Difference between grid connections of large-scale wind power and conventional synchronous generation

In China, regions with abundant wind energy resources are generally located at the end of power grids. The power grid architecture in these regions is typically not sufficiently strong, and the energy structure is relatively simple. Thus, connecting large-capacity wind power units complicates the peak load regulation and stable operation of the power grids in these regions. Most wind turbines use power electronic converter technology, which affects the safety and stability of the power grid differently compared with conventional synchronous generators. Furthermore, fluctuations in wind power cause fluctuations in the output of wind farms, making it difficult to create and implement suitable power generation plans for wind farms. The generation technology and grid connection scheme for wind power and conventional thermal power generation differ considerably. Moreover, the active and reactive power control abilities of wind turbines are weaker than those of thermal power units, necessitating additional equipment to control wind turbines. Hence, to address the aforementioned issues with large-scale wind power generation, this study analyzes the differences between the grid connection and collection strategies for wind power bases and thermal power plants. Based on this analysis, the differences in the power control modes of wind power and thermal power are further investigated. Finally, the stability of different control modes is analyzed through simulation. The findings can be beneficial for the planning and development of large-scale wind power generation farms.

Industrial Arrangement of Large-scale,Non-grid-connected Wind Power Industrial Zones in Coastal Areas of China

Constructing an industrial system for a large-scale,non-grid-connected wind power industry is a key step towards the diverse utilization of wind power.However,wind power exploitation is not only a technical challenge but an industrial problem as well.The objective of this study is to introduce a concept of large-scale,non-grid-connected wind power(LSNGCWP) industrial zones and establish an evaluation model to assess their industrial arrangement.The data of wind energy,industry,nature resources and socio-economy were collected in this study.Using spatial overlay analysis of geographic information system,this study proposes a spatial arrangement of the LSNGCWP indus-trial zones in the coastal areas of China,which could be summarized as the 'one line and three circles' structure,which will contribute to the optimization of the industrial structure,advance the wind power technology,coordinate the multi-industrial cooperation,and upgrade the industrial transformation of China's coastal areas.

A Review of Technical Requirements for High Penetration of Wind Power Systems

Renewable portfolio targets have been established in many regions around the world. Regional targets such as 20% renewable energy by year 2020 are not uncommon. As the levels of wind power penetration increase, there are many power system impacts. This work investigated possible challenges and technical requirements for high penetration of wind power systems. The main issues to discuss covers reserve determination, wind power forecasting, unit commitment with appropriate generation portfolio, wind turbine and storage system technical development, demand response management, electricity market design, and frequency stability.

Design of Large-Scale Prestressing Bucket Foundation for Offshore Wind Turbines

The key in the force transmission between the tower and the foundation for offshore wind turbines is to transfer the large moment and horizontal loads. The finite element model of a large-scale prestressing bucket founda- tion for offshore wind turbines is set up and the structural characteristics of the arc transition structure of the founda- tion are analyzed for 40-60 channels(20-30 rows) arranged with prestressing steel strand under the same ultimate load and boundary conditions. The mechanical characteristics of the key parts of the foundation structures are illus- trated by the peak of the principal tensile stress, the peak of the principal compressive stress and the distribution areas where the principal tensile stress is larger than 2.00 MPa. It can be concluded that the maximum principal tensile stress of the arc transition decreases with the increasing number of channels, and the amplitude does not change signifi- cantly; the maximum principal compressive stress increases with the increasing number of channels and the amplitude changes significantly; however, for the distribution areas where the principal tensile stress is larger than 2.00 MPa, with different channel numbers, the phenomenon is not obvious. Furthermore, the principal tensile stress at the top of the foundation beams fluctuantly increases with the increasing number of channels and for the top cover of the bucket, the principal tensile stress decreases with the increasing number of channels.

A Chance Constrained Optimal Reserve Scheduling Approach for Economic Dispatch Considering Wind Penetration

The volatile wind power generation brings a full spectrum of problems to power system operation and management, ranging from transient system frequency fluctuation to steady state supply and demand balancing issue. In this paper, a novel wind integrated power system day-ahead economic dispatch model, with the consideration of generation and reserve cost is modelled and investigated. The proposed problem is first formulated as a chance constrained stochastic nonlinear programming U+0028 CCSNLP U+0029, and then transformed into a deterministic nonlinear programming U+0028 NLP U+0029. To tackle this NLP problem, a three-stage framework consists of particle swarm optimization U+0028 PSO U+0029, sequential quadratic programming U+0028 SQP U+0029 and Monte Carlo simulation U+0028 MCS U+0029 is proposed. The PSO is employed to heuristically search the line power flow limits, which are used by the SQP as constraints to solve the NLP problem. Then the solution from SQP is verified on benchmark system by using MCS. Finally, the verified results are feedback to the PSO as fitness value to update the particles. Simulation study on IEEE 30-bus system with wind power penetration is carried out, and the results demonstrate that the proposed dispatch model could be effectively solved by the proposed three-stage approach. © 2017 Chinese Association of Automation.

