基于新型交直流协调控制抑制电力系统低频振荡的仿真试验

电力系统跨区联网在某些弱联系运行方式下容易诱发区域间低频振荡现象。通过挖掘多直流系统的控制敏感点,设计了直流附加阻尼控制器,并提出基于Matlab-Simulink环境的新型样机测试模式,完成了控制逻辑编辑,制作了实际的控制样机。搭建了Hypersim全电磁暂态实时仿真试验平台,通过仿真优化了直流附加阻尼控制器参数。利用华中—华北电网模型完成了直流附加控制器抑制区域间低频振荡有效性试验验证。     

汽轮机及调速器对共振型低频振荡的影响及改进措施

汽轮机调速器采用转速和功率作为控制信号,在调速器的控制下汽轮机输出功率会引入附加机械同步转矩和阻尼转矩,进而影响共振型低频振荡。分析了共振幅值与机械同步转矩系数Km、阻尼转矩系数Dm的关系,基于汽轮机及调速器的数学模型采用复转矩系数法推导了Km和Dm的表达式,并分析了汽轮机及调速器相频特性和转矩系数之间的关系。在此基础上提出了一种改进措施,通过在控制环路中加入超前滞后环节,使汽轮机在共振频率处输出的机械同步转矩和阻尼转矩为正值,从而有利于消除汽轮机及调速器对共振振荡的不利影响。在Matlab/Simulink中搭建典型单机无穷大系统进行仿真,仿真结果验证了理论分析的正确性和改进措施的有效性。     

基于EMD和TLS-Prony的次同步振荡模态辨识方法及电压反馈抑制策略

以减小次同步振荡模态辨识中的误差，提升Prony算法的抗噪性，抑制双馈风电机组并网次同步振荡为研究对象，提出一种基于经验模态分解（EMD）和TLS-Prony算法的次同步振荡模态辨识方法及电压反馈抑制策略。首先，使用EMD对振荡信号进行预处理，降低噪声对Prony算法辨识振荡模态的影响；然后，使用TLS-Prony算法进一步抑制噪声干扰，提取振荡特征，辨识振荡模态；最后，直接调整控制参数调制网侧变流器的输出电压，向系统注入等效正电阻，改善系统负阻尼特性，设计以串补电容电压为反馈输入信号的附加阻尼控制器。采用模态计算分析附加阻尼对系统稳定性的影响，基于Matlab/Simulink仿真平台验证所提阻尼抑制策略的有效性。     

基于有源阻尼控制的区域电网新能源基地次同步振荡抑制的研究

近年来,由于大规模新能源基地不断接入电网,导致系统转动惯量降低,产生次同步振荡问题。为此,提出了基于有源阻尼的新能源基地次同步振荡抑制策略。该控制策略将有源阻尼控制器附加于新能源并网装置的有功功率环上,通过采集电网频率,实现对振荡频段内的输出信号进行幅值和相位校正,改善系统的次同步阻尼特性,提高系统稳定性。在此基础上对有源阻尼控制器参数进行优化设计,并通过特征根分析法和Prony算法进行验证。最后,以某市区域电网为例进行仿真分析,当该电网出现次同步振荡后,在新能源基地上附加有源阻尼控制,可以快速抑制次同步振荡,提升系统阻尼,验证了有源阻尼控制的适用性和有效性。     

网间规模化光伏并网对系统阻尼的影响及优化措施

电力系统受到大扰动后,其振荡中心电压大幅波动,受此影响,其近区规模化光伏汇集线功率会出现显著波动,加剧光伏与电网交互作用。文章基于光伏暂态仿真模型,分析了并网电压低频跌落或回升过程中,光伏并网系统暂态功率特性;基于等面积原理,分析了不同控制方式下光伏并网系统等值电纳Bpv的Us-Bpv轨迹及其对振荡的影响,并据此揭示了光伏并网系统对电网振荡阻尼的作用机制。通过两区域四机系统受扰时域仿真,验证了基于光伏并网系统Us-Bpv轨迹特征,评估其对系统阻尼影响的有效性,在此基础上,指出利用附加阻尼控制的SVG具有增强系统正阻尼作用。     

