基于惯量响应支撑功率的电力系统一次调频功率估算

随着新能源渗透率不断提高以及高压直流电量HVDC的大规模应用,电力系统惯量响应与一次调频响应的能力不断减弱,威胁电力系统的频率稳定.目前的研究工作主要针对于惯量响应的估算、新能源发电参与惯量响应和一次调频的控制策略设计,并未展开电力系统一次调频功率估算的研究.论文提出了基于惯量响应支撑功率的电力系统一次调频功率估算.阐...     

考虑频率稳定的新能源高渗透率电力系统最小惯量与一次调频容量评估方法

随着新能源渗透率逐步提高,系统在大功率扰动下的频率稳定问题日益严峻,限制了系统新能源的消纳能力。为了合理规划新能源的接入容量,亟需对系统的最小惯量和一次调频容量进行评估。为此,针对大功率扰动下惯量响应与一次调频响应间的相互作用进行了研究。首先,以传统单机模型为基础,推导出了计及调频死区的频率响应过程表达式。然后,以扰动后的最低频率限值为动态频率稳定约束条件,建立了系统最小惯量与一次调频容量评估模型,估算了系统最小功频静态特性系数和最小惯性时间常数,计算并绘制了惯量响应和一次调频响应的功率曲线。最后,在DIgSILENT PowerFactory仿真软件中搭建了IEEE 10机39节点模型,验证了所提最小惯量与一次调频容量评估方法的准确性和研究价值。     

基于多新息辨识的电力系统节点惯量估计方法

随着高比例新能源并网、大容量直流密集接入和常规电源持续关停,电力系统原本相对均衡的惯量资源分布格局被打破,转动惯量在空间分布上发生了新的变化。为使系统运行人员及时感知惯量空间分布情况、精准定位惯量薄弱节点,提出一种基于多新息辨识的电力系统节点惯量估计方法。首先在分析系统惯量资源对节点惯量支撑作用的基础上,基于输出误差滑动平均模型构建惯量空间分布估计模型。进而采用多新息辨识方法求解模型中的待辨识参数,得出系统内所有节点的等效惯量,评判整个系统的惯量空间分布情况。最后在IEEE 39节点系统上进行仿真分析,验证了所提方法的有效性,以及对不同规模、不同位置故障的适应性。     

考虑频率响应分散性及系统分区的含风电系统等效惯量估计

随着电力系统中新能源机组渗透率的快速提高,系统惯量水平下降将威胁系统频率稳定性,惯量的空间分布特征也将更加凸显,频率响应的分散性将不能被忽略。针对以上问题,提出一种考虑频率响应分散性及系统分区的含风电电力系统等效惯量估计方法。首先,为降低频率响应分散性对估计精度的影响,基于谱聚类算法对电力系统进行分区,并基于皮尔逊相关系数定义频率相似度指标确定区域频率的最优测量节点。其次,由于测量所得的频率变化率(rate of change of frequency, RoCoF)曲线中包含大量的振荡分量,提出一种基于摇摆方程的数值积分方法估计区域及系统全局惯量。最后,在DIgSILENT/PowerFactory中建立改进IEEE10机39节点系统以验证所提方法的有效性。仿真结果表明,该方法适用于不同场景下含风电系统的等效惯量估计。     

考虑频率稳定约束的新能源电力系统临界惯量计算方法

针对新能源并网的弱惯量、零惯量特征对电力系统频率稳定的影响,提出一种计及频率稳定约束的新能源电力系统临界惯量的估算方法。首先,建立系统频率动态响应数学模型,求解惯量中心频率时域表达式。然后,基于频率响应模型求解并分析系统惯量与相关频率稳定性指标的关系,进而计及频率变化率和频率最大偏差约束估算系统临界惯量理论值和计算值。最后,基于临界惯量提出一项电力系统频率稳定性指标,来评估功率扰动后的电力系统频率稳定性,并结合电力系统实际运行惯量得出新能源虚拟惯量参考值。在DIgSILENT PowerFactory中以改进的IEEE 10机39节点新英格兰系统和某区域电网仿真算例对所提计算方法进行仿真验证。     

基于电力系统分区惯量估计的储能容量配置策略

针对大规模新能源接入导致电力系统惯量水平下降,提出了一种基于分区惯量估计的储能容量配置策略。基于传统电力系统的惯量机理分析,建立了含新能源电力系统的等效惯量模型和风光储能虚拟惯量模型。运用谱聚类对电力系统进行分区解决惯量空间分布不均影响估计精度问题,并基于皮尔逊相关系数确定测量节点。运用差值法对分区后系统的各个区域进行惯量估计,进而利用分区惯量估计结果设计电力系统储能容量配置策略。在DIgSLIENT/PowerFactory中搭建含风机的IEEE 10机39节点模型进行仿真验证。仿真结果表明所提方法可以减小惯量估计误差,基于惯量估计结果可以对储能容量进行合理配置,保证储能系统实现快速调频和提供虚拟惯量支撑。     

