IEEE Transactions on Power Systems, Vol. 5, No. 4, November 1990 1400

A REAL TIME POWER SYSTEM SIMULATION LABORATORY ENVIRONMENT

Mike Foley Y i lang Chen Anjan B O W

ARIZONA STATE UNIVERSITY, TEMPE, ARIZONA

ABSTRACT

A l a b o r a t o r y environment f o r research, teaching and

demonstrat ion o f power system behavior has been developed a t

Ar izona Sta te U n i v e r s i t y . The main d r i v e r i s a r e a l t ime

d i g i t a l s i m u l a t i o n o f a l a r g e power system. A f u l l - g r a p h i c

human i n t e r f a c e made up o f several l e v e l s o f one- l ine diagrams, t a b l e s and o t h e r d isp lays enable t h e observat ion o f the power system behavior i n r e a l t ime as we l l as e f f e c t i t s behavior by i n t r o d u c i n g supervisory c o n t r o l ac t ions . These

programs operate on a database, which can be changed t o

represent d i f f e r e n t power systems. The s imu la t ion and the

database a r e run on a VAX 11-785 mainframe computer w h i l e the

human i n t e r f a c e i s run on an Apo l lo ON570 works ta t ion w i t h a

19 i n c h f u l l - g r a p h i c c o l o r d isp lay . The two computers a re

l i n k e d v i a a h igh speed e thernet data l i n k . The program t o

program communication was s p e c i f i c a l l y developed f o r t h i s

a p p l i c a t i o n . The t o t a l environment created i s t h a t o f a

Apo l lo DN570 works ta t ion . This i n t e r f a c e c o n s i s t s o f a ser ies of d i s p l a y s which a r e used t o mon i to r the power system as i t i s being simulated. These d i s p l a y s combine t o mimic a power system man machine i n t e r f a c e (HI) t h a t i s a v a i l a b l e i n

a s t a t e of the a r t c o n t r o l center. The software on both

computers i s supported by one database t h a t res ides on the VAX. The two computers a r e l i n k e d by an e thernet network and software s p e c i a l l y designed f o r t h e program t o program communication. This paper provides an overview o f t h i s l a b o r a t o r y environment. F i r s t , the computat ional environment

i s presented. The d e t a i l s o f the power system s imu la t ion

have been pub l ished elsewhere [l-41 and a r e n o t repeated

here. Instead, the human i n t e r f a c e , the communications

software and the database a r e descr ibed i n t h a t order.

F i n a l l y , a b r i e f overview o f how t h i s l a b o r a t o r y i s u t i l i z e d

a t ASU i s given.

COMPUTATIONAL ENVIRONMENT

power system c o n t r o l cen ter . I t can be used t o demonstrate and teach power system behavior as w e l l as experiment w i t h REAL T I M E POWER SYSTEM S I M U L A T O R

a l l face ts o f t h e energy management system. This paper provides an overview o f t h e l a b o r a t o r y environment. The r e a l t ime power system s imu la to r (RTPSS) runs on a VAX

11-785 mainframe computer. The power system model i s

I N T R O D U C T I O N i n i t i a l l y loaded i n t o the s imu la to r from a database a l s o

r e s i d e n t on t h i s computer. The s imu la to r runs i n r e a l t ime.

A r e a l t ime power system s imu la t ion labora tory has been Each c y c l e cons is ts o f updat ing the system topology. loads,

developed a t Ar izona Sta te U n i v e r s i t y (ASU). r e l a y s and transformers. From t h i s updated system, vol tages, g ives students the o p p o r t u n i t y t o wi tness f i r s t hand how a l i n e f lows and o t h e r data a r e ca lcu la ted . Each c y c l e fo r

l a r g e power system behaves. Scenarios can be simulated t o updat ing the data represents f i v e seconds o f w a l l c l o c k time.

demonstrate system d is tu rbances o f var ious types, and proper The generator ou tpu ts have a slow dynamic s o l u t i o n behavior

recovery ac t ions . The l a b o r a t o r y i s a l s o used by researchers which i s modeled by d i f f e r e n t i a l equat ions. This dynamic t o study power system c o n t r o l methods, e f f e c t s o f var ious s o l u t i o n i s ob ta ined by i n t e g r a t i n g i n one second t ime steps, models and a lgor i thms i n the s imulat ion, t h e e f fec t i veness of thus r e q u i r i n g f i v e t ime steps i n every s o l u t i o n cycle. The f u l l g raph ic d i s p l a y s and computer communication methods. RTPSS i s designed t o be a b l e t o handle l a r g e systems up t o a

thousand buses [l]. The l a b o r a t o r y c o n s i s t s o f several sof tware processes

execut ing on two computers. The f i r s t process i s a s t a t e o f Models requ i red i n the r e a l t ime power system s imu la to r are

the a r t power system s imu la to r running o f a VAX 11-785 the dynamic models f o r the s l o w l y vary ing q u a n t i t i e s and

mainframe computer. Th is s imu la to r was s p e c i f i c a l l y s t a t i c models f o r those t h a t change too f a s t f o r the f i v e

developed t o p rov ide r e a l t ime s imu la t ion o f power systems second c y c l e and those t h a t a r e t r u l y s t a t i c . Changes i n

