Damping inter-area modes of oscillation using an adaptive fuzzy power system stabilizer

This paper introduces an indirect adaptive fuzzy controller as a power system stabilizer used to damp inter-area modes of oscillation following disturbances in power systems. Compared to the IEEE standard multi-band power system stabilizer (MB-PSS), indirect adaptive fuzzy-based stabilizers are more efficient because they can cope with oscillations at different operating points. A nominal model of the power system is identified on-line using a variable structure identifier. A feedback linearization-based control law is implemented using the identified model. The gains of the controller are tuned via a particle swarm optimization routine to ensure system stability and minimum sum of the squares of the speed deviations. A bench-mark problem of a 4-machine 2-area power system is used to demonstrate the performance of the proposed controller and to show its superiority over other conventional stabilizers used in the literature.     

Damping inter-area oscillation by generation rescheduling based on wide-area measurement information

Inter-area oscillations are inherent to power systems which can be caused due to oscillation of two coherent groups of generators against each other with low or negative damping. Poorly damped oscillations can pose various problems such as limiting transfer capabilities and in more severe cases can lead to uncontrolled islanding causing system blackout. In this paper, for damping inter-area oscillation a new method based on the wide area measurement system (WAMS) and using generation rescheduling (GR) is proposed. The proposed algorithm consists of three tasks; identification of inter-area mode, determination the most effective generators for rescheduling and enhancing damping of inter-area mode by GR. In this approach, first by means of Independent Component Analysis (ICA) and modified Random Decrement (RD) techniques and using on-line power and rotor angle oscillation data provided by WAMS, the frequency and damping of the inter-area mode is identified. In the case of low damping of oscillation, by using mode shape of the inter area mode, generation rescheduling is applied for improvement of damping. In this paper, a non-model based method is adopted for estimating mode shape from the measured data like generator rotor speeds. The proposed approach is applied on a two area small system and IEEE 39-bus test system and the results demonstrate effectiveness of the method for enhancing oscillation damping.     

Damping control of inter-area oscillations in the European power system using aggregated models

In the first part of the paper, a new approach to the reduction of large dynamic network models is presented. This method is implemented in the program package PSD and is used here in an exemplary fashion to reduce the model of the European power system to a model usable for the solution of a number of problems. In the second part, the paper describes a new damping concept of inter-area oscillations in large power systems. Additionally installed second-level damping controllers are acting on the voltage regulator reference inputs of selected generators. They are using global information about the swing profiles of the inter-area oscillations to be damped. The damping controllers are designed as a H_∞-norm optimal decentral control system based on both a topological and a frequency range decomposition of the control task. The solution is demonstrated for the reduced model of the European system. Received: 30 April 2001/Accepted: 8 June 2001     

Modal analysis of inter-area oscillations using the theory of normal modes

Based on the notion of normal modes in mechanical systems, a method is proposed for the analysis and characterization of oscillatory processes in power systems. The method is based on the property of invariance of modal subspaces and can be used to represent complex power system modal behavior by a set of decoupled, two-degree-of-freedom nonlinear oscillator equations.     

Damping of system oscillatory modes by a phase compensated gas turbine governor

The proliferation of gas turbines in power systems increases the scope for taking advantage of mechanical torque control for improved network damping. This paper describes a phase compensated governor for a gas turbine and explores its potential contributions to system damping in a multimachine context. It is shown that the inclusion of phase compensation in the governor control loop is capable of achieving dynamic stability for the system without the need of a power system stabilizer (PSS) in the generator excitation control loop and without adversely influencing terminal voltage control. In addition, it is demonstrated that a phase compensated governor (PCG) is also capable of significantly improving transient stability and by complementing the effectiveness of a conventional PSS, enables a superior overall contribution to network damping.     

