基于双馈风电机组控制参数优化的电网功角振荡控制

随着大量风电并网，双馈感应发电机（DFIG）与同步发电机（SG）间的动态交互，将加剧SG功角振荡。基于特征值分析的控制参数优化，未考虑非线性元件和大扰动场景。该文从抑制功角振荡出发，以SG转速为DFIG电力系统稳定器（PSS）输入信号，建立风电并网电力系统动态模型。在微分方程中引入中间变量，以解耦状态变量轨迹灵敏度。区分状态变量与代数变量对应的雅可比矩阵，推导DFIG并网电力系统轨迹灵敏度的解析表达。设定目标函数为SG功角偏差相对值二次方对时间积分，按时间顺序累加功角对控制参数的轨迹灵敏度，得到目标函数对控制参数的梯度信息。考虑DFIG-PSS可能弱化转子侧变流器（RSC）控制效果，提出基于轨迹灵敏度的RSC和DFIG-PSS参数协调优化方法。给出4机2区域系统仿真结果，验证了所提方法对DFIG并网系统功角振荡的阻尼效果。     

并网DFIG多通道附加阻尼控制器设计及其控制参数整定

针对双馈感应发电机(DFIG)并网电力系统中多低频振荡(LFO)抑制的问题,提出一种基于DFIG的多通道附加阻尼控制器(MBSDC)设计及其参数整定方法,用于增加系统多LFO模式的阻尼。建立DFIG并网系统状态矩阵,由特征值分析筛选出待抑制的LFO模式,并设计了MBSDC控制策略。在DFIG-MBSDC系统线性化模型基础上,推导目标LFO模式对相应抑制通道传递函数灵敏度的解析表达,以量化多LFO模式与MBSDC传递函数间的联系,应用于控制参数整定。特征值分析与时域仿真结果表明,所提DFIG-MBSDC能抑制DFIG系统中多LFO模式。基于传递函数灵敏度对控制参数进行整定,提高多LFO的抑制效果。     

基于灵敏度分析的电力系统稳定器参数优化

推导了电力系统稳定器(PSS)参数灵敏度指标的计算过程,并在小干扰稳定分析软件SSAP中实现了2种灵敏度计算功能,即振荡模式特征值及其阻尼比对PSS参数灵敏度的计算功能,以及控制器等效交流增益不变约束下的振荡模式特征值及其阻尼比对控制器补偿相位的灵敏度的计算功能,可以对低频振荡阻尼进行优化(或约束优化)。以红海湾电厂600 MW机组为例,通过PSS参数的灵敏度分析对低频振荡阻尼进行约束优化,特征值分析与现场抗扰动试验的实测录波结果相吻合,验证了SSAP灵敏度分析理论与计算的准确性及其在工程中的指导作用。     

基于混合特征值灵敏度的广域PSS设计

为抑制互联电力系统的低频振荡,提出了基于混合特征值灵敏度的广域PSS设计方法。介绍了混合特征值灵敏度的概念,然后根据模式—机组的关联特性,采用反馈信号机组和控制机组相分离的设计思想,提出采用混合特征值灵敏度的幅值指标选取控制机组,根据模态等值选取广域反馈信号,最后根据特征值灵敏度的相角指标对两层式结构的广域PSS进行参数设计。IEEE39测试系统上的仿真结果表明,基于模式—机组关联特性的灵敏度指标设计的广域PSS能够有效抑制电力系统的区间低频振荡,提高互联系统的传输容量,提高系统的小信号稳定性。     

基于TLS-ESPRIT的低频振荡负荷参与程度量化分析

为研究负荷侧引起的低频振荡,对负荷在低频振荡中的参与程度进行了量化分析和计算,通过引入负荷灵敏度作为该量化指标,分析了其影响振荡模态的方式。为避免大区电网在线计算特征值计算量大的困难,采用TLS-ESPRIT辨识计算负荷的功率振荡增量分布(oscillatory active powerincrement distribution,OAPID),以间接反映负荷灵敏度和负荷参与振荡程度。4机2区域系统和实际电网的仿真研究,验证了所述方法的有效性。     

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。     

多机系统PSS选址方法分析与对比

电力系统低频振荡是影响互联大电网运行的重要问题,电力系统稳定器(PSS)被广泛应用于抑制负阻尼引发的低频振荡,但是多机电力系统中如何布点PSS,从而更有效地抑制低频振荡是一个尚未解决的问题。文章详述了两种PSS选址方法,即参与因子法和特征值灵敏度法,利用特征值分析求出系统的状态矩阵,并在此基础上得到参与因子以及状态矩阵对任意参数的偏导数。通过对这两种方法原理的分析对比,指出了它们各自的优缺点及适用范围。最后利用典型两区域四机算例,分别求取所关心低频振荡模式的参与因子及灵敏度,验证了两种方法对于特定的低频振荡模式主导机判断的准确度,并对产生所得结果的原因进行了讨论分析。     

