水电机组孤网运行频率振荡及其抑制研究

孤网模式下,水电机组调速系统的参数设置不合理会造成频率振荡,从而影响电网可靠运行,因此有必要对调速系统参数与孤网频率稳定性之间的关系进行研究。为此,针对孤网运行的西南某水电机组的实际情况建立了孤网系统模型,并成功仿真出真实存在的频率振荡现象。在此基础上,通过深入分析调速系统人工频率死区、永态转差系数和控制参数对孤网频率稳定性的影响,提出了参数配置建议,并用PSD BPA软件进行了验证。结果表明,合理配置调速系统参数能显著提高水电机组对孤网频率的控制能力,增强孤网系统的稳定性。     

利用回热抽汽控制参与风电系统调频方法研究

随着风力发电在电力系统中发电比例的提升,风速的波动性所带来的风功率的随机波动性给电力系统调频带来了新的挑战,在不增加系统装机容量的前提下,如何提高现有火电机组的调频能力应对大规模风电并网具有较重要的意义。本文通过对再热式汽轮机的并网运行进行了仿真研究,证明了汽轮机在带负荷运行中,回热系统的抽汽量变化会影响汽轮机的功率,回热系统的抽汽效应对汽轮机频率调节有显著影响。并且,本文还重点讨论了低风速风电功率欠发时,火电机组处于高负荷运行工况下,回热系统抽汽效应对汽轮机频率调节的影响。因此,在高渗透率风电的电网系统中,通过调整回热抽汽量是一种能够提高汽轮机调峰调频出力的可行方法。     

变速风力发电机组调频控制策略研究

根据变速风力发电机组的运行特点,提出一种调频备用功率控制策略。在正常情况下,调整机组最优功率-转速曲线,使机组运行在次优功率捕获曲线上,减少一部分有功输出,留作调频备用功率;当系统频率变化时,通过调节桨距角和机组有功功率参考值,改变风电机组有功输出,参与系统频率调整。通过一个具体仿真算例分析了风电机组增加惯性响应控制、一次调频控制与备用功率控制等多种控制环节对系统频率的调节作用,并研究了当频率突变时有无AGC控制对风电机组调节特性的影响。     

电网遭受扰动后水电机组一次调频对电网频率的影响

当系统有功不平衡时,要求并网机组都能参加一次调频,长期以来水电机组都作为最可靠的一次频率调节机组,但是往往电网中某个地区正处在大检修期间或者该地区正处在枯水期等等,这些原因限制了该地区能够投入的一次调频容量,而水电机组的死区较火电偏大,且不同水电区域存在明显的水流惯性差异。针对这些问题建立了水火电机组互联的两区域互联系统,研究电网在受到负荷扰动后的频率品质。     

主动调频对大容量风电机组载荷灵敏度响应分析

为评估主动调频策略下机组载荷响应,获得较优的控制参数和机组载荷约束下的边界调频次数,文章采用单因素对比仿真研究的方法对电网支撑功率、支撑时间和恢复策略下的控制参数进行了仿真试验。试验研究了调频策略对风电机组各部件载荷的敏感度,试验结果表明:传动链扭矩Mx的敏感度最高;迭代获得了风电机组每日支撑电网的边界调频支撑次数为115～350次,为风电场电网调度提供了参考;基于部件敏感度和机组部件机械约束确定了主动调频控制策略较合理的参数范围,为风电场主动调频策略优化提供了仿真依据。     

基于改进SFR模型的含风电虚拟惯性/一次调频电力系统频率响应特性

文章利用等效虚拟惯性时间常数定量表征风电场惯性响应,采用传递函数模型描述风电场一次调频响应,结合再热式火电机组和水电机组的原动机-调速器模型,针对含多个风电场/火电机组/水电机组的电力系统提出了改进SFR解析计算等值模型,用于分析计算含风电虚拟惯性响应和一次调频的电网频率响应特性。仿真结果表明,改进SFR模型能更真实地反映含风电惯性/一次调频响应作用的电力系统频率特性,为客观评估高风电渗透率下的电力系统频率稳定运行状态提供了理论基础。     

直流调制策略对交直流混联系统的频率稳定性影响研究

在交直流混联电力系统中,交流侧系统发生故障将会引起互联系统区域间的频率振荡,从而导致常规机组的调频压力增大,机组阀门动作频繁。在不增加交流系统中常规机组调频压力的前提下,如何利用直流系统传输功率可进行快速调节和具有短时过载能力的特点进行直流输送功率的有效控制具有重要的意义。本文首先对直流输电系统的附加频率控制器进行建模,在此基础上对引入附加直流频率限制器后的两区域交直流电力系统进行仿真,重点分析交流系统发生故障时,附加直流频率控制器对系统频率稳定性的影响以及附加直流频率限制器控制参数对系统频率稳定性的影响。仿真结果表明,附加频率控制器可以有效减小系统频率波动,附加直流频率限制器的调频死区、比例增益K_(p1)和K_(p1)等参数能对电网频率产生影响。其中,调频死区的减小能有效的降低系统频率的波动,但死区值不能设置过小,以防直流频率限制器频繁动作。比例增益K_(p1)和K_(p2)越大,系统频率波动越小,调频效果越理想,但是由于限幅环节,比例增益有调频能力上限。     

