外文翻译文献

Control System for a PWM-Based STATCOM Pablo García-González and Aurelio García-Cerrada,Member,IEEE

Abstract—The always-increasing switching frequency of modern solid-state power switches,together with the application of multi-converter topologies,make it possible to use Pulse Width Modulation(PWM)in high power applications of STATCOMs (STATic Synchronous COMpensators).

This paper investigates the control system for a PWM-based STATCOM.First of all,a discrete-time model of the STATCOM is derived to take into account the discrete-time implementation of the controller.Secondly,the control algorithm is detailed.It en-sures decoupled control of the real and reactive power exchanged between the power converter and the electric-energy system.This is necessary to control the d.c.capacitor voltage during transients of the exchanged reactive power.Finally,the control of the capacitor voltage is explained in detail.The controller is tailored to keep the capacitor voltage almost constant in spite of the fast control of the reactive power.This helps to reduce the capacitor size significantly.The main contributions will be illustrated using a15kV A laboratory prototype.

Index Terms—Pulse width modulated power converters,reactive power control,static var vompensators.

I.I NTRODUCTION

R EACTIVE power compensation is an important issue in the control of electric energy systems.Reactive power in-creases the transmission system losses,reduces the power trans-mission capability of transmission lines and can cause large amplitude variations in the receiving-end voltage.Moreover, rapid changes of the reactive power consumption of loads can cause voltage-amplitude oscillations(for instance,arc furnaces cause flicker).In addition,voltage variations can change the real power demand in the electric system,resulting in power oscil-lations[1].

Reactive power compensation has been traditionally handled with devices such as:Thyristor-Controlled Reactors(TCR)and Thyristor-Switched Capacitors[2].However,if high dynamic performance is required,reactive power compensation must be handled with faster devices such as the STATCOM.Moreover, the reactive power compensation of TCRs and TSCs depend on the Point-of-Common-Coupling(PCC)voltage while the com-pensation of the STATCOM is independent of that voltage[3]. Previous research efforts focus mainly on the control and per-formance of STATCOMs based on square wave multipulse-con-verters[4]–[6]and[3].However,the increasing switching fre-quency of modern solid-state power switches,together with the application of multi-converter topologies make reliable to use PWM in high-power applications[7]–[9].

Manuscript received March31,1999;revised February23,2000.

The authors are with E.T.S.de Ingeniería(ICAI),Universidad Pontificia Comillas de Madrid,c/Alberto Aguilera23,28015Madrid,Spain(e-mail: pablo@dea.ixai.upco.es;aurelio@iit.upco.es).

Publisher Item Identifier S

0885-8977(00)10318-8.

Fig.1.Configuration of a STATCOM(left)and simplified model(right).p and

q are the instantaneous real and reactive power exchanged by the STATCOM in

PCC.

p is the power consumed in the filter+transformer inductance.p are the real and instantaneous

reactive power exchanged by the converter with the a.c.system.

This paper investigates in detail the control system for a

PWM-based STATCOM.The controller fundamentals were

already presented in[4]giving neither implementation details

nor results.A few years later,reference[5]shows good

transient performance of the reactive-power controller of a

STATCOM but it also shows undesirable variations of the

d.c.-link voltag

e.Here,implementation details and validation

in a prototype are the main objectives.It was soon clear that

the d.c-link voltage control deserved more attention than that

paid in the literature.First of all,the STATCOM configuration

and an equivalent linear model are presented.Secondly,the

control system is explained in detail taking into account its dis-

crete-time implementation.The controller is tailored to achieve

fast control of the instantaneous reactive power exchanged by

the STATCOM and to maintain the converter d.c.-link voltage

constant.It is shown that decoupled real and reactive power

control is necessary.Finally,a prototype is described and the

main contributions are illustrated with experimental results.

Good transient performance of the reactive-power controller is

shown together with almost-constant d.c.-link voltage during

transients.

