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.

Control Strategy of DC Link Voltage Flywheel Energy Storage for Non Grid Connected Wind Turbines Based on Fuzzy Control

The large-scale development of wind power is an important means to reduce greenhouse gas emissions, alleviate environmental pollution and improve the utilization rate of renewable energy. At the same time, large-scale non grid connected wind power generation theory avoids the technical difficulties of wind power integration [1]. However, due to the randomness and uncontrollability of wind energy, the output power of the wind power generation system will fluctuate accordingly [2]. Therefore, the corresponding energy storage devices are arranged in the non-grid-connected wind power generation system to ensure the power quality, and it has become the key to full utilization of renewable energy. In the case of wind speed fluctuation, the DC bus control strategy of the wind turbine is proposed in this paper. It can reduce the impact on the unit converter and the power load;this ensures safe and stable operation of non-grid connected wind turbines.

Renewable Energy Based Grid Connected Battery Projects around the World—An Overview

The environmental pollution,as well as gradual depletion of mineral resources has encouraged the world to move into renewable energy sources for generation of electricity.At present,the cost of using renewable energy sources,such as sunshine and wind in electricity generation has significantly reduced.This has led to higher penetration of renewable energy into the grid.However,both wind and solar energy photovoltaics are unpredictable energies which reduce the reliability and resiliency of the grid.The integration of battery energy storage system in the grid is one of the proficient solutions to the problem.There are numerous grid connected renewable energy based battery projects that have been deployed in different countries around the world for research,development and commercial application.This review paper will discuss some of the projects based on the battery connected wind and solar energy power generation systems that can operate both in grid connected and grid independent modes.The projects discussed in this paper are selected based on the availability of information.The battery energy storage system(BESS)incorporated in each of the project is found to increase the stability and performance of the grid by addressing the mismatch between power generation and the load of the grid created due to intermittent nature of renewable energy sources.

Impact of Reactive Power in Power Evacuation from Wind Turbines

Application of Distributed Generation (DG) to supply the demands of a diverse customer base plays a vital role in the renewable energy environment. Various DG technologies are being integrated into power systems to provide alterna-tives to energy sources and to improve reliability of the system. Power Evacuation from these remotely located DG’s remains a major concern for the power utilities these days. The main cause of concern regarding evacuation is con-sumption of reactive power for excitation by Induction Generators (IG) used in wind power production which affects the power system in variety of ways. This paper deals with the issues related to reactive power consumption by Induc-tion generators during power evacuation. Induction generator based wind turbine model using MATLAB/SIMULINK is simulated and its impact on the grid is observed. The simulated results are analyzed and validated with the real time results for the system considered. A wind farm is also modeled and simulations are carried out to study the various im-pacts it has on the grid &nearby wind turbines during Islanding and system event especially on 3-Phase to ground fault.

二阶LADRC在风电并网逆变器网侧直流母线电压控制中的运用

为提高风电并网系统中电网侧逆变器直流母线电压的稳定性和动态响应速度,文中设计一种无对象模型辅助的二阶线性自抗扰控制技术(linear active disturbance rejection control,ADRC)以取代电压外环的PI控制器,从而形成一种新的双闭环控制结构。文中利用频域分析法分析了ADRC控制器的稳定性、跟踪性和抗扰能力;最后在3.6 MW直驱永磁同步风力发电机组的物理实验平台中验证了该控制结构的可行性,将传统PI控制和文中所提出的控制模式在不同工作条件下的控制效果进行比较。实验结果表明,该文章设计的控制方案优于传统的PI控制器,具有良好的抗干扰性和鲁棒性,大大减少直流侧母线电压波动所造成的影响。