水电机组一次调频探讨

水电机组一次调频动态调节品质与机组型式、调速器控制模式及引水流道、水轮机的水力特性密切相关。比较了水轮机调速器的频率模式、开度模式、有功模式3种控制逻辑原理,分别计算了某水电机组在开度模式、功率模式控制下的一次调频动态响应试验数据,通过与考核指标进行比较,发现调整幅度偏差、调频响应指数等一次调频动态响应指标不能完全满足电网调度的要求,进而分析了部分动态响应指标不合格的原因和一次调频目前存在的问题,并提出了优化建议,为在保证水电机组安全稳定运行的条件下更好地发挥其一次调频作用提供了参考。     

浅析1000MW机组供热一次调频控制应用

1000MW机组经过热网系统的改造后,需要更大的抽汽量被供热使用,低压缸负荷调节幅度及响应速度降低,导致机组响应一次调频能力减弱。结合电厂实际运行情况,对供热调门进行适当优化,作为一次调频能力的补充手段,为机组安全经济运行提供了保障。     

基于系统仿真的火电机组一次调频性能优化

火电机组的一次调频性能不仅对电网的安全稳定有重要意义,也关系到机组本身运行经济性。为实现机组一次调频性能的优化,通过系统辨识构建符合机组实际特性的汽轮机调节系统,并增加一个阀门流量非线性环节使模型结构更为真实。基于模型实现了对一次调频影响因素的量化分析,根据分析结果修正了阀门流量函数,增加主汽压力修正环节,基于鲁棒性考虑实现了对一次调频控制参数的重新整定,最终使机组一次调频功能设置更趋合理。实际机组的一次调频试验表明:不同负荷条件下,调整后机组负荷响应速度指标均能满足规程要求,故其一次调频性能是令人满意的。     

Dynamic model and impact on power quality of large hydro‐photovoltaic power complementary plant

In recent years, with the rapid growth of photovoltaic (PV) power development and utilization, part of the PV power could not be transmitted to the power grid owing to the impact of PV power fluctuation on power quality, leading to a serious PV power rejection in some areas in China. A high‐order model of a hydro‐PV power plant is developed in this paper not only to predict hydropower compensation for PV power fluctuation but also to consider the impact of complementary regulation on power quality. Compared with the existing complementary models, the presented model accurately reveals the effect of water hammer on power quality, low‐frequency power oscillation, and power antiregulation phenomenon during the complementary regulation. Although the complementary control of the hydro‐PV power plant helps to suppress power fluctuation, when the PV power and objective power are negative covariation, the hydropower needs more regulation, which will cause an increase in frequency fluctuation. Moreover, with the increase of the ratio of hydro‐PV power in the power grid, the frequency fluctuation amplitude increases accordingly. Especially, when PV power exceeds the regulation ability of the hydropower, the system frequency deviation will increase rapidly. These problems are worth the attention to the future development of PV power.     

Investigation of oscillatory problems of hydraulic generating unitsequipped with Francis turbines

In the paper a method is presented for the study of oscillatory problems of hydraulic generating units equipped with Francis turbines. The accurate equations of the turbine are implemented for the simulation, taking into account water hammer effect. Partial derivatives of turbine flow rate and torque with respect to head and gate opening are deduced from real measurements for the whole leading range. Speed governor dynamics are fully simulated, and the influence of torsional vibrations is studied. The vibration response of the unit to draft tube surges is investigated and the risk of excessive oscillations is evaluated. The approach was developed for diagnosis of excessive vibrations of Kastraki hydro power station in Greece     

BP神经网络在水轮机调节过程中的应用

由于水轮机调节系统的大惯性、"水锤"效应等特点及其结构复杂等问题,采用传统的常规PID控制已很难满足控制要求,控制品质也难以改善,控制过程中易发生超调量大、震荡频次多、收敛时间过长等问题。对此,在常规PID控制基础上设计了基于BP神经网络自适应PID控制,并在Matlab软件中完成相关程序的编写及仿真试验。仿真结果表明,基于BP神经网络自适应PID控制是一种有效的水轮机调速器参数整定方法,相较于常规PID控制能获得更好的动态性能。     