水轮机及其调速系统对电力系统低频振荡的影响

传统上在对电力系统低频振荡的研究中,励磁系统被认为是造成低频振荡的主要原因。而目前认为,水轮机及其调速系统对电力系统低频振荡的影响也不能忽略。对低频振荡的研究主要从水轮机及其调速系统的作用着手,通过对实例的计算得出特征值、相关因子等,通过相关性分析等方法得出水轮机及其调速系统对电力系统低频振荡有影响的结论。     

天津电网小干扰稳定分析及控制

小干扰稳定中的一个中心和重要问题就是低频振荡问题,在系统扩大,特别是在大区联网下,这个问题更为突出。利用线性化分析和prony检测相结合的方法完成了大区联网条件下天津电网的低频振荡分析工作。求出了与天津电网相关的低频振荡模式,特别是弱阻尼低频振荡模式,并提出了增强系统阻尼,改进系统小干扰稳定的方法和措施。     

虚拟同步发电机对系统低频振荡的影响及抑制方法综述

为梳理虚拟同步发电机接入后对系统低频振荡的影响，进一步发掘其在提供阻尼和惯量方面的潜力和应用，开展相关梳理和研究工作。首先，归纳和总结电力系统低频振荡的研究现状；然后，对非同步发电机电源并网后对系统低频振荡的影响进行概括和分析；最后，综述伴随非同步发电机电源接入的虚拟同步发电机对系统低频振荡的影响和抑制方法，并针对虚拟同步发电机在新型电力系统应用过程中亟需解决的关键问题提出进一步的思考和展望。     

光伏并网对低频振荡的影响与抑制

以大型光伏电站并入多机电力系统为研究对象,通过模式分析和时域仿真的方法,首先推导出光伏电站并入多机系统的状态方程线性化模型,然后搭建含光伏电站的四机两区域测试系统。研究结果表明:光伏电站的不同接入地点以及不同渗透率对多机系统低频振荡会产生影响,光伏电站并网后并未产生新的振荡模式。采用综合功率调制设计的光伏广域附加阻尼控制器可以抑制低频振荡。     

一种低频振荡机组参与程度在线识别方法

发电机组是电力系统低频振荡的主要参与者,在线识别机组在振荡中的参与程度便于进行快速有效的控制。同时低频振荡是一种特殊的电力系统运动形式,振荡过程中伴随着振荡能量的传播和交换,而振荡能量的分布特点一定程度上反映了系统固有的振荡特性。以发电机经典模型为例,建立可描述电力系统低频振荡运动特征的振荡能量表示方法;研究了振荡能量分析方法与传统模式分析方法间的联系,提出了基于振荡能量分布在线识别低频振荡机组参与程度的方法;给出了机组阻尼变化对系统振荡能量的影响;最后通过四机两区域系统与IEEE 10机39节点系统的分析,验证了本文理论和方法的可行性和有效性。     

Contribution of Doubly Fed Wind Generators to Oscillation Damping

In this paper, the effects of increased wind power penetration by doubly fed asynchronous generators (DFAGs) on oscillation damping are investigated. With the help of an illustrative example, it is shown that the general trend for DFAGs is to increase interarea oscillation damping. However, there are exceptions for certain penetration levels (not necessarily large), for which the voltage control (VC) option of DFAGs can reduce damping. It is also shown that the modulation of active power generation of wind turbines is a powerful tool to introduce additional damping to interarea oscillations through a simple wind power system stabilizer design. The general trend for increased oscillation damping is verified in the case of a large interconnected system encompassing Southeastern Europe for a projected high level of wind penetration in Greece. For the same system, it is also shown that low-damping voltage oscillations possibly introduced by the VC mode of DFAGs can be adequately damped by properly adjusting control parameters.      

基于光传感器的输电线路盐密在线监测系统设计

采用Mann Kendall检验法和重标极差法（R/S）分析了泗合水流域1965~2010年全年及年内各时期的降雨量、蒸发量和径流量时间序列变化趋势及其持续性,分离和估算了气候变化和人类活动对径流的影响。结果表明,径流变化受人类活动的影响,但不足以颠覆最大月和旱季两个极端时期的降雨变化趋势。以径流系数突变年份2003年为界,显著变化期与平顺变化期相比,多年平均降雨量和蒸发量分别减少了73、34 mm,径流量却减少200 mm;并根据平顺变化期的降雨—径流相关关系,估算出显著变化期气候变化与人类活动对径流减少的贡献率分别为33.5%、66.5%。     