This l a b o r a t o r y

c o n s i s t i n g o f up t o one thousand buses. The second computer

hosts a s p e c i a l l y developed graph ica l user i n t e r f a c e on an

90 I N 073-7 P,'KS A paper recommended and approved by t h e IEES Power Engineering Education Corimittee of the IEZE Power Enqineerinc Societ,y f o r presenta t ion a t tne IEEf;/PdS 1990 Winter liee*"ing, Atlanta , Georgia, February 4 - 8, 1990. Au:;ust 31, 1989; made a v a i l a b l e f o r pr int in; January 5 , 1990.

Xanuscr ipt subni t ted

s t a t i c models a r e ad jus ted every cyc le . Slowly varying

dynamic models a r e solved by a numerical i n t e g r a t i o n

technique C2.31.

The power f l o w c a l c u l a t i o n s t h a t so lve f o r the s t a t i c power

network, which a r e computa t iona l l y the most t ime consuming,

a re based on the f a s t decoupled method. Care has been taken t o ensure t h a t a f t e r a topology change, the system c y c l e time

i s s t i l l f i v e seconds [4] . I f a component i s added o r removed. the s i m u l a t i o n s t i l l solves f o r the s t a t e o f the

system w i t h i n the f i v e second c y c l e per iod , i e . i n r e a l t ime.

0885-8950/90/1100-1400$01.00 0 1990 IEEE

1401

Sirnul at or

&' 1-1 , Database Communication

Display

Ethernet ,TI Communication Shared Memory

APOLLO WORKSTATION

An A p o l l o ON570 w o r k s t a t i o n was chosen as t h e computer t o

b u i l d the human i n t e r f a c e upon. Th is software simulates the

MI. The A p o l l o computer conta ins a MC68010 processor

runn ing a t 16 megahertz, mouse, and graphics support as

standard equipment. An enhanced c o l o r d i s p l a y system w i t h 1024 x 800 p i x e l r e s o l u t i o n which supports 256 c o l o r s

d isp layed s imu l taneous ly o u t o f a p a l e t t e o f over s ix teen m i l l i o n i s used f o r t h i s l a b o r a t o r y .

The A p o l l o w o r k s t a t i o n supports i t ' s n a t i v e A E G I S opera t ing

system as w e l l as BSO 4.2 UNIX and AT&T System V UNIX. These

opera t ing systems p r o v i d e the necessary in te r -p rocess

communication r e q u i r e d f o r t h i s mult i-process, mult i-computer

l a b o r a t o r y .

I t was env is ioned t h a t t h i s computer cou ld be used as a f r o n t end f o r t h e s i m u l a t i o n runn ing on the VAX computer. The A p o l l o s imu la tes t h e power system c o n t r o l cen ter MI, g i v i n g

the o p e r a t o r t h e o p p o r t u n i t y t o mon i to r the s t a t e o f t h e

power system, and i s s u e commands e f f e c t i n g i t ' s topology.

Th is i n c l u d e s opening and c l o s i n g breakers t o b r i n g l i n e s ,

generators and o t h e r system elements on or o f f l i n e .

HUMAN I N T E R F A C E

The graph ica l d i s p l a y system had t o capture the look and f e e l

o f t h e a c t u a l power system c o n t r o l cen ter . From the graph ica l works ta t ion , t h e o p e r a t o r has t h e same command o f

t h e system as he o r she would have i n the ac tua l c o n t r o l

cen ter . Th is inc ludes observ ing t h e power system on

s u b s t a t i o n o n e - l i n e diagrams, as w e l l as being a b l e t o ou tpu t superv isory c o n t r o l commands t o t h e system. This has t o

occur w i t h t h e same t ime c o n s t r a i n t s o f how the ac tua l

c o n t r o l c e n t e r ga thers da ta from the r e a l power system and

sends o u t commands. The s imu la ted system should n o t respond

too q u i c k l y o r s lowly , o r t h e r e a l i s m i s l o s t . This

diminishes t h e " f e e l " o f t h e system [5,6,7].

COOPERATING PROCESSES

Making the e n t i r e system f u n c t i o n as a s i n g l e u n i t requ i res a

t o t a l o f f i v e coopera t ing processes execut ing on two

computers. These a r e t h e RTPSS i t s e l f , a communication

program accessing t h e e t h e r n e t on each computer, a message

g e n e r a t o r / r e t r i e v e r on t h e Apo l lo , and t h e graph ica l d i s p l a y

system a l s o on t h e A p o l l o computer. The in te rconnect ions

between processes i s o u t l i n e d i n F igure 1.

