A compact control algorithm for reactive power compensation and load balancing with static Var compensator

A compact control algorithm for reactive power compensation and load balancing with the static Var compensator (SVC) in three-phase three-wire systems is developed in this paper. The required compensation susceptance of each SVC phase can be obtained from a very simple function of voltage and power signals which are measured by a three-phase voltage transducer and two single-phase active and reactive power (P–Q) transducers at the load bus. The calculation of compensation susceptances is based on the criterion of a unity power factor and zero negative-sequence currents after compensation. A simulation is made, as the first stage, to show the validity of the proposed compensation algorithm. Then, a laboratory size microcomputer-based SVC, which consists of thyristor-controlled reactors (TCRs) and fixed capacitors (FCs), is designed and implemented. Simulation and experiment results show that the algorithm is very suitable for on-line control of the SVC which is designed for phase balancing and power factor correction.     

静止无功补偿器对电压稳定性的影响

本文对静止无功补偿器（ＳＶＣ）的控制建立计算机仿真模型，并在三机十一母线系统中进行负荷微增的仿真，通过仿真的结果，我们可以看出，在到达其上限之前，对系统的电压稳定性有一定改善，并比较了不同功率因数的负荷微增下的ＳＶＣ对电压稳定的影响。     

Combined compensation structure of a static Var compensator and an active filter for unbalanced three-phase distribution feeders with harmonic distortion

A combined reactive power compensation method of a static Var compensator (SVC) and an active filter is described in this paper for unbalanced three-phase distribution feeders with harmonic distortion. The SVC acts as a classic reactive power compensator for load balancing and power factor correction. The small rating active filter is used to improve filtering characteristics of the passive filter in SVC and suppress possible resonance between the system impedance and the passive filter. The control signals are derived from the calculation of instantaneous active and reactive powers of the distribution feeder. Simulation results carried out by the electromagnetic transients program (EMTP) show that the proposed reactive power compensation configurations can effectively balance currents, correct power factor, and eliminate harmonic currents.     

微分同胚正规形理论在确定负荷控制地点及SVC安装地点中的应用

应用微分同胚正规形理论,以非线性参与因子为依据,提出了确定实施负荷控制的地点及静止无功补偿(static var compensator,SVC)安装地点的更准确方法。分别以美国西部9节点系统、新英格兰39节点系统为算例进行了有功负荷控制和SVC安装地点分析,并采用电压稳定性指标以及动态仿真对系统的稳定性进行了检验。结果表明,微分同胚正规形方法能更好地反映电力系统的非线性特性,有效地确定实施负荷控制措施的地点以及SVC的安装地点。     

Use of a static var compensator for generator negative-sequence current reduction

The presence of negative-sequence current in a generator, due to system imbalance, induces double-frequency currents in the rotor iron. These currents may cause rotor overheating and serious damage if permitted to persist. Negative-sequence current relaying practices that alarm or trip the generator before damage can occur are well established in the power industry. However, tripping major generation facilities may create social, security, and economic problems. In addition, for an isolated system with relatively poor frequency regulation, the combination of negative-sequence current and frequency perturbation may cause supersynchronous resonance in turbine blades if one of the mechanical resonance frequencies of the turbine blade is close to double the system frequency (60 Hz). This paper presents a method for correcting the problem at source by reducing the negative-sequence current through a specially designed delta-connected static var compensator (SVC). The derivation of the mathematical model and computer simulations verify and explain the capability of this approach. In addition, a scaled-down model is implemented in a physical simulation laboratory. Some laboratory test results are also presented.     

基于PSCAD/EMTDC的不平衡负载的静止无功功率补偿研究

在总结已有的研究成果基础之上,将瞬时无功功率理论应用于提高功率因数和补偿三相不平衡负荷的静止无功功率补偿器控制之中。用PSCAD/EMTDC软件建立了补偿三相不平衡负荷的静止无功功率补偿器的仿真模型。通过理论分析和仿真研究验证了该软件及所建立的仿真模型能很好地模拟补偿三相不平衡负荷的静止无功功率补偿器的电路。     

Adaptive control of a synchronous machine using the auto-searchingmethod

A novel adaptive control scheme is presented for the design of a power system stabilizer (PSS) and a static VAr (reactive volt-ampere) compensator (SVC). The developed adaptive proportional-integral (PI) controllers, whose gains are adjusted in real time using the online-measured system operating conditions and a look-up table stored in computer memory, can offer better damper effects for generator oscillations over a wide range of operating conditions than conventional PI controllers with fixed gain settings. The effects of the adaptive PSS and the adaptive SVC on generator damping and terminal voltage profile are examined by computer simulation of system dynamic responses to a major disturbance     

