Download - PV and Wind Plants
WECC Renewable Energy WECC Renewable Energy Modeling WorkshopModeling Workshop
Conducted by the WECC Renewable Energy Modeling Task Force (REMTF) and Modeling and Validation
Work Group (MVWG)
June 17, 2012 - Salt Lake City, UT
Abraham Ellis, Ryan Elliott, Ben Karlson – Sandia National LaboratoriesDonald Davies, Kent Bolton – WECC
Pouyan Pourbeik – EPRIJuan Sanchez-Gasca – General Electric
Jay Senthil – SiemensJamie Weber – PowerWorld
Irina Green – CAISO
PV and Wind Plants• Wind, and increasingly PV, represent a significant
amount of generating capacity in WECC– 2015HS case: 16GW wind, 4GW of PV (~15% of min load)– Additional >1GW of distribution-connected PV– PV and wind capacity projected to increase rapidly
• Adequate models are required for compliance with reliability standards and generator interconn. studies
• WECC REMTF is leading effort to develop generic, non-proprietary models for planning studies– Alternative to vendor-specific, proprietary, user-written,
which are generally not suitable for regional planning2
WECC REMTF Charter• The Renewable Energy Modeling Task Force shall
– Develop specifications for generic, non-proprietary, positive-sequence power flow and dynamic simulation models for solar and wind generation for use in bulk system studies
– Coordinate implementation of models in commercial simulation software
– Develop model application and validation guidelines– Coordinate with stakeholders
• REMTF reports to the WECC Modeling & Validation Work Group (MVWG), which in turns reports to WECC Technical Studies Subcommittee (TSS)
Modeling Needs and Standards• Improving accessibility to PV and wind power plant
models is indispensable to properly assess the reliability of the bulk power system
• NERC’s point of view:
“Validated, generic, non-confidential, and public standard power flow and stability (positive-sequence) models for variable generation technologies are needed. Such models should be readily validated and publicly available to power utilities and all other industry stakeholders. Model parameters should be provided by variable generation manufacturers and a common model validation standard across all technologies should be adopted...”
Reference: NERC IVGTF Special Report, Accommodating High Levels of Variable Generation,http://www.nerc.com/files/IVGTF_Report_041609.pdf
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Different Types of Models• Power flow representation
– Facility loading, voltage stability & control
• Positive-sequence dynamic models– Large-signal stability, rotor angle stability
• Short circuit models– Breaker duty, protection design/coordination
• Detailed, full-order models– Electromagnetic phenomena– Control interaction
5
RE
MT
F S
cope
REMTF Efforts Over Time• Wind Generation Modeling Group (WGMG)
established in 2005– Produced 1st generation of generic wind models
• Transitioned into Renewable Energy Task Force (REMTF) in 2011– Worked on 2nd generation of generic wind models
and generic PV models
• Recent scope expansion (work in progress)– Short circuit guides, plant controller, energy storage
WECC-Approved Models
REMTF Module Usage
REPC_A Wind/PV plant controller
REE_A, REE_B Wind /PV electrical controls
REGC_A Generator/Converter model
WTGT_A Drive Train
WTGAR_A Aerodynamic model
WTGPT_A Pitch control
WTGTQ_A Torque control
Type
3 W
TG P
lant
s
PV P
lant
s
Type
4 W
TG P
lant
s
• Approved models for distributed PV and Type 1/2 wind plants– PVD1 for small and distributed PV (simplified model)– WT1G + WT1T + WT1P/A for Type 1 wind plants– WT2G + WT2T + WT2P/A + WT2E for Type 2 wind plants
• Approved REXX models for PV and Type 3/4 wind power plants
Proposed WECC Renewable Energy Model Implementation Plan
Key stakeholder input (REMTF, IEEE, IEC)
Model specifications approved by MVWG and TSS
Prototype model implementation tested
Model validation against plant-level field data (difficult and ongoing)
Models implemented in release version of commercial software programs
Model user guidelines
Webinar on WECC/REMTF model development, deployment process
Update Approved Dynamic Models List
WECC workshop on RE modeling
Model validation guidelines and tools (in process)
WECC request for data submittal using new models, with grace period
Workshop AgendaTime Topic Speaker
8:30 – 8:45 Introduction and REMTF Overview Abraham Ellis8:45 – 9:15 Standards basis Donald Davies
9:15 – 10:00 Power Flow Representation RE PlantsDynamic Model Specifications for PV Abraham Ellis
