SVC与STATCOM联合运行协调控制设计与仿真
岑华蒙毕业设计外文翻译-SVC与STATCOM在电力系统中应用的效益
广西科技大学毕业设计外文翻译院别电气与信息工程学院专业电气工程与自动化班级电气101班学号 201000307027 姓名岑华蒙指导教师周晓华2013年12月28日Benefits of SVC and STATCOM for ElectricUtility ApplicationAbstract-- Examination of the behavior of SVCs and STATCOMs in electric power systems is presented. The paper is based on analytical and simulation analysis, and conclusions can be used as power industry guidelines.We explain the principle structures of SVCs and STATCOMs, the models for dynamic studies, and the impact of these devices on steady state voltage and transient voltage stability. Sensitivity analysis is provided which shows the impact of SVCs and STATCOMs with regard to network strength. Harmonic issues, space requirements, and price discussions are also briefly addressed.Index Terms—Dynamic Compensators, SVC, STATCOM, Short Circuit Capacity, Gain Sensitivity, Short Term Voltage Stability, HarmonicsI. INTRODUCTIONSHUNT-connected static var compensators (SVCs) are used extensively to control the AC voltage in transmission networks. Power electronic equipment, such as the thyristor controlled reactor (TCR) and the thyristor switched capacitor (TSC) have gained a significant market, primarily because of well-proven robustness to supply dynamic reactive power with fast response time and with low maintenance.With the advent of high power gate turn-off thyristors and transistor devices (GTO, IGBT, …) a new generation of power electronic equipment, STATCOM, shows great promise for application in power systems [3,4].This paper aims to explain the benefits of SVCs and STATCOMs for application in utility power systems. Installation of a large number of SVCs and experience gained from recent STATCOM projects throughout the world motivates us to clarify certain aspects of these devices.II. BASIC DESCRIPTIONThis section explains briefly the basic configuration of SVCs and STATCOMs:A.SVCThe compensator normally includes a thyristor-controlled reactor (TCR), thyristor-switched capacitors (TSCs) and harmonic filters. It might also includemechanically switched shunt capacitors (MSCs), and then the term static var system is used. The harmonic filters (for the TCR-produced harmonics) are capacitive at fundamental frequency. The TCR is typically larger than the TSC blocks so that continuous control is realized. Other possibilities are fixed capacitors (FCs), and thyristor switched reactors (TSRs). Usually a dedicated transformer is used, with the compensator equipment at medium voltage. The transmission side voltage is controlled, and the Mvar ratings are referred to the transmission side.The rating of an SVC can be optimized to meet the required demand. The rating can be symmetric or asymmetric with respect to inductive and capacitive reactive power. As an example, the rating can be 200 Mvar inductive and 200 Mvar capacitive, or 100 Mvar inductive and 200 Mvar capacitive.B. STATCOMThe voltage-sourced converter (VSC) is the basic electronic part of a STATCOM, which converts the dc voltage into a three-phase set of output voltages with desired amplitude, frequency, and phase.There are different methods to realize a voltage-sourced converter for power utility