电力系统阻尼特性规律探索

为了探索电力系统阻尼特性规律,给出了电力系统小干扰稳定模型的一般形式,推导了考虑发电机励磁控制作用、定子侧电阻及线路电阻等情况下单机-无穷大系统小干扰分析线性化数学模型.利用特征分析法,分析了定子侧电阻对振荡模式阻尼的影响,振荡模式总阻尼的守恒现象,阻尼守恒成立的基本条件,阻尼在不同振荡模式之间的传递规律.结果表明:随着励磁放大倍数的增加,系统机电模式阻尼减少,系统阻尼由机电模式流向非机电模式;系统引入电力系统稳定器(PSS)后,系统机电模式总阻尼随着PSS放大倍数的增加而增加,系统阻尼从非机电模式流向机电模式.     

Stable region for autoparametric resonance in longitudinal power systems

In longitudinal power systems, there is the possibility that a low‐frequency oscillation mode may become unstable because of autoparametric resonance. The resonance occurs through interaction between two oscillation modes. In this paper, we calculate the stable region for the resonance by considering the interaction of the modes. First, we calculate steady‐state solutions by the harmonic balance method. The steady‐state solutions are stable or unstable. If we decrease the amplitude of one mode in an unstable solution, the modes decay. Conversely, if we increase the amplitude, the modes diverge. Namely, the unstable solution is located on the boundary of the stable solution. The amplitudes of the modes are rarely the same as those of the steady‐state solution. However, the amplitudes approach a steady state after some transients. If the steady state is in the stable region, the system is stable. If it is in the unstable region, it diverges. Lastly, we estimate the amount of damping torques necessary to stabilize the system with the newly calculated stable region. We have obtained results similar to those derived from the Mathieu diagram, for example, a certain amount of damping torques can stabilize the system irrespective of its size. AVRs can substantially reduce the amount of damping torques and other quantities. © 2000 Scripta Technica, Electr Eng Jpn, 132(2): 29–38, 2000     

WAMS-based detection and early-warning of low-frequency oscillations in large-scale power systems

The phasor measurement units (PMU) and wide-area measurement systems (WAMS) have been widely established in modern power systems to improve the monitoring of the system behavior as well as the system control. In this paper, an integrated scheme for the monitoring and detection of low-frequency oscillations has been developed, based on our extensive experience in using Prony algorithm for oscillation analysis in practical WAMS projects. By analyzing the real-time synchro-phasors, the proposed scheme is competent to identify the characteristics of the low-frequency oscillations in real-time and alert the operators once the oscillation is under-damped or divergent. To ensure accurate monitoring of system dynamics and reliable detection of dangerous oscillations with noise-polluted WAMS measurements, several key signal-processing techniques are implemented, including delicate designing of prefilters, Prony analysis result correction, and comprehensive indices for stability evaluation. In the end, the developed scheme is tested with simulated signals and measurements from practical power systems. Its applications to large-scale power grids for detection and early-warning of low-frequency oscillations are also presented. The results have convincingly demonstrated the validity and practicability of the developed scheme.     

电力系统应用ZigBee技术初步研究

通过对ZigBee技术的分析与电力系统的情况相结合,得出利用ZigBee技术组成无线传感器网络对设备的各种信息进行监测是一个比较好的解决方案,将成为电厂监控发展的趋势。ZigBee技术射频信号会侵入电厂设备产生高频谐波,谐波超标会影响电厂的安全和经济运行。它正是针对这个问题进行解答,给出了测试方法和测试结果,根据测试结果与ZigBee技术设备的特性相结合进行分析,可以从一个侧面验证ZigBee技术应用于电厂的设备监测是可行的,是有安全保证的。并进一步给出了ZigBee技术应用在电厂设备监测系统中的基础和符合的技术条件、以及ZigBee技术适用对象。最后,给出了未来电力系统应用ZigBee技术的监控系统模型。     

Design of non-negatively interactive FACTS-based stabilizers in multi-machine power systems

In this paper, a method is proposed for the design of a non-negatively interactive FACTS-based stabilizer in a multi-machine power system. It is demonstrated in the paper that the FACTS-based stabilizer can be designed to impose positive interactions upon other stabilizers in the power system through the correct selection of non-negatively interactive installing locations and feedback signals of the FACTS-based stabilizer and the proper setting of the phase angle of the FACTS-based stabilizer. An example power system is presented in the paper, where a TCSC-based stabilizer is designed, which is not only able to damp the target inter-area oscillation mode effectively but also imposes a positive interaction with a PSS in the power system to damp a local oscillation mode.     

