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The Roles of Power Electronics in Renewable Energy Deployment
Eduard Muljadi National Renewable Energy Laboratory
Panel presented at the 2014 IEEE Power and Energy Society (PES)
Conference on Innovative Smart Grid Technologies (ISGT)
Washington, DC
February 19-22, 2013
NREL/PR-5D00-61378 Source: NREL
Outline • Introduction • Renewable energy resources • Grid integration • Power electronics control • Environment
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Introduction • Applications mW or MW level Isolated or grid connected
• Variability of the source Temporal (seconds, hour, day, week, season) Spatial (continental, local, plant)
• Large area coverage – Diversity (resource and electrical characteristics)
• Operation Normal/abnormal Balanced/unbalanced
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PV Plant (5~50 MW)
Rooftop PV (1~30 kW) Mobile 9-kW PV System Bechler Meadows Ranger Station Yellowstone National Park
Introduction
Phot
o fro
m S
unPo
wer
Cor
p.,
NR
EL 2
3816
Photo by Dennis Schroeder, NREL 22192
Photo from DOE/FEMP, NREL 27638
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California Region
Spring Peaking Summer Peaking
Peak
Shi
ft 24-Hour Wind Resource
24-Hour Solar Resource
Wind Resource – Midwest Wind Resource – West Coast
Low Output 8 a.m. – 14 p.m.
High Output 8 a.m. – 12 p.m.
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Offshore Wind Resource
U.S. Wind Resource
Solar Resource
Resources
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Synchronous Generator (left) vs. Wound Rotor Induction Generator (right)
What will happen if there is a sudden disturbance in the transmission network? To power AC-DC-AC power
converter to operate WTG in variable speed
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Generator Sgen 4,000-W (Siemens) 1,300 to 2,235 MVA
Wind Turbine Generator
1-6 MW
Conventional Power Plant vs. Renewable Energy Power Plant
Plant Diversity
Phot
o by
Dav
id H
icks
, NR
EL 1
8454
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o fro
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age
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iped
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Type 1 Wind Turbine Generator (1% Slip)
Type 3 Wind Turbine Generator ( + 30% Slip) Type 4 Wind Turbine Generator (Full Conversion)
(100% Slip)
Type 2 Wind Turbine Generator (10% Slip)
Examples of Renewable Energy Resources
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Phot
o by
Dav
id H
icks
, NRE
L 19
881
Photo by David Hicks, NREL 18557
Photo by Bill Timmerman, NREL 08989
Phot
o by
Gre
g G
latz
mai
er, N
REL
198
07
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Photo by Dennis Schroeder, NREL 27806
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Reference: Li, Y.; Yu, Y. H. (2012). Synthesis of Numerical Methods for Modeling Wave Energy Converter-Point Absorbers: Preprint. 36 pp.; NREL Report No. JA-5000-52115.
Grid Integration • Interconnection • Operation • Standards – Grid codes • Ancillary services (inertial response,
frequency and governor response, reserves)
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Transmission to other utilities
115kV and higher
Power plantUtility Scale Wind Farms (above 10 MW)
Small Wind Farm (less than 10 MW)
26-115 kV
Single Large Wind Turbine
Small Wind Turbine
SubtransmissionCustomers
DistributionCustomers
Distribution Customers
4-35 kV 120-480 V
Step-uptransformer
Step-uptransformer
Step-downtransformer
Step-downtransformer
Step-downtransformer
Distributed Interconnections per IEEE-1547 Wind Farm Interconnections
Interconnection
Credit: NREL’s TGIG presentation archive.
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Base Generators Adjustable
Generators (Conventional
Gen., RE)
Variable Generators
(RE)
Reserves
Storage
Base Loads
Adjustable Loads
Variable Loads
Power Losses
Real Power
Freq UP
Freq Down
Line Capacitance Switched
Capacitors Synchronous Generators/ Condensers
Static Compensation
Line Inductance
Inductive Load
Induction Motors/Generators
Reactive Power
Voltage UP
Voltage Down
Real and Reactive Power Balance (To Keep Frequency and Voltage Constant)
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Voltage Ride Through
0
0.2
0.4
0.6
0.8
1
1.2
1.4
-1 0 1 2 3 4
Time (sec)
Vo
lta
ge
(p
.u.)
