18 b mather_pv_sys_symposium_san_jose_ca_160510

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.

PV Inverter Island Detection Evaluation Using Power Hardware-in-the-Loop (PHIL) Techniques

Barry Mather, Ph.D. Senior Electrical Engineer Power Sys. Engineering Center [email protected] PV System Symposium PV Grid Integration Workshop San Jose, CA, May 10th, 2016

NATIONAL RENEWABLE ENERGY LABORATORY

Outline

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• Goal and motivation • Overview of the PHIL setup • Presentation of results

• PHIL vs. RLC tank (IEEE 1547/UL 1741 tests)

• A look at the strength of implemented island detection algorithms

• Island detection with induction motors on circuit

• Conclusions


PV Inverter Islanding – Still a major concern

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Motivation: • The risk of a high-pen PV circuit forming an

island has yet to be inexpensively mitigated: • Some utilities require DTT • Some PV inverter manufactures have

“beefed-up” detection algorithms • IEEE 1547.1 is under revision – what should

be tested? Goal: • Develop methods for evaluating PV inverter

island detection performance under more realistic conditions to better quantify risk


PV Inverter Island Detection Evaluation

What is present in the next slides was developed through a collaboration between NREL and FSU CAPS. Collaborators: K., Schoder, J. Langston, M. Steurer ,J. Hauer and F. Bogdan

IEEE 1547 – 2003 requires a DER to cease to energize within 2 seconds of a electrical island forming.

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PV Inverter

-

+ A

B

C

N

resonant at 60 Hz

DC Source

Va

Vb

Vc

R, L, C Load Bank

Islanding Switch

Simulated Grid DUT

IEEE 1547 / UL 1741 Anti-islanding test

See: K. Schoder, et al. Power Hardware-in-the-Loop-Based Anti-Islanding Evaluation and Demonstration, NREL Tech. Report TP-5D00-64241, Oct., 2015.

NATIONAL RENEWABLE ENERGY LABORATORY 5

Ampl

ifier

AC

Voltage References

Voltage Reference

RTS

Load bank and Feeder Emulation

PV Emulation

Protection Monitoring,

Trend Data Logging, Data capture

Simulation of PHIL-Setup

Amplifier DC

Voltage and current Measurements

VDCref

IDC VDC

Ia,b,c Va,b,c PV Inverter

3-ph

ase

DC String

-

+ L1

L2

L3

N

PE

References

Current measurement(s)

Voltage measurement(s)

Rs

VA,Bref

Tran

sfor

mer

4.

16kV

V/48

0V (D

Y)

O2(1)

Switch

Load Bank R-L-C wye

Ia,b,c Iga,b,c

SW

Vsw,c Va,b,c

PHIL Power Interface

RT Model

Va

Vb

Vc Rp

Rg

I1(10) 1:100

PHIL-Based Island Detection Evaluation

From: M. Steurer et al. Advanced Anti-Islanding Testing with Power Hardware-in-the-Loop, 3rd Annual International Workshop in Grid Simulator Testing, Nov., 2015.


RLC vs. PHIL Island Detection Results

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RLC type testing , 20 kW inverter operating at 8 kW with a QF = 1

Va, Vb, Vc Ia, Ib, Ic



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PHIL type testing , 20 kW inverter operating at 8 kW with a QF = 1

Va, Vb, Vc Ia, Ib, Ic



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Island detection time comparison for RLC and PHIL-based evaluation: RLC – Red PHIL - Blue


Determining the Strength of AI Detection

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A 60 kW PV inverter is operation at 54 kW but other perfect PQ sources are modelled at 1, 2, 3, and 4 times the inverters operating power to test the strength of island detection algorithms

Non-Islanding Inverter-based Generation


Investigating the Impact of Nearby Loads

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A 60 kW PV Inverter is operating at 54 kW and a 60 kVA induction motor is operating nearby (modelled in RTS). Result – half of the experiments resulted in detection times over 2 sec. – Please note that QF = 2 in this case.

Island Detection Times with a 60 kVA Induction Motor

Nearby


Investigating the Impact of Nearby Loads

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A 60 kW PV Inverter is operating at 54 kW and a 221 kVA induction motor is operating nearby (modelled in RTS). Result – no island is ever detected.

Vline-line

Freq.


Conclusions

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• PHIL methods were developed to evaluate PV inverter islanding scenarios – experimental results show reasonable agreement between island detection times.

• Island algorithms seem quite robust to non-islanding generators on the same circuit.

• Experimental results indicate that concern over induction motors/generators proves to be warranted

Moving forward: what level of island detection performance should we require of distributed PV and how should it be evaluated via certification tests?


Thank you for your attention

Contact: Barry Mather Ph.D. National Renewable Energy Laboratory [email protected] (303)-275-4378

Technology

18 b mather_pv_sys_symposium_san_jose_ca_160510