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8 wind and solar plant modeling print

Power Systems & Energy Course:
Wind and Solar Plant Modeling

Jason MacDowell


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…)





“PSS/e” -- by PTI-Siemens (here in Schenectady)
“PowerFactory” –- by DigSilent (in Germany)
Other regional, specialty s/w:
France: “Eurostag”

Brazil: “ANDESA“

Think EXCEL
vs. LOTUS….

China: “BPSP”
Etc…

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

2/


What is a ‘model’?
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

For illustration, we’ll compare a PSLF or PSS/E ®
‘model’ to an EXCEL spreadsheet ‘model’

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

3/


EXCEL
To solve problems in EXCEL (or Lotus 123) , one needs:
1)

A license to the software, sold by Microsoft (or ?)

2)

A workbook file for the problem at hand


3)

A library of built-in functions (e.g. SQRT, NPV, etc..). Users can’t change the function, but must
give it input data to produce output.

4)

Possibly some special MACROs, written to provide non-standard functions (e.g. tax depreciation
on capital equipment in Elbonia) User’s need the structure (code) of the macro AND input data.

5)

Data to drive calculations, functions and MACROs

PSLF and PSS/E ®
To solve problems in PSLF and PSS/E ®, one needs:
1)

A license to the software, sold by GE or PTI-Siemens

2)

A data set for the problem at hand (this is the grid “model”. )

3)

A library of built-in functions (called “standard library models”), e.g. GENROU (for synchronous
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.

4)

Possibly some special MACROs, written to provide non-standard functions (called “user-written models”),
e.g. HVDC, special relays, and some wind turbine generators…)

5)

Data to drive calculations, standard models, user-written models and ‘events’. Without data, the
functions and MACROs don’t work. Thus, the data is part of the ‘model’.

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

4/


WTG Model Development
Considerations
> Time-frame of Interest
> Adequate Detail
> Consistency with Similar Models

GE WTG Models
> Steady-state
> Dynamic

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

5/


Time-Scale of Dynamic Performance
EMTP Analysis
Small Signal Analysis
Fundamental Frequency Analysis
High Bandwidth, Non-Linear Systems
Control Design

Switching Transients
Harmonics &
Filter Design
Electro-Mechanical
Interactions
Transient Stability
Oscillatory Stability
Long-term Dynamic Stability

10 -6

10 -5

10 -4

.001

.01

.1

1 cycle

1

10

100

1000

1 minute

10 4
1 hour

TIME (Seconds)
© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

6/


Wind Farm Steady-State Model


Example Layout



Equivalent Model
>

Generator
-

Power Factor Range

-

Voltage Regulation

>

Transformer

>

Collector System

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

7/


Modeling a Wind Power Plant?


38 WTGs



8 Feeders



57 MW



Substation
>

34.5kV Collector

>

230kV Circuits to
POI

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

8/


Equivalent Model for System Level Studies

Point of
Interconnection
(POI) Bus

High Side Bus
(collector, e.g.
34.5kV)
P gen

Vreg bus

Substation
Transformer

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.

Q gen
Vterm

Substation transformers usually
have FOA rating roughly equal to
total MVA of WTGs.

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

9/


Equivalent Model for Plant Application Studies
Project Substation
Point of
Interconnection
(POI) Bus

High Side Bus
(collector, e.g.
34.5kV)

For most systems of N machines,
model an equivalent transformer
and machine as N times one
Terminal Bus
P gen

Collector
Equivalent
Impedance

Vreg bus

Substation
Transformer

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

Unit
Transformer

Q gen
Vterm

Unit Transformers are normally
1.75 MVA, 5.8% leakage reactance
delta-wye connected padmounts
The collector system may cover
several miles, and have different topologies.
Provide an approximate equivalent R & X.
Include charging, particularly for cable collector systems.

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

10 /


Volt/Var Control for Application Studies
Project Substation
Point of
Interconnection
(POI) Bus

High Side Bus
(collector, e.g.
34.5kV)

Terminal Bus
P gen

Collector
Equivalent
Impedance

Vreg bus

Substation
Transformer

The supervisory control will
instruct individual machines
to adjust their reactive
power output in order to
regulate system voltage;
normally at the point-ofinterconnection

Unit
Transformer

Q gen
Vterm

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

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

11 /


Typical Dynamic Model Development

– Appropriate for time-frame of phenomena
– Adequate detail

– Consistent with other models

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

12 /


Excitation System Structure
Voltage
Sensing

– Modeling depends on nature
and time scale of study
– Transient Stability

Manual
Voltage
Regulator

Automatic
Voltage
Regulator

Excitation
Power
Source

Tachometer

TurbineGenerator

De-excitation

– AVR

Protective
Relays

– Excitation power source

Field Current
Limiter

– V sensing & compensation

Overexcitation
Limiter (OEL)

– Oscillatory Stability
– add PSS
– Long-term Dynamics
– add OEL, UEL, FCL

Power
Transformer

Terminal
Voltage
& Current

Voltage Sensing
and Compensation
Underexcitation
Limiter (UEL)
Generator Flux
(Volts/Hertz)
Limiter

Power
System
Stabilizer

Power, Frequency
or
Other Signals

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

Rotor Speed

13 /


Excitation System Model
V ref
VT

AVR

Vref
VT

+





VR

VRmax
Ka
1+sTa +

VRmin

E fd

Exciter



Saturation
S e(E fd)*E fd

1
Ke+sTe

E fd

sKf
1+sTf

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

14 /


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)