II.S YSTEM C ONFIGURATION AND M ODELING

Fig.1depicts a STATCOM applied to an electric energy

system.Its components are the shunt converter

(

)and the connection filter.The shunt converter can be modeled as a controllable voltage source

(

).All other variables are explained in the figure caption for clarity and

will be referred later.Therefore,the STATCOM behaves as

a current controller.Note that the energy exchanged by the

STATCOM is limited by the capacitor stored energy.Hence,

only reactive power can be exchanged in steady state.

0885–8977/00$10.00?2000IEEE

The instantaneous three-phase variables of the STATCOM can be described in state-space from

by

and

is the angular speed of the reference frame

and

and

(2)

The Park’s transformation selected here keeps invariant the instantaneous power expression.In addition,

since

-axis lays

on the space vector of the connection point voltage

(

is the angular speed of the space

vector

is equal to the system frequency in rad/s.As shown

later,

)and the instanta-neous reactive power

(

(4)

Therefore,

are proportional to and ,respectively and the control of the power injected into the electric energy system reduces to the control of and .The control inputs

in

(1)

can be set arbitrarily

since can always be

measured

where

(5)

and

–

and

.Since the controller must be implemented in a micropro-cessor,it is useful to derive a discrete-time version of the model in (1).It is going to be assumed

that

(7)(8)

and

is not strictly constant in practice,the discrete-time

model is only an approximation.However,variation only of the

modulus

of

and the model will be correct.Variations

of

due to system har-monics must be filtered in the measurement system.These is-sues have not been a problem in the prototype tested here or in the previous simulation work [13].

Equation (6)gives the value of the state variables

()at time

instant

.

However,the controller will need most of the sampling interval to calculate the required system input from reference values and measurements.Therefore,it is reasonable,to assume that the system input at

time

.The

discrete-time model for (1)must be written

as:

(9)

As shown in Appendix A,the one-sampling-interval delay reflected in (9),can be easily taken into account when designing the controller.The discrete-time model (9)takes into account the effects of the digital performance of the control algorithms.As shown in (7)–(9)there are cross-coupling terms

between axis variables in the state

()matrices.Coupling in the input matrix cannot be seen in the continuous-time model and it is inherent to the discretization process.However,this problem may be easily overcome by arranging the system as

follows:

(10)

where

affects only through a simple

first-order transfer function

while affects only.Hence,de-coupled control of and is now very simple

using

and as control inputs obtained with independent control laws.The converter output

voltages

and must be calculated from the

required values

of

and using (11)

because

and integral control

laws have been applied to ensure zero tracking error in steady state and to increase the robustness of the closed-loop system.The design of the control laws can be reduced to the design of two state feedback proportional control laws using the aug-mented systems derived in Appendix A [see (18)].

Note that perfect decoupling is only possible

if

and are known [see (11)].These variables are not available

at

instant

.

Each prediction is done with the previous measurements and the control inputs.Summarizing,

?The reference value

for

is given by the d.c.-link voltage

controller.

Fig.3.Block diagram of the feedforward–feedback control system for the converter d.c.-link voltage.

?

The STATCOM controllers give the required

values

of

and [see (19)of Appendix A].?The required converter output voltages are calculated from (11),using the current prediction in (12)and (13).B.Control of the Capacitor Voltage

If capacitor-voltage variations are bounded the converter output voltage can behave as an independent voltage source.Capacitor-voltage variations can be naturally kept small in-creasing the capacitor value but this makes the device more expensive.Adequate transient performance of the voltage controller should make it possible to minimize the capacitor value but this problem has not been taken into account in the literature.

Fig.3depicts the capacitor-voltage controller.The simplest version is the one drawn with a solid line and it is the one proposed in the literature

[4].

models the real-power consumption of the filter (see Ap-pendix B).The filter power consumption consist of a)the losses in the filter resistance

(

in Fig.1)varies.

Therefore,

system losses.However,when there is a change in

the instantaneous reactive power reference

(

in

steady state due to the feedback controller.

