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KPE

Generator Controls Testing & ModellingGenerator Controls Testing & Modelling

December 6-7, 2000

SERC

Presented by

Les Hajagos

Kestrel Power Engineering

(905) 272 2191, [email protected]

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KPE

Testing to Meet NERC Requirements

F Reactive Capability

F Generator Modelling

F Excitation Systems/Limiters

F Power System Stabilizers

F Governors & Prime Movers

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KPE

Turbine-Generator Controls

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KPE

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

0 10 20 30 40 50 60 70 80 90 100

LOE RELAY

Acti ve Power(MW)

14.5 kV

13.1 kV

13.8 kV

UEL LIMITER

I n U n d e r e x c i t e d

R e a c t i v e P o w e r ( M V

A r )

O u t O v e r e x c i t e d

Generator

Reactive

Capability

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KPE

Generator Reactive Capability Tests

F Commonly misunderstood test

F Steady-state versus dynamic

F Q = f (V, P)

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Testing Reactive Capability - Single Unit

F Normal operation, high Qresults from low system andgenerator voltage

F Test operation high Q resultsfrom high generator voltagewith normal system voltage

F Often ends up being limited byvoltage not truly reactivecapability

F Function of stiffness of systemand transformer impedance

VG

VS

Q

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KPE

Testing Reactive Capability - Multiple Units

F Maintaining Q1+Q2 constantallows for relatively constantgenerator voltage

F Perform tests simultaneously

F Normally one limit is reachedfirst, meaning that it still maynot be possible to measure bothreactive limits

F Use calculations to extrapolate

results

VG

VS

QT

1 2

Q1 Q2

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KPE

Case Study - Combined Cycle & Peaker

VS

2 3

Q2 Q3

1

Q1

Combined

CyclePeaker

Steam Gas Limit

P Q V Ifd P Q V Ifd

17 20 14.0 5.3 42 -12 13.2 4.2 UEL

16 40 14.5 7.9 42 -9 13.3 4.3 OEL

18 -15 13.1 2.1 42 15 13.8 5.7 UEL

17 -10 13.3 2.3 42 20 14.0 6.2 4kV OV

Peaker Gas Limit

P Q V Ifd

40 20 14.2 6.1 4 kV OV

40 -13 13.3 4.0 UEL

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KPE

Reactive Capability Tests

F Use other units in plant wherever possible to control net

reactive power

F System may be able to switch capacitors or time tests for

high and low voltages

F Test or calibrate exciter UEL and OEL first

F Check all relevant relay settings (LOE, O/V, V/Hz, U/V on

unit and auxiliary buses)

F Monitor aux bus voltages and currents, switch loads where

possible

F Use calculations to supplement measurements

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KPE

Excitation Limiters

F Field current limiters (see ANSI C50.13-1977)

Time (seconds) 10 30 60 120

Field Voltage (%) 208 146 125 112F Coordinate with excitation capability

F V/Hz (over-flux) or Terminal voltage

F Under-Excitation Limiters (UEL) coordinated with LOE

and Core-End

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KPE

Testing Over-Excitation Limiters

F Location of limit determines test procedure

F Steady-state (operator control) and dynamics (signal

injection)

F

For high limits recommend two steps: off-line signal injection (relay test) for startpoint

on-line setpoint adjustment for dynamics

F Field current limiters are normally stable and dynamics can

be modelled using simple approximations

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KPE

Operation of Field Current Limiter

-0.1

0

0.1

0.2

0.3

R e a c t i v e P

o w e r

( p u )

0.97

0.98

0.99

1.00

1.01

T e

r m i n a l V

( p u )

30

35

40

45

50

55

F i e l d - V o l t s

( V o l t s )

4.25

4.75

5.25

5.75

0 5 10 15 20

Time (seconds)

F i e l d - A m p s

( A M P s )

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KPE

Testing Under-Excitation Limiters

F Location of limit determines test procedure

F Steady-state (operator control) and dynamics (signal

injection)

F For low limits recommend two steps:

off-line signal injection (relay test) for startpoint

on-line setpoint adjustment for dynamics

F UE Ls are often poorly-behaved. Caution should always be

exercised when engaging a UEL limit as the response may

be unstable. This is especially true for summing limiterswhere PSS units are installed.

