Developing static reactive power compensators in a power systemsimulator for power education

This paper describes a newly installed laboratory module microcomputer-based static reactive power compensator (SVC) in detail to teach students how an SVC affects system voltage, load balancing, power factor, and transmission line losses. The SVC is merged into an old power system simulator for extensive power engineering education. The structure of the SVC is thyristor controlled reactors with fixed capacitors (TCR-FC). Two control algorithms, feedback control and feedforward control, are developed and compared. For the purpose of program flexibility and portability, a VME-Bus based microcomputer is used to synthesize the controller of the SVC. Several suggested experiments are given to show the effects of the SVC on distribution system compensation. The SVC greatly promotes the performance of the power system simulator     

Dynamic equivalent load model for power systems

In this paper, a method based on the parameters identification technique is proposed to develop a reduced-order dynamic equivalent load model (DELM). The model can be developed without the need for data gathering from the load side of the distribution network. Two test systems are used in this study, and the validity for the DELM is demonstrated. The DELM can be easily included in existing stability and other dynamic programs.     

Developing a harmonics education facility in a power systemsimulator for power engineering education

This paper describes a newly installed harmonics education facility in detail to teach students about harmonics related problems in a power system. A nonlinear load, which produces harmonic currents, and a harmonic filter, which is a mitigation facility, are merged into an existing power system simulator for advanced power engineering education. The nonlinear load is a widely used three-phase, 6-pulse controlled rectifier. The filter bank is designed to eliminate the characteristic harmonic currents. This paper also shows the resonant condition caused by shunt capacitors which are usually used for power factor correction. Several suggested experiments are given to teach students about harmonics related problems including harmonic sources, measurement, resonance, limitation, and mitigation. The harmonics education facility greatly extends and promotes the performance of the power system simulator     

天津电网动态等值算法

随着我国电力系统向大电网、区域互联方向发展,各个地区的电力公司在进行本地电网暂态稳定性分析时必须考虑互联区域电网的运行状态对本区域的影响,这就导致了计算数据的过于庞大,影响计算速度。为此,需要研究一定的等值方法来对外网进行简化处理。针对天津电网的特点,采用同调等值法研究适合天津电网计算分析的方法,并通过对天津电网500kV电压等级线路的暂态稳定分析,验证了所研究方法的可行性。     

基于支路等值注入功率模型的外部网络等值修正方法

在基于外部网络等值的最优潮流计算中,不断对外部网络等值导纳矩阵进行重新计算导致计算效率下降.针对Ward等值和REI等值,通过采用支路等值注入功率模型消去变动支路对节点导纳矩阵的影响,获得与变动支路无关的外部等值导纳矩阵,只需修正变动支路的等值注入功率, 并把支路注入功率归并到边界点,即可对外部网络等值进行修正.以 IEEE 39节点系统作为试验系统,通过对外部网络等值修正效果进行评估,验证了所提方法的正确性和有效性.     

An induction machine model for an analog power system simulator

This paper proposes a useful analog induction machine model which is used in real-time analog power system simulators. The operation of the induction machine model is stable for large changes of an outside network impedance, and this model is accurate due to a length of 12 bits of data for the parameter setting. The steady state and the transient state response of the induction machine model are tested and evaluated     

Identification of a continuous time nonlinear state space model for the external power system dynamic equivalent by neural networks

Based on the concept of the external power system dynamic equivalent obtained for the study system, in this paper a reduced-order artificial neural network is proposed, to construct a model for the external part. The mastermind behind the proposed method is to identify the external part as a dynamic–algebraic ANN, and this separation between dynamic equations in the state space and algebraic equations is useful to solve the prediction problem. Moreover, using similarity transformations, the state space model can be simplified, such that all the nonlinearities are embedded in the algebraic part. Since usually the study system equations are available in the continuous time domain, the external part is converted to the continuous time domain by a novel method. To obtain this model, the system should be excited first by a sort of random disturbances, and then data measured on the boundary nodes is used to identify the model. Identification process is accomplished by training the proposed network which can be used to predict behavior of the external system with a high degree of accuracy. Such an equivalent has wide applications for dynamic stability studies.     