The performance of the closed-loop controller can be im-proved if the

perturbation

estimations

of

(

).Transfer

functions

can be easily obtained with the model of the STATCOM and

the control law developed in Section III.The nonlinear func-tion

(-

and

and

and

and

in Fig.1)has been built with three

single-phase transformers DY connected (380/220V ,2.9kV A each transformer).The primary is connected to the converter and the secondary to the electric system.5)The filter has been built with three inductances connected between the secondary of the transformer and the point of coupling to the electric energy system.The inductance is 39mH with

1.25

follows its reference closely with no error in

steady state

while

within

the

(1)]disturbance

estimation and without [V

V

A 15kV A prototype has been used to validate the system model and the controller design.The converter PWM has been implemented with a reasonably-low switching frequency to have realistic results.The experimental results show that

the overall-system model

(converter

controller)describes the prototype performance accurately.

The converter d.c.-link capacitor can be kept small if fast capacitor-voltage control is achieved.The proposed controller uses a model for the connection filter power consumption to en-sure fast d.c.-link voltage control.A closed-loop controller is also proposed to guaranty long-term voltage tracking in spite of modeling errors and neglected converter losses.

The paper has dealt with transient performance only.Har-monic injection is now been investigated in the prototype.A PPENDIX A

D ERIV ATION OF TH

E A UGMENTED S YSTEM WITH P

ROPORTIONAL

integral control law is going to be applied

to ensure zero tracking error in steady state and to increase the robustness of the control law.A discrete-time integral control law can be written as

[12]:

is the reference value

and

by

integral

control law of system (9)reduces to the design of the state-feedback control laws for (18)and the reactive power system.

The control law for the real power

(

.Note

that

and

and

,

(24)

Using the Backward Rectangular Rule approximation of the numerical integration [12],the discrete-time model

results,

and

[6]L.Gyugyi,N.G.Hingorani,P.R.Nannery,and N.Tai,“Advanced static

var compensator using gate turn-off thyristors for utility applications,”, Cigre paper23-302,1992.

[7]J.Kuang and B.T.Ooi,“Series connected voltage-source converter mod-

ules for force-commutated svc and dc-transmission,”Trans.on Power Delivery,vol.9,no.2,pp.977–983,1994.

[8] B.Mwinyiwiwa,B.-T.Ooi,and Z.Wolanski,“UPFC using multicon-

verter operated by phase-shifted triangle carrier spwm strategy,”IEEE Trans.on Industry Applications,vol.34,no.3,pp.495–500,May/June 1998.

[9] B.Mwinyiwiwa,Z.Wolanski,and B.-T.Ooi,“Current equalization in

SPWM FACTS controllers at lowest switching rates,”in IEEE Power Electronics Specialists Conference(PESC),vol.1,1997,pp.325–330.

[10]P.C.Krause,Analysis of Electric Machinery.New York,NY:Mc-

Graw-Hill Inc.,1986.

[11]H.Akagi,Y.Kanazawa,and A.Nabae,“Instantaneous reactive power

compensators comprising switching devices without energy storage components,”IEEE Trans.on Industry Applications,vol.IA-20,no.3, pp.625–630,May/June1984.

[12]G.F.Franklin and J.D.Powell,Digital Control of Dinamic Sys-

tems.Reading,MA:Addison-Wesley,1980.

[13] A.García-Cerrada,P.García-González,R.Collantes,T.Gómez,and

J.Anzola,“Comparison of thyristor-controlled reactors and voltage-source inverters for compensation of flicker caused by arc furnaces,”

IEEE Trans.on Power Delivery,2000,to be published.

[14]J.Holtz,“Pulsewidth modulation for electronic power convertion,”Pro-

ceedings of the IEEE,vol.82,no.8,pp.1194–1214,Aug.

1994.Pablo García-González(M.Sc.1992,Unversidad Pontificia Comillas)From Oct.1993to March1995 he was with Valenciana de Cementos where he was a Project Engineer involved in control applications. He is currently working toward his Ph.D.at the Department of Electronics and Control Engineering of Universidad Pontificia Comillas(UPCO).His research interests include power electronics applica-tions in electric energy

systems.