M M I

The graph ica l d i s p l a y system which mimics t h e power system

c o n t r o l cen ter runs on t h e A p o l l o computer under the UNIX System V opera t ing system. Th is process i s t h e simulated MI. I t i s w r i t t e n i n t h e C programming language.

The MMI c o n s i s t s o f m u l t i p l e d isp lays , each g i v i n g t h e user a

unique window i n t o t h e s imu la t ion . A d i s p l a y f i l e d e f i n i t i o n

c o n s i s t s o f two segments, a g raph ics mask and da ta l inkages . The mask c o n s i s t s o f a bitmap used f o r d i s p l a y on t h e Apo l lo

monitor. The l i n k a g e s a r e t h e l o c a t i o n o f da ta d isp layed on

the mask i n t h e s i m u l a t o r database. The d i s p l a y f i l e

d e f i n i t i o n s a r e s t o r e d on d i s k r e s i d i n g a t t h e Apo l lo

computer. When the opera tor c a l l s f o r a d i s p l a y , i t i s

loaded from d isk . The bitmap i s immediately displayed. The

l inkages a r e e x t r a c t e d from t h e d i s p l a y f i l e and sent t o the

VAX f o r data r e t r i e v a l from t h e database.

A complete s e t o f d i s p l a y s has been developed f o r the t e s t

power system be ing simulated. The o n e - l i n e d i s p l a y s are

organized i n th ree l e v e l s o f complex i ty . The h ighes t l e v e l

i s a system map t h a t g ives an overview o f t h e t e s t system. I t i s n o t drawn t o scale, b u t g i v e s t h e opera tor a f e e l f o r

how the system i s g e o g r a p h i c a l l y interconnected.

Transmission l i n e s above 230 KV a r e shown and c o l o r coded by

PllsnP TO PPDOE

TO PPDM

TO P I I P K

ro PIW

I PRRDS

Fig. 3. Typical Overview Display. I

l i n e vo l tage. The system map f o r t h e t e s t power system i s

shown i n F igure 2.

The second l e v e l o f d i s p l a y i s area overviews. These

d i s p l a y s represent l e s s o f t h e system, bu t show more d e t a i l .

Subs ta t ion bus vo l tages a r e given, as we l l as

in te rconnect ions . An example overview d i s p l a y i s shown i n

F igure 3.

The lowest l e v e l of d i s p l a y i s the subs ta t ion one- l ine

diagram. A l i b r a r y of common e l e c t r i c a l power system symbols was developed t o be inc luded on these displays. Using t h i s

l i b r a r y , t h e components on t h e one- l ine diagrams appear as

standard e l e c t r i c a l symbols. Breakers a r e c o l o r coded t o

s i g n i f y open o r c losed s ta tus . These conventions a l l o w f o r

easy r e c o g n i t i o n by the operator.

The bus vol tage, l i n e f lows, power

generat ion, e t c . a r e d isp layed and

cont inuous ly updated on the one- l ine diagrams. Commands may be issued t o open and c l o s e breakers. A f t e r the s i m u l a t i o n has rece ived the command,

t h e d i s p l a y w i l l r e f l e c t the new

s t a t e o f t h e breaker. A t y p i c a l

subs ta t ion o n e - l i n e diagram i s shown

i n F igure 4.

Tabular d i s p l a y s a r e a l s o a v a i l a b l e

t o t h e operator. A u n i t t a b l e shows

each u n i t s r a t i n g , scheduled power,

ac tua l power, and c o n t r o l s ta tus .

The i n p u t schedule may be updated from t h i s tab le . A l i n e alarm t a b l e

g ives a l i s t o f overloaded l i n e s , i f any e x i s t . For overloaded l i n e s the

s t a t i o n s connected, f low, ra te , and

percent load ing are l i s t e d . These

two t a b l e s a r e presented i n Figures 5 and 6.

The d isp lays were designed f o r ease

o f opera t ion . Moving from one

d i s p l a y t o another can be

accomplished by s imply " c l i c k i n g " the mouse b u t t o n i n an appropr ia te

l o c a t i o n . "Ac t ion Dots" a re placed

on the ends o f t ransmission l i n e s l e a v i n g a subs ta t ion . C l i c k i n g on

one o f t h e do ts w i l l d i s p l a y the

subs ta t ion on t h e o t h e r end o f the

l i n e . Other d i s p l a y s have a c t i o n

do ts a l l o w i n g f o r the movement t o

h igher and lower l e v e l s , or t o the

t a b u l a r d isp lays . Keyboard commands

a r e a v a i l a b l e i f des i red . More than

one d i s p l a y may be viewed a t any g iven time. The ease o f operat ion

a l lows f o r students or researchers

u n f a m i l i a r w i t h the t e s t power system

t o e a s i l y manipulate t h e HI and

issue commands t o the s imu la to r .