基于自抗扰的直驱风电机组强迫振荡抑制研究

风剪切和塔影效应会导致直驱式风电机组产生强迫功率振荡,影响系统的安全稳定运行。因此,提出了一种基于自抗扰控制的虚拟惯量控制方法,该方法通过扩张状态观测器观测估计系统扰动量,同时利用跟踪微分器调整系统频率的参考值,优化风电机组控制功率。仿真结果表明,相比传统的虚拟惯量控制,所提方法具有更好的抗干扰性,能更有效地对扰动进行观测估计并补偿,达到抑制直驱式风电并网系统强迫振荡的目的。

基于KPCA特征量降维的风电并网系统暂态电压稳定性评估

针对电力系统暂态电压稳定性评估中所需特征量数据庞大,影响模型训练时间,降低计算效率等问题,提出了一种基于核主成分分析方法KPCA和CPSO-BP组合的风电并网系统暂态电压稳定性评估方法.首先根据输入特征采集原始特征集,采用核主成分分析算法对特征量进行非线性数据处理,提取出最优的特征集.然后将降维后的特征集作为CPSO-BP神经网络输入量进行监督学习,将得到的模型按照临界故障切除时间裕度值的大小进行分类,将分类后的样本进行风电并网系统的暂态电压稳定性评估和临界故障切除时间裕度值预测.仿真分析结果表明,对输入特征进行降维,保留重要输入特征量,剔除冗余特征量,不仅简化了模型,还提高了网络评估的准确性和计算效率.

基于LADRC和准PR控制的风电并网逆变器控制策略

为了稳定风电并网逆变器直流母线电压的波动,提高其动态响应速度并减少并网电流中的谐波含量,本文提出了LADRC+准PR双环控制策略.首先根据两电平风电并网逆变器的拓扑结构建立其数学模型;然后,根据数学模型设计电压外环二阶LADRC控制器和电流内环准PR控制器代替传统的PI控制器,同时对两种控制器的参数进行了设计并整定;最后,在Matlab软件中构建仿真模型,进行了仿真分析和波形对比.结果表明:相较于传统的双闭环PI控制策略,新型控制策略不仅能够快速地稳定直流母线电压,而且交流侧电流的总谐波失真小;并且在电网电压发生扰动的工况下,仍有较好的控制性能.综上所述,基于LADRC和准PR控制的风电并网逆变器控制策略具有较好的抗扰性和优越的鲁棒性.

Simulation of grid tracking control of power system connection and maximum power brushless doubly-fed generator in point wind

In this paper, based on the analysis of the mathematical model in a common synchronous reference frame of the brushless doubly-fed generator （BDFG）, the grid connection strategy and maximum energy extraction control were both analyzed. Besides, the transient simula- tion of no-load model and generation model of the BDFG have been developed on the MATLAB/Simulink platform. The test results during cutting-in grid confirmed the good dynamic performance of grid synchronization and effective power control approach for the BDFG-based variable speed wind turbines.

基于综合效益评估的远海风电柔直并网拓扑方案优选

为解决远海风电柔直并网拓扑方案优选时缺乏对多方面性能定量分析与重要性衡量的现状,文中基于综合效益评估的角度对其展开研究。构建涵盖经济性、利用率、可靠性三个因素的多指标评估体系并给出各指标的计算模型,定量表征拓扑间的各项性能差异;基于改进AHP-熵权-NASH均衡法确定多指标权重,合理衡量各方面性能的重要程度;利用TOPSIS法联合指标数据与权重信息对各拓扑方案进行优选;算例中对如东海上风电柔直工程的点对点、环形、星形三种典型拓扑类型进行了综合效益评估与方案博弈,结果表明,所提改进AHP能够有效降低一致性检验误差,决策过程具备性能与权重的定量化、可视化,验证了文中方法的有效性与合理性。