application. Based on harmonics and loss considerations, pulse width modulation (PWM) or multiple converters are used.Inherently, STATCOMs have a symmetrical rating with respect to inductive and capacitive reactive power. For example, the rating can be 100 Mvar inductive and 100 Mvar capacitive. For asymmetric rating, STATCOMs need a complementary reactive power source. This can be realized for example with MSCs.VII. THE FUNCTIONAL RATING CONCEPTTraditionally, SVCs of a common design have been used to handle different types of network problems. The trend today, however, is to tailor SVCs for their intended use. This is important in order to make SVCs cost efficient.For steady state voltage support, i.e., to follow the daily load pattern, bulk reactive power combined with stepless smooth voltage control is desired. Vernier voltage regulation can be provided by a TCR running in parallel with harmonic filters. The bulk reactive power is provided by mechanically switched capacitor banks (MSCs) or reactors (MSRs) governed by the SVC controller. Thus SVCs serve the purpose of continuously maintaining a smooth voltage, piloting the MSC switching.If the task is to support a system limited by post contingency voltageinstability or unacceptable voltage levels, a large amount of quickly controllable reactive power is needed for a short time duration. An SVC with additional TSCs is an excellent choice. Post recovery voltage support may also be necessary—this is then preferably provided by MSCs governed by the SVC.For temporary over voltages, large inductive reactive power is needed for a short period of time. The standard TCR has some short-time over current capability. This capacity can easily be extended by lowering its steady state operating temperature and by “under sizing” the reactors.A.Enhanced SVCsThe SVC characteristic at depressed voltage can be efficiently improved by adding an extra TSC. This branch is intended to operate only during undervoltage conditions. It can be added without introducing additional cost in other parts of the SVC. Most important is that the current rating or the voltage capability of the power transformer does not need to be increased. Power transformers allow large overcurrent during limited time (IEEE C57-115 can be used as a guide for available capacity). In many cases three times overload in current for 10 seconds is available. The additional TSC rating is typically in the range of 50 to 100% of the SVC rating.B. SVC Short Term OverloadThe maximum power from an SVC at a given voltage is determined by its reactance. No overload capacity is available unless the reactance is lowered, e.g., by adding a TSC. For overvoltages, however, the SVC reactance is no longer the limiting factor; instead the current in components defines the limit. In most cases the thyristors set the limit. The design is made so that the thyristors are running at a maximum allowed temperature at maximum steady state system voltage. A margin to destructive temperatures is reserved in order to handle fault cases. The Forbes 500 kV static var system near Duluth Minnestoa USA is an interesting example of an Enhanced SVC [5].VIII. HARMONICSBoth SVCs and