ASPECTS OF ANCILLARY SERVICES

7/30/2019 ASPECTS OF ANCILLARY SERVICES

1/8

PROBLEMATICA SERVICIILOR DE SISTEM

ASPECTS OF ANCILLARY SERVICES

Lucian TOMA*, Mircea EREMIA, Constantin BULACUniversity POLITEHNICA of Bucharest

Spl. Independenei, Nr. 313, Sect. 6, 77206, Bucharest, Tel: 021/4029850*E-mail: [email protected]

Rezumat: Sistemele electroenergetice din lumea ntreag trecrintr-un proces de reorganizare ce are ca scop introducerea

competitivitii n scopul minimizrii preului energiei electrice.n acest sens, s-au creat diverse tipuri de piee de energie electricn care diveri participani prezint oferte putere-pre. O problemaparte, nc n dezbatere, o constituie serviciile de sistem care

au ca scop asigurarea parametrilor de calitate a energiei electrice.n lucrare se prezint problematica celor mai importante serviciide sistem att prin felul n care sunt furnizate cti prin costurile

e care le implic. Avnd n vedere modul diferit de asigurare aacestor servicii trebuie proiectate piee de servicii de sistem diferitei n acelai timp gndirea mecanismelor optime de tarifare cares-i mulumeasc att pe furnizori cti pe Operatorul de Sistem,care coordoneaz aceste servicii i care are interesul s leachiziioneze la preul cel mai mic.

Keywords: servicii de sistem, piaa de energie electric,competitivitate

Abstract: The power systems from worldwide undergo to changesof organizing and aim the introducing of competitively in orderto minimize the price of electrical energy. In this respect, severaltypes of electricity markets have been created where different

participants bid for amount-price of electrical energy. A specialproblem that arise, yet to be discussed, is the management of

ancillary services which aim to ensure proper quality of electricalenergy. In this paper some aspects about the most importantancillary services are presented from supplying point of view aswell as the costs involved. Taking into consideration differentways of ensuring these ancillary services, specific markets mustbe designated and in the same time realizing of optimal mechanismsor cost based price markets that would satisfy both suppliers as

well as System Operator, in order to coordinate these servicesand purchase it at the lowest price.

Keywords: ancillary services, electricity market, competition.

1. Introducere

Din dorina utiliz

rii eficiente a surselor

i resurselor

de energie, sistemele electroenergetice sunt supuse unorschimbri de organizare n ceea ce privete structura, prinfaptul c exist mai multe entiti cu destinaii diferite(producere, transport, distribuie, etc.) ct i prin respon-sabilitile pe care le are fiecare. Astfel, prin procesul dederegularizare, s-au format mai multe companii de elec-tricitate avnd funcii independente de producie, transportsau distribuie dari obligaia ndeplinirii parametrilor defiabilitate indicai n normativul PE 013/1994. n acestcontext, Operatorul de Sistem (OS) are obligaia, dupcum se prevede n Directiva 96/92/EC, articolul 7.3, sasigure securitatea, fiabilitatea i eficiena sistemuluienergetic, s supravegheze fluxurile de energie i s

asigure disponibilitatea unor utilizatori de reea n scopulfurnizrii serviciilor de sistem. Odat cu introducerea

pieei de energie electric a aprut, OPeratorul COMercial,cu rolul de a coordona ncheierea aranjamentelor comercialecu energie electric referitoare la cantitile tranzacionatei la pre. Att utilizatorii ct i coordonatorii sistemuluii ndeplinesc responsabilitile n conformitate cu nor-mativele i regulile stabilite de Autoritatea Naional deReglementare a Energiei electrice.

Pentru o funcionare n condiii de siguran att asistemului electroenergetic ct i a consumatorului, trebuiendeplinite standardele de calitate a energiei electrice ianume: ncadrarea frecvenei i a tensiunii n benzile admi-

1. Introduction

From the desire of efficient using energy sources andresources, power systems undergo to different changes oforganizing concerning the structure, by the fact that thereare several entities with different destinations (generation,transmission, distribution, etc.) and through responsibilitiesof each participant. Therefore, through deregularization

process, several electricity companies have been createdhaving independent functions of generation, transmissionor distribution and also the obligation to meet reliabilityrequirements given in normative PE 013/1994. In thiscontext, System Operator (SO) is responsible, as it isindicated in Directive 96/92/EC, article 7.3, to ensure thesecurity, reliability and efficiency of power system, tofollow the power flows and to ensure the availability of

some network users with the purpose of supplying theancillary services. In the same time, by introducingelectricity market it has been also created, COMmercialOPerator, having the responsibility to coordinate commercialagreements of electrical energy related to trade amount of

power and price. Network users as well as systemcoordinators meet their responsibilities according tonormative and rules settled by National RegulatoryAgency of Electrical Energy.