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KPE

Unit Operation Against UEL Limit

0 . 9610

0 . 9615

0 . 9620

0 . 9625

0 . 9630

T e r

m i n a l V

( p u )

- 2 0 0

- 1 0 0

0

10 0

20 0

30 0

F i e l d - V o l t s

( V o l t s )

2.5

3.0

3.5

4.0

4.5

5.0

0 2 4 6 8 10

T i m e ( s ec onds )

F i e l d - A m p s

( A m p s )

- 0 . 242

- 0 . 238

- 0 . 234

- 0 . 230

R e a c t i v e P o w e r

( p u )

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KPE

UEL Dynamic Response Test

340

360

380

400

420

440

0 2 4 6 8 10

Time (seconds)

F i e l d

( A m p s )

0.99

1.00

1.01

T e

r m i n a l V

( p u )

40

80

120

160

200

F i e l d

( V o l t s )

-0.10

-0.05

0

0.05

UEL limit (reduced for test)

R e a c t i v e P

o w e r

( p u )

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KPE

PF/VAR Regulators

F Response needs to be measured

F Guidelines should be in place for:

speed of response deadband

voltage supervision

F Identify where it is implemented

F Perform AVR step response with/without control in-

service

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KPE

AVR Step Response Performed with PF/VAR

1 .5

2 .5

3 .5

4 .5

0 5 10 15 20

T i m e ( s ec onds )

E x c F i e l d

( A m p s )

0.98

0.99

1.00

1.01

1.02

T e r m i n a l V

( p u )

-0.10

-0.05

0

0.05

0.10

R e a c t i v e P o w e r

( p u )

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KPE

Types of Stability on AC Power System

F Angular Stability: associated with changes in the angular

positions of generators relative to each other. Frequency

and voltage in normal range.

F Voltage Stability: associated with changes in the vol tage

profile of the system. Frequency and angular positions in

normal range.

F Frequency Stability: associated with islanded operation of

units and changes in the system frequency. Voltage innormal range.

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KPE

Definitions Applied to Angular Stability

F Steady-State Stability: ability of the power system to

maintain synchronism at all po ints for incremental slow-

moving changes in power outputs of units or power

transfer over transmission facilities

F Transient Stability: ability of the power system to maintain

synchronism during and immediately following a major

disturbance such as a transmission line fault or the loss of a

large generating unit

F Small Signal (Oscillatory Stability): ability of the power

system to maintain synchronism during small changes in

operating conditions which produce small changes in

generator angle, speed and power

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KPE

Relationship Between Rotor Motion and

Spring-Block Analogy

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KPE

Functional Description of Stabilizer

• Measure speed (or related quantity)

• Remove steady-state component

• Compensate for phase lags and gains of exciter

• Inject into AVR input

• Create torque change through excitation change

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KPE

Power System Stabilizers

F Speed-based

F Frequency-based

F Power-based

F Accelerating-power based

F Over 100 in-service in Ontario, most based on the

accelerating-power design

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KPE

Differential Angle Stabilizer

F phase measurement between generator internal voltage and

a remote system voltage

F

sensitive to system impedance variationsF measurement time lags

F high phase advance requirement

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KPE

Speed-Based Stabilizers

F direct shaft speed measurement using passive magnetic

probes and tach circuit

F

reasonable phase compensation requirementsF shaft runout (hydro)

F torsionals (thermal)

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KPE

Speed

s T5

1 + s T5

1

1 + s T6

1

1 + A1 s + A2 s

Ks 1

1 + s T1

1 + s T2

1 + s T3

1 + s T4

Vstmax

Vstmin

Output

High-Pass Filter Stabil izer Gain & Phase Lead Limits

Single-Input Power System Stabilizer (IEEE PSS1A)