AUTOMATED D I S P L A Y GENERATION

When c r e a t i n g a new d isp lay , t h e process o f en ter ing

numerical data l i n k s i n t o p i c t u r e f i l e d e f i n i t i o n s i s a very

tedious, t ime consuming, e r r o r prone task. The l inkages had

t o be manually determined from r e a l power system maps o f the

system being simulated. (Not t h e system map d i s p l a y used by

the MI program.) This process invo lved f i n d i n g each piece

o f equipment modeled on a system map, and determining i t ' s

p rec ise l o c a t i o n i n the database. Th is i n f o r m a t i o n includes

the area, tab le , and device s p e c i f i c in fo rmat ion , such as

t ype and name. Th is da ta was keyed i n t o the d i s p l a y d e f i n i t i o n f i l e f o r each dynamic component appearing

on t h e d i s p l a y . Since a l l t h e necessary da ta t o

generate such l i n k s was a l ready i n t h e database system

c o n f i g u r a t i o n , a program t o a u t o m a t i c a l l y look-up t h i s

i n f o r m a t i o n was developed.

When g iven a s t a r t i n g p o i n t , a subs ta t ion bus f o r

example, t h e computer searches t h e database f o r a l l equipment connected t o t h e s t a r t i n g p o i n t . When such

a p iece o f equipment i s found, t h e program looks up

t h e graph ica l symbol assoc ia ted w i t h i t . and draws i t

on t h e d i s p l a y . Th is process cont inues f o r each p iece o f equipment connected t o t h e s t a r t i n g l o c a t i o n .

The newly generated d i s p l a y can be used as i s , or modi f ied by t h e user. Th is g i v e s a q u i c k and r e l i a b l e

method o f genera t ing custom d i s p l a y s f o r the system being s imu la ted .

COMMUNICATION

The VAX mainframe and t h e A p o l l o works ta t ion a r e

connected on a high-speed e t h e r n e t data network. The e thernet f o l l o w s t h e I E E E 802.3 p r o t o c o l . The network

t r a n s f e r s da ta a t speeds up t o t e n megabits per second

throughout t h e eng ineer ing c o l l e g e a t ASU. I t

connects m u l t i p l e computers, and cannot be dedicated

t o any s i n g l e system o r a p p l i c a t i o n . Because o f t h i s

c o n s t r a i n t , t h e amount o f da ta passed between the two computers had t o be kept t o a minimum.

For the two computers t o work toge ther , program d r i v e n

communication on each computer was necessary. On the

VAX, t h e communication program rece ives requests f o r

data, fe tches i t from t h e database and r e t u r n s i t t o the Apo l lo . On t h e Apo l lo , t h e program rece ives data

requests from t h e M M I program. and forwards them t o

t h e VAX communication program. A f t e r r e c e i v i n g t h e

requested data, i t d e l i v e r s i t t o the MI program,

which p laces i t on the d i s p l a y .

MESSAGES

A message c o n s i s t s o f a stream o f ASCII characters. A

c o n t r o l header b l o c k precedes t h e da ta i n each

message. The header s t r u c t u r e i s shown i n F igure 7.

The "from" and " t o " f i e l d s a r e one charac ter names f o r computers. The VAX i s i d e n t i f i e d by t h e l e t t e r ' V '

and the A p o l l o by ' A ' . Th is can be expanded i f more

computers a r e incorpora ted i n t o t h e system.

The "code" and " type" f i e l d a r e bo th used t o c l a s s i f y messages. The code i s t h e more general o f t h e two,

w i t h types be ing subsets o f codes.

1403

ORYB

I 4 - 9 2 . 4 ~

92.5mua 394.11)IP 5.3mua-

Fig. 4. Typ ica l Subs ta t ion One-Line Diagram.

n F s m M UI w n F s m M u i I(

n F s m i u i w n t u m m uz w n c u w m u2 I(

ncurmn u2 w

couonmo T 22/500

COROWilDO T 22l500

CROSSCUT U 1 W

HORSMESA U1 N

HORSMESA U4 N

HOR%ESA U4 N

HORSHESA U4 M

KYREME SYNCH COW

KYREME SYNCH COW

LFClEDC ACC Oenand

LFClEDC RGC Denand

LFC/EDC ACC Oenand

LFClEDC RGC Oenand

LFClEDC ACC Denand

LFC/EOC ACC Denand

LFClEDC ilCC Denand

LFClEDC ACC Oenand

LFClEDC ACC Oenand

LFClEDC ACC Denand

LFClEDt AGC Denand

LFClEDC AGC Denand

LFClEDC ACC Denand

LFtlEDC AGC Denand

LFClEDC RCC Denand

111.0 18.0 87.3

111.0 18.0 18.0

182.0 26.0 143.9

78.0 4.0 4.0

67.0 4.0 4.0

67.0 4.0 4.0

363.0 -363.0 327.9

364.1 -364.1 328.9

3.3 -3.3 3.0

9.9 -3.9 8.9

9.9 -9.9 8.9

9.9 -9.9 8.9

93.5 -93.5 84.4

52.0 4.0 43.6

52.0 4.0 4.0

140.8

340.1

9.4

3.9

9.4

36.4

49.1

20.3

- 43.4

104.9

71.2

66. I 26.2

63.3

140.8

340.1

1.2

9.4

3.9

9.4

36.4

49. I 20.3

Fig. 5. U n i t Table.

