大型风电场运行的特点及并网运行的问题

随着国家能源结构的调整,并网运行的风电规模迅速增加,大规模风电集中并网相应安全问题如何评估和解决,是风电发展过程中急需解决的问题。文章分析了大规模风电场集中接入后对电网调频能力、无功电压控制、电能质量等方面的影响,并提出相应的对策建议。     

浅谈风电场的电能质量

风电场的电能质量是风电场并入电网运行的关键指标。文章从风电场的电压谐波、三相电压不平衡度和频率偏差三个方面分析了风电场的电能质量,并引用广东惠来海湾石风电场的实测数据,说明风电场的电能质量能够满足公用电网电能质量的要求。     

并网准则要求下的风电场设计和分析方法

随着风力发电比重的增加,电网对风电场并网的技术要求也越来越严格。为了确保规划的风电场满足电网的并网技术准则,并网运行风电场的方案必须根据并网技术准则的要求进行设计。对风电场并网准则的技术内容进行了分析,介绍了维斯塔斯公司根据并网准则进行风电场方案设计的方法。这些方法包括根据并网准则要求设计主回路;计算短路电流,检验方案的短路容量是否满足要求;通过潮流计算确定并网准则对无功补偿设备的容量要求;分析风电场在电网电压下降时的暂态行为,判断并网准则中的低电压穿越要求对方案的影响;给出了当规划的风电场不符合并网准则时应采取的解决措施,如采用无功补偿及相应的补偿设备和补偿量。文章最后给出了相应的算例分析。     

风电场并网对电力系统稳定性影响

稳定性是影响大电网区域互联的关键性因素。随着风电场规模的不断扩大,其接入电网会对电力系统的稳定性带来一定影响。介绍了风力发电系统建模方法及风力发电机模型,分析了风电场并网对电力系统无功电压、潮流分布、电能质量、系统短路容量、调峰调频等方面的影响,并对电力发电技术发展新动向作了展望。     

考虑风资源影响的风电场电压波动和闪变评估

风电并网后引起的电压波动和闪变水平可能超出国家有关标准,造成严重的电能质量问题,因此,在风电并网之前需对这两者进行评估。采用了一种新的评估方法。区别于国际电工标准(IEC61400-21)中电压波动与闪变的评估,此方法考虑了风电场的风资源情况对这2个指标的影响。对风电场在不同出力下由阵风引起系统的电压波动进行计算,并用IEC闪变仪计算短时间闪变值Pst。用所提方法和IEC标准对我国某一新建的风电场进行评估。结果表明,所提方法不仅能有效地进行电压波动与闪变评估,而且能更好地考虑风速变化对风电场带来的潜在影响。     

光伏电站并网对电能质量的影响及对策

由于光伏发电具有波动性和间歇性,且光伏发电系统中含有大量的电力电子设备,并网后会对当地电网的电能质量产生一定的影响。介绍了浙江嘉兴电网某光伏电站的概况及其并网对电能质量在谐波、电压偏差、频率偏差、闪变、电压不平衡度及功率等方面的影响,并进行评估和分析,提出加强电能质量监督的建议。     

风电机组不同控制模式下SVC在改善电网 电压质量中的应用

摘要： 回顾了国内外风电发展的研究现状,总结了风电的运行特点和影响风电场并网的主要因素。针对某风电场建立了双馈变速风电机组的风机模型和发电机模型,分析了风机2种控制模式的特点。以某电网一风电场为实例,计算了配置静止无功补偿器（SVC）接入前、后电网电压波动的情况。仿真结果表明,配置SVC后对电网电压质量有较大的改善,且恒功率因数控制模式的改善作用更为明显,接近恒电压控制模式的2倍。     

基于Hilbert-Huang变换的风电场闪变

随着风电场装机容量的增大,风电并网所带来的电压偏差、谐波污染、电压波动和闪变等电能质量问题日益严重,因此,需要对其进行评估和治理,而评估和治理的前提是参数的准确检测。将一种新的非平稳信号处理方法,即Hilbert-Huang变换用于风电场闪变的分析。该方法可以从频域和时域同时对信号进行分析,能够准确检测出非平稳电压闪变信号的时间、频率和幅值信息。仿真分析结果表明了该方法分析风电场闪变的有效性。     