STATCOMs generate harmonics. The TCR of an SVC is a harmonic current source. Network harmonic voltages distortion occurs as a result of the currents entering the power system. The STATCOM is a harmonic voltage source. Network voltage harmonic distortion occurs as a result of voltage division between the STATCOM phase impedance and the network impedance.The major harmonic generation in SVCs is at low frequencies; above the 15thharmonic the contribution is normally small. At lower frequencies the generation is large and filters are needed. SVCs normally have at least 5th and 7th harmonic filters. The filter rating is in the range of 25–50% of the TCR size.STATCOMs with PWM operation have their major harmonic generation at higher frequencies. The major contributions are at odd multiples of the PWM switch frequency; at even multiples the levels are lower. The harmonic generation decays with increasing frequency. STATCOMs might also generate harmonics in the same spectra as the conventional SVCs. The magnitudes depend on converter topology and the modulation and switching frequency used. In most cases STATCOMs as well as SVCs require harmonic filters.IX. FOOTPRINTMore and more frequently the footprint available for prospective STATCOMs or SVCs is restricted. The trend is, as in many other fields, more capacity on less space. Requirements for extremely tight designs, however, result in higher costs. In general the footprint issue seems not to hinder the utilization of STATCOMs or SVCs, but occasionally, STATCOM has been preferred based on anticipated smaller footprint.When comparing SVCs with STATCOMs, it is tempting to assume that the latter will fit within a much smaller footprint, as the passive reactive elements (air core reactors and high voltage capacitor banks) are “replaced” with semiconductor assemblies. In the authors’ opin ion, this assumption however remains to be practically proved. The main reason for this is that the voltage sourced converter concepts applied in STATCOMs to date have been built with several (even as many as eight) inverter bridges in parallel. This design philosophy implies many current paths, high fault currents and complex magnetic interfaces between the converters and the grid. All in all, not all STATCOMs come out as downsized compared to SVCs. Also the higher losses in the STATCOM will require substantially larger cooling equipment. However, as the STATCOM technology evolves, including the use of very compact inverter assemblies with series connected semiconductor devices, and with pulse width modulation, there is a definite potential for downsizing.In the case of SVCs, the industry has a long product development where, when necessary, measures have been taken to downsize the installation. Such measures include elevated design of apparatuses, stacking of components (reactors and capacitors), vertical orientation of busbars and use of non-magnetic materialin nearby structures. In a few extreme cases iron core reactors have been utilized in order to allow installation in very tight premises. In addition the development of much higher power density in high power thyristors and capacitors contributes to physically