OVERLOADED LINES IN SRI' AREA (WARNING!)

[RON STATION TO STATIOII

tWlFRIR(230.OKV) WtSTnMt(23B.BKV) Flou: 384.6 Rate: 377.2 Loading(Z)1@2.5

Fig. 6. L i n e Table.

1404

The "packets", "packet-number" . and "packet-1 en" f i e l d s a re

used t o d e f i n e t h e message. I f a message i s t o o long t o be

t r a n s f e r r e d i n one message, i t w i l l be d i v i d e d and sent i n

m u l t i p l e packets. When a message i s sent, the "packets"

f i e l d i s s e t t o t h e number o f packets i n t h e message, and the "packet-number" f i e l d i s s e t t o which packet t h i s i s w i t h i n

t h e t o t a l number be ing sent. The "packet-len" f i e l d i s an

a r r a y o f ASCII t e x t which i s t h e l e n g t h o f the packet.

Once a message i s received, t h e packet f i e l d s a r e converted from ASCII c h a r a c t e r s t r i n g s i n t o i n t e g e r s t o be used f o r f u r t h e r processing. These a r e a l s o s t o r e d i n t h e header, i n

t h e f i e l d s whose name corresponds t o the A S C I I f i e l d s

described above. I f the message was sent i n m u l t i p l e

packets, i t i s r e b u i l t upon t h e r e c e i p t o f each packet. The s t a t u s f i e l d i s used t o i n d i c a t e e r r o r cond i t ions . This f i e l d w i l l be non-zero i f an e r r o r occurred. I n t h i s case

t h e number w i l l be a coded representa t ion o f the e r r o r .

s t r u c t header (

char from,

to, type, code, packets,

packet-number,

packet-len,[ 5 3 ;

pckt-number,

pckt- len, s t a t ,

len ;

i n t pck ts ,

) mess;

F ig . 7. Message Header S t ruc ture .

COMMUNICATION DAEMONS

The communication processes execute i n the background w i t h o u t

user i n t e r a c t i o n . The processes accessing t h e e thernet use

the C-Socket model and a c l i e n t / s e r v e r r e l a t i o n s h i p between

processes. The model p rov ides a number o f system serv ices

f o r c r e a t i n g and opening sockets. The sockets can then be

used f o r read ing and w r i t i n g over the network. The daemon source code i s w r i t t e n i n t h e C programming language.

The VAX computer communication daemon, COMM ac ts as t h e

server process f o r t h e Apo l lo . COW w a i t s i n a system c a l l

u n t i l t h e A p o l l o computer sends a message. A t t h i s t ime COMM determines t h e type o f t h e message and responds accord ing ly .

I f t h e message was a reques t f o r data, COMM fe tches t h e

r e q u i r e d da ta from t h e database, and r e t u r n s i t t o t h e

Apo l lo .

The communications on t h e A p o l l o c o n s i s t s o f two d i s t i n c t

processes. The f i r s t , c a l l e d BSD, runs under the UNIX 8504.2

opera t ing system implemented on t h e Apo l lo computer. This

process accesses the e t h e r n e t i n t h e same manner as COW on

the VAX. The UNIX System V o p e r a t i n g system implemented on

t h e Apo l lo d i d n o t support t h e C-Socket model when t h i s

l a b o r a t o r y was developed. This i s why BSD was developed. I t acts as a b r i d g e between t h e VAX computer and t h e System V processes on the Apo l lo . BSD forwards a l l messages i t

rece ives from t h e VAX t o System V, and v i c e versa.

The second communication process on t h e Apo l lo , named LINK,

runs on the UNIX System V opera t ing system. Th is process shares memory b locks w i t h t h e MM1 program. When data i s needed, or a command i s issued by t h e user, the LINK program

forms t h e proper message and sends i t t o BSD, which forwards

i t the VAX. When data i s r e t u r n e d from t h e VAX, i t i s rou ted

t o LINK v i a BSD. The message i s then broken down i n t o i n d i v i d u a l datons and p laced i n t h e shared memory. From

here, the MMI program can access i t and d i s p l a y i t on the

screen.

