风电系统中异步电机机电模式研究

随着风电容量的增加,异步电机对同步电网动态特性的影响更加明显。提出在五阶异步电机模型中,计及定子电压相角变化引起的定子频率变化。将振荡模式对状态变量的参与因子按同步和异步电机类型分类,修改机电回路相关比定义以判别异步电机机电振荡模式。采用Prony算法,提取异步电机振荡曲线的特征参数。静态稳定和时域仿真得到的机电振荡模式,都证明了异步发电机比同步发电机更容易导致非失步振荡过程。     

基于机电回路相关比灵敏度的DFIG并网系统机电模式抑制

机电模式(EOM)是与同步发电机(SG)机械暂态强相关的振荡模式,对SG轴系和电网稳定影响较大.为了抑制EOM,可以调节SG出力以减小机电回路相关比(ρ),但需要以灵敏度为依据.双馈感应风电机组(DFIG)并网后,需要联立SG和DFIG以建立系统状态矩阵,增加了抑制EOM的难度.针对DFIG并网电力系统,筛选出EOM....     

基于机电回路相关比灵敏度的机电振荡模式抑制方法

机电振荡模式(electromechanical oscillation mode, EOM)是与同步发电机(synchronous generator, SG)机械暂态强相关的低频振荡(low-frequency oscillation, LFO)模式,对SG轴系安全和电网稳定影响较大。减小EOM机电回路相关比ρ能减小EOM与SG的相关度,抑制SG振荡。基于此,提出机电回路相关比对SG出力的灵敏度的模型:将ρ对控制参数的灵敏度展开为对参与因子的灵敏度;考虑参与因子由特征向量组成,补充后者幅值和相位约束,得到特征向量灵敏度的唯一解;考虑SG出力对节点电压和特征值的影响,但未出现在状态矩阵中,引入潮流雅可比矩阵的逆,建立特征值和特征向量对SG出力的灵敏度,提出ρ对SG有功和无功出力灵敏度的解析表达。最后利用算例分析检验了EOM及其特征向量、参与因子、ρ对SG出力的灵敏度的准确性,证实了调节SG有功和无功出力对抑制机电模式的控制效果。     

含不同风电机组的风电电网仿真研究

为了研究包含恒速异步风力发电机和双馈异步风力发电机的风电场对电网的影响,应用Matlab 7.0建立了含不同风电机组的风电场动态模型。分析了风电场对电网暂态稳定性的影响,风电机组电压恢复情况,有功、无功变化情况,以及不同风电机组的低电压穿越能力。仿真结果表明：双馈异步风力发电机变速平稳、低电压穿越能力较强,有利于优化电能质量;当电网发生故障时,应针对不同的风电机组采取不同的控制策略以提高电力系统稳定性。     

电压源型SPWM逆变器-异步电机系统发电工作原理的研究

分析了电压源型SPWM逆变器-异步系统发电的基本工作原理以及当异步电机从电动进入到发电运行时逆变器从无源逆变状态转换到将电机的发出的能量转送到直流侧这种类似于整流的工作状态的根本原因.最后通过Matlab软件进行仿真验证了理论的正确性.     

故障下双馈风电系统机电能量平衡的可行性分析

对于电网故障下双馈感应发电机（doubly fed induction generator,DFIG）机电能量失衡即风力机输入双馈电机能量和双馈电机输出至电网侧能量失衡的问题,现有文献鲜少涉及。双馈电机输出能量和机侧变换器的励磁控制策略有关,首先对现存几种励磁控制策略下双馈电机输出有功功率的情况进行分析,结果表明现有励磁控制策略下双馈电机无法达到机电能量平衡。进而从任意频率、幅值、相位转子电流入手,探讨转子电流三要素和双馈电机输出有功功率之间的关系,推导了使双馈电机达到能量平衡所需的转子电流指令。利用Matlab/Simulink搭建了系统的仿真电路,验证了以上推导过程的正确性。     

含双馈风电机组的系统阻尼优化研究

提出了一种在双馈异步风电机组中附加电力系统稳定器（PSS）以提高系统阻尼的控制策略.结合矢量控制,详细分析了双馈风电机组的阻尼控制原理,并设计了PSS模型,同时给出了相关参数的整定方法.在IEEE四机两区域系统中进行了时域仿真,验证了PSS在双馈风电机组上应用的有效性和可行性.     

电网接受风电能力的研究

在风电场接入电力系统规划设计阶段需要解决的首要问题是确定给定电网中允许接入的风电场最大装机容量.此处采用稳态分析与暂态分析相结合的方法,稳态分析对风电场进行处理时,根据风速确定有功,再由有功和节点电压初值确定无功;暂态分析中考虑了阵风、渐变风及系统故障方式的影响,确定能使系统保持暂态稳定的风电场容量.使用电力系统综合分析程序(PSASP)软件,对实际电力系统进行仿真,结果表明风电场的功率因数、并网联络线和风机的布置、风电场接入点的短路容量、阵风和渐变风的干扰、系统故障等因素都影响风电场的接入容量.     

基于STATCOM双馈风电系统低电压穿越能力研究

针对双馈异步风力发电系统,提出应用基于滑模变结构控制策略的STATCOM,提高风电机组低电压穿越能力.研究STATCOM的工作原理,以及滑模变结构控制策略的特点,建立了含STATCOM的双馈风电机组模型.仿真结果显示,应用基于滑模变结构控制策略的STATCOM,在电网电压跌落时,有效抑制了直流母线电压过压,转子电流激增,无功功率大幅振荡的现象,改善了并网电能质量,提高了风电机组低电压穿越能力.     