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

15 /


GE WTG Dynamic Models
Doubly Fed Asynchronous (DFG) WTG
P
net
P
net
Q net
Q net

3  AC Windings
fnet
P stator
frotor
P rotor

Collector
System
(e.g.
34.5kV
bus)

Collector
System

P rotor
F rotor

P conv
F network

Full Converter (FC) WTG

Wind Turbine

Wind Turbine

Wound --Rotor
Wound
Rotor
Induction Generator
Induction
Generator

Converter

Converter
Converter

P stator

 AC Winding

Wind Turbine

Q

Pnet= Pstator
Q net

f stator

stator

fnet

f stator
net
P stator
frotor
DC Winding
P rotor

Collector System
(e.g. 34.5kV bus)

E fd

… and Solar PV
© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

16 /


PSLF WTG Dynamic Model Structure
V reg bus
V term
Trip Signal
Ip (P)
Command

P elec

Electrical
Control
Model

Generator/
Converter
Model

Qelec

P gen , Q gen

E" or I Q (Q)
Command
Power
Order

Wind Profile
Model
(User-written)

Wind
Speed

P dbr

P elec
Turbine &
Turbine Control
Model

F term

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

17 /


DFG Generator/Converter
• Generator flux dynamics neglected
• Rotor inertia dynamics included in turbine model
• Injects P & Q currents based on Electrical Control command
Eq"cmd

1
1+ 0.02s

(efd)
From
exwtge

-1

High Voltage

X"

Reactive Current

s0

Management

LVPL & rrpwr
IPcmd

Low Voltage
Active Current

IPlv

1
1+ 0.02s

(ladifd)
From
exwtge

Isorc

Management
s1

LVPL

Vterm
1.11

LVPL

Low Voltage
Power Limit

V

V
zerox
(0.50)

brkpt
(0.90)

1
1+ 0.02s

jX"
s2

Fast regulator and PLL action captured by
current management function. Also limits
terminal voltage to 120%.
© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.
Low Voltage Power Logic

18 /


DFG Generator Protection
Recommended
PSLF and PSS/e LVRT II Setpoints
Low Voltage
Ride Through

vs. GE LVRT II & HVRT

Specs

Voltage at Point of Interconnection
(Percent)

140
120
100

PSLF LVRT II
80
60
40

GE LVRT II
20
0
-1.0

0.0

1.0

2.0

3.0

4.0

5.0

6.0

Time (seconds)

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

19 /


DFG Generator Protection
Recommended
PSLF and PSS/e ZVRT Setpoints
Zero Voltage
Ride Through

vs. GE ZVRT(Nov 2008) &

HVRT Specs

Voltage at Point of Interconnection
(Percent)

140
120
100
80

PSLF
60
40

GE ZVRT
20
0
-1.0

0.0

200 ms

1.0

2.0

3.0

4.0

5.0

6.0

Time (seconds)

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

20 /


DFG Generator Protection
• Over and under-voltage settings vary by project
• Low voltage trip data may be critical to performance so confirm with
manufacturer
ZVRT

LVRT

V (%)

DV (pu)

Time (sec)

V (%)

DV (pu)

Time (sec)

75

-0.25

1.9

75

-0.25

1.7

50

-0.50

1.2

50

-0.50

1.1

30

-0.70

0.7

30

-0.70

0.7

15

-0.85

0.2

15

-0.85

0.02

111

0.11

1.0

111

0.11

1.0

115

0.15

0.1

115

0.15

0.1

130

0.30

0.02

130

0.30

0.02

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

21 /


DFG Electrical Control
Plant-Level Controller
Vrfq

WTG Controller

WindCONTROL
Emulator

Vreg

Qord

Option for user
written model

Open
Loop
Control
Logic

Qcmd
Eq"cmd

Qref
PFAref
Pelec

Power
Factor
Regulator

Electrical
Control

To Generator
Model

Reactive Power Control
Qgen
From
Wind Turbine
Model

IPcmd

Vterm
Pord

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

22 /


DFG Reactive Power Control
WindCONTROL
Emulator
Vreg

Plant Voltage Control

Vrfq
(vref)

Vermx

+

1
1+ sTr

-

s3

+

s4

1/fN

-

Qmax

Kiv/s

+

Kpv
1+ sTv

Vermn

Vqd

Qwv
Qmin

1
1+ sTc

Qord

s5

s2

From Q Droop
Function

If yes, freeze
2 integrators

< Vfrz?

Power Factor Controller
PFAref
Pelec

Qref

tan

(vref)

1
1+ sTpwr

(vref)

x
s6

Qord

Qord from
separate
model
From
User Model

0

(vref)

1
pfaflg

0
1
varflg

-1

Qmax

Open
Loop
Control

Qcmd
Qmin

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

23 /


DFG Q Droop Function

Improves coordination between multiple controllers
Q Input

1
1+ sTlpqd

Kqd

Vqd

s7

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

24 /


DFG Electrical Control
Qgen

Vterm
Vmax

Qcmd

+

XIQmax

Vref

KQi / s

Eq"cmd

KVi / s

+
+

s0

Vmin

s1

XIQmin

(efd)

To Generator
Model

Auxiliary
Test Signal
( model[@index].sigval[0] )

Pord
(vsig)

From
Wind Turbine
Model

.
.

IPmax

IPcmd
(ladifd)

Vterm

© 2016 General Electric International, Inc. All rights reserved. Not for distribution without permission.

25 /


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