LINK and BSD communicate us ing t h e A p o l l o s p e c i f i c socket

model. This performs s i m i l a r l y t o t h e C-Socket model, bu t i s

t i e d t o the A p o l l o f i l e system. Th is l i m i t a t i o n p r o h i b i t s us ing t h i s model t o communicate w i t h VAX computer d i r e c t l y .

DATABASE

The database i s used t o s t o r e t h e system model as w e l l as

p rov ide a common access p o i n t f o r t h e c u r r e n t s t a t e o f the

system w h i l e t h e s i m u l a t o r i s executing. The RTPSS reads the

system model from t h e database a t i n i t i a l i z a t i o n . A l l f i l e

1/0 performed by t h e RTPSS i s processed through the database.

The database p h y s i c a l l y c o n s i s t s o f approximately four

megabytes o f access source code and 1 i b r a r i e s , two megabytes

o f network source da ta per thousand buses, one megabyte o f

superv isory c o n t r o l and data a c q u i s i t i o n (SCADA) source data, and twenty megabytes f o r t h e a c t u a l database f i l e per

thousand buses i n t h e system be ing modeled. The database

access r o u t i n e s a r e w r i t t e n i n t h e FORTRAN programming

1 anguage.

M u l t i p l e processes can open and access the database

simultaneously. This a l l o w s f o r var ious processes t o mon i to r

the system as i t i s be ing simulated, as w e l l as change the

topology o f the system.

The database conta ins t a b l e s f o r t h e c u r r e n t s t a t e o f the

system, and system elements. A f t e r each f i v e second cycle, the updated s t a t e i s w r i t t e n t o these tab les . A t t h i s time,

the database i s checked f o r topo logy changes t h a t may have

occurred from sources o t h e r than t h e s imu la to r , e.g. opera tor inpu t . I f changes a r e present, t h e power systems topology i s updated f o r t h e nex t s o l u t i o n cyc le .

ACCESS

Access t o the database i s p rov ided through a s e r i e s o f

i n t e r f a c e modules which a r e used t o read and w r i t e data t o tab les i n the database. When c a l l i n g these r o u t i n e s from

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locked records immediately a f t e r comple t ing W r i t i n g t o the

database.

programming languages o t h e r than FORTRAN, care must be taken

t o use t h e FORTRAN c a l l i n g convention.

A l l area and t a b l e access i s symbolic and data l o c a t i o n s are

reso lved t o numeric addresses a t execut ion t ime by i n t e r n a l database access code. I n t e r n a l d i r e c t o r i e s f o r symbolic t o abso lu te address convers ion a r e sor ted i n t o alphanumeric o rder d u r i n g database c r e a t i o n a l l o w i n g a b i n a r y search

a l g o r i t h m t o be implemented f o r t h e l o c a t i o n o f symbolic names.

A l l da ta i tems i n a named t a b l e may be t r a n s f e r r e d w i t h one

request i f des i red . Otherwise, p a r t i a l contents o f a t a b l e

may be t r a n s f e r r e d s t a r t i n g w i t h any i t e m f o r any number o f

items. The c u r r e n t number o f v a l i d i tems i n a t a b l e i s noted

and main ta ined by database access r o u t i n e s i n a separate

v a r i a b l e f o r each t a b l e . One and two dimensional tab les are supported.

ENSURING W R I T E THROUGH

When data i s w r i t t e n t o t h e database, i t must be ensured t h a t

t h e da ta i s d e l i v e r e d t o t h e database. and n o t h e l d w i t h i n

the processes 1/0 b u f f e r s . I f da ta i s n ' t immediately w r i t t e n t o t h e database, system updates w i l l n o t be seen by o t h e r

processes w i t h o u t delays. A more severe p o s s i b i l i t y i s t h a t

o n l y a p o r t i o n o f t h e da ta would be updated, w h i l e the r e s t

would remain i n t h e systems 1/0 b u f f e r s . Th is cou ld cause

t h e system be ing s imu la ted t o appear t o be i n an uns tab le s ta te , when i n f a c t t h i s i s n o t t h e case.

To ensure t h a t da ta i s w r i t t e n t o t h e database a f t e r each

c a l l t o a database access w r i t e r o u t i n e . t h e 1/0 data b u f f e r s

a r e f lushed. Th is has t h e e f f e c t o f copying a l l b u f f e r s t o

the d i s k and un lock ing any locked records. This i s

equ iva len t t o c l o s i n g and reopening the database, bu t i s

performed much qu icker .

DATABASE C O N T E N T I O N

Due t o the f a c t t h a t m u l t i p l e processes a r e accessing the

database concur ren t ly , a s i n g l e process may n o t be al lowed t o l o c k records f o r an extended t ime per iod . M u l t i p l e processes can read t h e same r e c o r d w i t h o u t conten t ion . W r i t i n g data,

on t h e o t h e r hand. must be done s e q u e n t i a l l y . When a process w r i t e s t o a record, t h a t record i s locked u n t i l t h e w r i t i n g process re leases i t . I f t h e w r i t i n g process f a i l s t o re lease

the record i n a t i m e l y manner, o t h e r processes may be blocked

from w r i t i n g t o t h e database. I f m u l t i p l e processes h o l d

locked records w h i l e per fo rming o t h e r computational tasks,

deadlock can occur when a t tempt ing t o update the database.