采用双馈机组的风电场无功功率控制研究

现今双馈风力发电机已成为风力发电的主流机型,然而在故障期间,转子侧变流器在转子保护的作用下退出运行,不能向电网提供无功功率以保持系统稳定运行。分析了网侧变流器的无功调节能力,提出了电压外环和功率外环两种控制模型。在DIgSILENT/Power Factory 仿真软件中建立了包含风电场的三机九节点系统,仿真结果表明在故障情况下,与传统的单位功率因数控制相比,两种控制模型下的网侧变流器均能产生较多的无功,在一定程度上提高了风电接入系统的暂态电压稳定性。最后对比分析了网侧变流器采用两种控制模型时的无功特性。     

Transient current analysis of induction generators for wind power generating system

In this paper we present a transient current analysis of induction generators used in a wind power system before and after three‐phase fault conditions. First, the basic equations of an induction generator connected to an infinite bus are developed and then transient current analysis formulas are derived for a three‐phase fault before and after fault clearance. We also determine the initial phase angle for the three‐phase fault or the restoration phase angle of the power supply voltages and the time at which the maximum or minimum transient currents flow in the system. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(1): 38–45, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10319     

Terminal voltage and power factor control of induction generators for wind power generation system

This paper deals with two types of control method for induction generators used in wind power generating stations. One is aimed at maintaining the voltage of the station node and the other is aimed at maintaining a constant power factor through the branch connecting to the station. Both can be in the controllable area by adjusting the generator reactive power with compensating capacitors. First, theoretical equations for the terminal voltage and power factor of an induction generator are derived, and then the compensating capacitance corresponding to the wind velocity variation is determined quantitatively. By using the proposed control method, it is shown to be possible to maintain the terminal voltage and operating power factor of a wind power generation system at the target values, even when abrupt deviations are caused by wind power disturbances. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(3): 19– 26, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20298     

双馈电机风电场等裕度无功分配策略

双馈式异步发电机可实现P-Q解耦控制,能够为电网提供无功支持,但其输出功率受变流器容量限制。为充分发挥双馈机无功调节能力,提出等裕度无功分配策略:根据各台风机无功极限的大小,以各机组具有相同的无功裕度作为无功分配的标准。该策略能够使风电厂在满足电网功率因数要求的同时,有效防止有功出力较大的双馈机由于变流器电流越限而发生跳机的现象,提高风电场运行可靠性。采用PSCAD/EMTDC软件进行仿真研究,通过与等功率因数无功分配策略进行比较,验证了等裕度无功分配策略的有效性。     

Reactive power control of wind farm made up with doubly fed induction generators in distribution system

In recent years, the number of small size wind farm made up with doubly fed induction generators (DFIG) located within the distribution system is rapidly increasing. DFIG can be utilized as the continuous reactive power source to support system voltage control by taking advantage of their reactive power control capability. In this paper, considering both reactive power control and distribution network reconfiguration can be used to reduce power losses and improve voltage profile, a joint optimization algorithm of combining reactive power control of wind farm and network reconfiguration is proposed to obtain the optimal reactive power output of wind farm and network structure simultaneously. The proposed algorithm has been successfully implemented on the 16 bus distribution network and the results obtained demonstrate the efficiency of the algorithm.     

风力发电机发展现状及研究进展

风力发电机是实现风能转换为电能的核心部件之一.自上世纪70年代末以来,涌现了多种风力发电机拓扑结构及发电系统.针对现有国内外主要类型风力发电机的技术特点进行评述,分析比较不同类型风力发电机的经济技术性能,讨论风力发电机的最新发展趋势与研究进展,为我国风力发电研发工作提供参考.     

含风电机组的配电网无功优化补偿

根据风电机组各运行状态发生的概率,计算出风机有功输出的期望,来近似代替随机变化的输出功率.用最大、一般和最小负荷运行方式代替规划时期的运行状况.建立了最大负荷方式下电容器投资成本最小、节省电能损失费用和静态电压稳定性最大的多目标优化模型,运用NSGA-Ⅱ算法进行求解;一般及最小负荷方式下以节省电能损失费用最大为目标进行优化.三种运行方式通过补偿后节省的资金最多来协调,得出电容器的最优配置,实现整体最优.算例验证了模型和算法的可行性.     

Insertion of wind generators in electrical power systems aimed at active losses reduction using sensitivity analysis

The study evaluates the electrical power system behaviour when wind turbines are inserted into the power grid. The assessment is made using a sensitivity analysis technique applied to the power flow solution. Unlike the typical algorithms, the sensitivity analysis technique does not require an iterative process, resulting in a fast method with great precision. This proposed method make easy to check the wind turbine behaviour to the changing of wind speed. Initially, the power flow solution is obtained and identified as the base case. When there are perturbations in the generators, the new solution is obtained directly by sensitivity analysis technique. The technique was applied in 34-bus, 70-bus and 126-bus test distribution system. The places chosen to connect the wind turbines were determined by the Incremental Transmission Losses method. The results demonstrate the effectiveness of the methodology. When wind turbines are inserted in the studied systems, active and reactive losses are reduced and voltage profile is improved.     

Multipolar permanent-magnet synchronous generators intended for wind power plants

The analytical method of calculating two-dimensional magnetic fields in the active section of permanent-magnet synchronous electrical rotating machines, as applied to their use in the wind energy industry, has been developed. The analytical relationships for calculating distribution of two-dimensional magnetic fields and determining output parameters with due regard for geometry of the active section, the number of pairs of poles, and magnetic characteristics of materials have been obtained. The criteria dependences needed for calculating the electromotive force and main inductive reactance of permanent-magnet synchronous electric machines, with consideration for the geometry of a machine and electrophysical properties of materials being used, have been derived. The procedure of evaluating parameters of permanent-magnet synchronous generators for large-size wind power plants is presented.