Coordinated design of under-excitation limiters and power systemstabilizers

The inherent dynamical relationship between the under-excitation limiter (UEL) and the power system stabilizer (PSS) control loops in synchronous generators is studied using the frequency response technique. While the stabilizers are effective in introducing electromechanical damping torque components into the generators, it is shown that the limiters should be designed to effect a much slower response characteristics as their main function is to prevent excessive stator end-core heating. The analysis also shows that a reduction in the values of the slope of the boundary curves, which prescribe the operating region of the limiters, is accompanied by a decrease in the damping level of the closed-loop excitation control systems. A method which decouples the design procedure of the UEL from that of the PSS is then proposed     

Impact of energy storage system on load frequency control for diverse sources of interconnected power system in deregulated power environment

This paper focuses Load Frequency Control (LFC) mechanism for multi-generating two areas interconnected power systems with energy storage system in a deregulated power environment. The two areas, demarcated as Area-I and Area-II, consist of thermal, hydro and gas power units. This paper also incorporates the economic load dispatch mechanism into the LFC for economical division of load during load deviation. Small signal stability analysis through participating factor has also been done to determine the oscillation state of the system, i.e., frequency deviation in both areas. Therefore, proper controller is required to reduce the oscillation of the system. The optimum value of the integral gain of the integral controller has to be selected to achieve the goal. Hence, Opposition-based Harmonic Search (OHS) technique is used for the optimization purpose. During major disturbance in the areas, primary and secondary controllers are not sufficient to reduce the frequency and tie-line power oscillation due to slow response of the governor mechanism. Therefore, energy storage system, i.e., Redox Flow Battery (RFB), is used for improvement of the dynamic response of the system which has very small time constant and quick response. The proposed control mechanism has been analyzed in a deregulated power environment with the help of different simulation case studies to find out improved dynamic performance over integral control strategies.     

Impact of the exciter voltage limit to small signal stability region of a three-bus power system

We investigate the influence of non-differential components to the power system small signal stability region in this paper. A method named unified expression function (UEF) is introduced to describe the piecewise, continuous and non-differential function in the small signal stability study. It converts non-differential points of the original function to poles of the UEF’s derivative function. Then the derivative at those poles can be approximated by UEF’s left-hand or right-hand derivative limits according to the requirement. Based on this method, impact of the exciter voltage limit to power system small signal stability region is then deeply discussed using a simple three-bus power system. We find that the exciter voltage limit can change elements of the system Jacobian matrix so as to cause jump of the system critical eigenvalue. As a result, two new Hopf bifurcation boundaries and a new instability hole emerge in the small signal stability region. When the exciter voltage limit varies, the new instability hole and the new Hopf bifurcation boundaries will change significantly. It makes the topological characteristics of the small signal stability region much more complicated. Since there are many non-differential components in power systems, they should be correctly considered in power system stability studies.     

电力系统的柔性评价与风电穿透功率极限计算

提出了电力系统柔性概念,通过不确定参数的柔性化表示,建立了面向不确定信息的电力系统柔性评价模型。将柔性概念引入到风电出力随机性的建模研究中,通过风电功率的柔性化表示,提出了基于电力系统柔性评价的风电穿透功率极限计算方法。针对IEEE 30节点系统的研究结果表明,风电功率的柔性化表示充分反映了风电出力随机性强的特点,该方法实现了对风电出力随机性的客观建模,提高了风电并网容量规划方案的灵活性和适应性。     

无功协调控制策略对风电场并网系统小扰动稳定性的影响

提出基于双馈式风电机组(DFIG)变频器的无功协调控制策略,以提供足够的无功功率来维持系统稳定.在DigSILENT/PowerFactory平台上,搭建风电场的详细模型,通过协调风电机组网侧和转子侧的无功功率参考值,改善风电机组的输出有功和无功功率;采用特征值分析方法,分析大型风电场在采用无功协调控制策略后,对电力系统低频振荡和小扰动稳定性的影响.仿真结果表明,该策略通过自动调节风电机组发出的无功功率,改善了DFIG的输出特性,提高了风电场的输出有功功率(通过稳定机端电压实现),对故障过程中风电机组的连锁脱网有一定抑制作用.     