基于自启动系统的海上风电并网技术

针对目前海上风电项目建设存在并网周期长的问题,提出了一种自启动的风机并网方法,并基于该方法开发了一套风机并网调试自启动装置。该装置可以安装在海上升压站平台上,在大电网电源送达海上升压站前,通过海缆为风机提供稳定电源,在此期间提前完成风机各项调试与并网工作。待正式电源送达海上升压站后,风机直接并网,大幅缩短海上风电项目建设工期,帮助风机提前并网发电,创造可观的经济价值,并能够加速清洁能源并网,助力“碳达峰,碳中和”的能源环境战略目标实现。目前,该技术已在江苏如东多个海上风电场落地应用,现场试验数据验证了研制系统和所提方法的先进性与有效性。

基于EKS的风电并网系统频率特征参数辨识算法

新型电力系统建设背景下系统对接入风电的频率调节能力提出了要求。但风电在可调容量耗尽时将退出调频,导致系统等效惯量等参数和频率响应特性变化,影响系统切机切负荷等频率控制措施的正确动作。为此,提出一种基于扩展卡尔曼平滑算法(Extented Kalman Smoother, EKS)的风电并网系统频率特征参数辨识方法,可实现不同工况下系统频率特征参数的高效准确辨识。首先分析了风电场频率控制方法,建立了基于共模分量的风电并网系统频率响应模型,然后分析了EKS算法,进而提出了基于EKS的系统频率特征参数辨识方法,最后通过仿真算例进行了验证。仿真结果表明,所提方法可有效辨识不同工况下系统的惯量、阻尼等频率特征参数。

基于时空注意机制与LSTM的暂态电压稳定评估

针对新型电力系统发展背景下现阶段机器学习算法难以准确判断风电并网系统暂态电压稳定性的问题,提出一种基于时空注意机制与长短期记忆网络的暂态电压稳定评估方法。首先,基于支持向量机对初始单特征评价进行特征粗筛,并采用皮尔逊相关系数法判断剩余特征的相似度;其次,通过主成分分析-加权负荷评价获取与暂态电压稳定情况相关性较高的特征集;然后,通过时空注意机制,量化系统负载节点间的空间耦合关系和风电接入点间的空间相关性对整个系统暂态进程的影响,构建基于时空注意机制与长短期记忆网络的评估模型;最后,在算例上进行仿真分析,结果表明该模型有利于风电并网系统暂态电压稳定性判别准确率的提升,以及减少误判和漏判。

基于二维风速修正和多重集成的两阶段迁移学习短期风电功率预测

为了在数据量不足的情况下增强新投运风电场的功率预测能力,提出了一种基于二维风速修正和多重集成的两阶段迁移学习短期风电功率预测方法。首先,在数据增强阶段,引入投运前气象站的测风数据,基于风电场的时空相关性关系,通过时序特征构建和场景匹配,从时空2个维度对预报风速进行初步修正。然后,对初步修正后的结果进行数据重构,以重构后的数据作为下一次集成的输入,构建多重集成模型对预报风速进行二次修正。最后,在功率预测阶段,基于一阶段的修正结果,通过门控循环单元(gate recurrent unit,GRU)得到预测功率。算例结果表明,所提方法使预报风速的均方根误差降低了1.038m/s,功率预测精度提升了4.718%。论文研究可为新投运风电场的短期功率预测提供参考。

面向大容量风电并网的VSC-MTDC功率协调控制

基于电压源换流站的多端直流输电(VSC-MTDC)已成为大容量风电远距离传输并网的首要选择。针对含大规模风电场的VSC-MTDC系统的功率协调控制策略进行了深入研究。首先,分析大规模风电并网时下垂系数对有功功率分配的影响,指出采用固定下垂系数存在优先级电网功率缺额的可能性和缺乏有功功率分配灵活性等问题。然后,针对此类问题,提出一种基于主从控制与自适应下垂控制相结合的功率协调控制策略,该策略根据风电功率情况制定3种控制模式,从而实现风电功率灵活分配。最后,在MATLAB/Simulink上构建了风电并网的四端柔性直流输电系统,仿真结果验证了所提控制策略的可行性和有效性。