For a safe operation of power system as well asconsumers, it must fulfill normative related to powerquality such as: maintain the frequency and voltage inadmissible limits, continuity of supplying etc. In order to


2/8

The 5th

International Power Systems Conference508

sibile, continuitatea n alimentare etc. Pentru a satisfaceaceste standarde Operatorul de Sistem are obligaia de aasigura urmtoarele servicii de sistem: reglajul frecven-

putere activ, reglajul tensiune-putere reactiv, compensareapierderilor de putere din reeaua de transport, restaurareasistemului la rmnerea total sau parial fr tensiune,managementul congestiilor etc. Asemntor modului decomercializare a energiei electrice, achiziionarea serviciilor

de sistem se face n mod competitiv prin diferite forme depia. De aceea, accesul utilizatorilor la reea trebuie s sefac nediscriminatoriu.

De menionat c, n Romnia, nu exist nc o pia aserviciilor de sistem, prezenta lucrare fiind un punct devedere, bazndu-ne pe experiena altor ri, n ceea ce

privete problematica serviciilor de sistem.

2. Tipuri de piee de energie electric

Avnd n vedere particularitile pe care le prezintfiecare serviciu de sistem a fost necesar organizarea tran-zaciilor pe mai multe tipuri de piee de energie electricn care diveri participani prezint oferte putere pre.

Ofertele obinute de la toate entitile productoare suntintroduse ntr-un program de calcul care simuleaz distri-buia optim de puteri pe baza preurilor fcute i a prog-nozei de sarcin astfel nct se va obine preul marginalde sistem pe perioade de o or pentru ziua urmtoare. Esen-ial este faptul c operatorul pieei structureaz ofertele nordine de la cel mai mic pn la cel mai mare pre ofertat,corelate n acelai timp cu prognoza de sarcin. Licitaiase nchide la un punct n care cererea de energie electric

prognozat este satisfcut prin oferte de producie cumulat.Cel mai mare pre ofertat la care se nchide licitaia deter-min preul de nchidere al pieei. Procedura de stabilire aPreului Marginal de Sistem este prezentat n figura 1. nacelai timp, se stabilete i ordinea de merit, stabilit pe

baza ofertelor putere prei a caracteristicilor tehniceale productorilor, necesar pentru stabilirea ordinei dedispecerizare a grupurilor generatoare.

pre ul depie ei

nchidereal

preulofertat de

generatoare

prognoza cererii

Oferta de energie electric, MW per 1 h

Figura 1 . Stabilirea preului marginal de sistem

Modul de achiziionare a serviciilor de sistem prinlicitare de oferte reprezint un mecanism corect de stabilirea preului att din punctul de vedere al furnizorului ct idin punct de vedere al consumatorului. ns, acest mecanismnu este aplicativ n cazul furnizorii de putere reactiv avndn vedere faptul c reglajul tensiunii este o problem locali se realizeaz cu suport de putere reactiv ct mai aproapede zona cu probleme.

satisfy there those standards, System Operator have theresponsibility to ensure the following ancillary services:active frequency active power control, voltage reactive

power control, power loss compensation in the transmissionnetwork, black-start capability, congestion managementetc. Likewise to electrical energy market, purchasing ofancillary services is made in a competitive way throughdifferent types of markets. Because of that, users

access to the transmission network must be done in anondiscriminatory manner.

It should be mentioned that, in Romania, there is noancillary services market, the present paper being a pointof view, based on experience of other countries, concerningthe problem of ancillary services.

2. Types of electricity markets

Taking into consideration the particularities that involveeach ancillary service was necessary organizing of energytrade on several types of electricity markets where

participants bid for amount-price of energy. The obtained

bids from all the generating entities are introduced into asimulating program to achieve optimal dispatch of supplierin terms of the bid price and load forecasting in order toobtain the system marginal cost on a basis of one hour forthe following day. Essential in the fact that market operatorrank the power bid of participants from lowest to thehighest bidding price, taking into account of load forecast.The auction is ended in a point where the forecasteddemand of energy satisfies the amount of supply. Thehighest price where the auction is ended determines themarket-clearing price. The procedure of establishingSystem Marginal Cost is presented in figure 1. In thesame time, the merit order is established, on the basis of

power price bids and technica l characteristics ofgenerators, necessary to establish the merit order ofgenerator units dispatching.