smaller SVCs.X. LIFE CYCLE OR EVALUATED COSTSIt is the authors’ experience that the investment cost of SVCs is today substantially lower than of comparable STATCOMs. As STATCOMs provides improved performance, it will be the choice in the cases where this can be justified, such as flicker compensation at large electrical arc furnaces or in combination with active power transfer (back-to-back DC schemes). The two different concepts cannot be compared on a subsystem basis but it is clear that the cost of the turn-off semiconductor devices used in VSC schemes must come down significantly for the overall cost to favor the STATCOM. In other industries using high power semiconductors, like electrical traction and drives, the mainstream transition to VSC technology is since long completed and it is reasonable to believe that transmission applications, benefiting from traction and drive developments, will follow. Although the semiconductor volumes in these fields are relatively small, there is potential for the cost of STATCOMs to come down.Apart from the losses, the life cycle cost for STATCOM and SVCs will be driven by the efforts required for operation and maintenance. Both technologies can be considered maintenance free—only 1–2 man-days of maintenance with a minimum of equipment is expected as an annual average. The maintenance is primarily needed for auxiliary systems such as the converter cooling and building systems. In all, the difference in the cost for these efforts, when comparing STATCOM and SVC, will be negligible.XI. LOSSESThe primary losses in SVCs are in the “step-down” transformers, the thyristor controlled air core reactors and the thyristor valves. For STATCOMs the losses in the converter bridges dominate. For both technologies the long-term losses will depend on the specific operation of each installation. The evaluation of investments in transmission has also increasingly included the costs during the entire life cycle, not only the initial investment. Losses will then be increasingly important. With a typical evaluation at $3000/kW (based on 30 years), and additional average evaluated losses of say 300 kW (compared to an SVC), theadditional burden on the STATCOM is significant. The evaluated losses at full output will contribute significantly to this, but with less weight on these the difference will be much smaller. Here the evolution does not help the STATCOM as its adequate performance is assumed to be achieved with high frequency PWM, implying that the losses will be quite high even at small reactive power output.We expect most utilities to operate their facilities close to zero Mvar output, in order to have SVCs or STATCOMs available for dynamic voltage support. In these cases both technologies will operate with well below 0.5% losses (based on “step-down” transformer rating). However the losses will typically increase quite rapidly should the operating point be offset from zero. This is valid for both SVCs and STATCOMs. SVCs will frequently operate with both switched capacitors and controlled reactors at the same time, while converter losses of STATCOMs will increase rapidly with output current. The losses of STATCOMs at rated