This document summarizes improvements made to the System Advisor Model (SAM) for predicting photovoltaic module performance based on IEC-61853 test data. A new model was developed that estimates module parameters at any test condition or operating condition, resulting in an 88% reduction in error compared to the previous 6 parameter model. The updated model and its ability to more accurately reproduce module test data from the improved parameter estimation technique will be available in SAM around July.

1. Significant Improvement in Module
Performance Prediction Accuracy
Based on IEC-61853 Data
Janine Freeman
8th PV Performance Modeling Workshop
Santa Ana Pueblo, New Mexico
May 9, 2017

2. 2
Irradiance
Transposition using Isotropic, HDKR, or Perez
Measured plane of array (POA) input
Shading
Irregular obstruction shading from 3D scene
Self-shading for regularly spaced rows
External input from SunEye, Solar Pathfinder
Snow cover loss model
Module
Simple efficiency model
Single diode model (CEC database or datasheet)
Extended single diode model (for IEC-61853 tests)
Sandia PV Array Performance Model
Inverter
Sandia/CEC grid-tied inverter model
Datasheet part-load efficiency curve
System
Sizing wizard or electrical layout
Multiple subarrays
Fixed, 1 axis, backtracking, azimuth axis, 2 axis
Battery storage
Degradation
Extrapolated single year
Lifetime simulation of all years
Simulation
1 minute to 1 hour time steps
Detailed photovoltaic model
֍
System Advisor Model

3. 3
Background System Advisor Model
1. Equivalent circuit models
2. Point models
3. “Data” models

4. 4
Background System Advisor Model
Single diode model
Great at STC, but what about all these conditions?

5. 5
Background System Advisor Model
Original model
implementation in SAM:
“Procedure for applying
IEC-61853 test data to a
single diode model”,
Dobos, PVSC 2014
Based only on thin film data!
Curve fitting errors sometimes
reduced ability of the model
to accurately reproduce test
data

6. 6
Estimating Parameters at Test Conditions System Advisor Model

7. 7
Estimating Parameters at Any Condition System Advisor Model

8. 8
Estimating Parameters at Any Condition System Advisor Model

9. 9
Map Boundaries System Advisor Model
If desired operating
condition is…
• sufficiently near edge of
convex hull defined by
test points, nearest
known point used
• Too far away, model
reverts to standard
single diode model
equations
֍

10. 10
Comparison with 6 Parameter Model System Advisor Model

11. 11
Comparison with 6 Parameter Model System Advisor Model
88% reduction in error on average across 20 modules

12. 12
Upcoming Work System Advisor Model
Further validation compared to measured data using MPERT data

13. 13
• Desktop Application
• Built-in Scripting Language
• Software Development Kit (SDK)
o C/C++
o Matlab
o Python
o C#
o Java
• Upcoming: SAM open-sourcing
(more on that later!)
Where can I get the new model? System Advisor Model
Dobos, A.; Freeman, J.: Significant Improvement in PV
Module Performance Prediction Accuracy Using a New
Model Based on IEC-61853 Data, forthcoming
New Model Implementation Release Expected ~July

14. Our team
Janine Freeman Project lead, PV and wind models
Nick DiOrio Software architecture, Battery storage models
Steve Janzou Programming, financial structures (subcontractor)
Paul Gilman User support and documentation (subcontractor)
Ty Neises Concentrating solar power models
Mike Wagner Concentrating solar power models
Nate Blair Emeritus lead, financials, costs, systems
http://sam.nrel.gov
System Advisor Model