2

Torsional Filter

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KPE

Frequency-Based Stabilizers

F frequency derived from generator terminals or

compensated internal frequency

F

sensitivity to rotor oscillations increases for weak acsystems

F more sensitive to inter-area modes / not sensitive to inter-

machine modes

F system transients cause spurious output signals

F sensitive to other power system noise which is not present

in actual speed

F still requires torsional filtering

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KPE

Power-Based Stabilizers

F electrical power (inverted) leads speed by 90 degrees

F phase lead requirements met without increasing high-

frequency gainF most not equipped to adjust phase lead and therefore not

very flexible

F sensitive to mechanical power variations

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KPE

Accelerating-Power Based Stabilizers

F combines speed with measured electrical power to produce

a signal proportional to the integral-of-accelerating power

F

combines advantages of speed and power-based systemswhile eliminating or mitigating the side-effects

F no torsional filtering required

F allows aggressive phase lead selections and high gain to

match system requirements

F still need to assess effect of mechanical power variations

but effect is greatly reduced

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KPE

Power System Stabilizer Testing&Tuning

F Models rarely reflect reality (AVR/Generator)

F Models lack bandwidth to capture “exciter mode”

F PSS Step response/frequency response

F Measurement of the system phase compensation

requirements

F Step response tests to measure damping improvement at

local mode frequencies

F Load-ramping tests to ensure that the PSS does not

produce undesirable modulation of the unit’s terminal

voltage under normal or emergency operating conditions

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KPE

Preliminary Tests & Verification

F Verify values at all manufacturer supplied measurement

points

F

Inject signals using test source to verify the transferfunctions of various signal paths

F Install additional transducers as required

F Install any components required to inject test signal into

the AVR summing junction

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KPE

Measured Quantities

F RMS Terminal Voltage

F Field Voltage

F Active Power

F Shaft Speed or Frequency

F PSS Output

F Internal PSS Signals

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KPE

Example Test Setup for Measurement ofExample Test Setup for Measurement of

PSS PerformancePSS Performance

F i g . 7 . 10-07 / 97-

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KPE

0.99

1.00

1.01

1.02

1.03

T e r m i n a l V

( p u )

-0.050

-0.025

0

0.025

0.050

0 5 10 15 20

simulatedstabilizer test point

Time (seconds)

P S S - o u t

( p u )

0.80

0.81

0.82

0.83

0.84

A c t i v e P o w e r

( p u )

O n-Line Stabilizer Response

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KPE

Measurement of ClosedMeasurement of Closed-- Loop Voltage RegulatorLoop Voltage Regulator

Transfer FunctionTransfer Function

F i g . 7 . 9 -07 / 97-B e rube

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KPE

0

50

100

150

0.1 0.2 0.5 1 2 5

stabilizer phase compensationTw = 10 s, Tlead = 0.18 s, Tlag = 0.05 smeasured phase lead requirement

Frequency (Hz)

P h a s e ( d e g r e e s )

Power System StabilizerPhase Lead Compensation

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KPE

1.02

1.03

1.04

PSS ONPSS OFF T

e r m

i n a l V

(

p u )

-0.0010

-0.0005

0

0.0005

0.0010

d e l t a s p e e d

( p u )

-0.010

-0.005

0

0.005

0 1 2 3 4 5

P S S

O u t p u t

( p u )

0.90

0.95

1.00

A c t i v e P o w

e r

( p u )

Stabilizer On -Line Step Response

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KPE

P U BLIC A TIO N S / P R ES EN TA TIO N S

G . R. Bé ru b é , L . M. Ha j a g o s , Utility Experience with Gas Turbine Testing and Modeling , p r e p a re d fo r p r e se n t a t i o n a t t h e IEEE P ES P a n e l o n P o w e r P l a n t Mo d e l i n g , Ja n u a ry

2 0 0 1 .

G . R . B é r ub é , L . M. H a j a g os , R . E . B e a ul i e u , Pr ac ti ca l Ut il it y Ex pe ri en ce wi th Ap pl ic at io n of Po we r Sy st em Sta bi li ze rs , pr es en te d at th e I E EE PE S Pa ne l on P ow er Sy s t em

S t a b i l i z e r s , Ju l y , 1 9 9 9

G . R . B é r ub é , L . M . H a j a g os , Mo de ll in g Ba se d on Fi el d Te st s of Tu rb in e/ Go ve rn or Sy st em s , p r e se n t e d a t t h e IEEE S y m p o s i u m o n F re q u e n c y Co n t ro l Re q u i r e m e n t s , T re n d s a n d

Ch a l l e n g e s i n t h e N e w U t i l i t y En v i ro n m e n t , F e b ru a ry , 1 9 9 9

L . M . H a ja g o s, B . D a n a i , La bo ra to ry Me as ur em en ts an d Mo de ls of Mo de rn Lo ad s an d Th ei r Ef fe ct on Vo lta ge St ab ili ty Stu di es , I E E E T r a n s ac t i o n s o n P ow e r S y s t e ms , V o l 1 3 ,

No 2, M ay 19 98 .