A theory of maximum capacity of distributed generators connected to a distribution system using electric power density model

Recently, the number of distributed generators (DGs) connected to distribution systems has been increasing. System operators should know the maximum capacity of DGs that can be connected without problems to one feeder of the system in order to control the system appropriately. Many studies of the maximum capacity of the DG have been presented, but they have produced limited results calculated by a typical or average‐value model. However, many DGs will access one feeder if deregulation of the electric power industry is accelerated in the near future. In order to deal with this situation, the authors have derived a general formula to calculate the range of the maximum DG capacity per feeder. Copyright © 2004 Wiley Periodicals, Inc. In order to deal with sets of DGs that are dispersed completely on the distribution line, the authors have derived a differential equation for the complex power and one for the voltage drop, which are expressed as functions of distance from the substation. The general formula to calculate the range of the maximum DG capacity connected to the system is determined by solving these equations under the constraints of the line voltage, the line current, and the power factor of the DGs. By a numerical analysis, the authors have calculated the maximum capacity of DGs depending on many parameters, such as the length of the feeder, the DG power factor, and the like. In a short‐length system, the maximum DG capacity is governed by the current constraint, but in a long length system, it is governed by the upper voltage constraint. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(3): 18–28, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20330     

Estimation of reactive power export and import capability fornon-utility generators

Non-utility generators (NUG's) are typically required by their electric power sales agreement to have the capability to supply power to the purchasing utility near unity power factor. With the advent of large combustion turbine generators, many NUG's are simple or combined cycle facilities with generating capacities in excess of 100 MW. Utilities are recognizing that these large NUG facilities can be significant contributors to the reactive power [megavars (MVArs)] flow needed to support system requirements and transmission level grid voltages. NUG's are now being dispatched for MVAr export and import activities to meet utility requirements. The ability of a NUG to export or import MVArs is highly dependent on the actual transmission intertie voltage level. Unless plant-specific studies are performed, this capacity can be difficult to ascertain for the NUG operating and engineering personnel. This paper presents a method, based on system load-flow studies, for estimating the capacity of a NUG to export or import MVArs at a given transmission intertie voltage level. It also explores other key variables which determine the ability of a NUG to export or import VArs. This methodology can be used to aid operating personnel at existing facilities or as a guide during the design of a new facility     

基于有效惯量分布的电力系统惯量不足概率评估

高比例可再生能源和高比例电力电子设备(即“双高”)接入电网将打破传统的电力系统惯量支撑局面,削弱系统惯量水平的同时带来运行安全隐患。针对机组强迫停运对电力系统惯量水平的影响,提出一种基于有效惯量分布的电力系统惯量不足概率评估方法。通过构建考虑惯量支撑机组强迫停运率的有效惯量模型,在求取系统惯量评估参考值和源运行状态的基础上,利用半不变量法和Gram-Charlier级数展开获取有效惯量概率分布曲线,进而定义系统惯量不足概率指标,最终完成评估周期内系统惯量安全的动态评估。基于改进IEEE 39节点测试系统进行仿真,结果验证了所提方法的有效性。     

The measurement of power system frequency using a microprocessor

This paper proposes a simple algorithm for the real time measurement of power system frequency. Using simple microprocessor hardware results of acceptable accuracy can be obtained in the presence of substantial DC and harmonic components.     

A developed control strategy for mitigating wind power generation transients using superconducting magnetic energy storage with reactive power support

The fast variations of wind speed during extreme wind gusts result in fluctuations in both generated power and the voltage of power systems connected to wind energy conversion system (WECS). This paper presents a control strategy which has been tested out using two scenarios of wind gusts. The strategy is based on active and reactive powers controls of superconducting magnetic energy storage (SMES). The WECS includes squirrel cage induction generator (SCIG) with shunt connected capacitor bank to improve the power factor. The SMES system consists of step down transformer, power conditioning unit, DC–DC chopper, and large inductance superconducting coil. The WECS and SMES are connected at the point of common coupling (PCC). Fuzzy logic controller (FLC) is used with the DC–DC chopper to control the power transfer between the grid and SMES coil. The FLC is designed so that the SMES can absorb/deliver active power from/to the power system. Moreover, reactive power is controlled to regulate the voltage profile of PCC. Two inputs are applied to the FLC; the wind speed and SMES current to control the amount active and reactive power generated by SMES. The proposed strategy is simulated in MATLAB/Simulink®. The proposed control strategy of SMES is robust, as it successfully controlled the PCC voltage, active and reactive powers during normal wind speeds and for different scenarios of wind gusts. The PCC voltage was regulated at 1.0 pu for the two studied scenarios of wind gusts. The fluctuation ranges of real power delivered to the grid were decreased by 53.1% for Scenario #1 and 56.53% for Scenario #2. The average reactive power supplied by the grid to the wind farm were decreased by 27.45% for Scenario #1 and 31.13% for Scenario #2.     