三峡左岸电站电力系统稳定器现场试验

介绍了三峡左岸电站电力系统稳定器(PSS)的选型过程,主要介绍了PSS2A模型的构成和工作原理。对PSS2A模型进行了现场试验,分别在投入PSS和退出PSS的条件下,采用电压阶跃响应、强迫振荡和无功反调等试验以验证其阻尼能力。试验结果表明,PSS2A模型能有效地抑制低频振荡,且不会产生无功反调现象,满足国家电力调度中心对三峡左岸电站机组并网发电的要求。     

大坝发电厂电力系统稳定器(PSS)试验

分析了大坝发电厂电力系统低频振荡产生的原因及影响。通过对电力系统稳定器(PSS)进行的现场试验,论证了电力系统稳定器(PSS)在增加系统阻尼,抑制系统低频振荡,提高系统稳定性方面有明显的效果。     

A study on robust adaptive modulation controller for TCSC based on COI signal in interconnected power systems

This paper proposes a novel robust adaptive modulation controller (RAMC) for thyristor controlled series capacitor (TCSC) in interconnected power systems to damp low frequency oscillation. The main idea of the controller is to drive the area centers of inertia (COI) to a stable equilibrium point and keep system synchronization. COI-coordinate-based model is derived first. Then RAMC for TCSC is derived using back-stepping method with COI dynamic signals from WAMS. The new controller performance is tested through a three-area power system and the simulation results show clearly that the new controller using COI signals has superior performance as compared with the conventional controller.     

由风力发电引起的电力系统强迫功率振荡

强迫功率振荡理论可以解释电力系统非负阻尼功率振荡,建立了风力发电机组模型,仿真分析了计及风电场接入电网时风速扰动引起系统传输功率的振荡的情况,结果表明,风速扰动的频率接近或等于系统功率振荡的固有频率时,会引起大幅度的功率振荡.且随着风速扰动幅值的增大,系统功率振荡的幅值也增大.     

应用储能系统抑制电力系统低频振荡原理研究

基于线性化等面积法则和小干扰分析方法,提出储能系统抑制电力系统低频振荡的原理和方法.通过对装有储能系统的单机无穷大系统进行理论分析和仿真测试,结果表明储能阻尼控制能够提供系统阻尼,且控制储能系统和电力系统之间的有功功率交换获得阻尼的效果比控制无功功率交换获得阻尼的效果要好的多.     

The stability of voltage oscillation modes in longitudinal power systems with SVC

In this paper, we investigate the stability of voltage oscillation modes in longitudinal power systems equipped with static var compensators (SVC). These modes are usually stable, so they do not appear without external force. The conventional harmonic resonance is a phenomenon in which an oscillation mode is excited with a harmonic source. Hence, it is solved by removing the source with a harmonic filter. For this reason, an SVC is equipped with several filters. However, there is a possibility that an oscillation mode itself may become unstable. If a mode is unstable, it can have a large amplitude without any harmonic source. Since it needs no harmonic source, its frequency is not limited to a harmonic frequency, but can have any value. The harmonic instability in direct‐current transmission systems is an example of such phenomena. The PLL (phase‐locked loop) is considered to be effective to suppress harmonic instability with an SVC. However, no theoretical reason has been shown as yet. This paper clarifies the effectiveness of PLL based on a stability condition for the voltage oscillation modes. Frequency responses of a thyristor‐controlled reactor (TCR), a component of the SVC, are largely influenced by the presence of the PLL. If a PLL exists, the stability condition is always satisfied, and all modes are stable. Lastly, we perform numerical simulations to show the validity of our investigation. © 2001 Scripta Technica, Electr Eng Jpn, 137(2): 8–17, 2001     

直流阻尼调制在大规模交直流电网中的作用

采用一种暂态能量函数,剖析直流阻尼调制抑制低频振荡的机理。基于留数,指出制约直流调制效果的关键因素,对直流调制在交直流电力系统中的运行特性进行分析,认为采用广域信号可以提高直流调制对区间振荡的抑制效果。以我国第1个交直流混合电网——南方电网为背景,验证理论分析的正确性。在此基础上,对直流阻尼调制在大规模交直流电网中的作用进行总结。     