output will be higher than for comparable SVCs.XII. CONCLUSIONSWe have examined the performance of SVCs and STATCOMs in electric power systems. Based on the analytical and simulation studies, the impact of SVCs and STATCOMs on the studied power system is presented. It was shown that both devices significantly improve the transient voltage behavior of power systems. Though SVCs and STATCOMs work on different principles, their impact on increasing power system transmission capacity can be comparable. Specifically, we describe “ enhanced” SVCs with voltag e recovery performance similar to STATCOMs. Other issues such as losses, footprint, harmonics, etc., must be examined for each scenario for an optimum investment.SVC与STATCOM在电力系统中应用的效益摘要：提出了对电力系统中SVC和STATCOM的性能检测。
SVC、TCSC控制器间交互影响及其协调控制的研究的开题报告
SVC、TCSC控制器间交互影响及其协调控制的研究的开题报告一、研究背景分析电力系统作为现代社会中不可或缺的基础设施，其运行负责供给全社会电力能量，同时也直接影响着社会经济的发展。
电力系统作为一个复杂的动态系统，其稳定性、安全性等方面对电力系统的运行稳定起着至关重要的作用。
因此，为了保障电力系统的稳定运行，电力系统的控制和优化问题广受关注和研究，其中包括故障穿越能力、小扰动稳定性等方面。
而在电力系统中，由于电力网络的负荷和电源之间的失衡，导致电网中出现了因为供需不平衡而产生的各种电压和功率降低等问题，从而使得电力系统的稳定性出现问题，而导致供电的中断，这对整个社会经济的稳定都会造成非常不利的影响。
斯文森电厂控制器（SVC）和串联补偿控制器（TCSC）作为电力系统中常用的控制手段，在控制电力系统中扮演着十分重要的角色。
然而，在实际应用过程中，SVC和TCSC控制器间的交互和协调问题却经常被忽略或者存在不足之处。
当系统中出现故障时，SVC和TCSC控制器的交互作用会影响系统的稳定，这就需要对SVC和TCSC之间的交互影响进行研究，并提出相应的控制协调方法，实现控制器间协调作业，从而增加电力系统的稳定性。
二、研究内容和研究思路本文拟以SVC和TCSC控制器的交互影响及其协调控制为研究对象，对SVC和TCSC控制器之间的交互作用进行分析与探究，掌握SVC和TCSC控制器的基本工作原理及其控制策略，并探讨其在电力系统中的控制方法和应用前景，描绘出SVC和TCSC控制器在电力系统中的优势和不足之处。
此外，还将研究SVC和TCSC控制器间的协调控制方案，通过控制器间的协调作业，提高电力系统的稳定性和控制精度，增强系统的控制效果。
三、研究目标和意义本文的目标是掌握SVC和TCSC控制器的基本工作原理及其控制策略，深入了解SVC和TCSC控制器在电力系统中的应用与发展前景，分析其在电力系统中的优势和不足之处。
此外，我们还将进一步探讨SVC 和TCSC控制器的协调作业方法，提高电力系统的稳定性和控制精度，增强系统的控制效果。
statcom的直接控制策略与仿真-修改
s t a t c o m的直接控制策略与仿真-修改(总4页)--本页仅作为文档封面，使用时请直接删除即可----内页可以根据需求调整合适字体及大小--ip-iq算法在直接电流控制的STATCOM中的应用马立新，马天顺（上海理工大学光电信息与计算机工程学院，上海200093）摘要：为了提高静止无功补偿器（STATCOM）向电力系统输送无功功率的实时性和精确性，提出了一种STATCOM的直接电流控制策略，从无功电流的检测办法、控制方式等方面对STATCOM的整个工作流程进行了设计。
采用了三角波控制策略和瞬时无功功率理论中的ip-iq电流检测方法，提高系统响应速度。
在此基础上，利用MATLAB搭建STATCOM仿真模型，并对实验结果进行了详细分析，验证了直接电流控制的STATCOM的可行性和有效性。
关键词：静止无功补偿器（STATCOM）；瞬时无功理论；直接电流控制；MATLAB仿真中图分类号：TM76 文献标识码：APQ Algorithm In The Application Of Direct Current Control Of STATCOM MA Li-xin ，MA Tian-shun(Department of Electrical Engineering School of Optical-Electrical and Computer Engineering，University of Shanghai for Science &Technology，Shanghai，200093，China)Abstract:To improve the real-time performance and accuracy of the STATCOM,a strategy of STATTCOM based on direct current control is proposed,The whole work process of the STATCOM has been designed from the aspects of the reactive current detection method and the control triangle wave control strategy and the ip-iq current detection method of instantaneous reactive power theory have been adopted to improve the response speed of the the simulink of MATLAB to build the model of STATCOM，and a detailed analysis of the simulation result is presented,the feasibility and effectiveness of this method is verified.Key words:STATCOM；instantaneous reactive power theory；direct current control；Matlab/Simulink0引言随着工业生产过程的迅速发展，电网中的功率需求发生急剧变化，特别是冲击性负载日益增多（如大型轧钢机、电气化机车、功率变流装置等）。
STATCOM与SVC的性能比较与应用分析
第 ４期
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０ 引 言
