Power Systems

Engineering Center

Advanced Power Electronic Functionality for 

Renewable Energy Integration with the Power Grid

Ben Kroposki, PhD, PE, FIEEE

Director – Power Systems Engineering Center

National Renewable Energy Laboratory

2016 8th International Power Electronics and Motion Control Conference - ECCE Asia (IPEMC 2016-ECCE Asia) 

Hefei, China

May 22 - 25 2016

 NREL/PR-5D00-66741
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Evolution of the Power Grid

New Challenges in a Modern Grid 

• New energy technologies and services

• Increasing penetration of variable renewables in grid

• New communications and controls (e.g. Smart Grids)

• Electrification of transportation

• Integrating distributed energy storage and load controls

• More power electronics based generation, storage, and loads

Current Power System Future Power Systems

• Central Control

• Large Synchronous 

Generation

• Carbon Intensive

• Highly Regulated

DRIVERS

• Increased variable gen

• More bi-directional flow 

at distribution level

• Increased number of 

smart/active devices

• Evolving institutional 

environment
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Current Situation for 

Renewable Integration
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PV Module Prices
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Examples of Large PV and Wind Plants in USA

Alta Wind Energy Center

Tehachapi Pass, CA

600 Vetas Wind Turbines

1,547 MW

2,680.6 GWh/yr

Capricorn Ridge Wind 

Farm

Sterling and Coke 

County, TX

407 GE & Siemens 

Turbines

663 MW

Shepard's Flats

Arlington OR

338 GE Turbines

845 MW

2,000 GWh/yr

Photo Credit: NREL

Photo Credit: NREL

Solar Star

Rosamond, CA

Photovoltaic

579 MW

Topaz Solar Farm

San Luis Obispo 

County, CA

Photovoltaic

550 MW

Ivanpah

Mojave Desert, CA

Solar Thermal

392 MW
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Addressing High Pen PV in Hawaii

Technology Addressed

Interconnection challenges when 

connecting distributed PV into the 

electrical distribution grid such as in 

Hawaii (HECO).

Impact

Hawaii is moving towards 100% renewable 

energy and this project will work to improve 

the safety, reliability and stability of the 

electric power systems that include high 

levels of distributed PV. • Research demonstrated the ability of 

advanced power inverters to mitigate the 

impacts of high penetration of solar PV on 

distribution grids. 

• As a result, HECO has now indicated it will 

expedite the installations of solar PV systems 

on circuits up to 250% of daytime minimum 

load if the PV systems are installed with 

advanced inverters that meet stricter 

requirements. 

http://www.nrel.gov/docs/fy15osti/64173.pdf Photo Credit: Kroposki

Photo Credit: SolarCity
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NREL/Southern Cal Edison Hi-Pen PV Integration Project

Point-of-interconnection voltage and reactive power exchange 

before (left) and during (right) the field demonstration

Technology Addressed

• Demonstrate advanced PV 

inverters ability to mitigate 

impacts 

• Develop a high-pen PV 

integration handbook for 

distribution engineers

Impact

• Completed the first PHIL evaluation of a utility 

scale PV inverter

• Completed three field demonstrations of the 

capabilities/impact of advanced PV inverters

Case Study Circuit (5 MW PV system near the end-of-circuit)

System operating at 

-0.95 power factor

http://www.nrel.gov/docs/fy16osti/63114.pdf

• Develop PV impact study methods

• Benchmarked the use of 

quasi-static time-series 

simulations for PV impact 

studies against transientlevel analysis
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Active Power Control from Variable Generation

Technology Addressed

• Understanding how 

Variable Generation (Wind 

and Solar) can provide 

primary and secondary 

reserves.