Dynamic equivalents for transient stability studies of electrical power systems

Along with the growth in size of electrical power systems, attention is increasingly being given to various reduction techniques of dynamic system models for transient stability studies. One of these is the topological reduction that includes coherency-based aggregation. A theorem from the nonlinear vibrations theory is applied to derive analytical coherency-criteria for a classical model of the system. A simplified algorithm of coherency recognition is given and results for a sample system are shown. Important properties of topological equivalents are proved and a relationship to modal reduction is pointed out.     

Analysis of high‐frequency oscillations in voltage transformers

High‐frequency oscillations in voltage transformers are analyzed by the FFT method, using an equivalent lumped circuit. Such an analysis has been regarded as difficult because the transformers used in high‐voltage distribution systems have a large number of turns. The constants of the equivalent circuit are evaluated on a turn‐to‐turn basis. The frequency domain analysis is followed by time domain analysis using the FFT technique. Both characteristics are verified by an experiment on a 6.6‐kV voltage transformer. The nature of the high‐frequency oscillation is shown for a simpler model. It is found that the interlayer voltage becomes highest at the entrance to the incoming surge. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(1): 8–15, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20643     

HVDC输电系统次同步振荡(SSO)分析的GUI实现

为提高研究效率并普及研究结果，开发了一个用于分析HVDC输电系统次同步振荡(SSO)特性的图形用户界面（GUI)软件，这个GUI软件由人机界面及相关的回调函数组成，其中人机界面是利用MATLAB的GUI工具设汁的，而编写回调函数则利用了MATLAB的数值计算和数据可视化功能。实践表明在MATLAB环境下可容易、高效地开发出令人满意的GUI软件，通过GUI软件可实现SSO参数稳定域可视化分析及特征值分析和时域仿真分析，具有直观、方便的优点，适合广大技术人员对HVDC输电系统发生SSO失稳定可能性的检验。     

认识"系统振荡",改善电网结构,合理安排振荡解列

结合美加“8·14”事故中的功率振荡及我国华东、京津唐及华中系统中的事故实况,说明需认识功率振荡及其可能产生破坏性极强的电力事故。提出改善电网结构,设置快速起动电源、查清电网薄弱环节及合理安排振荡解列点等控制事故范围的对策。对西电东送及三峡系统防止振荡也提出建议。     

PSS在中心电网机组中的应用研究

阐述了甘肃电网网架结构的现状和投入PSS(电力系统稳定器)对电网安全的必要性和可靠性,并针对某电厂投入的8#机组对PSS抑制低频振荡效果进行分析研究。     

Fast evaluation of dynamic changes of electric power systems frequency during primary control

The paper presents the development of a simple method for the fast and sufficiently accurate assessment of dynamic changes of power systems frequency during the time period of primary control. Also, this model gives corresponding values of the total mechanical power of synchronous generators, during the some period. The development of a proposed low-order system frequency response model is based on the main assumption of uniform movement of generators, which enables representation of the power system through an equivalent controlled synchronous machine. The characteristics of the developed method were determined on an example of a real electric power system and a comparison was made with the results of a stricter approach.     

Fault localization in electrical power systems: A pattern recognition approach

Electrical power system is one of the most complex artificial systems in this world, which safe, steady, economical and reliable operation plays a very important part in social economic development, even in social stability. The fault in power system cannot be completely avoided. In this paper, we developed a method to resolve fault localization problems in power system. In our researches, based on real-time measurement of phasor measurement units, we used mainly pattern classification technology and linear discrimination principle of pattern recognition theory to search for laws of electrical quantity marked changes. The simulation results indicate that respectively study on the phase voltage, positive sequence voltage, negative sequence voltage, phase current, positive sequence current, negative sequence current of single-phase grounding faults and the positive sequence voltage, positive sequence current of three-phase short circuit faults, the pattern classification technology and linear discrimination principle are able to quickly and accurately identify the fault components and fault sections, and eventually accomplish fault isolation. In the study of electrical power systems, pattern recognition theory must have a good prospect of application.