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SVC与STATCOM在大容量输电通道上的应用比较
SVC与STATCOM在大容量输电通道上的应用比较丁理杰;杜新伟;周惟婧【摘要】静止无功补偿器( SVC) 和静止同步补偿器( STATCOM) 都是无功补偿的重要装置,在故障下的电压支撑、提高暂态稳定极限、阻尼功率振荡等方面对两者进行分析比较.仿真指出在输电通道上安装大容量无功补偿装置,单个节点上安装SVC和STATCOM对维持节点电压的能力一般,STATCOM好于SVC;在提高暂稳极限方面,STATCOM的效果好于SVC;在增强系统阻尼效果上,同容量的STATCOM明显优于SVC,同调节范围时两者阻尼控制效果基本一致;STATCOM响应速度高于SVC,但响应速度对控制效果影响不大.【期刊名称】《电力系统保护与控制》【年(卷),期】2010(038)024【总页数】6页(P77-81,87)【关键词】SVC;STATCOM;电压支撑;稳定极限;阻尼控制【作者】丁理杰;杜新伟;周惟婧【作者单位】四川电力科学研究院,四川,成都,610054;四川电力科学研究院,四川,成都,610054;四川电力科学研究院,四川,成都,610054【正文语种】中文【中图分类】TM710 引言静止无功补偿器(Static Var Compensator，SVC)和静止同步补偿器(STATic synchronous COMpensator，STATCOM)采用电力电子开关器件，能够快速调节注入系统的无功电流。
SVC 是目前应用较普遍的无功补偿装置，技术比较成熟，通过控制晶闸管的开通来改变阻抗特性，从而提供大小不等的无功功率。
而STATCOM是最近发展的新型无功补偿装置，通过控制可关断器件的通断来向系统提供无功[1]。
随着FACTS技术的广泛应用和智能电网的兴起，SVC和STATCOM受到越来越多的关注。
大容量SVC和STATCOM主要应用于输电系统，输电系统对静止型无功补偿装置的主要需求如下[2-3]：1) 故障下的电压支撑；2) 提高静态及暂态稳定极限；3) 阻尼功率振荡。
SVC并列运行协调控制技术
新能源SVC并列运行协调控制技术取得重要突破5月6日，采用新疆电力公司电力科学研究院研发的并行协调控制策略的静止无功补偿装置（SVC）在华电十三间房风电场完成测试验证并投入运行，标志着新疆电科院在SVC并列运行协调控制技术方面取得了重要突破。
随着清洁能源的快速发展，大量的SVC装置投入电网运行。
在系统扰动时，SVC装置可以连续、快速的进行无功调节，维持系统运行电压，防止大规模甩负荷和电网电压崩溃事故的发生。
当前并列运行的SVC主要通过增加协调控制装置来实时跟踪电压，实现动态调节。
但实际上当系统电压波动时，SVC协调控制系统响应时间慢，协调性、可靠性和稳定性能差，严重影响SVC装置功能发挥，制约了大规模风电发展。
针对这一现实问题，电科院创造性的把发电厂并列运行机组的调差理论应用到了并列运行的SVC中。
通过在ADPSS机电、电磁混合仿真系统反复试验论证，解决了SVC的调差系数设定等技术难题，在新疆电网全过程数字仿真中心完成动模实验后，于5月6日在华电十三间房风电场完成现场测试验证。
此项技术的突破改变了以往多套SVC仅能依靠另外配置的协调控制系统才能并列运行的局面，提高了新能源电厂并列运行SVC装置协调控制的快速性、可靠性和稳定性，减少了新能源电厂的投资，大幅提升了电网稳定运行水平。
该技术的推广应用，为大规模新能源并网提供了技术保障，将有效提高风电消纳和输送能力，促进绿色能源
发展。
考虑系统运行状态转变的变电站内STATCOM与V QC协调控制研究
考虑系统运行状态转变的变电站内STATCOM与V QC协调控制研究辛拓;韩文;罗滇生;杨银国;张勇;李帅虎【期刊名称】《广东电力》【年(卷),期】2014(000)001【摘要】针对传统变电站电压无功控制(voltage quality control,VQC)存在变压器分接头和电容器组投切频繁以及电容器投切对系统电压造成一定的冲击等问题,将动态无功补偿源---静止同步补偿器(static synchronous com-pensator,STATCOM)加入变电站电压无功调节控制中。
提出基于本地信息的系统状态辨识方法,实现考虑系统运行状态转变的变电站内 STATCOM 与 VQC 协调控制策略,协调有载调压变压器分接头、电容器组与STATCOM的运行。
并利用BPA 仿真软件对此策略下STATCOM装置在变电站的应用效果进行研究。
仿真结果表明：STATCOM与 VQC协调配合对改善变电站稳态、暂态运行均有明显效果,能有效减少变压器分接头和电容器的投切次数,2台主变压器均配置STATCOM的效果要好于1台主变压器配置STATCOM的情况。
%Aiming at problems of transformer tapping point in voltage quality control,frequent switch of capacitor bank and certain impact on system voltage by capacitor bank,this paper discusses join-in of static synchronous compensator in voltage quality control for substation.It proposes a discrimination method for system state based on local information in order to re-alize coordinated control strategy for STATCOM and VQC in substation and coordinate operation of tapping point of the on-load tap changingtransformer,capacitor bank and STATCOM.By using BPA simulation software,it studies application ef-fectiveness of STATCOM device in substation.The simulation result indicates coordination of STATCOM and VQC is of ob-vious effectiveness for improving steady state and transient operation of the substation and decreasing switch times of tapping point of the transformer and capacitor.In addition,it proves better effectiveness of arranging STATCOM for two main transformers than only arranging STATCOM for one main transformer.【总页数】7页(P30-36)【作者】辛拓;韩文;罗滇生;杨银国;张勇;李帅虎【作者单位】广东电网电力调度控制中心，广东广州 510600;广州智光电气股份有限公司，广东广州 510760;湖南大学电气与信息工程学院，湖南长沙 410082;广东电网电力调度控制中心，广东广州 510600;广州智光电气股份有限公司，广东广州 510760;湖南大学电气与信息工程学院，湖南长沙 410082【正文语种】中文【中图分类】TM761【相关文献】1.一种考虑变电站内部的电力系统可靠性分析 [J], 陈晨;刘俊勇;刘友波;蒋长江;苟竞;刘若凡2.变电站VQC协调控制研究 [J], 陈蔼莉3.变电站VQC协调控制研究 [J], 陈蔼莉4.AVC与变电VQC分层协调控制研究 [J], 覃飞龙;牛秋野;张青5.考虑机组运行状态的海上风电场无功协调控制 [J], 张祥文; 曲春辉; 孔爱良; 袁晓玲; 钱宸因版权原因，仅展示原文概要，查看原文内容请购买。
