Optimal power flow in multi-terminal HVDC grids with offshore wind farms and storage devices

This work presents a power flow strategy for multi-terminal HVDC grids. Energy is mainly generated via renewable energy sources and there are nodes in the network with the possibility to store energy. This energy is generated taking into account real weather conditions in order to make the best scheduling of the system in a realistic approach. An optimization scheme is proposed in which all these elements are included as well as real operation constraints. Distribution losses are minimized for the whole network. This gives as a result a control strategy being able to deal with the whole system and its inherent constraints giving the framework for a multi-objective optimization control.     

近海风电场关键技术

介绍了近海风电场特点、发展态势及关键技术,分析国外近海风电场建设实施案例,并围绕近海风电场优化配置与评估、近海风电场电气传输技术、近海风电场系统接入与稳定运行开展研究,提出了相应的实施及解决方案.     

多端多电平柔性直流系统在海上风电场中的应用

针对交流输电技术和传统直流输电技术在海上风电场应用中的不足,以及保障岛上负荷正常供电的要求,提出了多个海上风电场及岛上负荷经多端多电平柔性直流系统并网的策略。建立了d-q旋转坐标系下的VSC-HVDC数学模型,并且设计了各换流站的控制策略。仿真结果表明,风电场经多端直流系统与陆上电网实现了互联,风电场发力不足时功率反转,即陆上电网向岛上负荷供电,保障了岛上负荷的正常供电。该并网方式灵活可靠,是海上风电场及岛上负荷与陆上电网的最优联接方式。     

大容量陆地和海上风电场的电网接入方案

介绍大型风电场的规划和应用研究。探讨与风电相适应的输电技术和电网法规要求,以获得最经济、可靠的技术方案。从技术和经济的角度,比较高压直流和高压交流输电技术用于风电时的优缺点。介绍当前用于风电外送的可行技术和必要的规划及设计步骤,并结合实例说明风电技术的一些特别的设计原则以及不同技术方案的基本接线与配置,为遥远风电场向大型工业或居住区用户送电设计提供参考。     

大规模海上风电场电力输送方式研究

目前海上风电场建设迅速,正在向规模化、深远海化趋势发展,场内的功率送出需求已成为风电技术发展研究的热点之一。文中介绍了适用于海上风电的电力输送方式：高压交流输电、高压直流输电和分频输电,分析总结其拓扑结构、特点、研究现状及成果。高压直流输电技术应用研究广泛,根据实际需要衍生技术多样,本文对其进行了梳理。结合海上输电需求,思考现阶段发展境况,对大规模海上风电场电力输送方式做出总结。     

A critical survey of technologies of large offshore wind farm integration: summary, advances, and perspectives

Offshore wind farms (OWFs) have received widespread attention for their abundant unexploited wind energy poten tial and convenient locations conditions. They are rapidly developing towards having large capacity and being located further away from shore. It is thus necessary to explore effective power transmission technologies to connect large OWFs to onshore grids. At present, three types of power transmission technologies have been proposed for large OWF integration. They are: high voltage alternating current (HVAC) transmission, high voltage direct current (HVDC) transmission, and low-frequency alternating current (LFAC) or fractional frequency alternating current transmission. This work undertakes a comprehensive review of grid connection technologies for large OWF integration. Compared with previous reviews, a more exhaustive summary is provided to elaborate HVAC, LFAC, and five HVDC topologies, consisting of line-commutated converter HVDC, voltage source converter HVDC, hybrid-HVDC, diode rectifier-based HVDC, and all DC transmission systems. The fault ride-through technologies of the grid connection schemes are also presented in detail to provide research references and guidelines for researchers. In addition, a comprehensive evalu ation of the seven grid connection technologies for large OWFs is proposed based on eight specific indicators. Finally, eight conclusions and six perspectives are outlined for future research in integrating large OWFs.     