661
661A
LVRT-WECC Prop.
HVRT-WECC Prop.
Fault Ride-Through Capability • Wind power plants should be able to stay on-line under transient faults/disturbances. • The voltage should tolerate 0 p.u. for 15 ms (9 cycles). • Wind power plants should be able to regulate the power factor between 0.95 leading/lagging. • Wind power plants should have a SCADA system to allow remote access and monitoring.
Voltage vs. Maximum Clearing Time as Described in IEEE 1547
Adaptable to Regional Code
Power Electronics Control • Generator level • Plant level • Transmission level
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19 M
axim
ize
Ener
gy C
aptu
re
Load Control Gearbox Preservation
Pow
er Q
ualit
y R
eal a
nd R
eact
ive
Pow
er C
ontr
ol
Short/Long-Term DC Distributed Storage
Provide Active Damping to Power System Network
At the Generator Level
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Max
imiz
e En
ergy
Cap
ture
Pow
er Q
ualit
y R
eal a
nd R
eact
ive
Pow
er C
ontr
ol
Short/Long-Term DC Distributed Storage
Provide Active Damping to Power System Network
At the Generator Level
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•Many (hundreds) of wind turbines (1 MW to 5 MW each)
•Prime mover: Wind (wind turbine) – Renewable (free, natural, pollution free)
•Controllability: Curtailment
•Predictability: Wind variability based on wind forecasting, influenced more by nature (wind) than humans, based on maximizing energy production (unscheduled operation).
•Located at wind resource; may be far from the load center.
•Generator: Four different types (fixed speed, variable slip, variable speed, full converter) – Non-synchronous generation
•Types 3 and 4: Variable speed with flux-oriented controller (FOC) via power converter. Rotor does not have to rotate synchronously.
At the Plant Level
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A
B
C +
RPMARPMC
A
B
C +
RPMARPMC
5 10 15 20 250
1 106×
2 106×
Max Cp8 m/s9.2 m/s10.8 m/s12 m/s pitch=0 deg12 m/s pitch=4.75 deg
Power vs RPM for different wind speeds
RPM (low speed shaft)
Pow
er (W
) 1.5 106⋅
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A
B
C
D
D’
∆P
5 10 15 20 250
1 106×
2 106×
Max Cp8 m/s9.2 m/s10.8 m/s12 m/s pitch=0 deg12 m/s pitch=4.75 deg
Power vs RPM for different wind speeds
RPM (low speed shaft)
Pow
er (W
) 1.5 106⋅
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A
B
C
D
D’
∆P
Trated limit
Type 1 & 2
Type 3 & 4
At the Plant Level
Inertial Response from a Wind Turbine
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(Load Center)
Wind Power Generator
Other Generators
VAR Compensation
to Help Regulate Voltage
Storage
VR ∆δ, ∆V ∆P, ∆Q
∆δ, ∆V
Wind
At the Transmission Level
Variability
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Thermal Limit (Thin Wire)
Stability Limit (High Impedance, Long Distance,
Weak Grid)
Wind Power Generator
Wind Power Generator
Storage
Storage (Load Center)
FACTS
At the Transmission Level
Transmission Constraints
Environment 25
26 G
oogl
e M
ap o
f a w
ind
pow
er p
lant
, Teh
acha
pi, C
A
Photo by Stephen Drouilhet, NREL 05626
Reference: McNiff, B. (2002). Wind Turb ine Lightning Protection Project: 1999-2001. 100 pp.; NREL Report No. SR-500-31115.
Reference: NREL Software Aids Offshore Wind Turb ine Designs (Fact Sheet). Innovation Impact: Wind, NREL (National Renewable Energy Laboratory). (2013). 1 pg.; NREL Report No. FS-6A42-60377.
Conclusions • Cost reduction in the past 20 years • Many and diverse opportunities for Power Electronics Generation, transmission, and distribution
• Know the limitations Thermal, magnetic, electric (voltage, current) etc.
• Know the applications Environment: Ocean, land-based, isolated, clusters Opportunities to work in parallel (PV – Wind – CSP)
• Leverage existing and future technologies Other industries (drives, transportation, ship building) Modern technologies (smart control, wireless, condition monitoring,
cyber physical and security, synchrophasor, market driven)
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The information contained in this presentation is subject to a government license.