Stabilization of inter-area and/or oscillatory modes in large-scale power system by voltage impedance power system (VIPS) apparatus based on decentralized control scheme

New technologies such as power electronics have made it possible to change continuously the impedance of a power system not only to control power flow but also to enhance stability. A power system incorporating a variable impedance apparatus such as a variable series capacitor (VSrC) and high-speed phase shifter (HSPS) is called VIPS (Variable Impedance Power System) by the authors. This paper proposes a novel control method of VIPS apparatus such as VSrC and HSPS installed at an interconnecting point for stabilizing inter-area unstable and/or oscillatory modes. The proposed design method of the control system is a kind of hierarchical decentralized control method of a large-scale power system based on a Lyapunov function. Under the proposed control scheme, each subsystem can be stabilized independently by local controllers such as AVR, speed governor and PSS, and then the whole interconnected system can be stabilized by VIPS apparatus taking into account interactions between subsystems. The effectiveness and robustness of the VIPS apparatus control are shown by numerical examples with model systems including a large-scale power system.     

超低频区间振荡现象的机理分析

对我国东北、华北、华中、川渝电网的联网工程中出现的超低频区间振荡现象进行了深入的理论分析.提出区间振荡模式的特征值关于区间联系导纳的灵敏度的概念,通过对该灵敏度的数学分析,揭示了区间振荡频率受电网互联强弱的影响规律,指出区间振荡频率将随电网互联的减弱而降低.同时阐明系统容量对区间联系导纳的影响,在我国四大电网联网时由于系统容量较大,使得区间联系导纳较小,进而导致区间振荡频率较低,出现了超低频现象.对四机两区系统和四大区域联网系统进行小干扰稳定计算,比较并说明本文采用经典发电机模型近似复杂详细模型来定性研究区间振荡频率变化的方法的有效性,并且验证了理论分析的正确性.     

惯量对区域振荡模式的影响

机组的惯量对区域振荡频率和阻尼有着较大的影响。以两机系统为例推导了区域振荡模式与不同区域机组等值惯量之间的关系，并以两机与四机系统作为仿真算例．利用特征根分析法，得出区域振荡模式随着不同区域等值惯量以及不同区域内机组惯量的变化曲线。把仿真结果与估算公式相比较，分析得出区域内机组不同调因素对区域振荡频率影响较小。而对区域振荡阻尼影响较大的结论。     

A fundamental study of inter-area oscillations in power systems

A fundamental study of the nature of inter-area oscillations in power systems is presented. The effects of the system structure, generator modeling, excitation type, and system loads are discussed in detail. Both small signal and transient stability analyses are used to determine the characteristics of the system     

Analysis of inter-area oscillations in the South China Interconnected Power System

This paper presents a detailed analysis of low-frequency inter-area oscillations of the South China Interconnected Power System (SCIPS) for the year of 2005 based on the eigenanalysis method. Participation factors and mode shape diagrams of the generators participating the inter-area oscillations are figured out, and locations of PSS are determined accordingly, the parameter setting for the PSS is studied as well. The method of HVDC small signal modulation is applied to enhance the small signal stability of the system; the results are investigated based on the Prony method. The influences of component maintenances in the transmission corridors on the inter-area oscillations are further investigated, and some important conclusions are drawn.     

基于电压源换流器的高压直流输电系统的阻尼特性与阻尼控制

利用复数力矩分析方法近似推导了基于电压源换流器高压直流输电(voltage source converter HVDC,VSC-HVDC)系统的电磁力矩,定性分析了VSC-HVDC的快速功率控制可能会导致系统出现电气阻尼变弱或负阻尼现象。在建立包括VSC-HVDC及控制器在内的AC/DC混合系统的动态数学模型的基础上,应用最优控制理论设计了最优阻尼控制器,交直流并联系统数值仿真结果表明该附加阻尼控制方法的有效性。     

Use of energy and power concepts in the analysis of the inter-area mode phenomenon

This paper presents an energy-based small signal method of analyzing low-frequency inter-area oscillations. A comprehensive framework for the analysis of system oscillations is developed based on the analysis of energy relationships in the linear state representation of the power system. This approach provides insight into the nature of the inter-area phenomenon and can be used in conjunction with modern techniques for spectral analysis of complex power systems. The practical use of the proposed methodology is tested on a complex 46-machine, 190-bus test system. Detailed non-linear time domain simulations and frequency domain studies are finally conducted to check the validity of the results.     