高比例风电电力系统储能运行及配置分析

针对新能源随机性及波动性对电力系统安全稳定运行带来的不确定影响,为提高系统的经济性安全性,对高比例风电电力系统储能运行及配置进行了研究分析。通过研究分析“供给侧”低碳化转型对电力系统运行经济性、可靠性影响,以及风电渗透率(最大风电功率与最大负荷功率之比)递增对系统功率平衡的影响,建立了高比例风电电力系统的结构,并建立了高比例风电电力系统容量优化配置模型,构建了4种对比方案。利用CPLEX求解器对模型进行了求解,结果表明“供给侧”低碳化转型对电力系统运行经济性及可靠性的影响很小,增大风电渗透率及考虑储能能够提升系统的运行经济性及可靠性,有助于新型电力系统的构建,促进“碳中和”的实现。

基于重力储能的混合储能系统容量优化配置

针对以电化学储能电池技术为基础的储能系统的成本高、寿命短、污染环境等问题,以平抑风电输出功率而减少弃风弃电率为研究对象,提出了一种由重力蓄能电池和超级电容组成的混合储能系统。以储能系统投资成本最低和风电场弃电率最低为双目标,建立了混合储能系统容量优化配置模型,并采用Pareto档案多目标粒子群优化算法求解模型以确定风电场收益率最高的混合储能系统容量配置方案。通过对3种不同混合储能系统组合进行对比分析,进一步验证了所提出的混合储能系统及储能容量优化配置方案的可行性和有效性。仿真结果表明,基于重力储能的混合储能系统具有良好的经济性和可行性。

双馈变速恒频风电系统控制研究

文章以双馈异步电机为风力发电的变流器,分析了双馈式变速恒频风电系统在功率因数校正、电网电压畸变及无功补偿方面的控制策略,重点介绍了双馈变速恒频风电场系统,基于功率因数校正的控制方法分析了双馈异步发电机并网运行时电网电压畸变对风力发电系统运行稳定性和电能质量的影响,最后通过仿真验证了控制策略的正确性。仿真结果表明:文章提出的双馈变速恒频风电系统可以有效改善双馈异步电机并网运行时因电压畸变带来的性能下降问题。

基于边界圆限定的风电并网逆变器模型预测功率控制

随着风电机组单机容量不断增长,要求风电并网逆变器的开关频率较低以降低损耗,为此提出一种新型单边界圆限定模型预测功率控制策略。该策略根据当前时刻功率误差与预设边界圆的位置关系决定下一时刻最优矢量的选择原则,无需复杂的坐标变换即可将功率误差限制在系统允许范围内,同时通过选取合适的边界圆半径减小了风电并网逆变器的平均开关频率。最后,在Matlab/Simulink仿真软件中验证了该策略的有效性和正确性。

计及灵活运行碳捕集电厂的低碳调度模型研究

随着“双碳”政策的实施,计及可再生能源的电力系统低碳调度问题逐渐与碳交易市场深度耦合。保留部分燃煤发电对于维持电网稳定运行至关重要,采用碳捕集技术可使火电机组很好地实现碳减排。为此,搭建以综合成本最低为目标的计及灵活运行碳捕集电厂和风电联合运行的低碳调度模型。首先将火电机组加装分流、储液装置,改造为综合灵活运行的碳捕集电厂,它不仅可实现火电机组的低碳化,还可以利用碳捕集电厂的储液罐进行“削峰填谷”,储液罐的能量时移特性进一步扩大了碳捕集电厂的净出力范围。然后搭配碳交易机制,让碳捕集的低碳效应发挥积极作用。针对大规模风电并网后对系统产生的不确定因素,引入模糊机会约束,将确定性系统约束松弛为模糊参数下的系统约束。在改进的IEEE 30节点系统中进行求解,验证模型的有效性。结果表明,相比纯火电与风电的调度模型,计及灵活运行碳捕集电厂的低碳调度模型能有效降低系统总成本,降低碳排放量,增加风电上网率。