Power Electronics: Roles in Renewable Energy Generation –

Challenges and Opportunities Panel Session: Challenges/Issues for Smart Grid

Presenter: Eduard Muljadi National Renewable Energy Laboratory

IEEE PES General Meeting, July 17 - 21 2016, Boston, MA

NREL/PR-5D00-66794 NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

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Outline 2

• Background • Renewable energy • Grid integration • Power electronics control • Hardware/software • Testing • Storage • Environment

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Background • Applications

– mW or MW level – Isolated or grid connected

• Variability of the source – Temporal (second, hour, day, week, season) – Spatial (continental, local, plant)

• Large-area coverage—diversity – Resource – Electrical characteristics

• Operation – Normal/abnormal – Balanced/unbalanced

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Renewable Energy

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Renewable Energy

PV Plant (5~50 MW)

Rooftop PV (1~30 kW) Mobile 9-kW PV system Bechler Meadows Ranger Station Yellowstone National Park

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Image by Dennis Schroeder, NREL 22192

Image from DOE FEMP, 27638

Solar Photovoltaic (PV)

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Renewable Energy

Image by Dennis Schroeder, NREL 27806

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Conventional Power Plant vs. Renewable Energy Power Plant

Generator Sgen 4,000-W (Siemens) 1,300–2,235 MVA

Wind Turbine Generator 1‒6 MW

Plant Diversity

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Concentrating Solar Power Plant

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Reference: Li, Y.; Yu, Y.H. (2012). “Synthesis of Numerical Methods for Modeling Wave Energy Converter-Point Absorbers.” Preprint. NREL/JA-5000-52115.

Marine Hydrokinetic

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California Region

Spring Peaking Summer Peaking

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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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Integration

• 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

Image’s from NREL’s TGIG presentation archives

Interconnection

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Power Electronics Control • Generator level • Plant level • Transmission level

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Short-/Long-Term DC Distributed Storage

Provide Active Damping to Power System Network

At the Generator Level

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Control—Generator/Plant

•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)—nonsynchronous generation

•Types 3 and 4: variable-speed with flux-oriented controller via power converter. Rotor does not need to rotate synchronously.

At the Plant Level

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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

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Hardware

Hardware Testing

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Software Power Electronics—

Bridging Different Time Domains

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Storage Energy Storage

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Image from Stephen Drouilhet, 05626

Reference: McNiff, B. (2002). Wind Turbine Lightning Protection Project: 1999–2002. NREL/SR-500-31115.

Reference: “NREL Software Aids Offshore Wind Turbine Designs.” (2013). Fact Sheet. NREL/FS-6A42-60377.

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Summary • 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, and concentrating

solar power • Leverage existing and future technologies

– Other industries: drives, transportation, shipbuilding – Modern technologies: smart control, wireless, condition

monitoring, cyber physical and security, synchrophasor, market driven.