G . R . B é r u b é, L . M . H a j a g o s , Te sti ng an d Mo de ll in g of Ge ne ra to r Co nt ro ls on th e On ta rio Hy dr o Sy st em , p r e se n t e d a t t h e WS CC Wo rk sh o p o n S y n c h ro n o u s U n i t D y n a m i c

Te s t i n g a n d Co m p u t e r Mo d e l V a l i d a t i o n ( Ja n u a ry 3 0 , 1 9 9 7 ) a n d t h e N ERC S y s t e m D y n a m i c s D a t a Wo rk i n g G ro u p S y m p o s i u m (A p r i l 3 0 , 1 9 9 7 )

G . R. Bé ru b é , L . M. Ha j a g o s , Utility Experience with Digital Excitation Systems , IEEE P ES Wi n t e r Me e t i n g 1 9 9 7 , Ne w Y o rk , N Y , P E 5 81 -P WRS -0 0 3 -1 9 9 7 .

G . R. Bé ru b é , L . M. H a j a g o s , R . E . Be a u l i e u , A Ut il it y Pe rsp ec ti ve on Un de re xc it at io n Li mi te rs , IEEE Tra n sa c t i o n s o n En e rg y Co n v e r s i o n , V o l 1 0 , N o 3 , S e p t e m b e r 1 9 9 5 .

G . J . Ro ge r s , R . E. Be a u l i e u , L . M. Ha j a g o s Pe rf or ma nc e of St at io n Se rv ic e In du ct io n Mo to rs Fo ll ow in g Fu ll Lo ad Re je ct io n of a Nu cl ea r Ge ne ra ti ng Un it , IEEE Tra n sa c t i o n s

o n P o w e r S y s t e m s , V o l 1 0 , N o 3 , A u gu s t 1 9 9 5 .

K . S. S h ah , G. R . B é r u b é, R . E . B e a u li e u , Test ing and Modell ing of the Union Electr ic Generator Excitat ion Systems, p r e se n t e d a t t h e 1 9 9 5 Mi sso u r i V al l e y E l e c t r i c a l

A sso c i a t i o n m e e t i n g i n K a n sa s C i t y , MO , A p r i l , 1 9 9 5 .

G . R. Bé ru b é , L . M. Ha j a g o s , R .E . Be a u l i e u , A Ut il it y Pe rs pe ct iv e on Un de re xc it at io n Li mi te rs , IEEE P ES Ex c i t a t i o n S y s t e m S u b c o m m i t t e e P a n e l P re se n t a t i o n , Ju n e 1 9 9 4 .

J . R . R . S e rv i c e , L . M. H a j a g o s , Pr ac ti ca l As pe ct s of On -L oa d Ge ne ra to r Te st in g , EP RI TR-1 0 2 3 5 1 , P ro j e c t 2 3 2 8 -0 2 , F i n a l Re p o r t , Ma y 1 9 9 3 .

G . R . B é r ub é , T . A. G o u g h , Po we r Sy st em Di st ur ba nc e Re co rd er , Ca n a d i a n E l e c t r i c a l A sso c i at i o n , T ra n sm i ss i o n , S t a t i o n P l a n n i n g a n d O p e ra t i o n s S u b se c t i o n , Ma rc h 1 9 8 9 .

G . R o g e r B é r u b é L e s M . H a j a g o s

S en io r E ng inee r S en io r E ng inee r

K es tr el P ow er E ng in ee ri ng K es tr el P ow er E ng in ee ri ng

P h: (4 16 ) 76 7-7 70 4 P h: (9 05 ) 27 2-2 19 1

E - ma il : r o ge r @k e st r el p ow e r. c o m E - ma il : l es @ k e s t r e l p o w e r . c o m

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