10:00 – 10:30 BREAK 10:30 – 11:30 Dynamic Model Specifications for Wind Pouyan Pourbeik11:30 – 12:00 User Experience with New REXX models Irina Green12:00 – 1:00 LUNCH 1:00 – 1:30 PowerWorld Tutorial Jamie Weber1:30 – 2:00 PSS/E Tutorial Jay Senthil2:00 – 2:30 PSLF Tutorial Juan Sanchez-Gasca2:30 – 3:00 Questions for Tutorial All3:00 – 3:30 BREAK
3:30 – 4:30 Experience with Wind and PV Model Validation
Pouyan Pourbeik,Ryan Elliott
4:30 – 5:00 Open mic: questions, feedback All5:00 ADJOURN
Standards Framework for Wind and PV Modeling in WECC
D. Davies
Power Flow Representation of PV and Wind Power Plants
A. Ellis
Example of a PV Plant
DeSoto PV Plant (2009) DeSoto PV Plant (2009) Fort Myers, FL. (courtesy of FPL)Fort Myers, FL. (courtesy of FPL)
Substation with Substation with plant transformersplant transformers
PV Array on fixed of PV Array on fixed of tracking structure tracking structure
PV Inverters and Pad-PV Inverters and Pad-mounted transformersmounted transformers
Substantial MV collector system Substantial MV collector system network, OH or UG radial feedersnetwork, OH or UG radial feeders
Interconnection Interconnection LineLine
PV Inverter and Transformer
Transformer and AC switchgear
DC switchgear and inverters
Skid
PV/Wind Plant Power Flow Model• Single machine model is suitable for bulk studies
– Equivalent representation of inverters, pad-mounted transformers, and MV/LV collector system
– Explicit representation of substation transformer and plant-level reactive support, if any (e.g., switched caps, STATCOM)
– The goal is to approximate aggregate behavior at the POI
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Power Flow Equivalencing
15
How to obtain equivalent collector system parameters?
1.Estimate based on typical design parameters2.Best way: Calculate from collector system design data (example follows)
Single-machine power flow model
1 4
2
3
59
7
6
SUB
8
PV Inverter1 MW+/-0.95 pf
Pad-mounted Transformer3 MVAZ=6%, X/R=10
UG feeders24 kV
Inverter cluster
To utility
Model station transformer and interconnection line explicitly, if they exist.
Example – 21 MW PV Plant
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From To R X B n R n^2 X n^2
1 4 0.03682 0.00701 0.000000691 3 0.33136 0.06307
2 4 0.02455 0.00467 0.000001036 3 0.22091 0.04205
4 5 0.02455 0.00467 0.000001036 9 1.98816 0.37843
3 5 0.02557 0.02116 0.000000235 3 0.23016 0.19042
5 SUB 0.02557 0.02116 0.000000235 12 3.68251 3.04673
6 8 0.03747 0.00868 0.000000561 3 0.33726 0.07809
7 8 0.02455 0.00467 0.000001036 3 0.22091 0.04205
8 9 0.02109 0.02501 0.000000199 6 0.75925 0.90025
9 SUB 0.02109 0.02501 0.000000199 9 1.70831 2.02555
RESULTS
Partial R sum 9.4788 Partial X sum 6.7666 N 21 Collector System Equivalent(Same units as R, X & B data) Req 0.021494 pu Xeq 0.015344 pu Beq 0.000005 pu
j0.008530.000857
j0.05970 0.00597
M
ZZ TTeq
Pad-mounted Transformer Equivalent
Collector System Equivalent on 100 MVA and 24 kV base
pu on 3 MVA base
21
2
N
nZjXRZ
I
iii
eqeqeq
I
iieq BB
1
Collector System Equivalengcing Technique:
Example – 21 MW PV System
17Useful Resource: WECC PV/Wind Power Flow Modeling Guidelines
Reactive Capability• Equivalent generator reactive capability
– Varies with output level, voltage level, type of generator
• Inverter/WTG and plant-level reactive control– PF or Q control, V/Q droop, or closed-loop V-control
• May need to adjust according study scenario
18Useful Resource: WECC PV/Wind Power Flow Modeling Guidelines
Dynamic Models for PV Power Plants
A. Ellis
REMTF Dynamic Model Specs.• Consistent with established modeling approach at the
transmission (bulk system) level– Positive-sequence, for large-scale bulk-level simulations– Suitable for use with equivalent (single-generator) power
flow plant representation – Reproduce fundamental dynamic characteristics following
electrical disturbances (as opposed to wind/solar events)– Bandwidth: Steady-state to 5 Hz; faster dynamics expressed
algebraically or ignored– Generic: parametrically adjustable so that equipment of the
same type (e.g., Type 3 WTG plants, PV plants, etc.)– Available as standard library models in commercial software
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Plant-Level Controls
PV Inverter Topology and Controls (One Example)
GATE DRIVE
CIRCUITRY
PV Array Voltage Source Converter Grid
Iac, Vac at inverter terminals
Vdc
AC Current ControlsLine Current Synch.AC Current ControlsLine Current Synch.