Aurelio García-Cerrada(M.Sc,1986,Univer-sidad Politécnica de Madrid,Spain),(Ph.D.1991 University of Birmingham,UK).He is currently a Member of the Staff of the Electronics and Control Engineering Department and the Inst.de Investi-gación Tecnológica(IIT)at Universidad Pontificia Comillas in Madrid.His research interests include power systems,monitoring and control and power electronics and its applications.

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变电站_外文翻译_外文文献_英文文献_变电站的综合概述

英文翻译 A comprehensive overview of substations Along with the economic development and the modern industry developments of quick rising, the design of the power supply system become more and more completely and system. Because the quickly increase electricity of factories, it also increases seriously to the dependable index of the economic condition, power supply in quantity. Therefore they need the higher and more perfect request to the power supply. Whether Design reasonable, not only affect directly the base investment and circulate the expenses with have the metal depletion in colour metal, but also will reflect the dependable in power supply and the safe in many facts. In a word, it is close with the economic performance and the safety of the people. The substation is an importance part of the electric power system, it is consisted of the electric appliances equipments and the Transmission and the Distribution. It obtains the electric power from the electric power system, through its function of transformation and assign, transport and safety. Then transport the power to every place with safe, dependable, and economical. As an important part of power’s transport and control, the transformer substation must change the mode of the traditional design and control, then can adapt to the modern electric power system, the development of modern industry and the of trend of the society life. Electric power industry is one of the foundations of national industry and national economic development to industry, it is a coal, oil, natural gas, hydropower, nuclear power, wind power and other energy conversion into electrical energy of the secondary energy industry, it for the other departments of the national economy fast and stable development of the provision of adequate power, and its level of development is a reflection of the country's economic development an important indicator of the level. As the power in the industry and the importance of the national economy, electricity transmission and distribution of electric energy used in these areas is an indispensable component.。Therefore, power transmission and distribution is critical. Substation is to enable superior power plant power plants or power after adjustments to the lower load of books is an important part of power transmission. Operation of its functions, the capacity of a direct impact on the size of the lower load power, thereby affecting the industrial production and power consumption.Substation system if a link failure, the system will protect the part of action. May result in power outages and so on, to the production and living a great disadvantage. Therefore, the substation in the electric power system for the protection of electricity reliability,

外文文献翻译助手

五分钟搞定5000字－外文文献翻译 在科研过程中阅读翻译外文文献是一个非常重要的环节，许多领域高水平的文献都是外文文献，借鉴一些外文文献翻译的经验是非常必要的。由于特殊原因我翻译外文文献的机会比较多，慢慢地就发现了外文文献翻译过程中的三大利器：Google“翻译”频道、金山词霸（完整版本）和CNKI“翻译助手"。 具体操作过程如下： 1.先打开金山词霸自动取词功能，然后阅读文献； 2.遇到无法理解的长句时，可以交给Google处理，处理后的结果猛一看，不堪入目，可是经过大脑的再处理后句子的意思基本就明了了； 3.如果通过Google仍然无法理解，感觉就是不同，那肯定是对其中某个“常用单词”理解有误，因为某些单词看似很简单，但是在文献中有特殊的意思，这时就可以通过CNKI的“翻译助手”来查询相关单词的意思，由于CNKI的单词意思都是来源与大量的文献，所以它的吻合率很高。 另外，在翻译过程中最好以“段落”或者“长句”作为翻译的基本单位，这样才不会造成“只见树木，不见森林”的误导。 注： 1、Google翻译：https://www.sodocs.net/doc/6313173711.html,/language_tools google，众所周知，谷歌里面的英文文献和资料还算是比较详实的。我利用它是这样的。一方面可以用它查询英文论文，当然这方面的帖子很多，大家可以搜索，在此不赘述。回到我自己说的翻译上来。下面给大家举个例子来说明如何用吧 比如说“电磁感应透明效应”这个词汇你不知道他怎么翻译， 首先你可以在CNKI里查中文的，根据它们的关键词中英文对照来做，一般比较准确。