基于PCS功率越限判据的独立型微电网紧急控制策略

紧急控制作为微电网系统的最后一道防线,在系统受到大扰动以后,能够维持频率稳定,对微电网的稳定运行具有重要意义。文中分析了频率紧急控制策略以及轮次减载策略在微电网中存在的定值整定难、无法精准减载的问题,提出了一种基于储能变流器(PCS)输出功率越限判据的独立型微电网紧急控制策略:在外部扰动导致PCS输出功率越限时,通过计及电池荷电状态(SOC)的均衡控制策略计算PCS的越限功率,采用负荷精准减载方案精确切除负荷,并针对工程实施采用面向通用对象的变电站事件(GOOSE)通信技术、提出小步长趋势变化采样算法和防一点大数算法,提高了控制系统的响应速度,提升了大容量独立微电网运行的稳定性。通过新疆某独立型微电网项目工程案例验证了本方案的可行性和有效性。     

Heirarchical power system control

The present status and future problems of hierarchical power system control are reviewed. Special emphasis is placed on the hierarchical structure of power system control. Power system control has been developed in close association with the progress of the power system itself. The hierarchical structure of the control system is closely connected, therefore, with that of the power system, and this structural relationship is reviewed. Motivations of using a hierarchical structure of power system control are reviewed in terms of power system control and planning. Required performances of computers installed at respective levels of hierarchical control system are discussed. Benefits resulting from the introduction of such control systems are summarized, and future problems associated with the further development of hierarchical power system control are considered.     

超导电力设备失超对电力系统的影响

超导体失超会影响超导电力设备的运行，是超导电力技术实用化的一重点问题，总结了超导体失超研究方面的成果，主要包括失超原理，失超传播特性及失超检测几个方面，并以超导电力设备和常仙电力设备并存的超导电力系统为基础，从正反两方面详细分析了超导电力设备失超对系统的安全、稳定、经济运行的影响，介绍了超导储能，超导变压器，超导发电机的设备级失超保护方法，并就未来超导电力系统失超研究提出了参考性建议，只要采取适当的措施，超导电力设备失超不会给电力系统带来很大损失。     

Impact of automatic switches on power distribution system reliability

In this paper quantitative impact of automatic switches on the reliability of power distribution systems is studied. Based on the characteristics of the studied system's topology, the reliability model is developed for the implementation of Monte Carlo simulation. Reliability indices on each load have been computed to obtain an overall reliability assessment of the system, and the sensitivity of the reliability indices to the location of automatic switches is also studied. Simulation results are used to illustrate the validity of the approach and are compared with the historical reliability records.     

关于电力系统稳定控制方式的探讨

电力系统安全性与经济性之间的矛盾随着电力系统的发展而不断加剧。系统互联从一定程度上缓和了这一矛盾,然而大电网中由于故障引起连锁反应,而导致大面积停电的可能性也大大增加了。实践表明采用紧急控制则是经济、灵活和有效的。文中介绍了稳定控制装置的控制原理、结构组成和可采取的控制模式,提出了一种“集中管理,分区控制”的现代稳定控制模式。     

双馈风电场穿透功率增加对电力系统稳定影响综述

针对装有双馈感应发电机(DFIG)风电场穿透功率增加带来的稳定性问题,从小干扰稳定性、电压稳定性、频率稳定性3个方面对国内外研究现状进行了分析和总结.综述了基于电力系统稳定器、柔性交流输电技术以及高压直流输电技术的双馈风电场并网系统的改善措施.最后对该领域的未来发展方向进行了展望,指出忽略风速波动和塔影效应,缺乏定量的...     

OLTC对含DG电力系统静态电压稳定极限的影响

在静态范围内利用三元分析法阐述了OLTC动作引起的Pmax－、Vcr－曲线的变化,研究了在接入分散,电源的电力系统中,OLTC变比调整对其静态电压稳定极限的影响,并采用两机系统进行了仿真分析得出,OLTC变比变化改变了系统的最大传输功率稳定极限Pmax和临界电压稳定极限Vcr,影响了电力系统稳定运行范围;由于分散电源在配电网的接入,OLTC变比变化对Pmax和Vcr的影响程度不同。     

Stabilizing control of power system using fuzzy control

This paper presents an application of fuzzy control to enhance power system stability. The proposed control consists of the controller for large disturbance (FU 1), the fuzzy controller for small disturbance (FU 2), and the fuzzy judgment mechanism (FU 3). FU 1 is determined based on the fuzzy controller [FU 1(F)] is determined according to the control rules and its input signals, i.e., speed deviation and acceleration at every sampling time of the machine. FU 2 consists of two controllers, namely, FU 2-ω and FU 2-P; FU 2-ω has the same mechanism as FU 1, while the output signal of FU 2-P is determined according to the rules together with the change of error of electrical power and terminal voltage. To obtain the optimal desired control signal during both the large and the small disturbances, the operations of FU 1 and FU 2 are judged by FU 3, where the magnitude of speed deviation is chosen as its input signal. The determined control signal is fed to AVR of the machine. The implementation of the proposed control is simple due to the small amount of calculations and required data. The effectiveness of the proposed control is demonstrated by the one-machine infinite-bus system model and very good system performance is obtained throughout all the simulations.     