风电场接入长兴电网的影响与措施

上海申能长兴岛风电场并网运行,不仅对长兴电网增加了能源补充,而且具有良好的社会和环保效益。在长兴电网分网运行或孤立运行时,由于长兴电网容量较小,风电场在并网瞬间会使电网电压下跌较大,影响同一电网上的其他电气设备的正常运行,甚至会影响到整个电网的稳定与安全运行。为此,长兴电网对风电场接入电力系统采取了相应的技术措施,用以提高风电机组和风电场的运行特性,降低大规模风电接入对长兴电网带来的不利影响。     

分布式光伏电站接入电网电能质量评估计算

光伏电站接入配电网后,在改变电网原有拓扑结构和潮流方向的同时,其电能输出特性直接影响到电网的电能质量。为保障现有电网的安全稳定,更好利用太阳能,在光伏电站接入系统前的设计阶段需对光伏发电接入系统进行电能质量评估。结合实际工程案例,以某MW级分布式光伏电站为研究对象,根据分布式光伏电站接入电网时的电能质量要求,基于Matlab/Simulink仿真平台进行建模,对并网电能质量进行评估计算,并进行相应的分析。计算结果表明：该分布式光伏电站接入点符合电能质量要求,允许接入系统。     

Design and evaluation of PV-wind hybrid system with hydroelectric pumped storage on the National Power System of Egypt

National and international policies encourage increased penetration of solar and wind energy into electrical networks in order to reduce greenhouse gas emission. Solar radiation and wind speed variations complicate the integration of wind and solar generation into power systems and delay the transition of these sources from centralized to distributed energy sources. The increased penetration of nontraditional energy sources into the electric grid stimulates the demand for large capacities in the field of energy storage. A mathematical model, which describes the operation of a proposed hybrid system, including solar PV, wind energy, and a pumped storage hydroelectric power plant is developed in this paper. This hydropower plant utilizes seawater as a lower reservoir, and only a tank has to be built in order to reduce the installation cost of the storing system. The pumped storage power plant used for compensation of the variation of the output energy from the PV and wind power plants by discharging water from the upper reservoir, which is previously pumped in the case of surplus energy from PV and wind turbine power plants. The impact of the proposed system on the grid utility is investigated in accordance with the values of energy exchange (deficits and surpluses of energy) between the considered hybrid system and the grid. The optimum design is determined by the pump and turbine capacities, upper reservoir volume, and the volume of water left in the tank for emergencies. Different scenarios of the optimum operations are presented for analysis. The results obtained from the examined scenarios indicate the ability of such a hybrid energy system to reduce the exchange of energy with the grid. This paper indicates the technical feasibility of seawater pumped-storage hydropower plant for increasing the Egyptian national grid’s ability to accept high integration of renewable energy sources.     

The economics of large-scale wind power in the UK A model of an optimally mixed CEGB electricity grid

Previous calculations of the economics of large-scale wind power have been generally limited to the evaluation of the marginal cost of energy, assuming that the addition of a wind farm to an electricity grid does not change the mix of base, intermediate and peak load plant in that grid. Here a simple but powerful numerical generation planning model has been constructed for grids containing wind farms and three classes of thermal power station, but no storage. Electricity demand and available power are specified by empirically based probability distribution functions and the plant mix which minimizes the total annualized costs of the generating system is determined. Capacity credit of wind power is automatically taken into account in the optimization. Using the model, the breakeven costs of wind energy in a model British CEGB grid, containing coal, nuclear, oil and wind driven power plant, are evaluated under various conditions. For a wide range of parameter values, large-scale wind power is likely to be economically competitive in this grid.     

风电场的继电保护

大规模风电接人系统对电力系统电能质量的影响较大.风能的随机性和不可控性,使风电占系统容量的份额增大时,向系统提供的短路电流也越来越大,因此,风电保护配置对电网的影响也是重要的.文章对风电系统保护进行了论述,分析了风电对电网继电保护的影响,使用MATLAB的动态仿真工具SIMULINK、对包含风电场的单机无穷大电力系统发生联络线故障时进行动态仿真.通过分析双馈发电机不同故障类型下的故障电压、电流曲线,指出风电场应采用的适应性保护.     