Market clearingprice

generatorsbids

load forecasting

Electrical energy bid, MW per 1 h

Figure 1. Establishing system marginal cost

The way of purchasing ancillary services throughauction is a fair mechanism manner of establishing the

price form the seller point of view as well as from thebuyer. Instead, this mechanism can not be applied in thecase of reactive power suppliers taking into considerationthe fact that voltage regulation is a local problem beingachieved through reactive power support as close as

possible from the area with voltage problems.


3/8

06-07.11.2003, Timioara, Romania 509

n continuare se prezint principalele tipuri de piee deenergie electric [2].a) Piaa Forward

n cadrul pieelor de energie electric, piaa forwardcu o zi nainte este destinat programrii resurselor

pentru fiecare or a zilei urmtoare. O pia forwardintra-zilnic este destinat corectrii deviaiilor de la

programul stabilit cu o zi nainte. Att energia electric

ct i serviciile de sistem pot fi comercializate pe pieeleforward.b) Piaa de Echilibrare (Piaa n Timp Real)

Pentru a garanta fiabilitatea sistemelor electroenergetice,producia i consumul de energie electric trebuie s fieechilibrate n timp real. Totui, valorile n timp real aleconsumului i produciei pot fi diferite fa de programele

pieei forward. n consecin, piaa n timp real are scopulde a satisface cerinele de echilibrare producie-consum.Piaa n timp real este de obicei administrat de OPCOM.Acesta primete oferte de energie electric pentru acoperireacurbei de sarcin. Totui, dac exist congestii pe piaa ntimp real, preurile sunt stabilite pe zone. OS are rolul de

a dispeceriza unitile generatoare, ierarhizate prin ordineade merit, pornind de la cele cu preul ofertat cel mai mic,cu condiia s nu apar constrngeri n reea. n cazul ncare consumul depete producia n timp real, se potefectua ajustri prin oferte de scdere a consumului. Furni-zorii care i-au folosit capacitatea de producie a energieielectrice, exceptnd cea de reglaj, pentru una din pie elede servicii de sistem sunt pltii pentru energia furnizatsuplimentar la folosirea capacitii.c) Contractele Bilaterale

Contractele bilaterale sunt acorduri negociabile delivrare sau consum de energie electric ntre doi actori de

pia. Aceste contracte stabilesc termenii i condiiileacordului, independent de Operatorul de Sistem. n cadrul

acestui model, OS trebuie s verifice dac exist o capacitatede transport suficient astfel nct s se asigure securitateasistemului electroenergetic. Modelul contractelor bilateraleeste foarte flexibil deoarece ambele pri i pot specificacondiiile dorite privind livrarea energiei electrice. Totui,dezavantajul provine din costul de negociere mai ridicatdari din contractul scris.

3. Prezentarea principalelor servicii de sistemServiciile de sistem sunt acele servicii furnizate de ctre

instalaii de producie, transport i control, necesare asigu-rrii transportului energiei electrice de la productor laconsumator. Aceste servicii sunt necesare pentru asigurarearesponsabilitilor pe care le are Operatorul de Sistem nceea ce privete sigurana, securitatea i fiabilitatea func-ionrii sistemelor electroenergetice interconectate.

3.1. Reglajul frecven - putere activReglajul frecvenei n sistemele electroenergetice se

realizeaz pe mai multe niveluri, n funcie de semnaleleprimite i de timpul de rspuns al grupurilor generatoarela o abatere a frecvenei de la frecvena nominal.

n momentul n care n sistem se produce o perturbaie(ex: variaia puterii consumate), se creeaz un dezechilibruntre puterea produs i puterea consumat, urmat de oscdere a frecvenei. Scderea frecvenei este urmatinstantaneu de o ajustare a puterii active produse prin

In the following the main types of electricity marketsare presented [2].a) Forward Market

In the framework of electricity markets, day aheadforward market is designated for dispatching of energysources for each hour of the following market. A hourahead is market designated to meet load disturbancesfrom the forecasted schedule on day ahead basis. The

electrical energy as well as ancillary services can be tradedon a forward market.b) Balance Market (Real Time Market)