岑华蒙毕业设计外文翻译-SVC与STATCOM在电力系统中应用的效益
广西科技大学毕业设计外文翻译院别电气与信息工程学院专业电气工程与自动化班级电气101班学号201000307027姓名岑华蒙指导教师周晓华2013年12月28日Benefits of SVC and STATCOM for ElectricUtility ApplicationAbstract-- Examination of the behavior of SVCs and STATCOMs in electric power systems is presented。
The paper is based on analytical and simulation analysis，and conclusions can be used as power industry guidelines.We explain the principle structures of SVCs and STATCOMs, the models for dynamic studies, and the impact of these devices on steady state voltage and transient voltage stability. Sensitivity analysis is provided which shows the impact of SVCs and STATCOMs with regard to network strength。
Harmonic issues，space requirements，and price discussions are also briefly addressed.Index Terms—Dynamic Compensators, SVC，STATCOM, Short Circuit Capacity，Gain Sensitivity, Short Term V oltage Stability，HarmonicsI. INTRODUCTIONSHUNT-connected static var compensators (SVCs）are used extensively to control the AC voltage in transmission networks. Power electronic equipment，such as the thyristor controlled reactor （TCR）and the thyristor switched capacitor (TSC）have gained a significant market，primarily because of well-proven robustness to supply dynamic reactive power with fast response time and with low maintenance.With the advent of high power gate turn—off thyristors and transistor devices （GTO, IGBT，…）a new generation of power electronic equipment, STATCOM, shows great promise for application in power systems ［3，4]。
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SVC 与STATCOM 联合运行协调控制设计与仿真陈 栋,涂春鸣,罗 安,盘宏斌,彭双剑(湖南大学电气与信息工程学院,湖南省长沙市410082)摘要:针对静止无功补偿器(SVC )装置无法抑制电压闪变的缺点,提出了一种新型SVC 与静止同步补偿器(STA TCOM )构成的混杂装置以及基于模糊预测的联合运行方案,即利用小容量STA TCOM 抑制闪变配合大容量SVC 补偿无功。
对于抑制电压不平衡问题,探索了SVC 分相控制的实现方法和效果。
对含有混杂装置的单机无穷大系统的仿真结果验证了协调控制策略的有效性以及不平衡控制方法的正确性。
关键词:静止无功补偿器(SVC );静止同步补偿器(STA TCOM );协调运行;闪变抑制;无功补偿;模糊预测;三相电压不平衡中图分类号:TM712收稿日期:2008205209;修回日期:2008207214。
国家高技术研究发展计划(863计划)资助项目(2004AA001032)。
0 引言随着电网技术的发展和用户对电能质量要求的不断提高,传统的开关电容器等无功调节手段由于技术落后、响应缓慢、连续可控性差等原因正在逐步退出电力市场。
新型电力电子技术———灵活交流输电系统(FAC TS )技术通过对交流电的无功(电压)、电抗和相角的有效控制,能有效提高交流系统的电能质量和系统稳定性,成为代替传统控制手段的重要技术改革措施,获得电力界的广泛关注。
本文所研究的静止无功补偿器(SVC )和静止同步补偿器(STA TCOM )正是FACTS 家族已获得工业应用的最重要的2种设备[1]。
目前,SVC 作为解决电压稳定和电压崩溃问题的最有效措施之一,不仅可以实现电网的调相和调压,降损节能,还可以提高线路的输送能力,已在世界范围内获得广泛应用。
国内对SVC 的研究与应用始于20世纪70年代末,至今已积累了较多的运行经验,其制造技术已相当成熟,在钢铁企业中也有较多的应用[2]。
然而,由于其自身的技术特点(响应速度慢、谐波含量高),对诸如电压闪变等电压瞬时质量问题“力不从心”的弱点日益突出。
STA TCOM 的硬件系统采用了绝缘栅双极晶体管(IG B T )、门极可关断晶闸管(GTO )等可迅速关断的器件,软件系统采用了瞬时无功算法,响应时间被缩短在10ms 以内,从而在抑制电压闪变方面效果比较突出[3],根据ABB 公司的资料,采用IG B T 作为换流器件组成的STA TCOM 可使电压闪变降低约3/4。
三菱公司在美国安装的第1台5MVA/4.16kV D 2STA TCOM 就是用于抑制附近废铁再生厂的电压闪变。
由于成本昂贵,控制复杂,STA TCOM 的推广较为困难,而且对于抑制三相不平衡,暂态过程中容易过流,经常出现“要么处于封锁状态,要么只能以小容量工作”[4]的情况,不对称控制方法[527]大多仍处于实验室试验阶段,未能实际应用。
因此,单独运行时为了防止其遭受损害,不得不使STA TCOM 停止工作甚至退出系统[8]。
文献[9]研究了人工投切电容器与STA TCOM 的联合运行策略,其目的是增大电压降落时的动态无功备用,然而,由于采用人工投切电容器,装置的实时控制性能不佳,难以与STA TCOM 有效协调。