基于系统等值的电压控制方法

利用电力网络两母线等值模型进行电压控制方法的研究,通过控制系统等值电势实现系统电压协调控制.基于此构建电压控制问题的模型及控制策略,并给出了电压稳定在线预警及控制系统的结构.该方法在线监视系统电压稳定性并选择较危险的节点,同时能获得各电压源点对危险节点等值电势影响的大小,与电压控制节点剩余控制能力相结合来选择合理的电压...     

新型电力系统综合负荷广义离散等值模型

针对新型电力系统中不同组成、不同复杂程度的综合负荷,亟需一种通用的模型结构来满足新型电力系统在线安全分析精度的要求。对含电动机负荷和静态负荷的综合负荷模型进行研究,分别建立新型电力系统下考虑电压相角变化和忽略电压相角变化的综合负荷广义离散等值模型,得到综合负荷广义离散等值模型的参数,并分析模型参数与电力系统各元件的内在联系以及各模型系数间的物理特性。通过CEPRI-36节点系统的仿真对比验证了所建模型的普适性和有效性。     

一种基于等效模型电网动态过程状态估计方法

提出了一种电网动态过程状态估计算法,利用快速、带时标的PMU量测估计电网扰动后的动态过程.该算法以扰动前的静态状态估计结果作为初始断面,对PMU量测不可观测区域的电网模型进行等效处理,在有限的PMU量测条件下可获得电网扰动后动态过程中的连续断面.动态过程状态估计的信息矩阵一次形成后保持恒定,可对连续的PMU量测断面进行计算,满足电网动态过程实时监视和控制的需要.对七节点系统支路故障后的扰动过程进行动态状态估计,验证了所提算法的可行性.     

考虑安控措施的交直流电力系统动态等值边界确定方法

特高压交直流电网的快速发展使得故障对系统的冲击由局部化转向全局化,因此有必要对系统进行暂态安全评估以提高供电可靠性。为了能在安全评估中准确模拟交直流系统发生故障后的动态特性及响应,并减小仿真规模及计算量,需对系统进行动态等值。提出了一种综合考虑交直流连锁故障及采取安控措施的交直流电力系统动态等值边界的确定方法,基于图论利用Dijkstra算法自动获取不同故障条件下的等值边界,根据误差要求调整等值区域,为不同预想故障下的不同动态等值模型的建立提供一个较为合理的等值边界。最后,基于IEEE 39节点标准系统构造的两区四直流互联电网与山东电网的模型,验证了所提方法的有效性。     

A reduced model for power system observability: analysis andrestoration

An algorithm for observability analysis and restoration in power system state estimation is presented. The problem of P-δ, Q-V and complete observability is addressed. In the proposed algorithm, groups of buses are represented by supernodes and the problem of observability analysis and restoration is examined with a reduced network. The proposed algorithm is easily implemented and it is independent of the state estimation solution algorithm. In case of unobservability, the proposed methodology identifies directly the maximal islands and determines the number and the placement of the required pseudomeasurements for observability restoration. Results from several test cases are presented     

基于电网等值模型的电能质量试验电源研究

为了使电能质量试验电源更好地模拟实际电网的外特性,提出了基于电网等值模型的电能质量模拟方法。基于相似理论,进一步提出了相似程度d这一指标用于评价试验电源模拟的电能质量与"原型"的相似性。针对H桥级联型逆变器的试验电源拓扑结构,亦提出了基于重复学习控制的电压源虚拟阻抗控制策略,其能对基波情况下实际电网的外特性进行模拟,且可信度较高。最后,通过仿真验证了所提控制策略的有效性以及指标的可行性。     

基于可编程电源的数模动模混合仿真系统研究

为满足现代电力系统实时仿真的发展需求,提出一种基于可编程电源的数模动模混合仿真系统。利用动模实验室搭建动模仿真系统,并在RTDS中搭建39节点系统作为数字仿真系统模型,结合以理想变压器模型算法作为功率接口算法的接口系统,形成一个800 V/345 kV的动模数模混合实时仿真系统实验平台。在研究混合仿真接口两端系统延时对系统稳定性和准确性影响基础上,提出用二阶相位超前环节对下发通道和上传通道的接口延时进行相位补偿,以提高系统稳定性和准确性。通过对所搭建的数模动模混合仿真系统的实验,并与纯数字仿真进行对比分析,进一步验证了混合仿真系统的有效性。     