The RTPSS w r i t e s l a r g e s e c t i o n s o f da ta t o the database a f t e r each s o l u t i o n c y c l e . Th is i s one o f t h e slowest operations

of t h e system. Performance would be severe ly degraded i f the s i m u l a t o r has t o w a i t on o t h e r processes d u r i n g data updates.

Because o f t h i s i t i s c r i t i c a l f o r o t h e r processes t o re lease

When commands a r e en tered from t h e MMI. smal l da ta sec t ions

a r e w r i t t e n t o the database. These o f t e n i n v o l v e one record i n a tab le . I t i s impor tan t t o c a l l the proper database access r o u t i n e t o w r i t e o n l y a s i n g l e va lue t o t h e tab le , no t

t h e e n t i r e t a b l e . Th is ensures t h a t t h e database w i l l be

locked f o r t h e smal les t amount o f t ime poss ib le . A t t h i s

time, a f l a g i s s e t i n t h e database. Th is f l a g s i g n a l s the RTPSS t h a t a topology change has occurred. When t h i s f l a g i s

set , t h e RTPSS reads t h e new system s t a t u s from t h e database.

I f t h i s f l a g i s n ' t se t , t h e s i m u l a t o r can proceed w i thout

having t o read the system c o n f i g u r a t i o n from t h e database.

LABORATORY U T I L I Z A T I O N

Curren t ly , t h i s l a b o r a t o r y i s used p r i m a r i l y as a research t o o l . Research by graduate s tudents has been conducted i n

such areas as computer communications, d i s t r i b u t e d processing

algori thms, databases s e r v i n g m u l t i p l e processes. as w e l l as

human i n t e r f a c e design. P r o j e c t s have been completed i n

these areas, and o thers a r e c u r r e n t l y be ing pursued. Current

research p r o j e c t s u t i l i z i n g t h i s l a b o r a t o r y inc lude i n v e s t i g a t i n g t h e newest types o f g raph ica l user i n t e r f a c e s

and t h e i r e f f e c t on user i n t e r a c t i o n w i t h t h e system.

A l i m i t e d number o f simple scenar ios have been developed f o r

demonstrat ional purposes. These have been used t o

demonstrate the opera t ion o f a l a r g e power system t o students and v i s i t o r s o f ASU. Enhanced scenar ios a r e be ing developed

which w i l l more f u l l y demonstrate s p e c i f i c areas o f power

system a n a l y s i s and design t o s tudents s tudy ing power

systems. The l a b o r a t o r y w i l l then be a v a i l a b l e f o r use i n

courses designed f o r the s e n i o r undergraduate o r f i r s t year

graduate student. I t w i l l a i d i n t h e s tudy o f such areas as

power system models, load f lows, f a u l t c o n d i t i o n s and others.

Wi th t h e graph ica l user i n t e r f a c e , t h e s tudent i s encouraged

t o experiment w i t h the power system. By opening and c l o s i n g

breakers, equipment such as genera tors and t ransmiss ion l i n e s can be taken on and o f f l i n e . The s tudent can then witness

the consequences o f t h e i r a c t i o n . The same type o f "what i f " exper imenta t ion t h a t i s g e n e r a l l y assoc ia ted w i t h

spreadsheets can be a p p l i e d t o t h e power system. The

s imu la t ion can be r e s t a r t e d and repeated m u l t i p l e t imes t o

t e s t the e f f e c t o f d i f f e r e n t a c t i o n s on system behavior.

CONCLUSIONS

A graph ica l user i n t e r f a c e and a r e a l t ime power system

s i m u l a t o r were combined t o form a r e a l t ime power system

s i m u l a t i o n l a b o r a t o r y a t Ar izona S t a t e U n i v e r s i t y . This

l a b o r a t o r y g ives s tudents t h e o p p o r t u n i t y t o witness f i r s t

hand how a l a r g e power system behaves i n r e a l time.

Scenarios can be run t o demonstrate system disturbances o f

var ious types, and proper recovery ac t ions . The vantage

p o i n t i s t h a t o f a power system opera tor and t h e superv isory

c o n t r o l s a re t h e same as t h a t i n a c o n t r o l cen ter . Students

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can a c t u a l l y t r y o u t c o r r e c t i v e a c t i o n s d u r i n g an emergency

scenar io and f i n d o u t t h e consequences, thus o b t a i n i n g c o n f i r m a t i o n o f t h e i r t h e o r e t i c a l learn ing .