In order to ensure the reliability of power systems,generation and demand of electrical energy must be balancedin real time. However, the amount of real time generationand demand can be different comparative with forwardmarket schedule. Consequently, real time market aim tosatisfy the requirements of generation - demand balance.Commercial Operator - OPCOM, usually coordinates realtime market. This one receives energy bids to cover loaddemand. However, if there are congestion in real time, the

prices are established on areas. SO have the responsibility

to dispatch generator units, ranking them on the basis ofmerit order, starting form the lowest price units, with thecondition not to appear any constrains in the network. Whenconsumption exceeds generation in real time, adjustmentsthrough load decreasing bids are performed. The suppliersthat has used their capacity of electrical energy generation,aside from the regulation one, for one of the ancillarymarkets, supplementary to capacity payment these are

paid for energy generation.c) Bilateral Contracts

Bilateral contracts are negotiated agreements forconsumption of electrical energy between two marketactors. These contracts establish agreement terms andconditions, independent of System Operator. For this

model, SO must check if there is sufficient transmissioncapacity in order to ensure the security of power systems.The model of bilateral contracts is very flexible because

both parts can specify the desired conditions concerningsupplying of electrical energy. However, the disadvantageis the higher negotiated price and the written contract.

3. The main ancillary servicesAncillary services are those services supplied by

generating units, transmission and control, necessary toensure electrical energy transmission from the generation

point to the consumer. These services are also necessarymeet the responsibilities of System Operator concerningsafe, security and reliability of interconnected powersystems.

3.1. Frequency active power control

Frequency control into power systems is made onseveral levels, in terms of received signals and speed ofresponse of generating units to a deviation of frequencyfrom the nominal value.

When a disturbance occurs in the system (i.e. variationof demanded power), imbalance between generated andconsumed power is produced followed by decreasing offrequency. Decreasing of frequency is instantaneousfollowed by an adjusting of active generated power by


4/8

The 5th


aciunea regulatorului de vitez al turbinei care are rolulde a realiza un reglaj fin al frecvenei. Aceast aciuneeste, n general, cunoscut sub numele de Reglaj Primarde Frecven (eng: governor regulation). Rezerva de reglaj

primar trebuie s poat fi mobilizat ntr-un timp pn la30 secunde i trebuie s fie meninut n funcionare pe o

perioad de cel puin 15 minute. n condiiile interconectriicu reeaua UCTE, factorul de participare al SEN la reglajul

primar de frecven este de 0,02 avnd o sensibilitate de423 MW/Hz, rezerva necesar pentru acest reglaj fiind de85 MW [8]. Att n Romnia ct i n alte ri, capacitatea dereglaj primar al frecvenei constituie o cerin de conec-tarea grupurilor generatoare la reea i nu face obiectul unei

pli ca serviciu de sistem.Reglajul Secundar de Frecven (cunoscut i sub numele

de Controlul Automat al Produciei) este de tip centralizati poate fi realizat numai de acele grupuri generatoare caresunt conectate la regulatorul central i care au capabilitateade a rspunde la semnalul primit ntr-un timp mai mic de15 minute. Scopul acestui reglaj este de a reface rezervade reglaj primari de a readuce frecvena i soldul puteriide schimb cu celelalte sisteme la valoarea programat.

n ultima perioad de timp s-a discutat introducerea,n Romnia, unei piee a rezervelor de putere (care maieste numit i pia de echilibrare) prilej cu care stadiulserviciilor de sistem n ara noastr va deveni mai clar din

punct de vedere al competitivitii i al serviciului oferitdari al modului de tarifare al acestora. n acest sens, sedefinesc mai multe rezerve de putere [3] care au scopulde a reface rezervele de reglaj primari secundar: rezervade reglaj secundar, rezerva turnant, rezerva teriar rapid irezerva teriar lent. Reglajul frecvenei la acest nivel senumeteReglaj Teriar de Frecven. Acesta se deosebetede reglajul primari cel secundar prin faptul c este activatmanual adic prin apel telefonic sau fax. Operatorul de

Sistem achiziioneaz aceste rezerve de putere ca serviciude sistem n mod competitiv, iar dispecerizarea grupurilorgeneratoare care au ctigat licitaia este fcut dup ordineade merit.

Pe lng productori, la reglajul frecvenei ca serviciude sistem pot participa i consumatorii de putere mare pentrucare exist un sistem automat de deconectare a sarcinii

pentru a rspunde unei variaii majore a frecvenei. Deaceea, pentru a stimula consumatorii s participe la acestreglaj, este necesar tarifarea energiei electrice la consumatorn funcie de gradul de continuitate n alimentare care esteun factor de calitate al energiei electrice.

n Australia [2], asigurarea cerinelor reglajului defrecven este fcut de NEMMCO (National Electricity