多运行方式下风电机组变频器参与次同步相互作用的分析与抑制

大规模风电经串补线路进行远距离传送存在引发次同步相互作用的风险,系统运行方式、串补度及变频器控制参数为主要影响因素。采用概率法和模式分析相结合,分别在含双馈感应型和永磁同步型风电场系统中,研究多运行方式下风电串补系统的次同步相互作用。利用参与因子进行模式识别,研究了串补度对次同步振荡模式及概率稳定性的影响,引入概率灵敏度指标分析起主导作用的变频器PI控制参数,并基于风电机组变频器提出一种鲁棒抑制次同步相互作用的附加阻尼控制策略。仿真结果表明,双馈风电串补系统中易产生次同步控制相互作用,在网侧变频器加装鲁棒DFIG-PSS能实现其有效抑制,而永磁同步风电机组对这一相互作用具有免疫特性。     

基于EWT和改进Prony算法的含风电区域电网低频振荡模态及影响因素研究

区域电网风电渗透率的提高使得电力系统的惯量降低,同时由于风电的随机波动性及不确定性增加,使得区域电网间联络线传输功率变动范围扩大,因此含风电区域电网低频振荡模态辨识方法及影响因素有待深入研究。文中提出一种基于经验小波变换方法(EWT)与改进Prony方法相结合的低频振荡模式辨识方法;在扩展四机两区域系统中,分析了含风电区域电网惯量变化和风电功率波动对区域间振荡模态的影响,基于极限传输功率下分析了双馈风电机组虚拟惯量控制参数对振荡模式的影响,给出了抑制含风电区域电网低频振荡的虚拟惯量参数设定值。     

百色—兴义区域互联电网低频振荡模式分析及抑制措施

针对百色—兴义区域互联电网出现的低频振荡问题,利用特征值分析法分析了该区域互联电网的低频振荡模式,并计算出与低频振荡模式强相关的发电机组,最后提出了低频振荡的抑制措施,即在与低频振荡模式强相关的发电机组上配置电力系统稳定器(Power System Stabilizer,PSS)。计算结果表明,在与低频振荡模式强相关的发电机组上配置PSS可增强系统阻尼,从而有效抑制了百色—兴义区域互联电网低频振荡的发生。     

Towards an extended power system stability: An optimized GCSC-based inter-area damping controller proposal

Due to the crucial importance of the FACTS based damping controllers in mitigation the deteriorative impacts of the power system low frequency oscillations, particularly the inter-area modes, improving the system stability margins seems indispensible. This paper proposes an optimization approach to effectively carry out the multi-machine based stabilization function of the Gate-Controlled Series Capacitor (GCSC) in providing a robust damping to the power system low frequency oscillations. It is aimed to provide a reliable damping framework by means of an optimized GCSC based supplementary damping controller. Thus, to attain the most efficient set of the damping controller parameters, Particle Swarm Optimization algorithm as a proficient optimum hunter is employed to explore for the global stabilization solution in accordance to a vast range of power system operating conditions. Moreover, as a weighty assessment, the eigenvalue analysis is taken into account as the cornerstone of the performed studies in order to investigate the damping methodology in which the unstable or lightly damped inter-area modes are scheduled to effectively shift to some predominant stability zones in the s-plane. Meanwhile, derived results through the nonlinear time domain simulation as well as two dynamic performance evaluators manifestly demonstrate the impressiveness and verify the robustness of the proposed GCSC based damping scheme in enhancing the power system stability, especially regarding to the inter-area modes.     

基于改进能量集中度的S变换与随机森林的电能质量扰动识别

鉴于S变换的窗口函数对不同频带信号的自适应能力差,提出一种新型的改进S变换(Modified S-Transform,MST),该方法通过引入四个辅助参数,优化高斯窗函数尺度因子的自适应能力,使改进S变换的能量集中度最大化,获得了更出色的时频分辨能力。建立了基于扰动信号幅值和相位的特征值评价体系,采用随机森林(Random Forest,RF)算法对包括标准信号和电压暂降、电压暂升、高次谐波、暂态振荡等10种扰动信号共11类电能质量信号分类识别。与已有文献采用的决策树、支持向量机和神经网络分类结果进行了对比分析,仿真试验结果表明,该方法分类准确率高,抗干扰能力强,且在训练样本少、低信噪比(Signal-to-Noise Radio,SNR)条件下分类结果优势明显。     

PSS抑制次同步谐振的研究

次同步谐振对电力系统的安全稳定有严重的影响,电力系统稳定器(PSS)广泛应用于抑制低频振荡和提高系统小扰动的稳定性。基于机电系统小信号模型,采用特征值分析法,研究了PSS励磁控制对次同步谐振的抑制效果,分析了三种形式的PSS对阻尼特性的影响。结果表明,选择合适的输入信号和加装扭转滤波器的PSS在合适的增益下,可以使PSS在提高低频振荡稳定性的同时,实现缓解次同步谐振的目的。     