直驱永磁风电机组虚拟惯量控制对系统小干扰 稳定性影响分析

虚拟惯量控制方式下,直驱永磁风力发电机组(DDPMSG)能够为电力系统提供较好的频率支撑,但虚拟惯量控制使DDPMSG与系统之间产生了新的耦合关系,给系统的小干扰稳定带来新的影响。建立了包含DDPMSG的风电并网系统状态空间平均模型,并通过线性化得到其小信号模型。基于该小信号模型,利用特征分析法分析了虚拟惯量控制的比例系数和微分系数对风电并网系统的小干扰稳定性的影响,同时对比分析了虚拟惯量控制及最大功率跟踪控制对系统小干扰稳定的影响。结果表明虚拟惯量控制对系统阻尼特性的影响与DDPMSG接入系统的位置及容量有关,且主要影响其所接入区域的局部振荡模式和系统的区域振荡模式。     

直驱永磁风电机组虚拟惯量控制对系统小干扰稳定性影响分析

虚拟惯量控制方式下,直驱永磁风力发电机组(DDPMSG)能够为电力系统提供较好的频率支撑,但虚拟惯量控制使DDPMSG与系统之间产生了新的耦合关系,给系统的小干扰稳定带来新的影响。建立了包含DDPMSG的风电并网系统状态空间平均模型,并通过线性化得到其小信号模型。基于该小信号模型,利用特征分析法分析了虚拟惯量控制的比例系数和微分系数对风电并网系统的小干扰稳定性的影响,同时对比分析了虚拟惯量控制及最大功率跟踪控制对系统小干扰稳定的影响。结果表明虚拟惯量控制对系统阻尼特性的影响与DDPMSG接入系统的位置及容量有关,且主要影响其所接入区域的局部振荡模式和系统的区域振荡模式。     

电力电子变压器在输电系统中的控制策略研究

电力电子变压器(PET-Power Electronic Transformer)是一种新型的电能转换设备,它通过电力电子变换技术实现电力系统中的电压变换和能量传递.研究了PET在电力系统中的控制问题,提出了在单机无穷大系统中与发电机相连的PET的控制策略,并在MATLAB环境中进行了时域仿真研究.仿真结果表明,在系统中出现扰动的条件下,PET能有效的提高系统阻尼,改善系统电压特性,提高了电力系统的稳定性.     

浅谈电力系统中电压无功功率的控制

电力系统的负荷需要消耗大量的无功功率,而无功功率平衡要满足众多的结点电压,就需要分级分层就地平衡。地区电网的电压无功控制,主要是控制其管辖范围内的各级变电站,使电网的电压合格,并实现无功的就地平衡,降低网损。为此,通过分析变电站电压无功控制的主要设备：有载调压变压器、并联电容器以及并联电抗器,说明变电站电压无功控制的原则、要求、实现方式。     

电力电子变压器在输电系统中的控制策略研究

电力电子变压器(PET—PowerElectronicTransformer)是一种新型的电能转换设备,它通过电力电子变换技术实现电力系统中的电压变换和能量传递。研究了PET在电力系统中的控制问题,提出了在单机无穷大系统中与发电机相连的PET的控制策略,并在MATLAB环境中进行了时域仿真研究。仿真结果表明,在系统中出现扰动的条件下,PET能有效的提高系统阻尼,改善系统电压特性,提高了电力系统的稳定性。     

厂用电监控系统在火电厂的应用

介绍了电厂厂用电监控系统的构成模式,利用智能终端设备和现场总线技术实现对设备的控制、监视、保护和通信。简述了智能终端设备的主要功能。分析了电气监控系统的发展前景,归纳了其控制特点,并总结了现场总线技术的优势。在此基础上,设计了未来发电厂监控系统的整体结构。