Plant SupervisoryController
Plant SupervisoryController
Process Control (slower)(MPPT, P/Q control)
Process Control (slower)(MPPT, P/Q control)DC D
ynam
ics
DC Dyn
amics
Not M
odel
ed
Not M
odele
d
Representation of Discrete PV Plants• Two options for dynamic representation
– Full-featured PV Plant Model (REXX)– Simplified Model (PVD1)
• Both require generator explicitly represented in power flow and equivalent feeder/collector
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÷
Vt
N
D×
Q Priority (Pqflag =0)Iqmax = ImaxTDIqmin = -IqmaxIpmax = (ImaxTD2-Iqcmd2)1/2
P Priority (Pqflag =1)Ipmax = ImaxTDIqmax = (ImaxTD2-Ipcmd2)1/2
Iqmin = -Iqmax
÷
0
Ipmax
Iqmin
Iqmax
0.01
N
D
×
Vt0 Vt1 Vt2 Vt3
1
0
V0 V1
DqdvQmx
QmnQref
Vrflag
Freq
Ft0 Ft1 Ft2 Ft3
1
0
Frflag
Ip
Iq
It = Ip +j Iq
-11 + sTg
11 + sTg
Ipcmd
Iqcmd
PVD1
XcIt
Qref
-Freq_ref Ddn
fdbdPdrp
Pref
Pext
Pdrp
Fvl
Ffh
Ffl
MINIMUM
Fvh
FvlFfhFfl Fvh
Q Control
P Control
Current Limit Logic
IqcmdIqcmd’
IpcmdIpcmd’
Generator Model
Network Solution
Plant Level V/Q Control
Plant Level P Control
VrefVreg
QrefQbranch
PrefPbranchFreq_ref
Freg
Qext
Pref
REPC_A
Pqflag
REEC_B REGC_AVt Vt
Iq
Ip
REXX Model
PVD1 Model
REXX PV Plant Model Structure• Requires plant control (REPC_A), inverter control
(REEC_B), grid interface (REGC_A), protection
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Q Control
P Control
Current Limit Logic
IqcmdIqcmd’
IpcmdIpcmd’
Generator Model
Network Solution
Plant Level V/Q Control
Plant Level P Control
VrefVreg
QrefQbranch
PrefPbranchFreq_ref
Freg
Qext
Pref
REPC_A
Pqflag
REEC_B REGC_AVt Vt
Iq
Ip
PV Plant Controller
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• Reactive control options: V control, Q control, V/Q droop control• Active power control options: P control, P/freq droop control (governor
response)
Inverter P/Q Electrical Controls
26
• Local PF or Q control with overriding voltage dip response• Active power limits and rate-of-change limit• Current limiter with P or Q priority
Generator/Converter Model
• High voltage Iq logic: (software-specific, integration with network solution)• Low voltage Ip control: (approximate PLL response during voltage dips)• Low voltage Ip control: allow for controlled active current response during and following voltage
dips
27
Voltage & Frequency Tolerance
Voltage and frequency tolerance can be roughly represented using standard (V,t) and (f,t) protection models
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Sample Simulations
29
Simple Dynamic Model (PVD1)
30
÷
Vt
N
D×
Q Priority (Pqflag =0)Iqmax = ImaxIqmin = -IqmaxIpmax = (Imax2-Iqcmd2)1/2
P Priority (Pqflag =1)Ipmax = ImaxIqmax = (Imax2-Ipcmd2)1/2
Iqmin = -Iqmax
÷
0
Ipmax
Iqmin
Iqmax
0.01
N
D
×
Vt0 Vt1 Vt2 Vt3
1
0
V0 V1
DqdvQmx
QmnQref
vrrecov
Freq
Ft0 Ft1 Ft2 Ft3
1
0
frrecov
Ip
Iq
It = Ip +j Iq
-11 + sTg
11 + sTg
Ipcmd
Iqcmd
PVD1
XcIt
Qref
-Freq_ref Ddn
fdbdPdrp
Pref
Pext
Pdrp
Fvl
Ffh
Ffl
Fvh
Fvl
Ffh
Ffl
Fvh
×
• Reactive power control with Q-V droop and line drop compensation• Active power (high) frequency droop • Voltage-frequency protection with dead band and recovery logic• Dynamic inverter current limit logic with P or Q priority
Intended for use with a smaller PV plant or distribution-connected MW-scale plant
Dynamic Model Specifications for Wind Power Plants
P. Pourbeik
User Experience With REXX Models
I. Green
Software Tutorials
J. Sanchez-Gasca, J. Senthil, J. Weber
Experience with Model Validation
P. Pourbeik, R. Elliott
Open Discussion