Power system analyses(Dynamic modeling)

Using PSS/E for power system analyses- Turbine & Turbine Governor modeling -

Istanbul, May 2011

IntroductionIt is important to model turbine governing and turbine of a generator due to the crucial influence to the power and frequency in a system during the entire dynamic process.Largest influence in:

maintaining power balance between mechanical and electrical power of generation unitmaintaining frequency of the power system, capability of machine to dampen the small signal oscillations (small signal stability)

Least influence in Reactive Power-Voltage loop (QV control)

Introduction

There are three types of conventional power plant turbines:

Hydro turbinesSteam turbinesGas turbines

Recently wind turbines for wind farms emerge as a new large scale power source

Principle scheme of turbine governing

Governing systems

Turbine governors are also separated into two types depending on their purpose:

Static droop governors (used for steam and gas turbines)

Static & Transient droop governors (used for hydro turbines)

σ1

=K Main servomotor with oil distributor

Main servomotor with oil distributor

Mechanical damping circuit

Hydro turbines

Type of hydro power plant dictates technical parameters (construction)

Run of riverHigh dam (storage)

DerivationTurbine type

PeltonFrancisBladeKaplan

Hydro turbines

Primary driving force is water which is conducted from a water reservoir or from a river flowFirst actual power plant was hydropower plant Usually separated by the Net Head to:

Pelton turbines (500m<Net Head )Francis turbines (<Net Head)Kaplan turbines (low Net Head and run of river)Propeller (Bulb) turbines (run of river)

Hydro turbines

Advantages:High controllability of power generationFast rate of power change

drawbacks:Highly nonlinear element (many physical values affect the operation)Slow response during the transient processesLimitation of maximum unit power up to 600 MW

Hydro turbines and governors

There are several models for hydro turbines in PSS/E library:

generic models: IEEEG3, PIDGOV, HYGOV2more detailed models: HYGOV, HYGOVM, WEHGOV, WSHYDD

nG

h0 = static head of water columnl = length penstockA = area penstockq = turbine flow rateh = head at the turbine admissionnG (ωG) = generator speed

PTurbine

Dampingfunction

h

+

G q

-

no load flow

+-

proportionalityfactor Turbine

Gate

– setpointspeed

Governorspeed

Governor

1

0 Servomotor Gate

–

Turbine Generator Transformer Network

friction

water time constant

water

hf head loss due friction

hq

Ah0= 1

q Pmech PG

mechanical electricalPower Power

ValveGate

lT G

speed limitclose

speed limitopen

speed limitclose

speed limitopen

speed limitclose

speed limitopen

permanent and transient Droop

servo

gain

servo

gain

h

–

–

GgGg

s1s1

ΣΣΣΣ

efGRn

Gn

2

⎟⎠⎞

⎜⎝⎛=Ggh WsT

1

ΣΣ ΣΣ

nlgpuh 10 =

fh

TATA ΣΣ

DD

gnΔ

sT+11sT+1

1

ππ

ππππ

Hydro turbines

Recommendation is to use IEEEG3 and for more detailed representation use HYGOV

Hydro turbines

1a23 (>0)

1.5a21

1a13

0.5a11 (>0)

1.16TW (>0) (sec)

6TR, (>0) (sec)

0.31δ

0.05σ

0PMIN

0.95PMAX

-0.167Uc (<0.)(pu per sec)

0.167Uo (pu per sec)

0.04TP (>0) (sec), pilot value time

0.2TG, (>0) (sec)

1a23 (>0)

1.5a21

1a13

0.5a11 (>0)

1.16TW (>0) (sec)

6TR, (>0) (sec)

0.31δ

0.05σ

0PMIN

0.95PMAX

-0.167Uc (<0.)(pu per sec)

0.167Uo (pu per sec)

0.04TP (>0) (sec), pilot value time

0.2TG, (>0) (sec)

In case of absence of data about certain HPP, use IEEEG3 with default parameters

Hydro turbine partGovernor part

Hydro turbines

Parameter ranges for IEEEG3 and HYGOV

Static and transient droops

Steam turbines

Primary driving force is steam which is conducted from a boiler, heat exchanger or nuclear reactor Usually separated to the pressure stages:

High pressure stageMedium pressure stage (reheat stage)Low pressure stage

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Steam turbines

Advantages:Installed powers up to 1500 MW

drawbacks:Slow start, slow stopSlow response and rate of change of powerReliability is highly influenced by the mechanical limitations

Steam turbines

There are several models for steam turbines in PSS/E library:

Simplified models: TGOV1, CRCMGV, BBGOV, IEEEG1, TURCZT…more detailed models: TGOV2/3/4/5, WSIEG1

ΣΣ

mediumpressure turbine

turbinepowerbasedon Sn

generator activepower based on Sn

frequency

Ps =steam (throttle) pressure(may be assumed as constantfor stability calculations )

If there exist fast valving,power/load unbalance Relay,acceleration Relay,intercept valves and so on,please give a more detailedmodel see I3I

1

+ -

based on Pn

setpoint

speedcontroller

DeadBand

(if availablewith hysteresisor back slash)

Valve

PsAs

high pressure partVopen

Vclose

1

0 position

area

Electro-hydraulicTransducer

lowpressure turbine

interceptionvalve

boiler

storage

-

Reheater

Dead Band

rate limiter

+

+

FKFKgenerator

speed

measurement

–setpoint

(transducer)(filter)

111

RsT+ 111

RsT+

ΣΣ ΣΣ

ENsT+11

ENsT+11

VT1

VT1

s1s1

ΣΣ

ssT1

ssT1

HPsT+11

HPsT+11

RsT+11

RsT+11

HPKHPK

ΣΣ

MPsT+11

LP

LP

sTK+1 LP

LP

sTK+1

1=++ LPMPHP KKK

ππ

1,0

0

1,0

0

power controller

PI

isT+11

isT+11

PK PK

ΣΣ

fcorK fcorK

reff ΣΣ

[ ]puf

ΣΣefGRP

GP

211

RsT+ 211

RsT+

GP

measurement

n

vϕcos

1=

measurement

n

vϕcos

1=

[ ]puGω

efGRω

– nϕcosTP

steam flowsm&

steam flowsm&

m&

typical values:TR1 = sec 0.02TR2 = sec 0.05-1KP = pu 0-1Ti = sec 10TV = sec 0.1-0.3Vopen = pu/s 0.1...4Vclose = pu/s -0.1...-4KHP = pu 0.25THP = sec 0.27

typical values:TR = sec 5-9KMP = pu 0.25TMP = sec 0.3KLP = pu 0.50TLP = sec 0.7TS = sec 30 - 100Kfcor = pu 20Kf = pu 20 (1/ σ)TEH = sec 0.1 - 2Dead Band = mHz ±5

ππ

ππ

MPK

Steam turbines

Recommendation is to use WSIEG1, since it emphasizes all characteristics of multistage steam turbines for cross compound or tandem compound

Steam turbines

Parameter ranges for WSIEG1

Gas turbines

Primary driving force is the exhaust gas from burned mixture of air and gas in the combustion chamberJet engine technology fixed to the groundControl of power is achieved through control fuel injection and not through flow of working fluid (water or steam)It can be used in Open Cycle (alone) or Combined Cycle (with steam turbines)

Gas turbines

Advantages:High controllability of power generationVery fast rate of power change

drawbacks:Due to the extreme operating conditions, it requires several other control loops (temperature control, NOx control)Installed powers up to 300 MW (for the open cycle)

Gas turbines

There are several models for gas turbines in PSS/E library:

generic models: GAST, WESGOV

more detailed models: GAST2A, GASTWD, GGOV1, URCSCT, URGS3T

Gas turbines

Recommendation is to use GAST, since it emphasizes all characteristics of a single gas turbine

Gas turbines

For a more detailed approach and in case of often actions of temperature control, recommendation is to use GAST2A or GASTWD (which is PID controlled)

Gas turbines

Parameter ranges for GAST

Static droop

Limitations of power are given through the limitation of valve opening

In many cases Dturbcould be ignored

Generic turbine models

In case of absence of any knowledge about the turbine parameters, use IEEEG3 (for Hydro), TGOV1 (for steam) and GAST (for gas) with ADEQUATE parameters (droop, limitations etc).

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