1) The document describes a high-speed monitoring system for multiple grid-tied photovoltaic array configurations located at the National Institute of Standards and Technology (NIST). 2) The monitoring system collects data every second from four PV arrays totaling over 500 kW, including two ground-mounted arrays, a canopy array, and a roof array. 3) In addition to PV performance data, the system also monitors weather conditions, sky images, and module temperatures to better understand PV system behavior and validation of models.

1. High-Speed Monitoring of
Multiple Grid-Tied PV Array
Configurations

2. Motivation
2
1) Test engineers who can maintain a
calibrated test facility
2) I-V curve tracers, IR cameras, etc. to
intermittently evaluate performance
3) Large scale test facilities monitored
over many years in a variable
climate
4) Long-term system performance,
durability, and reliability data over the
actual lifetime, or at least five
years
5) Monthly sampling of DC IV curves at
array, string, and module level
6) Detailed collection of operation and
maintenance data and analysis
7) Statistical sampling of modules/cells
and outdoor characterization
8) Continuous string level monitoring
9) Validation of degradation rates and
documentation of failure modes
10) High accuracy instrumentation,
including meteorological, and given
uncertainties
11) Spectral measurements
12) High-speed sampling (1 s)
13) Sky imaging
14) Obstruction data
a) Shading
b) Snow/ice
c) Soiling
15) PVsyst validation
Modeling and Validation Needs
Will meet this year —
rest met/commenced
next year

3. Motivation (cont.)
3
1) Ability to examine:
a) Inverter MPPT speed,
accuracy, modes of
operation
b) Anti-islanding test
perturbations
c) Effects of fast moving
clouds
d) Causes of module and
BOS component failures
e) Dynamic electrical
effects from irradiance
enhancement and
transitions
2) More accurate mean
power and energy yield
values
3) Identify fluctuating DC
offsets from aliasing errors
4) Validation of
a) Short-term irradiance
forecasting
b) Inverter/grid interaction
models
High-Speed Sampling (1 Hz)

4. Locations
4
(271 kW, 20° tilt)
(243 kW, ±5° W/E)
(73 kW, 10° tilt)

5. Locations
5
Canopy Array
• Commissioned June 2012
• 1032 Mono-Si Modules
• 243 kW (DC rated)
• 5° East/West
Ground Array
• Commissioned July 2012
• 1152 Mono-Si Modules
• 271 kW (DC rated)
• 20° due south
Tilted Roof Array
• Commissioned June 2012
• 312 Mono-Si Modules
• 73 kW (DC rated)
• 10° due south
Horizontal Roof Array
• Commissioned September 2001
• 234 Mono-Si Modules
• 35 kW (DC rated)
Weather Station
• Commissioned August 2014
• Shortwave, Longwave, UV,
Spectral
• DNI, DHI on Solar Tracker
• Wind, snow depth, rain
• I-V Traced Modules
• Sky Camera

6. Location
6

7. 7
Positions per IEC 60891
Instrumentation (Arrays)
8-10 module temperature
measurements per array
31-52 data streams from each inverter
21 data streams from each AC meter
GHI, POA x 2, wind, ambient air
temperature

8. Dual Communications
8

9. Data Loggers
9

10. 1 sec. vs. 1 min.
10
• Details lost at slower sampling rates
and longer averaging intervals
• Example:
o Irradiance
o Inverter Power
o Inverter Operating State
at:
o 1 sec. sampling rate
(no averaging)
o 10 sec. sampling rate
(no averaging)
o 60 sec. sampling rate
(no averaging)
o 1 sec. sampling rate, 60 sec.
averaging
17 Sep 2014

11. Instrumentation (Weather Station)
11
Domed Diffused Si
Pyranometer
Thermopile Pyranometers
900 – 1700 nm
Spectroradiometer
UV-B Radiometer
Flat-plate Si Irradiance Sensor
UV (Total) Radiometer
350 – 1000 nm
Spectroradiometer
UV-A Radiometer

12. Reference Modules
12
1
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ref
c c ref oc oc ref therm s
E
T T V V V N
E
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14 Sep 2015, 10:49 EDT

13. Array Images
13
26 Sep 2014
22 Feb 2015
Output Circuit Power and Efficiency
Output Circuit Power and Efficiency

14. All-Sky Images
14

15. Bonus: Inverter Arcing Event
15
25 Aug. 2015

16. Contact (to obtain data):
16
Boyd, M., “High-Speed Monitoring of Multiple Grid-Connected Photovoltaic Array
Configurations”, NIST Technical Note 1896, http://dx.doi.org/10.6028/NIST.TN.1896 .

17. 17