Market Management Company) pe baza unor contracte cudiveri actori, iar compensarea financiar a acestora seface pe baza urmtoarelor componente: componenta deactivare, compensare fcut pe baza cantitii de putereactiv disponibil stabilit prin contract n procesul dedispecerizare i componenta de utilizare, compensarefcut pentru anumite servicii (n special delestajul desarcin) pe baza utilizrii serviciului respectiv asemenea

pli nu se fac n cazul reglajului instantaneu de frecvencare const n acionarea valvelor turbinei. n acelai timp,energia activ produs ca serviciu de sistem este tarifatla preul energiei electrice stabilit n ziua respectiv i carereprezint Preul Marginal de Sistem.

means of governor auction having the role of accuratefrequency control. This action is, in general, known as

Primary Frequency Control. Primary reserve regulationmust response in a timeframe of 30 seconds and must bemaintained in operation at least 15 minutes. For theconditions of interconnection with UCTE network,

participating factor of National Power System to primaryfrequency control is 0,02 having a sensitivity of

423 MW/Hz, the necessary reserve power for this type ofregulation being 85 MW [8]. In Romania as well as inother countries, the capacity of primary frequency controlis a connection rule of generating units to the network anddoes not make the object of payment as ancillary service.

Secondary Frequency Control(known also as AutomaticGeneration Control) is a centralized one and could beachieved only by the generating units connected to centralregulator having the capability to respond to the receivedsignals in a time less than 15 minutes. The goal of thistype of control is to restore primary frequency controlreserve and to bring back the frequency in the admissible

band and the frequency bias to scheduled value.In the last period of time have been discussed the

introducing, in Romania, of reserve powers market (alsocalled balanced market) being an opportunity ancillaryservices state in our country become more clear form thecompetitively point of view and of the offered service butalso form their payment point of view. In this regard, several

power reserves are defined [3] having the destination torestore primary and secondary power reserve: secondarycontrol reserve, spinning reserve, rapidly tertiary reserveand slowly tertiary reserve. Frequency regulation at thislevel is called Tertiary Frequency Control. This isdistinguished from the primary and secondary frequencycontrol by the fact that this is activated manually that is

by means of phone or fax communication. System Operator

purchases these power reserves in a competitive manner,and the dispatching of the winners generating units ofauction process in terms of merit order is made.

Additional to generator units, to frequency control asancillary service can also participate the big consumersfor which there is an automatic control system of loadshedding in order to respond to a major frequency disturbance.For this reason, in order to stimulate the consumers to

participate to this type of frequency control, the cost ofelectrical energy at the consumer in terms of supplyingcontinuity, being a power quality parameter, must be

performed.In Australia [2], Ensuring of frequency control

requirements is performed by NEMMCO (National

Electricity Market Management Company) on the basis ofthe agreements with different market actors, and theirfinancial compensation is made on the basis pf the followingcomponents: activation component, compensation madeon the basis of the available amount of active powerestablished through contract in process de dispatching andusing component, compensation made for those services(especially load shedding) on the basis of the respectiveservice used such payments are not made for instantaneousfrequency control which consists in turbine valve action.In the same time, the generated electrical energy as ancillaryservice is financial compensated at the energy price estab-lished for the respective day at the System Marginal Cost.


5/8


3.2. Reglajul tensiune putere reactivTensiunea este un parametru de calitate a energiei elec-

trice i trebuie meninut n limitele admisibile. n acestsens, Operatorul de Sistem are rolul de a realiza o coor-donare a surselor de putere reactiv. Pn n prezent, nara noastr, optimizarea producerii puterii reactive nvederea realizrii reglajului de tensiune a fost neglijat.Avnd n vedere faptul c reglajul teriar de tensiune se

realizeaz pe baza unor coeficieni de sensibilitate, asigu-rarea suportului de reactiv n vederea controlului tensiuniica serviciu de sistem este dependent de amplasarea nsistem a potenialilor actori. n cazul reelelor electricedin UCTE, se are n vedere s nu existe circulaie de puterereactiv, iar producerea acesteia trebuie s se fac local;ns, acest aspect este condiionat att de disponibilitateact i de capacitatea surselor de putere reactiv. n ceea ce

privete SEE Romnesc, liniile electrice de transport fiind slabncrcate prezint o surs important de reactiv, fapt ce trebuieluat n considerare n planificarea reglajului de tensiune.

Cel mai important mijloc de reglare a tensiunii l repre-zint generatoarele sincrone deoarece, prin structura siste-

melor electroenergetice, acestea constituie elemente exis-tente; instalarea altor surse de putere reactiv la fel deeficiente necesit noi investiii care, n ara noastr,reprezint o problem deosebit. n ara noastr [3], princriteriile tehnice de calificare a grupurilor generatoare nvederea furnizrii puterii reactive ca serviciu de sistem, seimpune ca acestea s fie capabile s furnizeze puterea activnominal pentru un factor de putere ntre 0,85 inductiv i0,95 capacitiv. Dealtfel capabilitatea generatoarelor de reglaja tensiunii prin producerea / absorbia de putere reactivconstituie o condiie de conectare la reea.

