varying active power support from wind farm on frequency control have been investigated. Integral gains of AGC loop are optimized through craziness-based particle swarm optimization (CRPSO) in order to have optimal transient responses of area frequencies, tie-line power deviation and DFIG parameters.     

基于电池储能系统和双重扩展卡尔曼滤波的风能发电智能调度技术研究

风能等新能源发电系统在供电体系中的占比越来越大,但其随机性和波动性问题,将风力发电厂输出的电力直接向电网调度会造成安全隐患。为了解决这一问题,基于电池储能系统提出了一种风能发电智能调度技术,该技术以风力发电动力学模型和电池储能系统状态模型为基础,利用双重扩展卡尔曼滤波算法实现了风能发电系统的稳定输出。以某地风速实测数据和电网需求功率为参考,对不同算法的输出功率预测值进行了仿真分析和实验对比。结果表明：提出的改进算法预测的风速值误差相比于传感器观测值平均误差降低了28%以上,可以更准确地提供发电系统输出功率;提出的智能调度技术可以使电压波动幅度降低60%以上,系统整体输出功率稳定在参考功率附近,误差不超过2%,有一定的实用意义。     

Value of Bulk Energy Storage for Managing Wind Power Fluctuations

This paper considers the impact of uncertain wind forecasts on the value of stored energy (such as pumped hydro) in a future U.K. system, where wind supplies over 20% of the energy. Providing more of the increased requirement for reserves from standing reserve sources could increase system operation efficiency, enhance wind power absorption, achieve fuel cost savings, and reduce CO₂ emissions. Generally, storage-based standing reserve's value is driven by the amount of installed wind and by generation system flexibility. Benefits are more significant in systems with low generation flexibility and with large installed wind capacity. Storage is uniquely able to stock up generated excesses during high-wind/low-demand periods, and subsequently discharge this energy as needed. When storage is combined with standing reserve provided from conventional generation (e.g., open-cycle gas turbines), it is valuable in servicing the highly frequent smaller imbalances     

A Monte-Carlo Simulation Method for the Economic Assessment of the Contribution of Wind Energy to Power Systems

A method for determining the costeffectiveness of wind energy and the economic limitations of penetration into electrical power systems is presented. It is based on a Monte-Carlo approach which simulates the hour-by-hour operation of the power system. The hourly random variations in wind and load are modeled in addition to the operating constraints inherent in conventional generation. The economic assessment is based on a selected one-year simulation period, Two examples of the application of this method are given.     

A new synchronous generator based wind energy conversion system feeding an isolated load through variable frequency transformer

This paper aims to explore the possibility of synchronous generator (SG) based wind energy generation system feeding an isolated load using a latest power transmission technology i.e. variable frequency transformer (VFT). The proposed configuration does not employ any power electronics based interface as in conventional SG based stand-alone wind energy conversion systems (SWECS). For analysis, the simulation models of proposed configuration as well as conventional configuration have been developed under MATLAB-Simulink environment. A series of studies on power fed from the SG to the different loads at various SG input speeds has been carried out with the developed models. Further to analyze the effectiveness of the proposed method; the efficiency, total harmonic distortion (THD) of output voltage and THD of output current of the proposed method have been compared with those of the conventional method. From obtained results, it is observed that the proposed method is simple and does not produce harmonics. Moreover to validate the proposed scheme, an experimental analysis has been carried out. Further, the cost analysis of both systems has also been carried out. From the cost analysis, it is observed that the proposed system is cheaper than the conventional system.     

面向友好接入含氢能系统海上风电场台风期间的协同控制方法

目的  随着双碳目标的稳步推进,越来越多的分布式可再生能源接入电网。其中,在经济发达、沿海电力负荷大的地区大力开发海上风力发电已成为国内外学者广泛关注的热点。然而,风力发电固有的间歇性,特别是台风期间海上风电场与主网主动断开时,会对受端电网造成不利影响。 方法  为了实现台风期间海上风电友好接入,考虑到氢储能具有储存效率高、排放低和应用广泛等优点,文章提出了一种海上风电场与氢能管理系统（Hydrogen Management System,HMS）之间的协同控制方法,一方面,台风临近时期,可在正常运行下最大限度地利用风能发电;另一方面,台风过境,海上风电逐步脱网时氢能系统释放电能以缓解风电场的有功骤降,弥补传统发电机组启用存在爬坡率等问题,以减小其对受端电网的不利影响,有效平移海上风电输出的波动性。文章首先详细介绍了海上风电场与氢能系统的物理建模方法及控制模型,并说明了台风期间二者之间的协同控制策略。 结果  最后,通过仿真验证,所提方法可使海上风电场能够更灵活、更友好地满足台风期间的并网运行。此外,氢储能系统可在正常运行下最大限度地利用风能发电。 结论  在台风期间,可通过控制氢能系统释放电能以弥补传统发电机组启用存在爬坡率等问题,以减小其对受端电网的不利影响。     

