8 wind and solar plant modeling print

WTG and Solar Dynamic Models• WTG Overview • Model Structure  Generator/Converter with Voltage Protection  Electrical Control  Turbine and Turbine Control for WTG  Wind Power or Irra

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Power Systems & Energy Course: Wind and Solar Plant Modeling

Jason MacDowell

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Alphabet Soup: Software

There are several software programs used by the

electric power industry for planning studies:

• “PSLF” by GE EA&SE (us: Energy Consulting, EC, PSEC, PSED,

EUSED, etc…)

• Other regional, specialty s/w:

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Utilities represent their entire system in a simulation model

(using software such as GE PSLF or Siemens PSS/E ®)

This model is a mathematical representation of all

components in the network, such as:

• Generation (Thermal, Renewables, etc…)

• Transmission (Lines, Transformers, FACTS, etc…)

• Loads

What is a ‘model’?

‘model’ to an EXCEL spreadsheet ‘model’

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EXCEL

To solve problems in EXCEL (or Lotus 123) , one needs:

give it input data to produce output.

on capital equipment in Elbonia) User’s need the structure (code) of the macro AND input data.

PSLF and PSS/E ®

generators), IEEEST1 (for one standard type of excitation system), GGOV1 (simple governor for gas

turbines)… There may be thousands of these models in the grid model.

e.g HVDC, special relays, and some wind turbine generators…)

functions and MACROs don’t work Thus, the data is part of the ‘model’.

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Time-Scale of Dynamic Performance

Switching Transients

Electro-Mechanical Interactions Transient Stability Oscillatory Stability

Long-term Dynamic Stability

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Wind Farm Steady-State Model

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Modeling a Wind Power Plant?

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Equivalent Model for System Level Studies

Substation Transformer

High Side Bus (collector, e.g

34.5kV)

Substation transformers usually

have FOA rating roughly equal to

total MVA of WTGs

For most systems of N machines,

model an equivalent transformer

and machine as N times one

Represent entire farm capability

in power factor range, voltage regulation, etc.

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Equivalent Model for Plant Application Studies

Point of Interconnection (POI) Bus

CollectorEquivalentImpedance

Unit Transformers are normally 1.75 MVA, 5.8% leakage reactance delta-wye connected padmounts

For most systems of N machines,

model an equivalent transformer

and machine as N times one

The collector system may cover several miles, and have different topologies.

Provide an approximate equivalent R & X.

Include charging, particularly for cable collector systems.

Substation transformers usually

have FOA rating roughly equal to

total MVA of WTGs Substation

collector bus may have additional

shunt reactive compensation to

augment machine var capability

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Point of Interconnection (POI) Bus

CollectorEquivalentImpedance

GE 1.5 MW machines offered in a range of steady-state reactive power capabilities at their terminals

A common range:

• 0.90 pf overexcited (delivering 730 kVARs to the system)

• 0.90 pf underexcited (drawing 730 kVARs from system)

Frequently provides +/- 0.95 pf at POI

The supervisory control will

instruct individual machines

to adjust their reactive

power output in order to

regulate system voltage;

normally at the

point-of-interconnection

Volt/Var Control for Application Studies

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Typical Dynamic Model Development

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Excitation System Structure

Power, Frequency

orOther Signals

VoltageSensingManualVoltageRegulatorAutomaticVoltageRegulator

ExcitationPowerSource

Generator

Turbine-meter

Tacho-PowerTransformer

Field CurrentLimiterOverexcitationLimiter (OEL)

Voltage Sensingand Compensation

UnderexcitationLimiter (UEL)

Generator Flux(Volts/Hertz)Limiter

PowerSystemStabilizer

De-excitation

ProtectiveRelays

Rotor Speed

TerminalVoltage

& Current

– Modeling depends on nature

and time scale of study

– Transient Stability

– AVR

– Excitation power source

– V sensing & compensation

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Excitation System Model

Exciter AVR

V ref

Ka 1+sTa

+ –

–

1 Ke+sTe –

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WTG and Solar Dynamic Models

• WTG Overview

• Model Structure

 Generator/Converter with Voltage Protection

 Electrical Control

 Turbine and Turbine Control (for WTG)

 Wind Power (or Irradiance)

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34.5kV bus)

… and Solar PV

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PSLF WTG Dynamic Model Structure

Generator/

Converter Model

Electrical Control Model

I

p (P) Command

Turbine &

Turbine Control Model

Wind Speed Wind Profile

Model

(User-written)