水轮机调节系统的适应式变参数控制

研究，总结了适应式变参数控制在水轮机调节系统中的应用情况，指出现代电力系统对调速器运行的新要求；现代水轮机调速器的主要功能是起机组频率调节器和机组功率控制器的作用。     

叠压供水方式下支管管径对干管水锤影响

长距离输水工程的水锤防护目前多集中于干管研究,而对预留口分支管的研究涉及较少,尤其在不同类型支管对输水系统水锤影响方面还有待深入研究。为了研究叠压供水方式下不同管径支管对干管水锤影响,以某水利枢纽工程为例,结合水锤仿真模拟试验对不同工况条件下水锤进行分析。结果表明,当支管与干管管径比(简称支干管径比)大于1/6时支管对干管水锤影响较大,干管的水锤防护措施不再适用;而当支干管径比小于1/6时支管对干管水锤影响减弱,已有的措施能基本满足水锤防护要求。研究结果对于类似工程水锤防护及安全稳定运行具有重要的借鉴意义。     

水轮机调节系统被控对象模型辨识

建立了水轮机调节系统被控对象的非线性模型,用递推最小二乘法(RLS)对被控对象进行参数辨识。仿真实验证明,该模型与被控对象模型相吻合、过程简单、效果良好、易于实现编程。基于此对控制参数进行了优化,改善了系统的动态品质。具有实用价值。     

调速器液压系统的故障诊断及可靠控制策略

在分析水轮机微机调速器液压随动系统失效机理的基础上,总结了系统基于专家知识的故障诊断方法,并提出了一种模型参考故障诊断方法．同时应用智能技术将故障诊断与相应的可靠控制策略结合起来,在故障诊断定位的基础上,通过控制策略的变化,消除或弱化故障的影响,达到保证机组安全的目的．仿真研究和工业应用实践充分证明了这些理论和方法的实用性、有效性和可靠性     

基于改进飞蛾优化算法的水火互联电网负荷频率控制

负荷频率控制是互联电网进行有功调频的重要方法,设计了一种基于改进飞蛾优化算法的水火互联电网负荷频率控制方案,该方案将Lévy飞行策略引入到飞蛾优化算法中,同时在飞蛾的更新公式中引入动态惯性权值和历史最优火焰平均值以改善算法性能,并对互联电网分数阶PID控制器参数进行优化整定,以提高收敛速度及寻优精度。建立三区域水火互联电网LFC系统仿真模型,采用改进飞蛾优化算法搜索获得最优的分数阶PID控制器参数,并在阶跃负荷扰动下进行仿真分析。结果表明,所提方案具有很好的鲁棒性和控制效果。     

Discrepancy study of modal parameters of a scale jacket-type supporting structure of 3.0-MW offshore wind turbine in water and in air

The discrepancy of modal parameters of a scale offshore wind turbine is studied by using the proposed assessment method. One theoretical development is that weak genuine modes can be separated from strong noisy modes; and the other is the size of the reconstructed Hankel matrix will not be changed to ensure the comparability of modal parameters from different scenarios. A numerical signal is synthesized to demonstrate the proposed method. Numerical results indicate that the approach can isolate the two genuine modal parameters respectively, by applying estimated pass band with a 2 by 2 Hankel matrix of the Eigensystem Realization Algorithm, which means it can be used as a criterion to assess modal parameters from different scenarios. An experiment with model scale 15 from a 3.0-MW offshore wind turbine is tested. Experimental results indicate that natural frequencies are considerably reduced and damping ratios are increased, with the rate of frequency change varies from 15.33% to 17.97%. The modal parameters obtained in water with waves are close to those obtained in still water even if the structure is excited by a hammer or waves. The modal parameters estimated from the reconstructed responses of different accelerometers are in excellent agreement.     

A review on hydropower plant models and control

The recent increased number of black outs in the power system has been largely due to growing competition and deregulation among the power industry. Power systems are complex nonlinear systems and often exhibit low frequency electro-mechanical oscillations due to insufficient damping caused by severe operating conditions. This needs an advanced modeling and control techniques for effective control of power plants. In case of hydroelectric plant the hydro turbine is a non-linear, non-stationary multivariable system whose characteristics vary significantly with the unpredictable load on it and this presents a difficulty in designing an efficient and reliable controller. A conservatively designed control fails to perform as expected. Keeping this in mind, hydro plant control is an application area with an interesting set of problems for control engineering people. Mainly some of these problems focus towards regulation of turbine with large load variation in the power system. These problems have not been adequately solved and continue to pose challenges to the control community. In this review paper, the authors have tried to broadly categorize the research work done so far on the basis of hydro plant model development and its controller design under different sections. A substantial number of relevant research papers can be found on the plant modeling, design aspects of control methodologies and their performance study.