A dynamic load model for analysis of power system voltage

It has become important in recent years that power systems be protected from voltage instability caused, in part, by heavy loads and the concentration of air conditioning loads during certain hours. Many studies have explored the problems and possible countermeasures. However, the load representations used in these studies are based on power values, i.e., P and Q; therefore, these analytic models are insufficient to express load responses and, thus, investigation is somewhat limited. This paper introduces a load model expressing load admittance responses by a first-order delay differential equation and uses this model in tandem with power network solutions to analyze power system voltage stability. This load model is shown to work reliably and effectively. Using this model, it is possible to investigate more precisely and widely than before the power system voltage stability phenomenon of arbitrary characteristic loads in lower voltage ranges and on propagations of instability through the networks.     

动力电池动态模型参数辨识的研究

为实现动力电池状态的精确估计,需要提高电池模型的精确性.对选定的电池模型进行在线参数辨识能够实时反映电池真实的工作状态.采用含遗传因子的递推最小二乘算法（FFRLS）对二阶RC模型进行参数辨识,并在Matlab/Simulink环境下搭建仿真模型用于验证辨识结果.仿真验证结果表明：由FFRLS算法得到的模型参数较为精确,可以作为模型参数在线辨识的一种有效手段.另外,FFRLS算法还能完成电池开路电压的估计,可作为估计电池SOC的参考,有利于了解电池性能状态.     

Low-order dynamic equivalent estimation of power systems using data of phasor measurement units

This paper utilizes data measured by phasor measurement units (PMUs) to extract a low-order dynamic equivalent model for power system stability studies. The estimated model is a 2-order model for synchronous machines. This model has the advantage of simplicity of classical model and considerably reduces the oversimplifying error of classical model. This method offers an alternative approach to analytical model reduction techniques based on the detailed system models. The proposed method uses the synchronized bus voltage and current phasors measured by PMUs. Using post disturbance data, electrical and mechanical parameters of the equivalent generator are estimated sequentially. Furthermore, a new approach for estimation of two-machine and single machine infinite bus (SMIB) equivalent systems are presented for analysis of electromechanical oscillations. To evaluate the performance of the proposed approach, simulations are performed on a two area 13-bus test system and real measured PMU data. Simulation results show that the estimated model can represent the dynamic behavior of the studied system with good approximation.     

基于多层次启发式动态规划算法的电力系统动态等值

针对电力系统运行工况变化后动态等值系统响应精度不够的问题,提出一种基于多层次启发式动态规划(Global representation heuristic dynamic programming,GrHDP)算法的动态等值方法。该方法在基于同调等值得到的模型的基础上,在等值边界上加入基于GrHDP算法的动态补偿环节,实时补偿同调等值系统与原系统间动态特性的差额,从而实现精确跟踪原系统的动态特性。以10机39节点系统为例进行仿真研究,结果表明:在不同运行工况、故障方式和故障地点下,基于所提算法的动态等值系统相比传统的同调等值能更精确地跟踪原系统的动态特性。     

基于动态等效电路的含DG电力系统电压稳定性分析

分布式电源(Distributed generation, DG)接入电网对电力系统电压稳定有一定影响。首先对DG接入节点内部系统进行综合动态等效,将动态等效电路的分析方法应用于含DG的电力系统。然后将DG视为“负”的负荷,提出DG接入后评价系统静态电压稳定性的广义阻抗模裕度指标。基于广义阻抗模裕度指标,具体分析了DG不同接入方式、出力大小对系统电压稳定性的影响和优化无功补偿的效果。最后通过仿真验证了所提方法是研究含DG电力系统静态电压稳定性的一种实用和方便的方法。     

锂电池一阶RC等效电路模型的动力学特性分析

为分析锂离子动力电池一阶RC等效电路模型的动力学特性,将荷控忆阻器、电阻及电感作为一阶RC等效电路的负载构成一个四阶混沌系统,运用四阶变步长Runge-Kutta法详细分析了该系统的一些基本动力学行为.结果表明,该混沌系统随一阶RC等效电路欧姆内阻参数的变化具有复杂的动力学行为,随欧姆内阻增大,系统通常经混沌进入倍周期分岔序列,且欧姆内阻越小,系统混沌现象越明显.通过对系统的动力学特性分析,可以在线获取欧姆内阻值,为锂离子动力电池寿命的在线监测提供一种全新的方法.