High-Speed Monitoring of

Multiple Grid-Tied PV Array

Configurations

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

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)

Locations

4

(271 kW, 20° tilt)

(243 kW, ±5° W/E)

(73 kW, 10° tilt)

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

Location

6

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

Dual Communications

8

Data Loggers

9

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

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

Reference Modules

12

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14 Sep 2015, 10:49 EDT

Array Images

13

26 Sep 2014

22 Feb 2015

Output Circuit Power and Efficiency

Output Circuit Power and Efficiency

All-Sky Images

14

Bonus: Inverter Arcing Event

15

25 Aug. 2015

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