直流输电技术在海上风电场并网中的应用

海上风电场具有风速高、风力稳定、各种干扰少及发电量大等特点,风电场由陆地向海上延伸,是未来风电发展的大趋势。根据海上风力发电的特点,介绍和分析海上风电场采用交流输电技术、基于相控换流器(PCC)的传统高压直流(HVDC)输电技术和基于电压源换流器(VSC)的轻型HVDC输电技术的3种并网方式,说明采用后面2种HVDC并网方式的特点和应用场合,并指出HVDC应用于海上风电场并网需要研究的问题。     

含具有风速相关性风电场的发输电系统可靠性评估

提出了一种改进相关矩阵蒙特卡罗模拟法与拉丁超立方采样法相结合的多维相关风速抽样方法,并把该方法应用于含多个风电场的发输电系统可靠性评估。通过实际风速数据对模型的验证表明：提出的风速相关模型能够充分保持实际风速数据的概率分布,基本统计量和相关特性。将该模型和方法应用到 MRTS可靠性测试系统中,证明了该方法适用于含具有风速相关性的风电场的发输电系统可靠性评估。并通过算例,对风速相关性程度、风电场接入位置和风能渗透水平三个因素对含风电场的发输电系统可靠性的影响进行了分析。     

含大型风电场的弱同步电网协调控制策略

针对含大型风电场的弱同步电网频率稳定问题,提出了一种基于模型预测控制(MPC)技术的风电机组多模型预测控制(MMPC)调频控制策略。该控制策略根据风速条件设定预测模型库,能够在不同风速条件下协调控制桨距角与发电机转矩改变风电机组出力响应弱电网频率的变化,从而有效提升风电机组的频率调节能力。同时,针对弱同步电网的电压稳定问题,引入静止同步补偿器(STATCOM)建立中心控制系统。通过中心控制系统实时的有功-无功协调控制,可以保证在负荷波动和故障情况下风电机组不脱网并维持弱电网电压和频率的稳定。仿真分析表明所提出的控制策略的有效性。     

基于概率的含大规模风电场的多目标输电网规划

提出了电力市场环境和大规模风电接入下的多目标输电网规划算法.考虑到风场出力波动性对输电阻塞成本的影响,建立了输电网规划的多目标函数即输电阻塞成本、投资成本及风险成本.结合蒙特卡罗模拟法和两点估计算法来处理风场出力的不确定性,在此基础上通过分析规划目标与问题本身的特性,设计了非支配排序遗传算法Ⅱ和模糊决策方法来求解问题并确定最终的最优解决方案.算例分析验证了规划方法的正确性和求解算法的有效性.     

海上风电场柔性直流输电变流器的无源性控制策略

由于海上风能并网直流输电变流器模型本身存在非线性强耦合特性,常规PI调节器控制方式需调节的参数较多,难以获得理想的动态特性.提出利用非线性系统无源性理论.将变流器两相同步旋转坐标系下的数学模型以拉格朗日方程形式表达,验证被控对象为严格无源系统,选取光滑可微的正定存储函数作为Lyapunov函数,满足控制系统在原点渐近稳...     

Loss evaluation of HVAC and HVDC transmission solutions for large offshore wind farms

This paper presents a comparison of transmission losses for different technical transmission solutions for large offshore wind farms. Three technical solutions are analyzed, i.e. HVAC, HVDC Line Commutated Converter (LCC) and HVDC Voltage Source Converter (VSC). The losses for each technology are calculated for wind farms with different ratings and various distances to shore. In addition, solutions with combinations of two and the three different transmission technologies are analyzed and compared. Based on this comparison, further analysis regarding the economical feasibility can be performed in order to determine the most economic solutions for the transmission system of an offshore wind farm.     

A novel fault detection method for VSC-HVDC transmission system of offshore wind farm

VSC-HVDC transmission system is going to become the most economical way of power delivery for large and remote offshore wind farms. An accurate and fast fault detection method is necessary to protect sensitive devices of these systems and maintain uninterrupted power delivery. This paper investigates an innovative technique for recognizing DC zone faults including HVDC cable faults and unbalancing of DC capacitor bank. Sheath voltage is presented as a novel criterion for detecting abnormal situations in the system. Transient voltage of cable sheath and Wavelet transform are used to identify different types of DC faults. Extensive simulation examples are performed on EMTDC–PSCAD platform and post-processed using MATLAB. The results illustrate that the proposed technique gives a robust performance and can be applied to protection scheme of offshore wind farms.     