Power Order

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DFG Generator/Converter

• Generator flux dynamics neglected

• Rotor inertia dynamics included in turbine model

• Injects P & Q currents based on Electrical Control command

From exwtge

V term

High VoltageReactive CurrentManagement

Low VoltageActive CurrentManagement

I sorc -1

1 1+ 0.02s

Low Voltage Power Logic

V

LVPL

brkpt (0.90)

1.11

zerox (0.50)

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DFG Generator Protection

• Over and under-voltage settings vary by project

• Low voltage trip data may be critical to performance so confirm with

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WindCONTROL Emulator

Pord

From Wind Turbine Model

To Generator Model

QrefPower Factor Regulator PFAref

Reactive Power Control

Pelec

Vreg

Plant-Level Controller

WTG Controller

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1 1+ sTr

1 1+ sTpwr

0

pfaflg 1

Qref

(vref)

0

varflg 1

+ +

DFG Reactive Power Control

From User Model Power Factor Controller

Plant Voltage Control

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DFG Electrical Control

+

s0

s1

XI Qmin

.

K Qi / s

(efd)

(ladifd) (vsig)

-

-+

( model[@index].sigval[0] )

Auxiliary Test Signal

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DFG voltage control, via

reactive power control at

zero real power, is

available with reduced

VAR range.

Wind Power Model

Wind Speed



Blade Pitch

Torque Control X

Pitch Control

rotor

+

+ +

Pset

Pord

Power Response Rate Limit

Pinp

Pitch Compensation

Pitch Actuation

Speed Reference Function

err



Power Control



Active Power Control (optional)

(from generator model)

Trip Signal (to generator model)

(to electrical control model)

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1 1+ sTp

Wind Speed





Blade Pitch

Torque Control

X

Anti-windup on Power Limits

Under Speed Trip

To getwg

Anti-windup on Pitch Limits

Kptrq + Kitrq/ s

s4 s2

s1 s0

s3

P elec

Rotor Model

(elimt)

+ +

Auxiliary Signal

(psig)

WTG Terminal Bus Frequency

fbus

pstl

sTw

1 + sTw s10

P setAPC

Power Response Rate Limit pinp

plim

perr

wsho

+ +

s6 s9

1 + 60s

dpwi +

- 0.75P 2 elec + 1.59P elec + 0.63

WindINERTIA Control (optional)

P min

P max

1.

0 1

apcflg

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Wind Power Model

( 2

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From ewtgfc

Vterm

High Voltage Reactive Current Management

Low Voltage Active Current Management

Isorc -1

(efd)

IPcmd

(ladifd)

1 1+ 0.02s

s0

s1 LVPL & rrpwr

1 1+ 0.02s LVPL

IQcmd

IPlv

s2 V

Low Voltage Power Logic

V

LVPL

brkpt (0.90)

1.22

zerox (0.40)

Full Converter (FC) Generator/Converter

Current commands from Electrical Control

Representation of fast regulator/PLL action similar to DFG

Applies to Full Converter WTG and PV Solar

Similar generator protection

Was 1/X”

for DFAG

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Option for user-written model

Qcmd

IPcmd

WindCONTROL Emulation

Vref

Qgen

Vterm

Electrical Controller

Pord

(from wind turbine model)

(to generator model)

Qref

Power Factor Regulator PFAref

Reactive Power Control

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FC Electrical Control

+ +

KQi/ s

IPcmd

(ladifd)

to Wind Generator Model

(efd)

to Wind Generator Model

+

(elimt)

to Wind Turbine Model

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FC Converter Current Limit

-1

P Priority

1 0

1.0

Vt

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P mech 

Wind Speed



Blade Pitch

Torque

Pitch Control

rotor

+

+ +

Pset Power Response

Rate Limit

Pinp

Pitch Compensation

Pitch Actuation

Speed Reference Function

err



Power Control



(from generator model)

Trip Signal (to generator model) 1.0

WindINERTIA

+ +

FC Turbine &

Turbine Control

Functional

Overview

FC voltage control, via

reactive power control at

zero real power, is

available with full VAR

range

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Wind Speed





Blade Pitch

Torque Control

X

Anti-windup on Power Limits

Anti-windup on Pitch Limits

Kptrq + Kitrq/ s

s4 s2

s1 s0

s3

P elec

Rotor Model

s5

1

1 + s5 - 0.67P

2 elec + 1.42P elec + 0.51

(elimt)

+ +

Frequency Response Curve

1 1+sTpav

Auxiliary Signal

(psig)

WTG Terminal Bus Frequency

P min

s11

P max

Release Pmax

P setAPC

Power Response Rate Limit pinp

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Model Validation

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Why Model Validation?