Providing Frequency Support of Hydro-Pumped Storage to Taiwan Power System with Wind Power Integration

The combination of wind and pumped storage is a useful method to compensate the fluctuation of wind power generation, which would exploit the abundant wind potential and increase wind power penetration. Taiwan Power Company (TPC) develops renewable energy actively in recent years. Moreover, TPC has started planning a high penetration wind power system and building offshore wind farms around the coast of Zhangbin, Yunlin and Penghu. The target of the offshore wind power installed capacity is up to 3 GW by 2025. However, the integration of the large scale of wind power would give huge challenges to the system operator because wind is randomly characterized. In this study, after high penetration wind power is integrated, the impacts of system frequency and the dispatch of conventional units will be discussed. Additionally, the hybrid system combing wind power with pumped-storage will be planning to reduce the effect of system frequency.

Research on the Critical Buckling Pressure of Bucket Foundations with Inner Compartments for Offshore Wind Turbines

In the process of suction penetration of bucket foundations with inner compartments for offshore wind turbines,most researches focus on soil seepage failure and soil plugs,while the buckling of foundations is rarely investigated.Therefore,theoretical calculation methods for critical buckling pressures of the skirt and bulkheads of the bucket foundation are first presented according to the stability theory of a cylindrical shell and the small deflection theory of a thin plate,respectively.Furthermore,two types of models with and without considering the skirt-soil interaction are developed for the calculation of critical buckling pressure of the bucket foundation.Taking a practical project as an example,theoretical and numerical methods are used to obtain the critical buckling pressures of a bucket foundation.In this work,the theoretical method and the finite element model considering the skirt-soil interaction for calculating the critical buckling pressure of bucket foundations are firstly proposed.The results can help to optimize the design process of offshore wind turbine foundations and improve the safety of offshore wind power systems.

砂土中桩靴插桩对临近筒型基础的影响研究

通过物理模型试验和有限元法研究砂土中风电安装船桩靴插桩对临近筒型基础的影响。首先通过物理模型试验,验证有限元模型的合理性,初步确定桩靴在砂土中贯入的影响范围大致在2.5倍桩靴直径。基于有限元CEL方法进一步研究桩靴和筒型基础的净距与桩靴直径之比(S/D)对筒型基础在位稳定性的影响。结果表明:筒型基础的倾斜率、最大竖向位移以及筒壁应力随着S/D的增大而逐渐减小,插桩过程中,靠近桩靴一侧的筒裙和分舱板应力远大于远离桩靴一侧的筒型基础应力,且筒顶的土压力远小于筒底土压力。

避免频率二次跌落的风储联合调频控制策略

风电高渗透电力系统中,风机释放转子动能参与频率响应改善系统频率稳定性,但存在欠响应支撑效果不足或过响应导致系统频率二次跌落现象。储能响应不受时空因素影响,通过整定储能响应参数,可提升风电频率响应的有效性。该文首先基于统一结构模型分析系统频率二次跌落与风机控制策略之间的作用机理。其次,整定充分利用风机频率响应能力及避免系统频率二次跌落的风电机组频率响应系数。然后,引入频率稳定裕度概念,并基于关系矩阵整定的储能最小出力,等效扩展系统频率稳定裕度。基于以上分析,综合考虑时空因素对系统频率响应影响,提出一种多时间尺度下避免频率二次跌落的风储联合调频控制策略。最后,基于DIgSILENT搭建风电高渗透4机4区系统进行仿真验证。结果表明,所提控制策略在不同风速下兼顾风机频率响应能力,同时避免频率二次跌落,提高全网频率安全稳定裕度。

大规模风电接入场景下的失步振荡中心定位方法

振荡中心的准确定位是失步保护正确动作的基础,大规模风电并网导致系统阻抗参数发生变化,使得传统基于阻抗轨迹的失步定位方法的适应性严重下降。针对该问题,提出基于节点频差的失步振荡中心定位方法。首先分析大规模风电并网对系统总阻抗的影响。进一步根据发电机功角,计算其曼哈顿距离相似度并构建启动判据。最后,通过移动平均法对广域测量频率进行平滑处理,提出基于节点频差的失步振荡中心定位方法。仿真验证表明,所提基于节点频差的失步振荡中心定位方法受噪声影响较小,不受风电渗透率的影响,能够准确定位失步振荡中心位置。