变速恒频风力发电系统及其控制技术研究

为了最大限度地利用风能,风力发电系统应采用变速恒频控制策略。分析了鼠笼异步发电系统、双馈发电系统、无刷双馈发电等变速恒频风力发电系统的原理、性能及特点,通过对比各种风力发电机和各种控制方法的优缺点,对未来风力发电机和风力发电控制技术的发展趋势做了展望: 风力发电机大型化;采用变桨距和变速恒频技术;风力发电机采用直接驱动;采用智能化控制等。     

Prospects for tapping solar energy on a large scale

As a result of the energy conversion and storage research underway at Oklahoma State University since 1961, several components needed to engineer a continuous-duty energy system operating on replenishable solar energy have been developed to the prototype stage and are being tested. This paper presents and discusses these components and how they fit together in the solar energy systems envisioned for the long-term and immediate future.A simplified economic analysis of solar energy systems is presented, and the calculated generation costs are compared with those of conventional fuel burning systems for different fuel costs, load factors and interest rates. One result of this study is that wind energy systems, costing $125 to $150 per installed kW and pumping power directly into a.c. mains for 20 per cent of the time using the field-modulated generating systems developed at OSU, are competitive with conventional systems costing $250 to $350 per installed kW operating at a load factor of 80 per cent and fuel cost of $0·50 per MBtu. More such comparisons are included in the text of the paper.     

储能对含高风电渗透率系统暂态稳定性的影响

由于可再生能源并网会带来随机性和波动性,高比例可再生能源并网的暂态特性与传统电力系统有显著区别。因此,研究了在高比例可再生能源并网中加入储能装置对系统暂态稳定性的影响。首先建立了双馈风力发电机的模型和等值的双机群系统节点导纳矩阵,并对送端机组机械功率增量和双馈风机外特性的关系进行了理论推导,在此基础上分析了高比例风电渗透率对风火打捆系统功角稳定性的影响,然后建立储能模型,仿真分析了有无储能装置对风电渗透率的影响。结果表明,加入储能装置后,可使同步机的第一摆角度有效减小,且在风电渗透率增大的同时,更好地维持了系统的暂态稳定性。     

Wind energy and assessment of wind energy potential in Turkey

In this study, the potential of wind energy and assessment of wind energy systems in Turkey were studied. The main purpose of this study is to investigate the wind energy potential and future wind conversion systems project in Turkey. The wind energy potential of various regions was investigated; and the exploitation of the wind energy in Turkey was discussed. Various regions were analyzed taking into account the wind data measured as hourly time series in the windy locations. The wind data used in this study were taken from Electrical Power Resources Survey and Development Administration (EIEI) for the year 2010. This paper reviews the assessment of wind energy in Turkey as of the end of May 2010 including wind energy applications. Turkey's total theoretically available potential for wind power is around 131,756.40 MW and sea wind power 17,393.20 MW annually, according to TUREB (TWEA). When Turkey has 1.5 MW nominal installed wind energy capacity in 1998, then this capacity has increased to 1522.20 MW in 2010. Wind power plant with a total capacity of 1522.20 MW will be commissioned 2166.65 MW in December 2011.     

Economic assessment of the engineering basis for wind power: Perspective of a vertically integrated utility

If wind park configurations are globally coordinated across the service area of a power utility, then electricity can be generated for the grid with substantial cost advantages. Based on this premise, the paper introduces a model by which large scale assessment of grid connected wind based power generation may be undertaken for a utility service area. The model can be useful to the policy maker for decisions regarding suitable wind portfolio standards (WPS) definition. The utility on the other hand, may use the model to study its service area for prospective wind based generation. Aspects of the problem modelled include cost-of-energy from individual generating units, daily load variations for the utility with emphasis on limited penetration, features of wind at prospective installation sites, makes of wind energy conversion systems (WECS) available, and recovery of expenditure through revenue. Application of the model to an assessment exercise for the state of Andhra Pradesh (India) is presented as an example.