Multi-PCC 

Electric Distribution System 

Power Hardware-in-the-Loop

Blake Lundstrom

Fifth International Workshop on Grid Simulator Testing

Tallahassee, Florida

November 15–16, 2018 

NREL/PR-5D00-72907
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Contents

1 Background: Applications/implementation of RT distribution system sim.

2 Examples of recent NREL multi-PCC distribution system sim. projects

3 Multi-PCC CHIL + PHIL platform development
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• Differences in distribution 

system RT simulation

– More nodes

– More devices with more 

sophisticated models

– Unbalanced power flow

– Different assumptions.

Background

1. R.F. Arritt and R.C. Dugan, “The IEEE 8500-Node Test Feeder,” presented at the IEEE PES T&D 2010, New Orleans, LA, 2010, 1–6.

Figure from [1]

The IEEE 8,500-Node Test Feeder
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• Quasi-static time-series (QSTS) 

simulation

– Model scale: full system

– Purpose: study of system voltages, 

voltage regulation equipment, systemwide coordination.

• Dynamic/electromechanical 

transient simulation

– Model scale: reduced order

– Purpose: study of system/device 

interaction, system frequency 

response, combined distribution/bulk 

power system dynamics.

Applications vs. Common Implementation

Validation of outer-loop 

controls, system-wide 

coordination, integrated 

T&D modeling

10ms10s 50000

Number of

Nodes/Buses

Simulation

Time step

2. M.O. Faruque et al., “Real-Time Simulation Technologies for Power Systems Design, Testing, and Analysis,” IEEE Power and Energy 

Technology Systems Journal 2, no. 2 (June 2015): 63–73.

Updated version of figure from [2]
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QSTS Examples: Multisite Cosimulation and Coordinated Control

3. B. Lundstrom, B. Palmintier, D. Rowe, J. Ward, and T. Moore, “Trans-Oceanic Remote Power Hardware-in-the-Loop: Multi-Site Hardware, Integrated Controller, and 

Electric Network Co-simulation,” IET Generation, Transmission, and Distribution (Dec. 2017).
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QSTS Examples: System Impacts of DER Autonomous Control

4. B. Lundstrom and P. Gotseff, “Analyzing the Impact of Widespread DERs on Power Systems Using Data-Driven Models, Automated 

Scenario Building, and Integrated Power Hardware,” IET Generation, Transmission, and Distribution (submitted).
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Dynamic Examples: Oahu Frequency Response

5. A. Nelson, A. Nagarajan, K. Prabakar, V. Gevorgian, B. Lundstrom, S. Nepal, A. Hoke, M. Asano, R. Ueda, J. Shindo, K. Kubojiri, R. Ceria, and E. Ifuku, Hawaiian Electric 

Advanced Inverter Grid Support Function Laboratory Validation and Analysis (NREL/TP-5D00-67485) (Golden, CO: National Renewable Energy Laboratory, 2016).

6. A. Nelson, K. Prabakar, A. Nagarajan, S. Nepal, A. Hoke, et. al, “Power Hardware-in-the-Loop Evaluation of PV Inverter Grid Support on Hawaiian Electric Feeders,” 

presented at the IEEE ISGT, 2017.

7. A. Hoke, M. Elkhatib, A. Nelson, J. Johnson, J. Tan, R. Mahmud, V. Gevorgian, J. Neely, C. Antonio, D. Arakawa, and K. Fong, The Frequency-Watt Function: Simulation 

and Testing for the Hawaiian Electric Companies (NREL/TP-5D00-68884) (Golden, CO: National Renewable Energy Laboratory, July 2017).
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Dynamic Examples: Anti-Islanding of Multiple Inverters with GSF