电力市场环境下含大规模风电场的输电网规划

对传统的启发式的电网规划算法进行了改进,使其能适应电力市场化改革和大规模风电场给电网规划带来的挑战。利用蒙特卡洛模拟法分析了风电场出力的概率密度函数,根据市场交易体制研究了其他机组出力的概率密度函数,利用直流潮流模型分析了网络中各支路有功潮流的概率密度函数和过负荷概率。综合考虑建设成本和盈利预期提出了衡量线路重要性的效应指标,以此指标为依据得出电网规划方案。以Garver 6节点系统为仿真算例证明了该方法的可行性。仿真结果还表明:电力市场化改革和并网风电场出力的随机性会显著改变网架结构,并有可能增加网络投资。     

海上风电场电气系统现状分析

海上风电发展呈现风电场容量扩大、离岸距离增加、并网要求标准化的特点,这为海上风电场电气系统设计带来重大挑战。大规模海上风电场电气系统与传统电厂相比,具有鲜明的要求与特点。在阐述了现有几种海上风电场电气系统接线方案的基础上,对目前海上电气设备的技术特点与成本状态进行了分析与比较,并就目前海上风电场电气系统研究存在的主要问题与前景进行了展望。     

用于海上风电场并网的多模块变压器耦合型VSC-HVDC技术

给出了海上风电场并网系统结构,提出了一种新型的多模块变压器耦合型VSC-HVDC系统,各模块交流输入端通过多绕组变压器进行相互隔离,直流输出端由多个功率模块串联构成,通过灵活地增减模块数目,以获得不同的直流电压,各功率模块可以独立控制;建立了VSC-HVDC在两相同步旋转坐标系下的数学模型;研究了VSC-HVDC的基本...     

具有低电压穿越能力的集群接入风电场故障特性仿真研究

结合风电机组的结构和并网原理,对直驱风电机组提出了"卸荷电路+无功补偿"的低电压穿越改进控制方法,对双馈风电机组采用了DC-Chopper和SDBR(series dynamic braking resistor)代替Crowbar的低电压穿越改进控制方法。以PSCAD为平台分别构建了具备低电压穿越能力的直驱风电机组和双馈风电机组的并网仿真模型;结合风电并网技术规程,采用电压跌落器仿真验证了直驱、双馈风电机组在电网电压跌落下的低电压穿越能力。参照新疆达坂城实际风电场群接入系统方案,构建了包含具备低电压穿越能力的直驱、双馈风电机组的集群风电场仿真算例,研究了风电场送出线故障、集群风电场送出线电压跌落、系统线路电压跌落时风电场群故障穿越特性。仿真结果表明:集群接入风电场送出线电压跌落会影响相邻风电场及系统的电压和频率,故障结束后整个风电接入系统可以在风电接入技术规程要求的时间内恢复至稳态运行状态。研究成果有助于分析风电大规模集群接入系统的运行特性,提高电力系统对风电的接纳能力。     

大规模近海风电场VSC-HVDC并网拓扑及其控制

针对大规模近海风电场地理分布上高度分散以及主要采用双馈式或直驱/半直驱式风电机组的特点,提出了相应的电压源型变流器的高压直流(voltage source converter based HVDC,VSC-HVDC)并网传输拓扑结构,并设计了相应的控制策略。为验证所提方案的可行性,利用Matlab/Simulink构建了一个近海风电场的5端口VSC-HVDC并网传输系统,并进行了系列仿真。仿真结果表明,所提VSC-HVDC方案可为大规模近海风电场的并网传输提供优化的解决方案。     

基于时间序列分析的风电场风速预测模型

风速预测是风电场规划设计中的重要工作因风速序列本身已经具有时序性和自相关性．提出了基于时间序列分析的风电场风速预测模型。为了检验时间序列分析模型的有效性．使用了信息准则AIC(An Information Criterion)函数在算例中,将预测风速的分布特性与实际风速分布特性相比较,验证了文中提出的时间序列模型用于风电场风速预测的可行性。     

Designed damping controller for SSSC to improve stability of a hybrid offshore wind farms considering time delay

This paper presents the stability improvement results of hybrid doubly fed induction generator (DFIG)-based and permanent magnet generator (PMG)-based offshore wind farms (OWFs) using a static synchronous series compensator (SSSC). An adaptive-network-based fuzzy inference system (ANFIS) controller of the proposed SSSC is designed to render adequate damping characteristics to the studied system. A frequency-domain approach based on a linearized system model using eigenvalue technique analysis is performed. A time-domain scheme based on a nonlinear system model subject to a three-phase short circuit fault at infinite bus with variations in the signal transmission delays has also been investigated to compare the damping of the studied system in cases of with and without controller. The simulation results with MATLAB/SIMULINK toolbox have been presented. It can be concluded from the simulation results that the proposed SSSC joined with the designed ANFIS damping controller can offer adequate damping performance to the studied hybrid DFIG-based and PMG-based OWFs under severe disturbance.