此外,由于固定电容器或电抗器通常始终在系统中运行,在稳态情况下消耗STA TCOM 的感性无功容量,性价比不高。
为解决上述问题,本文设计了SVC 进行无功补偿结合适当小容量STA TCOM 抑制电压闪变的运行方案。
这种运行策略针对2种装置的特点,扬长避短,既发挥了STA TCOM 抑制电压闪变的技术优势,又避免了大容量STA TCOM 造价昂贵的缺点,是对现有SVC 工程进行改造的可行性措施。
针对SVC 与STA TCOM 联合运行时的协调问题,提出了基于模糊预测的控制方法,使得混杂装置具有较高的性价比,充分发挥STA TCOM 的技术优势。
针对混杂装置在三相电压不平衡条件下的运行问题,提出利用SVC 分相控制的方法,避免了STA TCOM 在不平衡条件下运行的风险,具有较高—67—第32卷 第19期2008年10月10日Vol.32 No.19Oct.10,2008的实用价值。
最后通过仿真验证了控制策略的正确性以及抑制电压不平衡的效果。
1 混杂装置系统结构和工作原理为研究SVC 与STA TCOM 混杂装置的运行策略,建立如图1所示的单机—无穷大仿真系统。
仿真详细参数见附录A 。
STA TCOM 和SVC 均三相并联挂接于电网,安装在10kV 母线上。
STA TCOM 组成包括一个直流电容器、两电平三相桥逆变器(采用GTO 器件)、连接电抗器。
SVC 组成包括2组三角形连接晶闸管投切电容器(TSC )和1组晶闸管控制电抗器(TCR )。
10kV 母线经升压变压器接入无穷大系统,即110kV 母线。
图1 仿真模型系统结构Fig.1 Conf iguration of simulation model with hybridequipment系统工作原理如图2所示,SVC 等效为一个可变电纳,STA TCOM 等效为一个无功电流源。
它们都根据负荷无功功率Q 的变化,通过调节晶闸管触发角和逆变器脉宽调制(PWM )输入占空比,使得混杂装置输出无功功率补偿负荷吸收的无功功率,从而维持110kV 母线电压U 1的稳定。
U 1表达式为:U 1=nU 2+QU 2-B SVC U 2+I CR X T 2+PX T U 2(1)图2 系统原理示意图Fig.2 Schem atic diagram of system2 SVC 与STATCOM 的协调控制分析SVC 与STA TCOM 两者协调运行的主要原因在于SVC 与STA TCOM 在动态特性上有差异,动态响应时间也不同(SVC 的开环响应时间常数约为2个周期,STA TCOM 的响应时间常数一般约为0.25个周期),它们的控制目标之间也会发生相互影响,从而使两者的动态特性发生相互影响。
当需要较大的无功电流时,STA TCOM 会率先做出响应,进入极限输出状态,而SVC 还未开始动作。
若没有进行协调,STA TCOM 会保持这种状态,导致小容量STA TCOM 没有充足的无功备用,限制其在抑制电压波动和闪变方面的调节能力;其次,两者输出相互影响,延长了系统的调节时间;再次,如果两者的动态特性设计不合理,稳态输出时STA TCOM 可能会部分抵消SVC 的输出,形成无功环流,变相降低了STA TCOM 的容量。
因此需要对SVC 与STA TCOM 的同步运行进行协调控制。
3 控制策略分析3.1 协调控制策略为了解决以上问题,最大限度地发挥STA TCOM 抑制电压闪变的能力,设计了一个基于模糊预测的协调控制方案,如图3所示。
图3 混杂装置的协调控制策略框图Fig.3 Diagram of coordinated control strategy forhybrid equipment模糊预测控制的控制目标是电压缺损程度的差值ΔU ε(k )与STA TCOM 无功功率输出引起的电压的差值Δu ST (k +1)相等,即STA TCOM 能够跟踪并抑制电压闪变。
输出量为SVC 的无功功率变化值ΔQ SVC (k )。
STA TCOM 控制策略如下:正常情况下为了避免在电压有效值变化较小时出现不必要的补偿,启动补偿时可先将缺损电压U ε与STA TCOM 的补偿电压最大值U maxST 进行比较,决定是否进行解耦控制还是进入极限输出状态以提供电压支撑;对于三相不平衡故障,进入限幅输出状态,防止过流或过压情况的发生。
SVC 控制策略如下:根据模糊预测控制得到的控制参数,调整SVC 控制器的输入参数,以保证—77—・研制与开发・ 陈 栋,等 SVC 与STA TCOM 联合运行协调控制设计与仿真STA TCOM 跟踪电压波动,抑制闪变和波动,模糊预测的实现原理如图4所示;对于三相不平衡故障,则进行分相控制。
图4 模糊预测的原理框图Fig.4 B lock diagram of predictive fuzzy control加入模糊预测控制模型是为了提高SVC 的控制精度和与STA TCOM 的协调能力。
由一个3层反向传播(BP )网络实现反映STA TCOM 输出无功功率与接入点电压关系的预测模型,B P 神经网络训练方法参考文献[10],这里不再详述。
由图4,控制目标评价模块根据预测模型的输出Δu ST (k +1)与ΔU ε(k )的跟踪关系,对SVC 模糊控制器的输入r (k )进行调整,从而实现与SVC 的协调控制。
调整原则是|Δu ST (k +1)|<|ΔU ε(k )|,则增大|r (k )|,反之则减小。
很显然,预测精度会影响控制量的输出,但考虑到模糊控制的容错性,因此问题不大。
SVC 模糊控制器模糊变量的隶属度函数和模糊控制规则见附录B 。
解模糊采用加权平均法:ΔQ SVC =∑7i =1Q iμ(Q i)∑7i =1μ(Q i)(2)式中:ΔQ SVC 为解模糊化的控制量输出值;Q i 为控制量第i 个划分的典型值;μ(Q i )为最终控制量对第i 个划分的隶属度。
3.2 不对称运行策略电网电压不平衡对STA TCOM 的运行影响主要体现在2个方面:一方面,当电网电压不平衡时,STA TCOM 逆变器直流侧电容器两端电压会产生2倍频的电压波动,导致STA TCOM 逆变器的交流侧输出3次谐波电压和谐波电流,从而影响STA TCOM 的输出性能[11];另一方面,当电网电压不平衡时,电网电压中的负序分量对于采用对称控制的STA TCOM 来说相当于短路,会导致很大的负序电流流过STA TCOM ,严重影响装置的安全运行。
而采用不对称控制技术存在如下问题:①计算复杂,特别是当涉及正、负序2个同步坐标变换时;②谐波含量增大,例如分相控制将在装置的电压与电流中产生3次谐波。
本文考虑到SVC 与STA TCOM 联合运行的特点,利用SVC 分相控制方法抑制三相不平衡,快速改善STA TCOM 的运行环境。
该方案实现容易,可行性高,可靠性也可以保证。
实现方法见附录C 。
4 仿真分析建立混杂装置的实施步骤通常是在已有的SVC 基础上加装STA TCOM ,因此,本文首先研究一个独立SVC 系统联合一个独立STA TCOM 系统的动态性能,仿真详细参数见附录A 。
考虑到工程实际中两者所使用的控制方法仍然是常规比例积分(PI )控制,因此两者的控制器选取了2种比较典型的控制结构,如图5所示。
图5 SVC 和STATCOM 的控制框图Fig.5 Controller diagrams of SVC and STATCOMSVC 控制器[12]通过改变X s 的大小,调整其电压—电流特性。