在此主要是说在google里怎么知道这个翻译意思。大家应该都有词典吧，按中国人的办法，把一个一个词分着查出来，敲到google里，你的这种翻译一般不太准，当然你需要验证是否准确了，这下看着吧，把你的那支离破碎的翻译在google里搜索，你能看到许多相关的文献或资料，大家都不是笨蛋，看看，也就能找到最精确的翻译了，纯西式的！我就是这么用的。 2、CNKI翻译：https://www.sodocs.net/doc/6313173711.html, CNKI翻译助手，这个网站不需要介绍太多，可能有些人也知道的。主要说说它的有点，你进去看看就能发现：搜索的肯定是专业词汇，而且它翻译结果下面有文章与之对应（因为它是CNKI检索提供的，它的翻译是从文献里抽出来的），很实用的一个网站。估计别的写文章的人不是傻子吧，它们的东西我们可以直接拿来用，当然省事了。网址告诉大家，有兴趣的进去看看，你们就会发现其乐无穷！还是很值得用的。https://www.sodocs.net/doc/6313173711.html, 3、网路版金山词霸（不到1M）：https://www.sodocs.net/doc/6313173711.html,/6946901637944806 翻译时的速度： 这里我谈的是电子版和打印版的翻译速度，按个人翻译速度看，打印版的快些，因为看电子版本一是费眼睛，二是如果我们用电脑，可能还经常时不时玩点游戏，或者整点别的，导致最终SPPEED变慢，再之电脑上一些词典（金山词霸等）在专业翻译方面也不是特别好，所以翻译效果不佳。在此本人建议大家购买清华大学编写的好像是国防工业出版社的那本《英汉科学技术词典》，基本上挺好用。再加上网站如：google CNKI翻译助手，这样我们的翻译速度会提高不少。 具体翻译时的一些技巧（主要是写论文和看论文方面） 大家大概都应预先清楚明白自己专业方向的国内牛人，在这里我强烈建议大家仔

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博物馆 外文翻译 外文文献 英文文献

第一篇： 航空博物馆与航空展示公园 巴特罗米耶杰·基谢列夫斯基 飞翔的概念、场所的精神、老机场的建筑---克拉科夫新航空博物馆理性地吸取了这些元素，并将它们整合到一座建筑当中。Rakowice-Czyzyny机场之前的旧飞机修理库为新建筑的平面和高度设定了模数比例。在此基本形态上进一步发展，如同裁切和折叠一架纸飞机，生成了一座巨大的建筑。其三角形机翼是由混凝土制成，却如同风动螺旋桨一样轻盈。这个机翼宽大通透，向各个方向开敞。它们的形态与组织都是依据内部功能来设计的。机翼部分为3个不平衡的平面，使内外景观在不断变化中形成空间的延续性，并且联系了建筑内的视觉焦点和室外的展览区。 新航空展示公园的设计连接了博物馆的8栋建筑和户外展览区，并与历史体验建立联系。从前的视觉轴线与通道得到尊重，旧的道路得到了完善，朝向飞机场和跑道的空间被限定出来。每栋建筑展示了一个主题或是一段飞行史。建筑周围伸展出巨大的平台，为特殊主题的室外展览提供了空间。博物馆容纳了超过150架飞机、引擎、飞行复制品、成套的技术档案和历史图片。这里的特色收藏是飞机起源开始的各种飞行器，如Jatho1903、Grade1909、莱特兄弟1909年的飞机模型和1911年的鸽式单翼机。 The first passage: Museum for aviation and aviation exhibition park Bartiomiej Kislelewski The idea of flying, the spirit of place, the structure of the historic airfield – the new Museum of Aviation in Krakow takes up these references intellectually and synthesizes them into a building. The old hangars of the former airport Rakowice Czyzyny set the modular scale for the footprint and the height of the new building. Developed from this basic shape, as if cut out and folded like a paper airplane, a large structure has been generated, with triangular wings made of concrete and yet as light as a wind-vane propeller. The wings are generously glazed and open in all directions. Their form and arrangement depend on the interior uses. In the floor plans of the wings, the three offset