Funcionarea generatorului sincron se urmrete cuajutorul diagramei de performan a generatorului sincroncare mai este numit domeniu de ncrcare, pentru care sedefinesc benzile primar, respectiv secundar de reglaj atensiunii. Dac generatorul va funciona n banda secundar,adic n zonele indicate prin Q1 i Q2, apar pierderi supli-mentare de putere activ, iar deintorul grupului generatorrespectiv va solicita o compensare financiar.

Qmin QC

Pmin

P

Pmax

regim capacitiv regim inductiv

Q

B

QBQA

A

CPC

P =PA B

Q1 Q2

Figura 2. Domeniul de ncrcare al generatorului sincron

Se presupune c punctul de funcionare al generatoruluise afl n A(PA, QA). n cazul n care este necesar o absorb-ie suplimentar de putere reactiv, punctul de funcionarese mut din punctul A n punctul B de coordonate (PB, QB)fr ns a fi necesar o scdere a puterii active. n schimb,funcionarea generatorului n acest punct se realizeaz cu

pierderi suplimentate de putere activ. Dac se dorete

3.2. Voltage reactive power control

The voltage is a parameter of power quality and mustbe maintained in admissible limits. In this regard, SystemOperator has the responsibility to realize a coordination oreactive power sources. Up to now, in our country, optimalgeneration of reactive power in order to achieve voltageregulation has been neglected. Taking into considerationthat tertiary voltage control is done by using some sensitivity

coefficients, ensuring the required reactive power for voltageregulation as ancillary service is dependent of location inthe system of the potential actors. In the case of UCTEelectrical networks, System Operator aim to avoid reactive

power flow in the system, its generation must by local;instead, this aspect is conditioned by the availability ofthe units as well as the capacity of reactive power sources.Concerning Romanian Power System, the transmissionelectrical lines, being low loaded, presents an importantreactive source and must be taken into account in planningof voltage regulation.

The most important mean of voltage regulation representthe synchronous generators, through the power systems

structure, these are existent equipments; the installing ofother sources of reactive power as efficient as the generatorsneeds additional investments, in our country, being a special

problem. In Romania [3], through technical criteria forqualifying of generator units in order to be dispatched forreactive power support as ancillary service, is requiredthese to be capable of supplying rated active power for a

power factor in the interval from 0,85 inductive and 0,95capacitive. Furthermore, voltage regulation capability ofgenerator units through generation / abortion of reactive

power is a condition for connection to the network.Operation of synchronous generator is analyzed by

using performance domain or synchronous generator alsoknown as loading capability, for which primary band,respectively secondary band of voltage regulation aredefined. If the generator will operate in the secondary

bandthatisintheareasindicatedbyQ1andQ2,supplementaryactive power losses occur, and the owner of the respectivegenerator unit will ask for a financial compensation.

Qmin QC

Pmin

P

Pmax

leading regime lagging regime

Q

B

QBQA

A

CPC

P =PA B

Q1 Q2

Figure 2. Loading capability of synchronous generator

Assume that the operation point of generator is locatedin A (PA, QA). In the case when supplementary absorptionof reactive power is required, the operating point is movingfrom point A to point B of coordinates (PB, QB) not to benecessary decreasing of active power. Instead, operationof generator in a point in this point is performed withsupplementary active power losses. If additional increasing


6/8

The 5th


creterea n continuare a absorbiei de reactiv, de exempludin punctul B n punctul C de coordonate (PC, QC), pentruca funcionarea generatorului s se realizeze n condiii desecuritate, productorul va fi nevoit s scad puterea activgenerat pn la valoarea PC. De aceea, generatorul res-

pectiv trebuie s fie compensat financiar pentru pierdereaprofitului de pe urma scderii puterii active generate.

n scopul de a compensa financiar capabilitatea grupu-

rilor generatoare de a produce putere reactiv, n Australiase folosesc urmtoarele mecanisme de plat [1]:

-plata disponibilitii, acordat acelor servicii pentrucare se cere o disponibilitate din partea furnizorului

pentru asigurarea serviciului atunci cnd este necesar;-plata de activare, acordat n cazul n care serviciul

este activat la cererea Operatorului de Sistem;-plata de compensare, bazat pe costul de oportunitate,

adic pentru cazul n care productorul este nevoit sscad producia de putere activ n schimbul creteriisuportului de putere reactiv. Excepie de la acest tipde compensare financiar o fac compensatoarele sin-crone i serviciul de restaurare a sistemului.