数字化波浪补偿分离式液压钻机的研制

基于能源绿色、风力大等优势,海上风力发电技术近年来越来越受到重视,正由浅海向深海发展,且小型发电机逐步被大功率发电机取代。海上风力发电中风电场的选址、风机的基础设计、桩基施工、地层测试等,都离不开钻探和井内静力触探技术。为了满足海上勘察钻机的要求,研发了数字化波浪补偿分离式液压钻机,主要是在数字化、自动化、回转、波浪补偿等功能,以及模块化设计、制造工艺等方面进行了创新。通过理论参数核算、海上应用测试、深海生产施工验证,证明该钻机不仅可满足使用需求,并且比常规钻机更加方便管理、高效安全,还降低了钻探的辅助成本。

砂土中筒型基础临界吸力计算方法研究

开展砂土中筒型基础吸力沉贯的系列模型试验,测试筒型基础下沉过程中吸力的发挥过程,并通过反分析得出筒内外土体渗透系数比的变化规律。结果表明:当筒内土体出现管涌现象时,筒内负压会瞬间降低;随着沉贯深度的增加,临界吸力值也逐渐增大;此外,筒内外土体的渗透系数比呈指数函数型增长;假设在沉贯过程中土体的渗透系数不变,则临界吸力的预测结果均小于实测值。根据试验结果改进砂土中筒型基础沉贯过程临界吸力的计算公式,并进行工程案例验证。

计及电解铝高耗能负荷调控和火电深调的高比例风电系统分层优化策略

对于高比例风电系统,风电出力典型的随机波动性和反调峰特性极大增加了其调峰负担,火电机组深度调峰虽已常态化,但系统调峰资源仍显不足,弃风问题有待解决。提出利用电解铝高耗能负荷(electrolytic aluminum energy-intensive load,EAL)作为新的调峰资源参与电网调度。首先,根据电解铝高耗能负荷的真实生产调节特性,耦合电流、温度及产量等多种因素,建立电解铝负荷参与电网调峰的精细化调节模型;然后,结合火电机组深度调峰模型,以系统弃风量最小和运行成本最小为目标,建立电解铝负荷和火电深调联合调峰的分层优化模型;最后以某实际区域系统为例,采用商业优化软件GUROBI进行求解分析,验证了所提方案可大幅减少系统弃风量,改善系统调峰运行经济性,并优化了火电机组深度调峰结构和发电经济性。

国内外静力触探液化判别方法对比检验

静力触探试验(cone penetration test,简称CPT)具有独特优势,使其成为了海上风电工程的主要勘察方法。海上风电工程位于液化易发区,因此研究基于CPT液化判别方法的适用性和可靠性就成为亟待解决的突出问题。详细介绍了4种国内外具有代表性的CPT液化判别方法,并采用理论分析及大量CPT液化实测数据检验,对现行的美国国家地震工程研究中心(National Center for Earthquake Engineering Research,简称NCEER)方法、《岩土工程勘察规范》(GB50021-2001)方法(岩规法)、《软土地区岩土工程勘察规程》(JGJ 83-2011)方法(软土规程法)和《建筑工程抗震性态设计通则》(CES 160:2004)方法(通则法)等4种方法进行对比检验,提出了4种主要方法的评价结果。结果表明:NCEER法液化判别临界线在低烈度区存在不合理的回弯现象,在高烈度区存在临界值增大过快的问题,在Ⅶ度区深层偏于危险,在Ⅸ度区深层明显偏于保守,在Ⅶ、Ⅸ度区浅层和Ⅷ度区判别结果较好;岩规法液化判别临界线存在很大的问题,液化判别临界线随深度递减,液化判别时在Ⅶ度区浅层偏于危险,在深层明显偏于危险,在Ⅷ、Ⅸ度区浅层偏于保守,在深层偏于危险;软土规程法液化判别临界线在土层深度约6 m处存在不合理的回弯现象,在Ⅶ度区浅层判别较好,在Ⅸ度区浅层偏于保守,在不同烈度区深层均偏于危险;通则法液化判别临界线是符合目前认知的,在不同烈度区和深度下的判别效果是最好的。研究成果可为相关规范修订和工程应用提供参考与支持。