Calculation of distribution system voltage and power flow state using measured values

This paper describes a techique of calculating voltage and power flow state of a distribution system using the information measured with two or more switches with sensors installed in a distribution system. In the proposed technique, a set of the power distribution section where two or more switches with a sensor are connected is defined as the large section, and the active power and reactive power consumption in the large section are calculated based on measurement information, voltage (RMS), current (RMS), and power factor. Using the simple distribution system model consisting of the large sections, the power consumption of the large section is calculated by the power flow calculation to separate power consumption and power distribution loss. It is distributed to the small sections that constitute the large section, and detailed power flow calculation is performed. Verification of the proposed technique and basic estimation of the calculation error were performed using the simple power distribution system model. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(4): 33–42, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20416     

Wavelet network-based classification of transients using dominant frequency signature

This paper presents a novel approach of classification of transients resulting from changes in circuit topology in a radial distribution system. The analysed data are obtained from experiments as well as simulated model based on Simulink in Matlab environment. Continuous wavelet transform-based dominant frequency signature (DFS) has been used as the key features for identification of circuit topological changes. Conclusions have been drawn after classification of the transients based on DFS using wavelet network.     

发电机中间过热时间常数对电力系统频率动态过程仿真影响

针对电网频率质量造成的电网崩溃事故,讨论了单机带综合负荷系统模型引入蒸汽容积效应环节后,过热环节中发电机中间过热时间常数对系统频率动态仿真的影响。制定了轨迹评价指标,并通过仿真的方法获得发电机中间过热时间常数变化与轨迹评价指标变化的关系。实例验证:引入蒸汽容积效应环节后,发电机中间过热时间常数对于频率仿真曲线回升斜率的校核效果优于调差系数的效果,有利于电力技术人员在电网事故后,对电网频率动态过程进行再现分析。     

惯性时间常数对互联系统暂态稳定性影响的仿真研究

通过对单机无穷大系统和等值两机系统进行数学推导,得出系统惯量的变化与互联系统暂态稳定水平的关系;应用EUROSTAG进行时域仿真,在IEEE-39系统中分别验证了受端与送端系统转动惯量对弱互联电网暂态稳定性的影响.系统惯量越大,系统相对角变化速度越慢,在大区弱互联系统中,送端系统与受端系统间相对角变化速度不一致.因此,当送端系统惯量增加时,提高了系统暂态稳定水平;受端系统惯量增加时,降低了系统暂态稳定水平.     

Contributions of generators for power flow and loads in a power system

Because of the introduction of deregulation and competition in the electricity supply industry, large numbers of IPPs (Independent Power Producers) will get into the market. It has become much more important to be able to determine which generators are supplying a particular load, which generator is responsible for transmission line congestion, and what is each generator's contribution to the system losses. In this paper, we propose a way to calculate these contributions automatically. The applicability of the proposed technique is demonstrated using the EAST 10 47‐bus power system. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(3): 28–35, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10181     

一种采用高频PWM整流电路的大功率不间断电源

介绍了采用PWM整流电路的不间断电源的系统结构,分析了PWM整流电路工作原理和控制方法,在此基础上,研制了一台30kVA 不间断电源样机.实验结果表明,采用PWM整流电路的不间断电源具有注入电网的谐波电流小、输入功率因数接近1等优点,是一种很有发展前途的不间断电源.     

一种采用高频PWM整流电路的大功率不间断电源

介绍了采用PWM整流电路的不间断电源的系统结构 ,分析了PWM整流电路工作原理和控制方法 ,在此基础上 ,研制了一台 30kVA不间断电源样机。实验结果表明 ,采用PWM整流电路的不间断电源具有注入电网的谐波电流小、输入功率因数接近 1等优点 ,是一种很有发展前途的不间断电源。     

基于PLC的掘进机恒功率变频调速系统仿真分析

悬臂式掘进机在工作过程中负载随机变化且变化幅度较大,以PLC为控制核心,构建自适应模糊控制的掘进机恒功率变频调速系统,根据截割电机电流的偏差变化及变化率,采用模糊推理和自适应调节进行变频调速控制,实现掘进机截割电机的恒功率控制,采用MATLAB/Simulink软件进行仿真分析,结果表明,基于PLC自适应模糊控制的掘进机变频调速系统能够更好的进行掘进机的恒功率控制,提高了系统的稳定性.     

大容量双馈风电机组虚拟惯量调频技术

针对风电机组不主动参与电网频率调节的问题,量化评估了大容量双馈风电机组利用风轮旋转动能进行调频的能力,提出了基于附加转矩的风电机组虚拟惯量调频控制方法,并研究了其实现原理与控制策略,建立了大容量双馈风电机组Bladed+MATLAB联合仿真模型,实现了虚拟惯量调频全过程动态仿真。首次在MW级风电机组上进行了虚拟惯量调频现场试验,揭示了大容量风电机组虚拟惯量调频的动态特性与技术特点。试验结果表明了理论与仿真分析的准确性及控制策略的有效性。