n figura 3 se prezint grafic costul de producie algeneratorului sincron n funcie de puterea reactiv [5]

absorbing reactive power is desired, for example frompoint B to point C of coordinates (PC, QC), in order toachieve a secure operating of generator, the generationowner must decrease the active power up to the point P C.By this reason, the respective generator must be financialcompensated for profit losing from the reducing of active

power.In order to compensate financial the capability of

generator units to generate reactive power, in Australiathe following payments mechanisms are used [1]:

-Availability payment, given for those services forwhich the availability of suppliers in order to ensurereactive control service when is necessary;

-Activation payment, given in the case when the respec-tive service is activated at the System Operator demand;

-Compensation payment, based on opportunity costs,that is in the case when the supplier is enforced todecrease its generation of active power in exchangeof increasing reactive power generation. Exceptionsfrom this financial compensation are synchronouscompensators and black-star capability.

In figure 3 is illustrated the curve of generation cost ofsynchronous generator in terms of reactive power [5]

Costul pierderilor+

Costul de oportunitate

Costulpierderilor

QB QC QQMin

Figura 3. Dependena costului de producie n funcie de puterea reactiv

Cost of losses+

Opportunity cost

Cost oflosses

QB QC QQMin

Figure 3. Dependency of generation cost in terms of reactive power

n cadrul reglajului de tensiune, n vederea producerii/ absorbiei de putere reactiv se mai pot folosi i alte dispo-zitive cum ar fi: compensatoarele sincrone, bateriile cucondensatoare, bobinele i dispozitivele statice (SVC,STATCOM, etc.) dari transformatoarele. Din punct devedere al reglajului de tensiune sunt favorabile generatoa-rele i compensatoarele sincrone, iar din punct de vedereal costului cele mai interesante sunt bateriile cu condensa-toare. n aceast privin, generatoarele sincrone au costuride funcionare foarte ridicate deoarece ele sunt proiectates produc putere activ, i nu reactiv. n plus este foartedificil de separat costul de producere a puterii active de

In the framework of voltage regulation, for generation/ absorption reactive power other devices can be used suchas: synchronous compensators, capacitor banks, reactorsand static devices (SVC, STATCOM, etc.) bat alsotransformers. Form the voltage point of view the most

proffered devices are generators and synchronouscompensators, and from the cost point of view the mostefficient devices are capacitor banks. In this regard,synchronous generators have very high operating costs

because these are designated to generate active power, notreactive power. Furthermore, it very difficult to separategeneration cost of active power from the reactive power


7/8


costul puterii reactive. Dispozitivele SVC i STATCOMsunt foarte costisitoare dei costul lor de funcionare estemai sczut dect cel al generatoarelor ns, au o capabilitatesuperioar de reglaj a tensiunii.

n continuare se prezint cteva din caracteristicile iparticularitile puterii reactive pe piaa serviciilor de sistem:

Puterea reactiv trebuie s fie furnizat local datoritproblemelor tehnice asociate cu transportul pe liniile

electrice;Valoarea puterii reactive este dependent n funcie de

locul n care este furnizat; de exemplu, influena unuiMVAr poate fi diferit de la nod la nod;

Localizarea strategic a furnizorilor de putere reactivpoate avea multe avantaje;

Exist un numr limitat de poteniali actori pe aceastpia;

Piaa pare a fi mai mult un monopson (cu un singurcumprtor Operatorul de Sistem)Introducerea pieei de putere reactiv este o problem

dificil avnd n vedere evaluarea costurilor de producerea puterii reactive. Problemele necesare a fi rezolvate n

aceast privin sunt urmtoarele:a) Sunt considerate generatoarele / compensatoarele sin-crone considerate ca furnizori de servicii de sistem ?

b) Sunt companiile de transport / distribuie, ali consu-matori i furnizori de puterea reactiv considerai cafurnizori de servicii de sistem ?

c) Cum este capabilitatea unui furnizor de a da putereareactiv cuantificat ntre furnizorii mputernicii nacest scop i serviciul de sistem oferit ?

d) Care este structura cea mai potrivit a pieei de puterereactivi a mecanismului de tarifare ?

e) Care sunt problemele implicate n gsirea unui optimal puterii reactive ca serviciu de sistem ?