直驱风电机组次同步振荡阻尼控制方法及其适应性

由风电波动引发的次同步振荡具有振荡频率多变、涉及动态装置多、影响因素复杂等特点,现有的阻尼控制类装置难以实现有效抑制,需研究适用的附加阻尼控制方法。文中通过线性化方法推导了直驱风电机组并网系统的特征方程和传递函数,并获取了风电机组并网系统在不同工况下的频率响应特性。然后提出了基于奈奎斯特稳定判据的风电机组次同步振荡阻尼控制器的参数设计方法,以及基于粒子群优化算法的参数优化方法;结合特征值法及时域仿真法,分析了阻尼控制器对于次同步振荡的抑制作用。研究结果表明,依据前述方法设计的阻尼控制器在多种运行条件下均具有较好的适应性。     

基于WAMS及逆迭代转Rayleigh商迭代 计算的弱阻尼模式特征提取

面向调度运行的低频振荡在线分析与抑制方法主要是基于模式匹配思想,而互联系统固有振荡模式分析成为该方法成功与否的关键.提出一种分析大规模互联系统的固有振荡模式的实用分析方法.该方法根据WAMS对系统小扰动事件的统计确定系统固有振荡模式,对实测振荡曲线进行prony分析得出振荡模式特征值的估计值,作为逆迭代转Rayleig...     

基于相图法的水电二阶切换系统动力学特性与振荡分析

高比例水电系统在大扰动下出现了死区、限幅作用的超低频频率振荡,其所对应的切换系统仍缺乏动力学特性分析。鉴于此,基于二阶切换系统动力学特性,结合相图法分析系统参数对其动力学特性的影响,揭示系统在不同扰动、阻尼下发生频率振荡的动力学机理。首先给出水电二阶切换系统描述,分析了系统的平衡点存在性。其次结合相图法分析不同运行条件下系统的动力学特性,证明了相关极限环的存在性。最后分析了系统的非光滑分岔特性。结果表明：当平衡点正阻尼、系统调节区域负阻尼时存在1个稳定极限环,对应严重大扰动下的频率振荡;当平衡点负阻尼、系统有限幅时存在2个稳定极限环,分别对应一般、严重大扰动下的频率振荡,且二者振荡频率较为接近。     

Damping inter-area oscillation by generation rescheduling based on wide-area measurement information

Inter-area oscillations are inherent to power systems which can be caused due to oscillation of two coherent groups of generators against each other with low or negative damping. Poorly damped oscillations can pose various problems such as limiting transfer capabilities and in more severe cases can lead to uncontrolled islanding causing system blackout. In this paper, for damping inter-area oscillation a new method based on the wide area measurement system (WAMS) and using generation rescheduling (GR) is proposed. The proposed algorithm consists of three tasks; identification of inter-area mode, determination the most effective generators for rescheduling and enhancing damping of inter-area mode by GR. In this approach, first by means of Independent Component Analysis (ICA) and modified Random Decrement (RD) techniques and using on-line power and rotor angle oscillation data provided by WAMS, the frequency and damping of the inter-area mode is identified. In the case of low damping of oscillation, by using mode shape of the inter area mode, generation rescheduling is applied for improvement of damping. In this paper, a non-model based method is adopted for estimating mode shape from the measured data like generator rotor speeds. The proposed approach is applied on a two area small system and IEEE 39-bus test system and the results demonstrate effectiveness of the method for enhancing oscillation damping.     

Optimal multiobjective design of robust power system stabilizers using genetic algorithms

Optimal multiobjective design of robust multimachine power system stabilizers (PSSs) using genetic algorithms is presented in this paper. A conventional speed-based lead-lag PSS is used in this work. The multimachine power system operating at various loading conditions and system configurations is treated as a finite set of plants. The stabilizers are tuned to simultaneously shift the lightly damped and undamped electromechanical modes of all plants to a prescribed zone in the s-plane. A multiobjective problem is formulated to optimize a composite set of objective functions comprising the damping factor, and the damping ratio of the lightly damped electromechanical modes. The problem of robustly selecting the parameters of the power system stabilizers is converted to an optimization problem which is solved by a genetic algorithm with the eigenvalue-based multiobjective function. The effectiveness of the suggested technique in damping local and interarea modes of oscillations in multimachine power systems, over a wide range of loading conditions and system configurations, is confirmed through eigenvalue analysis and nonlinear simulation results.     

STRONG CONTROLLABILITY AND OBSERVABILITY AND THEIR EFFECTS ON TRANSIENT STABILITY OF POWER SYSTEMS

ABSTRACT

An algorithm is developed for identifying bus clusters called control areas that have strong local controllability and observability property for measurements and controls at the buses or on generators within the control area. Two types of control areas are identified; one that is based on weak boundaries of the reactive power voltage jacobian and is called voltage control area; the other is based on the jacobian of both real and reactive power balance equations with respect to voltage and angle at network buses. The two control areas are identical under light load conditions, but are different as the system approaches voltage collapse or poorly damped low frequency oscillations. The understanding of strong controllability and observability in terms of real power angle dynamics and reactive power voltage dynamics (voltage control areas) and the strong controllability and observability of voltage and angle dynamics (control areas) helps understanding of voltage instability and inter-area oscillations.