静止无功补偿器与有源电力滤波器联合运行系统

提出一种具有功率因数校正、补偿负载不平衡和滤除电网谐波电流的静止无功补偿器(static var compensator,SVC)和有源电力滤波器(active power filter,APF)联合运行系统电路结构。其中,SVC由晶闸管控制电抗器(thyristor controlled reactor,TCR)及固定电容器(fastness capacitor,FC)组成,主要用来快速补偿无功,并通过对其三相不对称控制来消除电网三相不对称和负序电流;APF部分主要用来消除电网及SVC引起的谐波电流,同时抑制固定电容器与电网等效阻抗间可能的串并联谐振。在分析SVC和APF联合运行系统基本工作原理的基础上,对联合运行时的控制方法进行研究。仿真和实验结果证明了该联合运行系统的可行性。     

应用静止无功补偿器抑制次同步谐振的仿真研究

针对华北地区某大型坑口电厂（A电厂）串联补偿送出系统次同步谐振（subsynchronousresonance,SSR）引发发电机组轴系扭振的问题,采用基于电力系统计算机辅助设计和电磁暂态模拟程序软件（powersystemcom-puteraideddesignandelectricmagnetictransientinDCsystem,PSCAD／EMTDC）的时域仿真与频域仿真分析相结合的方法,通过大量的仿真计算,对静止无功补偿器（staticvarcompensator,SvC）抑制SSR的工作原理、控制策略及其影响因素等进行了系统的研究和验证。仿真结果与实际工程应用结果均表明,SVC能有效抑制SsR的发生。该方法可解决南方电网系统内交流串联补偿输电工程中的SSR问题。     

基于快速等效电纳计算的静止无功补偿器复合控制方法

提出了一种静止无功补偿器(static var compensator,SVC)的不平衡补偿方法。针对不平衡情况下的功率补偿需求,提出了基于佛布迪(fryze-buchholz-depenbrock,FBD)算法的等效电纳检测方法,有效减小了系统的计算量;为了提高SVC的补偿性能,提出了一种开环和闭环复合控制方法,并利用单纯形算法对控制参数进行动态调整,提高了系统的鲁棒性,大大提高了SVC的补偿精度和补偿性能,实现了三相系统的功率平衡。最后,仿真和实验验证了所提出方法的有效性和正确性。     

基于负序电流补偿的并联风电变流器故障容错控制

海上风电运行环境恶劣,风电功率随机波动性大,导致功率器件极易发生故障.故障容错控制是提高风电并联变流器运行可靠性以及功率可用度的有效手段.并联风电变流器某相发生开路故障后,对并联风电变流器的故障运行机理进行了详细分析.在此基础上,提出一种基于负序电流补偿的并网风电变流器故障容错控制,利用非故障变流器模块对故障变流器模块进行负序电流补偿.当系统功率小于或等于0.5 p.u.时,在保证并网侧电流平衡的条件下实现变流器最大输出功率;当系统功率大于0.5 p.u.时,首先满足系统有功输出要求,然后对负序电流进行补偿.最后通过仿真验证了该控制理论的正确性与可行性.     

针对暂态电压稳定问题的自动电压控制系统与切负荷协调控制策略

建立了暂态电压稳定分析的微分代数方程组,并提出了应对暂态电压稳定问题的自动电压控制(automatic voltage control,AVC)体系下二级电压紧急控制与切负荷协调控制策略。该协调控制策略把低压切负荷作为与AVC体系下二级电压紧急控制并行的一种控制手段,在这种协调控制的过程中优先考虑采用二级电压紧急控制,当计算发现仅依靠二级电压紧急控制不能使系统保持暂态电压稳定的时候再采用切负荷控制。在PSAT仿真环境下建立了含AVC体系下二级电压紧急控制和切负荷控制的电力系统暂态电压稳定仿真模型,对广东电网748节点系统进行仿真,验证了所提出的控制策略和模型的正确性和有效性。     

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     

Tuning a static var compensator controller over a wide range of load models using an artificial neural network

A novel approach using an artificial neural network (ANN) for tuning a static var compensator (SVC) controller over a wide range of load models is presented in this paper. To enhance power system damping over a wide range of load models, it is desirable to adapt the SVC controller gain in real time based on load models. To do this, online measurements of load parameters which are representative of load models are chosen as the input signals to the neural network. The output of the neural network is the desired gain of the SVC controller. The neural network, once trained by a set of input-output patterns in the training set, can yield a proper SVC controller gain under any load model. Simulation results show that the tuning gain of a SVC controller using the ANN approach can provide better damping of the power system over a wide range of load models than the fixed-gain controller.     

