18 b mather_pv_sys_symposium_san_jose_ca_160510
TRANSCRIPT
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
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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
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PV Inverter Islanding – Still a major concern
3
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
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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.
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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.
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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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RLC vs. PHIL Island Detection Results
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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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RLC vs. PHIL Island Detection Results
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Island detection time comparison for RLC and PHIL-based evaluation: RLC – Red PHIL - Blue
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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
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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
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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.
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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?
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Thank you for your attention
Contact: Barry Mather Ph.D. National Renewable Energy Laboratory [email protected] (303)-275-4378