Inverter 1 

Real-time computer simulation

Voltage 

amplifier

~

Inverter 1 

model

VPCC1

IInv1

Test hardware

ZSC

PV / DC 

source

LP filter

+ -

Inverter 2 

~

VPCC2

IInv2

PV / DC 

source

LP filter

+ -

Inverter 3 

~

VPCC3

IInv3

PV / DC 

source

LP filter

+ -

Voltage 

amplifier

Voltage 

amplifier

Inverter 2 

model

Inverter 3 

model

Island circuit transient model 

with load and 3 DER PCCs

Island 

breaker

Grid 

source

Test Case Number

1 2 3 4 5 6 7 8 9 10

Trip Time (ms)

0

100

200

300

400

500

600

Inverter 1

Inverter 2

Inverter 3

Test 

Case Circuit Topology and Impedances

# Transformers

# Overhead 

Lines

# Underground 

Lines

1 1 0 3

2 1 3 0

3 3 0 3

4 3 3 0

5 3 1 2

6 3 2 1

7 2 0 3

8 2 3 0

9 2 1 2

10 2 2 1

Run-on time

8. A. Hoke et al., “An Islanding Detection Test Platform for Multi-Inverter Islands Using Power HIL,” IEEE Transactions on Industrial Electronics 65, no. 10 (Oct. 2018): 7944–7953.

9. A. Hoke, A. Nelson, B. Miller, S. Chakraborty, F. Bell, and M. McCarty, Experimental Evaluation of PV Inverter Anti-Islanding with Grid Support Functions in Multi-Inverter Island Scenarios (NREL/TP5D00-66732) (Golden, CO: National Renewable Energy Laboratory, 2016).

10. S. Chakraborty, A. Hoke, and B. Lundstrom, “Evaluation of Multiple Inverter Volt-VAR Control Interactions with Realistic Grid Impedances,” presented at the IEEE PES GM, 2015.

 

 

 

 

 

 

 

To rest of 

distribution 

system

Breaker/fuse/switch;

Island forms when open

Zgrid

~

Z1

~

Z2

~

Z3

Topology 3:

Two inverters on 

one transformer 

and one on a 

second

Zline1
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Next Applications 

• Maximize customer and system operator 

objectives while respecting system limits

• Inertial response

• Primary frequency response

• Secondary frequency response

• Follow dispatch signals.

• Distributed control applications 

requiring full-scale models at 

dynamic timescale

• More power devices under test 

(100+)

• More control devices under test 

(100+)

• More PHIL PCCs

• Larger distribution + bulk power 

system networks.
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Power- and Controller-Hardware-in-the-Loop Test Platform
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• Real-world distribution system model from Southern California Edison with 366 single-phase nodes, 100+ DER models, 

real-time load and generation inputs, running at 50–200 us time step using SSN solver

• 100+ powered hardware devices and 20+ controllers in (5) disparate lab locations

– PV string inverters

– PV microinverters

– Battery inverters

– EVSE + EV

– Controllable load, including residential appliances

– Community-scale hybrid power system

– Beaglebone Black and Raspberry PI microcontrollers.

• Sensing: 200 kHz+ LEM voltage and current sensors

• Grid Sim: Various—Ametek RS and MX, and Chroma families

• Distribution of analog I/O via fiber.

Implementation Aspects

Photo by Dennis Shroeder, NREL

NREL PIX54238
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Power-Hardware-in-the-Loop Interface

• Closed-loop control of voltage at device 

under test terminals using PR0 + delay 

compensation controller

• VITM-type interface algorithm leveraging 

power computation of the form:
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Power-Hardware-in-the-Loop Interface: Current, Power Tracking
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Power-Hardware-in-the-Loop Interface: Voltage Tracking
www.nrel.gov

Thank you

Blake.Lundstrom@nrel.gov

This work was authored by the National Renewable Energy Laboratory, operated by Alliance for Sustainable Energy, LLC, 

for the U.S. Department of Energy (DOE) under Contract No. DE-AC36-08GO28308. Funding provided by the U.S. 

Department of Energy Advanced Research Projects Agency-Energy (APRA-E). The views expressed in the article do not 

necessarily represent the views of the DOE or the U.S. Government. The U.S. Government retains and the publisher, by 

accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, 

irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for 

U.S. Government purposes.