海上风电场吸力筒基础沉贯特性研究

吸力筒沉贯特性是影响其工程应用的重要因素。基于海上风电场吸力筒导管架基础筒体下沉过程的实测数据,研究真实海床地基条件下吸力筒沉贯阻力的CPT计算方法的可行性以及DNV规范推荐的土体沉贯阻力的经验系数的适用性,分析黏土层和砂土层中沉贯阻力的组成和负压下沉过程中的筒内土塞机制。研究结果表明:CPT计算方法能够较精确地计算吸力筒沉贯阻力,DNV规范推荐的经验系数高估了海床地基中淤泥质土、粉质黏土层的黏土经验系数k_(f)(z)以及砂砾、中砂、粗砂层等砂土经验系数k_(p)(z);负压下沉过程中,筒内土塞体积的发展规律与海床土层分布及土体物理力学性质密切相关。

电力需求增长和负荷灵活性提升视角下的风光资源密集地区可再生能源消纳研究

中国风、光资源密集地区与电力负荷集中地区的不匹配为可再生能源大规模发展后的消纳问题带来重大挑战,“双碳”目标下,如何促进可再生能源消纳已成为中国能源结构转型亟需解决的问题。从增加电力需求和提升负荷灵活性的创新视角出发,以内蒙古自治区为例探究风、光资源密集地区可再生能源消纳情况、形成原因及其破解思路。研究发现,2030年,内蒙古可能产生约2000亿kWh弃风弃光量;经济发展、人口规模、第二产业与第三产业发展、居民供暖等是内蒙古电力需求增长的主要驱动因素,当前工业发展对地区电力消费和可再生能源消纳的带动作用有待提升;内蒙古钢铁行业和电解铝行业通过采用电弧炉炼钢工艺、电解槽改造技术等方式,可以为电力系统提供巨大的负荷灵活性潜力。鉴于此,风、光资源密集地区应积极推动能源结构转型和产业结构电气化转型的协同机制,激励工业用户等市场主体提供负荷灵活性,鼓励最终消费端采用绿色清洁电力实现对传统化石能源的替代,进而有效促进可再生能源的消纳。

基于CPTU解释黏性土不排水抗剪强度方法研究

黏性土的不排水抗剪强度Su是海上风电工程设计中重要的力学参数之一,孔压静力触探测试(简称CPTU)无法直接测得黏土强度,但其所提供的锥尖阻力、侧摩阻力以及孔隙水压力与土体的不排水抗剪强度存在映射关系,国内外基于CPTU已经演化出多种解释土体不排水抗剪强度计算公式。基于滨海某海上风电项目,开展了原位CPTU试验、三轴不固结不排水(UU)、三轴固结不排水(CU)、固结快剪(CQ)以及船上微型十字板剪切(MVST)试验,对已有计算公式的适用性进行了校验,分析发现需根据区域场地情况对其中经验系数进行相应的调整以提高计算精度。研究基于CU试验结果,结合工程实例对原有公式中经验参数进行优化修正,最后通过误差分析,验证了修正预测模型的准确性与合理性,利用改进后的修正预测模型可使江苏地区海域黏性土不排水抗剪强度的计算得到更准确的结果。

大规模风力发电等值仿真技术研究

随着电网系统风电渗透率的提高,对所在地区电网的电能质量以及电能调度产生重大影响。为研究风电场在大扰动下的宏观动态响应特性,对风电场进行动态等值建模非常重要。针对风电场的动态等值建模研究,文章首先对现今主流的风机类型及其模型结构进行了简要介绍;然后对等值建模方法中的降阶法、单机等值法以及多机等值法做了比较和详细阐述,并对等值参数计算和集电网络等值进行了概述;最后总结了风电场动态等值建模尚存在的挑战,并对未来的研究方向进行了展望。

不同运行方式的大规模新能源接入电网后的调频特性研究

给出了双馈风力发电机(doubly-fed induction generator,DFIG)参与电网调频的基本数学模型,推导出了大规模风电接入电网后,在不同运行方式(如惯性控制或者最大功率跟踪)下风电功率的渗透率、可调频风电机组所占比例以及风电机组的频率调节系数等与风电利用率之间的关系,提出了不同运行方式的风电机组参与电网调频的控制策略。以南方某片区电网为例,分析了风速改变及负荷变化的情况下风电功率注入比例对接入电网调频的影响特征,验证了可调频新能源发电对电网调频作用的有效性。将可调频风电机组接入4机2区域的电网模型,给出风电注入比例不同情况下所需要的可调频风机所占比例最小值及电网对新能源的综合承载能力。仿真结果表明,大规模风电场参与调频时应尽可能使运行在额定风速附近的机组参与调频,从而最大程度确保电网的频率偏差变小,维持频率在安全运行范围内。