Wind farms connected to weak grids in India

This article describes the mutual influence between the wind turbines and the power quality in the Indian power systems. The Indian power systems are weak in general and the wind energy development has been very fast and concentrated in a few rural areas where the existing transmission and distribution grids are very weak. Therefore the mutual influence between wind turbines and power quality is particularly strong in India. The wind farms influence power quality aspects such as steady state voltage, power factor, flicker and harmonic and interharmonic distortion. The power quality of the grid influences the power performance and safety of the wind turbines and the lifetime of mechanical and electrical components. The findings presented are general for wind farms connected to weak grids, but the Indian case is pronounced concerning weakness of grid as well as wind energy penetration level. Copyright © 2001 John Wiley & Sons, Ltd.     

Economics of wind power when national grids are unreliable

Power interruptions are a typical characteristic of national grids in developing countries. Manufacturing, processing, refrigeration and other facilities that require a dependable supply of power, and might be considered a small grid within the larger national grid, employ diesel generators for backup. In this study, we develop a stochastic simulation model of a very small grid connected to an unreliable national grid to show that the introduction of wind-generated power can, despite its intermittency, reduce costs significantly. For a small grid with a peak load of 2.85 MW and diesel generating capacity of 3.75 MW provided by two diesel generators, the savings from using wind energy (based on wind data for Mekelle, Ethiopia) can amount to millions of dollars for a typical July month, or some 5.5–17.5% of total electricity costs. While wind power can lead to significant savings, the variability of wind prevents elimination of the smaller of two diesel units, although this peaking unit operates less frequently than in the absence of wind power.     

The capacity credit of wind power: A theoretical analysis

A probabilistic model of capacity credit (or value) is constructed for wind power in an electricity grid, The model-which is initially based on the assumptions that electricity supply, electricity demand and the output of a system of aerogenerators are Normally distributed and that the conventional power plant in the grid comprises units of identical capacity—provides simple analytical expressions for four different concepts of capacity credit and elucidates the qualitative differences between them.Two of these concepts of wind power capacity credit, the “equivalent conventional capacity” and the “equivalent firm capacity”, are then studied in more detail by introducing a much more realistic probability distribution of wind power output than the Normal distribution and by calculating the Loss of Load Probability. For small penetrations of wind power into the grid, the capacity credit is approximately equal to the average wind power output, while for large penetrations the credit tends to a limit which is determined by the probability of zero wind power and the conventional plant characteristics.     

风机并网对电能质量影响因子研究

为了给电网控制策略提供可靠的参考依据,对电网在接入风机后电能质量的变化进行了详尽的分析。风机作为电源同时也作为非线性负载接入配电网中使得电能质量的分析更加复杂。首先对国标中着重介绍的稳态电能质量：电压偏差,三相不平衡度,谐波以及电压波动进行理论介绍,然后在Matlab／Simulink上建立了配电系统与风机并网的模型,得到风机对电能质量不同方面的影响程度,最后采用先进电力电子设备为平稳电压电流输出提供一定的方法,并进行验证。研究结果表明,电力谐波和电压波动闪变是风机对电网的最主要的影响因素。     

Market and regulatory aspects of trans‐national offshore electricity networks for wind power interconnection

Subsea cable connections are an essential part of offshore wind power projects. Apart from direct connections between an offshore wind park to the national grid, several alternatives can be envisaged, including the connection to interconnectors between countries or direct connection to a country outside the jurisdiction where the wind park is based. Besides the technical‐economical constraints of these new types of grid connection, market and regulatory aspects need to be assessed. The paper gives an overview of these trans‐national connection schemes for wind power and considers integration into electricity markets and discusses regulatory implications. The scope of the research is Western Europe. Copyright © 2009 John Wiley & Sons, Ltd.     

基于PC测量仪器的风电机组电能质量测试系统

风电机组的电能质量测试不同于传统负荷的电能质量测试,需要排除电网特性和其他负荷的影响,并考虑不同风速对测试结果的影响．目前常规的电能质量测试仪器无法完成测试。风电机组电能质量测试系统选择高性能的PC测量仪器作为硬件采集平台．通过搭建虚拟电网排除电网结构及其他负荷产生的影响,采用适合风电机组的数字化闪变仪算法实现了风电机组的电能质量测试。测试系统通过对典型风电机组实际测试,证明测试系统完全能够满足风电机组电能质量测试标准IEC61400—21的要求。