SVC对电力系统频率稳定性影响的仿真分析

用Matlab软件建立电力系统仿真模型,负荷模型包括异步电动机模型和恒阻抗静态模型,静止无功补偿器(SVC)采用一阶线性化实用模型,对系统遭受双回线永久断一回线和系统负荷突然剧增这2种典型大干扰后SVC动作对系统频率造成的影响进行仿真和分析,包括SVC出力大小、动作时间及控制策略的影响。针对断一回线故障,当负荷端电动机比重较小时,SVC可使频率稳定在额定值。对系统在不同调频能力下负荷剧增时所做的频率变化仿真表明,SVC对系统的频率稳定性产生负面影响,SVC无功出力越大,则频率质量越差,当系统调频能力较弱而SVC无功出力很大时,会加速系统的频率崩溃。因此,在SVC的控制系统中应引入频率反馈,当监测频率低于某一定值时,应减少SVC出力至合理值。     

电力系统变电站用电能质量综合控制器的研制

晶闸管控制电抗器(TCR)型静止无功补偿装置(SVC)被普遍应用于电力系统中，其具有反应时间快，分相、连续调节无功等优点，但其本身也是一个谐波电流源。本文提出了一种电能质量综合控制器改进了传统的TCR型SVC补偿系统，不仅能够连续补偿系统无功功率、不平衡等问题，还能滤除由TCR本身与负载产生的谐波电流，提高系统的功率因数。仿真和实验结果都表明该电能质量综合控制器能够很好的解决电站的无功与谐波问题。     

电网故障下的电能路由器直流电容电压平衡控制策略

针对传统方法无法实现电网故障下的电能路由器直流电容电压平衡问题,文中提出了三层结构的直流电容电压平衡控制策略。在对不平衡的功率进行理论分析的基础上,通过动态调整定义的加权系数,来灵活控制注入的零序电压和负序电流各自承担的相间移动功率,提高系统控制自由度。在MATLAB/Simulink环境下搭建电能路由器仿真平台,仿真结果表明:当某一相电网故障(电网电压跌落95%)时,采用单一的零序电压、零序电压和负序电流加权组合、单一的负序电流的注入均可实现电能路由器直流电容电压平衡控制目标。     

一种新型同相供电系统分析与设计

为提高供电系统的电能质量和取消变电所电分相,提出一种基于V/v接线变压器的新型同相供电系统。首先,分析了该系统的拓扑结构及工作原理,完成负序电流和补偿电流的理论计算;其次,为实现对三相系统负序、谐波和无功综合改善的目标,采用一种基于dq变换的系统协同控制策略;最后,根据某牵引变电所典型实测负荷数据在Simulink中搭建系统仿真模型,验证了所提系统在取消变电所电分相的同时能有效提高供电系统的电能质量,并且具有良好的动态性能和综合补偿性能。     

双级饱和磁控SVC补偿电铁牵引不平衡负荷的研究

由于电气化铁路运行的不对称性,会产生快速波动的负序电流,并流入电力系统各处,对系统发电、供电设备产生严重的不良影响.首先分析了目前负序电流的抑制方法、存在问题,并提出采用磁控SVC,即双级饱和磁控电抗器与固定电容器并联,进行无功、负序综合治理,并通过仿真对其可行性进行了验证.     

静止无功补偿装置的实用化技术与措施

静止无功补偿装置(SVC)是柔性交流输电控制装置的重要内容之一,具有动态平滑的调节特性及向电力系统提供阻尼的作用。介绍了SVC实用化技术,如进行自动电压控制(AVC),预防电网电压失稳,提高电网的输送能力,防止事故扩大,紧急情况下可以形成有效的反电压崩溃防线,在冶金、电气化铁路等行业治理电压波动、闪变、谐波污染并平衡随时间变化的非对称负荷,防止发生次同步谐振,给直流输电提供无功等在提升电力系统安全优质经济运行水平中的作用。简要介绍了SVC国产化的现状,并提出了推行SVC的具体建议。