Impact

• Inertial control, Primary 

Frequency Control (PFC), 

and Automatic Generation 

Control (AGC) from Wind 

and Solar is feasible with 

negligible impacts on 

loading

http://www.nrel.gov/docs/fy14osti/60574.pdf
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PV provides grid services for Puerto Rico

Technology Addressed

• PV participated in Automatic 

Generation Control (AGC)

o Follow AGC signal within 40% of 

available power 

• PV provided frequency droop 

response

o Both up and down-regulation

o 5% and 3% symmetric droop

• Fast Frequency Response (FFR) 

tests

o Test plant’s ability to deploy all 

reserve within 500 ms

o Three new controls were 

implemented and validated 

AES Illumina 20MW PV Power Plant

http://www.nrel.gov/docs/fy16osti/65368.pdf

Impact

First of a kind real-world experiment 

using PV systems to maintain large 

grid stability

Photo Credit: AES
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Additively Manufactured PV Inverter (AMPVI)

Develop a unique PV inverter that combines 

high-voltage Silicon Carbide with additive 

manufacturing to achieve better 

performance and reliability at lower cost. 

Technology Addressed

• Superior technical capabilities in term of 

energy conversion, but also mitigates 

market barriers for SiC-based PV 

inverters.

• A cost-optimized yet flexible controller 

board based on a motherboarddaughterboard approach.

• Superior grid support capabilities from the 

PV inverter due to the use of SiC with a 

wider safe operating area and better 

control bandwidth.

Impact

Motherboard

Stacked 

Daughterboards
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Future Grids with High 

Levels of Power Electronics 

Based Sources
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Stabilizing the Grid in the Future

To inverter dominated 

power system using 

next-generation 

grid-forming controls

Synchronous generator 

based power system with 

inverters using gridfollowing controls
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Stabilizing the Grid in 2035 and Beyond Project

Technology Addressed

Develop distributed inverter controllers

which provide a low- resistance path from

the current inertia-dominated grid

paradigm to a future grid paradigm

dominated by low-inertia power systems

with 100's of GWs of PV integration.

Impacts

• Develop modeling, analysis, and design 

framework for grid-stabilizing PV inverter 

controllers.

• Design, build, and prototype digital 

microcontrollers to implement proposed 

PV inverter controllers.

• Extensive evaluation of control strategy 

via analytical modeling, simulation, and 

experimentation.

• Engage with PV inverter manufacturers 

and utilities during project

To next-generation 

grid-forming controls From grid-following 

controls
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Distributed Controls and Optimization

As we migrate from a centrally controlled, 

synchronous generator based grid to a highly 

distributed, inverter based system... 

We need smart inverters with 

advanced functionality to maintain 

grid stability and... 

Improved optimization for 

millions of controllable 

devices in the grid 

Research Needs

• Control theory

• Advanced control and 

optimization algorithms

• Imbedded controllers in devices

• Linkage to Advanced 

Distribution Management 

Systems (ADMS)

• Validation of concepts and 

deployment

http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=6920041
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Physical and Cyber Security

Solutions

Interconnection

Power

Electronic

s

Characterization

Solar Interoperability

EVs

Wind

Loads

Energy 

Storage

Integrated 

Devices and 

Systems

Operations 

& Controls Operations & 

Controls

Reliability and Markets

Grid Sensors

Resource Measurements

Sensing, 

Measurements, 

and Forecasting

Forecasting

Design & 

Studies

Design & 

Studies

Institutional Support

NREL – Power Systems Research
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NREL’s Energy Systems Integration Facility (ESIF)

Smart buildings & 

controllable loads

Power Systems Integration

Grid Simulators - Microgrids

Energy Systems

Integration 

Fuel Cells, Electrolyzers

Outdoor Test Areas

EVs, Transformers, 

Capacitor Banks, 

Voltage Regulators

Rooftop PV Energy Storage -

Residential, Community

& Grid Scale Storage

HPC & Data Center

Advanced 

Distribution 

Management 

Systems

http://www.nrel.gov/esif/
Thank You!

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.

www.nrel.gov

NREL Power Systems Engineering Center