4. Concluzii

n aceast lucrare au fost examinate diverse aspecteprivind serviciile de sistem n sistemele electroenergeticen contextul descentralizrii sectorului energetic. Analizaserviciilor de sistem reprezint o problem complex avndn vedere noua abordare a acestora n funcie de restriciileimpuse prin deschiderea pieei de energie electric. Scopul

pieei de energie este vnzarea energiei la preul cel maimic prin crearea competitivitii ntre toi utilizatorii sis-temului electroenergetic. Acest lucru se poate realiza

printr-un management eficient al serviciilor de sistem ianume prin obinerea optimului de achiziionare a puteriireactive, a rezervelor de putere activ etc., toate n condiii

de competitivitate.Trebuie avut n vedere faptul ci consumatorul este

un furnizor foarte bun al serviciilor de sistem dar acestlucru asigurndu-se prin scderea productivitii i scderiieficienei economice. ns mult mai important este asigu-rarea securitii i fiabilitii sistemului.

O problem deosebit n tarifarea serviciilor de sistemo reprezint msurarea cantitii i calitii acestora.De aceea, sunt necesare sisteme automate performante demonitorizare dari reglementri clare care s stabileasccare sunt responsabilitile tuturor participanilor implicain asigurarea calitii energiei electrice i a securitiisistemului.

cost. SVC and STATCOM devices are very expensivealthough their operation cost is lower then the cost ofgenerators instead, have high capability of voltageregulation.

In the following some characteristics and particularitiesof reactive power on ancillary services market: Reactive power must be supplied locally due to technicalproblems associated with transmission on electrical lines;

Reactive power value is dependent of supplying point;for instance, the influence of one MVAr can be differentfrom node to node;

Strategic placement of reactive power suppliers havemany advantages;

There is an limited number of potential actors on thismarket;

The market seems to be a monopson (only one buyer System Operator)Introducing of reactive power market is a difficult

problem taking into consideration the assessment of reactivepower generation costs. Problems necessary to be solvedin this regard are the following:

a) Are generators / synchronous compensators considerateas ancillary services suppliers?b) Are transmission companies / distribution, other

consumers and suppliers of reactive power consideredas ancillary services suppliers?

c) How the capability of a supplier of reactive powerquantified among all such suppliers and the tenderedservice?

d) What is the best structure of reactive power market andtheir payment mechanism?

e) Which are the involved problems in choosing theoptimum of reactive power as ancillary service?

4. Conclusions

In this paper, several aspects concerning ancillaryservices into the power systems in the context of energysector deregularization have been debated. Ancillaryservice analysis is a complex problem taking into accountthe new approach of these in terms of the constraintsimposed by the opening of electricity market. The purposeof electricity market is selling of electrical energy at thelowest price by introducing competitivity among all usersof power system. This can be made through an efficientmanagement of ancillary services namely by achievingthe optimum of reactive power, of active power reservesetc., all in a competitive manner.

It should be taken into consideration the fact that theconsumer is a very good supplier of ancillary services butthis can be achieved by decreasing productivity andeconomic efficiency. Instead, more important is ensuringof security and reliability of power system.

A special problem in payment of ancillary services isthe measurement of their quality and quantity. By thisreason, preferment automatic systems for metering andalso clear rules which can establish the responsibilities ofall participants involved in ensuring power quality andsystem security.


8/8

The 5th


Bibliografie (References)

1. Bhattacharya, K., Boolen, M., Daalder, J., Operation of restructured power systems, Kluwer Academic Publisher, 20012. Shahidehpour, M., Yamin, H., Li, Zuyi,Market Operations in Electric Power Systems, IEEE, Wiley, Interscience N.Y., 20023. Codul Tehnic al Reelei Electrice de transport. TRANS-ELECTRICA S.A., 20004. Bhattacharya, K., Zhong, J.,Reactive Power as an Ancillary Service, IEEE Transactions on Power Systems, Vol. 16, No. 2, May

20015. Zhong, J.,Design of Ancillary Service Markets: Reactive Power and Frequency Regulation, Chalmers University of Technology,

Gteborg, Suedia, 20016. Hirst, E., Kirby, B.,Ancillary Services,

http://www.ornl.gov/ORNL/BTC/Restructuring/pub.htm7. ConnectionRules for Generation and Management of Ancillary Services, EURELECTRIC, Date: May 2000, Ref: 2000-130-

00038. Studiu UCTE,Load-Flow Analysis with Respect to a Possible Synchronous Interconnection of Networks of UCTE and IPS/UPS,

May 2003.9. Directiva 96 / 92 / EC

10. Glosar de termeni, ANRE, www.anre.ro

ASPECTS OF ANCILLARY SERVICES

Documents

Transcript of ASPECTS OF ANCILLARY SERVICES