基于CBR和OAPID的互联电网区间模式振荡预警

采用基于广域测量系统(WAMS)的量测数据,提出基于范例推理(CBR)理论及功率振荡增量分布(OAPID)理论的互联电网区间模式振荡预警方法。该方法在系统未发生低频振荡时进行区间模式振荡预警;在系统发生振荡时提供系统运行方式的调整建议来改善系统阻尼。某区域电网WAMS实测数据的测试结果验证了所提方法的可行性和有效性。     

Nonlinear controller design of thyristor controlled series compensation for damping inter-area power oscillation

A design method of nonlinear controllers of thyristor controlled series compensation (TCSC) for damping inter-area power oscillation based on direct feedback linearization (DFL) is presented in this paper. To damp inter-area power oscillation of power systems, the power modulation action of the TCSC is illustrated firstly. Then the nonlinear model of a two-area power system with the TCSC control is constructed, and is linearized by the DFL. Finally, the design of the nonlinear optimal controller of the TCSC has been completed using the criterion of integration for time and absolute error (ITAE). The digital simulation results using NETOMAC program and detail models show that the presented controller of the TCSC can efficiently improve inter-area power oscillation damping of power systems.     

可控串补对次同步谐振的抑制作用初步探讨

简要介绍可控串补的组成，运行方式及主要功能，并分析托克托电厂4期串联补偿进出方案存在的次同步谐振问题．用EMTP仿真程序详细探计可控串补(TCSC)抑制次同步谐振(SSR)的可行性。     

利用SSSC阻尼电力系统低频振荡

提出了一种改进的装有静止同步串联补偿器(SSSC)的单机、多机系统Phillips-Heffron模型,并由此得出了SSSC在单机、多机系统中能够抑制低频振荡的理论依据.通过重新构建控制量的方法,得到了装有SSSC的单机系统仿射非线性方程,进而应用非线性变换与非线性反馈理论求解SSSC的非线性控制策略.结合最优控制理论,得到了单机系统SSSC非线性最优控制策略,并将其应用于提高系统阻尼.基于实时数字仿真(RTDS)的仿真结果,证实所做理论分析的正确性以及所提出的非线性控制策略的有效性.     

STATCOM与SSSC改善电力系统阻尼的比较研究

电力系统故障过程中暂态能量的消失速率可以作为系统能否快速到达静态平衡点的一个标准,同时也可以看作系统阻尼的一个指标.基于这个理论,针对静止无功补偿器(STATCOM)和静止同步串联补偿器(SSSC)在系统故障过程中对系统作用的不同,分析并得出了一个单机无穷大系统故障过程中STATCOM与SSSC向系统提供的附加阻尼的表达式.仿真结果表明,STATCOM与SSSC都能够显著改善系统阻尼,但SSSC比STATCOM能更好地为系统提供阻尼,改善系统动态性能.     

探讨10 kV同杆双回电力线路不同架设方式的经济运行

从运行方式着手,对１０ｋＶ双加电力线路完全同杆和不完全同杆架设方式的经济运行情况进行分析对比,探讨１０ｋＶ配电网降损节能的新途径,为目前城市、农村电网改造制定线路整改方案提供参数。     

SVC安装地点对次同步振荡抑制效果的影响

静止无功补偿器（Static Var Compensator,SVC）可用于抑制次同步振荡,根据SVC抑制次同步振荡的机理设计了SVC的次同步阻尼控制器（SSI）C）,基于次同步振荡研究的IEEE第一标准模型,分别研究了将SVC并联安装在发电机机端母线上、升压变压器的二次侧母线上、输电线路中点上和输电线路末端时的电气阻尼频率特性和时域仿真分析;提出了SVC不同的安装地点会对次同步振荡的抑制效果产生一定的影响,甚至会诱发次同步振荡。     

Damping improvement by FACTS devices: A comparison between STATCOM and SSSC

Following a disturbance, the machines in a stable power system initially oscillate, and then settle at the stable equilibrium point where the transient energy is zero. This paper uses the rate of dissipation of transient energy as a measure of system damping. The above concept is then applied to determine the additional damping provided by a static synchronous compensator (STATCOM) and a static synchronous series compensator (SSSC). Analytical expressions for additional damping provided by these devices are carefully derived and compared for classical model of a simple power system. The proposed technique of evaluating system damping is then tested on a single-machine system and for some special faults in the 10-machine New England system. The results obtained in both the systems are then systematically described.