• Good models of wind plants are more important as wind

penetration increases

• Development of stability models is on-going

> Grid codes are driving increased functionality in wind plants

> Continuously evolving equipment and models create on-going need for

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Faulted Bus

DFG Model Validation

Test system:

Disturbance: 3-phase, 150msec bus fault with impedance at POI (bus 2)

Compare PSLF positive sequence dynamic response to EMTP based

cycle-by-cycle response

Strong

Network

Wind Plant Substation Aggregate Wind Turbine and Transformer

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DFG Model Validation

1.5 MW DFAG PSLF and WindTrap (EMTP) Real Power Response

-1.0 0.0 1.0 2.0 3.0

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Full Converter (FC) Model Validation

Similar test system, similar disturbance…

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FC Model Validation

2.5 MW FC PSLF and Windtrap (EMTP) Real Power Response

0.0 1.0 2.0 3.0 4.0

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Field Test Results

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0

pfaflg 1

(vref)

0

varflg 1

+ +

Slower Plant-Level Control

s0

s1

XI Qmin

.

K Qi / s

(efd)

(ladifd) (vsig)

-

-+

Slower WTG Q Control Fast WTG V Control

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Individual WTG Test

+

s0

s1

XI Qmin

.

K Qi / s

(efd)

(ladifd) (vsig)

-

-+

Voltage Step Stimulus

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Unit Internal Voltage Reference Step Test

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Unit Internal Voltage Reference Step Test

Unit Internal Voltage Reference Step Test

10x expanded time scale

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Vt PSLF Vref PSLF

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Plant Level Volt/Var Test

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s1

XI Qmin

.

K Qi / s

(efd)

(ladifd) (vsig)

-

-+

1 1+ sT r

1 1+ sT pwr

0

pfaflg 1

Q ref

(vref)

0

varflg 1

+ +

V qd -

Slower Plant-Level Control

Slower WTG Q Control Fast WTG V Control

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WTG and Plant Reactive Power Response

Multi-modal response is grid friendly

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Model closely replicates field response

Field Test vs Simulation – Reactive Power

Q_TURBINES - TEST

Qg - MODEL

Cap Bank Switched Offline

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Cap Switching Test vs Model – (100 MW Plant)

Second s

0.98 5

0.9 9

0.99 5 1

1.00 5

-20 -10 0 10

-6 -3 0 3 6 9

W43: Q POI (Blue = Measured Green = Simulated) [(W14)|overplot(W46)]

POI Voltage Response

POI Q Response

Plant Qcmd BLUE = MEASURED GREEN = SIMULATED

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Field Test - Voltage Regulation

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Wind Turbine-Generator Technology – Primary Alternatives

3

GEAR BOX

WOUND ROTOR INDUCTION GENERATOR TRANSFORMER

GRID

IGBT R Control Rectifier

GRID Rectifier

3 3

IGBT Inverter

Fixed Speed System

• NEG-Micon, Bonus, traditional Nordex

Variable Slip System

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Plant reactive coordination problems and solutions

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WTG terminal Voltage with Uncoordinated

PI regulators with PT error

WTG Terminal Voltage Plant Reactive Power

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Wind Plant Voltage Control

interconnection voltage

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Dynamic Models & Simulation Results

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Plant and WTG Electrical Control

1 1+ sTr

-+

Test Signal

Slow Plant Level Voltage Regulator (WindCONTROL Emulation)

Fast Turbine Level Voltage Regulator

Intermediate Turbine Level Reactive Power Regulator

Converter Current Limit

P,Q priority flag

+

Doubly Fed

Full Converter

to generator / converter model

+

KVis

Test Signal

Doubly Fed

Full Converter

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1 1+ sTr

-+

Test Signal

+

Doubly Fed

Full Converter

+

KVis

Test Signal

Doubly Fed

Full Converter

* Ipmx is fixed for the doubly fed model, or calculated by the converter current limit

function for the full converter model

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1 1+ sTr

-+

Test Signal

+

Doubly Fed

Full Converter

+

KVis

Test Signal

Doubly Fed

Full Converter

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Response of One Plant

to a major line outage

Reactive Power Output

Point-of-regulation Voltage

Terminal Voltage Behavior

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Wind Plant Droops Field and Tuned Gains

(on plant MVAr base)

Proportional

Gain

Integral Gain

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Field test results

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Voltage Behavior – 5 Uncoordinated Wind Plants

System conditions moving

Grid capacitor switching

Voltage Limit overrides power factor control

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System conditions moving

System conditions moving Grid capacitor switching

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Dynamic Behavior and Field Validation

of Simulation Model

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No Droop - Simulation

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No Droop – Field Measurement

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With Droop - Simulation

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