Mitigating subsynchronous resonance and damping power system oscillation in a series compensated wind park using a novel static synchronous series compensator control algorithm

This paper presents a novel damping control algorithm for static synchronous series compensator (SSSC) in a series compensated wind park for mitigating subsynchronous resonance (SSR) and for damping power system oscillations. The sample test system, adapted from the IEEE first benchmark model on SSR replacing the synchronous generator, is employed aggregating wind park based self‐excited induction generator. Consequently, it investigates the SSR phenomena and the damping power system oscillation while integrating large wind park based on SEIG. The potential occurrence and mitigation of the SSR caused by induction generator effects as well as torsional interactions, in a series compensated wind park, are investigated. The auxiliary subsynchronous damping control loops for the SSSC based on a novel design procedure of non‐linear optimization are developed. The performance of the controller is tested in steady state operation and in response to system contingencies, taking into account the impact of short circuit ratios (SCRs). The simulation results are presented to demonstrate the capability of the controllers for mitigating the SSR, damping the power system oscillation and enhancing the transient stability margin in response to different SCRs. Copyright © 2011 John Wiley & Sons, Ltd.     

Comparison of oscillation damping capability in three power control strategies for PMSG‐based WECS

With the aid of small signal analysis and digital simulations, this paper compares the mechanical and power oscillation damping performances of three power control strategies for the multi‐pole permanent magnetic synchronous generator (PMSG)‐based direct driven wind energy conversion system (WECS). Maximal power point tracking (MPPT) control implemented in the generator side has inherent abilities on the oscillation damping. For the smoothed or constant power requirements, power oscillations are hard to damp, and additional active damping controller is required. Active damping can be achieved with power control on the generator or grid side and DC link voltage control on the generator side. With additional compensator in the power or DC link voltage control loop, a damping torque is produced to suppress the oscillations. An improved control structure, which has inherent oscillation damping capability, is proposed for the power control of WECS. Combined with different power control strategies, this structure can be applied to achieve different power outputs. The validation of the proposed control structure is verified by the simulations. Copyright © 2010 John Wiley & Sons, Ltd.     

Application of superconducting magnetic energy storage unit toimprove the damping of synchronous generator

A systematic approach to the design of a controller for superconducting magnetic energy storage (SMES) units to improve the dynamic stability of a power system is presented. The scheme employs a proportional-integral (PI) controller to enhance the damping of the electromechanical mode oscillation of synchronous generators. The parameters of the PI controller are determined by the pole assignment method based on modal control theory. Eigenvalue analysis and nonlinear computer simulations show that SMES with the PI controller can greatly improve the damping of the system under various operating conditions. Although the PI controller is designed for a special load condition, it can also provide good damping under other load conditions     

Improvement to observability measures of LFO modes in power systems with DFIGs

Observation of the low-frequency oscillation (LFO) modes in power systems is important to design the damping scheme. The state equations of the power system with the doubly-fed induction generators (DFIGs) are derived to find the LFO modes related to the synchronous generator (SGs) and the DFIGs. The definition of the observability measure is improved to consider the initial output and the attenuation speed of the modes. The sensitivities of the observability measures to the control parameters are derived. The numerical results from the small and large-disturbance validate the LFO modes caused by the DFIGs, and different observability measures are compared. Adjustment of the control parameters is chosen based on the sensitivity model to improve the observability and damping ratio of the LFO mode, and the stability of the wind power system.     

混流式水轮机调节系统的鲁棒控制策略研究

水轮机及其调节系统是水力发电系统中的重要组成部分,承担着能量转换的重要作用。水轮机运行于复杂工况下,往往表现出各种复杂的非线性行为,危害水力发电系统安全。基于刚性水击下混流式水轮机调节系统的数学模型,采用T-S模糊控制方法建立了水轮机调节系统的非线性T-S模糊模型,基于Lyapunov稳定性定理,提出了一种鲁棒控制策略,设计了相应的鲁棒控制器。仿真计算表明,所设计的鲁棒控制器能够极大地抑制水轮机调节系统的振荡,并在较短时间内将水轮机调节系统的运动控制到稳定运行状态,研究结果可为混流式水轮机调节系统的安全稳定运行控制提供参考依据。