The l a b o r a t o r y i s a l s o used by researchers f o r var ious

purposes. The t r a d i t i o n a l research i n power system models

and s o l u t i o n a lgor i thms i s p rov ided a very convenient environment, by a l l o w i n g t h e researcher t o watch on one- l ine

diagrams t h e e v o l u t i o n o f p o i n t s o f i n t e r e s t throughout the s imu la t ion . I n a d d i t i o n , t h e newer research areas o f

computer graphics, human i n t e r f a c e design (MMI), computer

communications, and d i s t r i b u t e d processing as a p p l i e d t o

power systems a r e be ing a c t i v e l y pursued i n t h i s labora tory .

ACKNOWLEDGEMENT

The RTPSS so f tware was developed as p a r t o f the E P R I RP1415-2

p r o j e c t on o p e r a t o r t r a i n i n g s imu la to rs . Cont ro l Data

Corpora t ion prov ided some o f t h e p r e l i m i n a r y MMI and database

software. The des ign and development o f t h i s l a b o r a t o r y was

funded by S a l t R i v e r P r o j e c t and Arizona Sta te U n i v e r s i t y .

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REFERENCES

M. Pra is , G. Zhang. Y. Chen, A. Bose, D. Cur t i ce , "Operator T r a i n i n g S imula tor : Algori thms and Test Results", I E E E Transactions on Power Systems, Vol . 4, NO. 3, pp. 1156-1159, August 1989.

V . Kola, A. Bose, P. M. Anderson, "Power P l a n t Models

f o r Operator T r a i n i n g Simulators", I E E E Transactions on

Power Systems, Vol . 4, No. 2, pp. 559-565, May 1989.

M. Pra is , C. Johnson, A. Bose, D. Cur t i ce , "Operator

T r a i n i n g S imula tor : Component Models", IEEE Transactions

on Power Systems, Vol . 4, No. 3, pp. 1160-1166, August

1989.

M. Pra is . A. Bose. "A Topology Processor That Tracks Network M o d i f i c a t i o n s Over Time", IEEE Transactions on

Power Systems, Vol. 3, No. 3, pp. 992-998, August 1988.

D. J. Winward, H. F. I r v i n g , "So lu t ions t o F u l l Graphics

Implementations I n The Real-Time Mon i to r ing and Control

Environment", PICA 1987, pp. 197-202.

E. E. M i l l e r , "Data E x t r a c t i o n from an Automated Mapping

and F a c i l i t i e s Management System: S p e c i f i c vs Generic

Graphics Software". IEEE Transactions on Power Systems, Vol . 3, pp. 236-238. February 1988.

F. L. Alvarado, R. H. Lasseter, Y . L iu, "An I n t e r g a t e d

Engineering S imula t ion Environment" , I E E E Transacti "ns

on Power Systems, Vol . 3, pp. 245-253, February 1988.

BIOGRAPHIES

Mike Fo ley rece ived h i s B.S. from t h e U n i v e r s i t y o f Iowa i n

1987, and h i s M.S. from Ar izona S t a t e U n i v e r s i t y i n 1989,

bo th i n e l e c t r i c a l engineering. He began h i s Ph.0. s tud ies a t ASU i n 1989. He i s a member o f Tau Beta P i and Eta Kappa

Nu.

Y i lanq Chen rece ived h i s B.Eng. from Zhe j iang I n s t i t u t e o f

Engineering, China, i n 1982, and h i s M.S. from Zhejiang

U n i v e r s i t y , China, i n 1984. He worked as an Ass is tan t Professor a t Zhe j iang U n i v e r s i t y (1984-85). and began graduate s tud ies f o r h i s Ph.0. a t Ar izona S t a t e U n i v e r s i t y i n

1985. He i s a member of Phi Kappa Phi , Eta Kappa Nu, and a Student Member o f t h e IEEE.

Anjan Bose rece ived h i s B.S. from t h e I n d i a n I n s t i t u t e o f Technology, Kharagpur, h i s M.S. from t h e U n i v e r s i t y of

C a l i f o r n i a , Berkeley and h i s Ph.0. f rom Iowa Sta te

U n i v e r s i t y , a l l i n E l e c t r i c a l Engineering. He worked f o r the

Consolidated Edison Co. o f New York (1968-70). he was a post-

d o c t o r a l f e l l o w a t t h e IBM S c i e n t i f i c Center, Palo A l to ,

(1974-75)' and A s s i s t a n t Pro fessor o f E l e c t r i c a l Engineering a t Clarkson U n i v e r s i t y (1975-76). He served as Manager, Power System Ana lys is , i n Cont ro l Data Corpora t ion (1976-81) and a t present i s Professor, and D i r e c t o r o f the E l e c t r i c Power Research Labora tory a t Ar izona S t a t e U n i v e r s i t y . He i s

a Fel low o f t h e I E E E .