2014 PV Performance Modeling Workshop: AE's Perspective on PV Inverter Modeling Opportunities: Tucker Ruberti, Advanced Energy

1. AE Internal and Confidential
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Sandia PV Performance
Modeling Workshop
May 5th 2014
Tucker Ruberti

2. AE Internal and Confidential
Inverter Performance Modeling Perspective
Three Categories of Opportunities:
1. Immediate Opportunities for Improvement
2. Emerging Needs that require heavy(ish) lifts
3. Intellectually interesting, but maybe not worth the effort
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3. AE Internal and Confidential
Creating an .OND file (aka Inverter model for PVsyst)
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4. AE Internal and Confidential
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Creating an .OND file (aka Inverter model for PVsyst)

5. AE Internal and Confidential
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Creating an .OND file (aka Inverter model for PVsyst)

6. AE Internal and Confidential
1. Immediate Opportunities for Improvement
A. Better efficiency curves input
I. Today: Best case is CEC default- 3 curves and 24 points
II. Better: Photon International- 275 points below
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7. AE Internal and Confidential
1. Immediate Opportunities for Improvement
B. 2-Stage Inverter Modeling
I. Today: very limited ability to model above/below maximum
power. Ex- 450 Vdc and above 850 Vdc below
II. Better: DC Voltage/Maximum Power curve, start-up/shut-
down behavior modeled more accurately
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8. AE Internal and Confidential
1. Immediate Opportunities for Improvement
C. Temperature derate/inflate
I. Today: Must post-process inverter derate for high ambient
temp, or increase at low ambient temperature
II. Better: Ambient Temperature/Maximum AC Power Curve
D. 1500 Vdc System
I. Today: Need to model as bi-polar. Must have even
number of modules per string
II. Better: Simply Add an option for 1500 Vdc systems
D. Multi-Orientation on one inverter
I. Today: Need to model as 2 inverter
II. Better: Define 2 or 3 “arrays” for an inverter, even on a
single MPPT tracker
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9. AE Internal and Confidential
2. Emerging Needs that require heavy(ish) lifts
A. AC Line Voltage Derate
I. Today: Inverters can behave in VERY unexpected ways at
low AC line voltage, especially when there is low DC voltage,
and reactive power demand
II. Better: Publish derate curves based on AC line voltage, at
least for 1.0 PF
B Power Factor/Volt-Var/1547a/1547.8/Rule 21
I. Today: No way to account for “off-unity”, voltage support, or
other advanced inverter functions
II. Better: I don’t know… Variability makes this very complex
C. DC Coupled Storage
I. Today: Exponential increase in requests for storage solutions,
but solutions providers have proprietary modeling tools
II. Better: Integrate storage into industry standard tools
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10. AE Internal and Confidential
3. Intellectually interesting, but maybe not worth the effort
A. Minute Level Data
I. Today: Hourly weather data, static AC line voltage, fixed PF
II. Better: At what point is more dynamic modeling valuable?
B Dynamic MPPT Efficiency
I. Today: Default for losses- No direct way to model MPPT
performance
II. Better: Dynamic MPPT data like IEC 53530? – Again, would
require minute level data, or better…
C. Reliability/Uptime
I. Today: Not accounted for directly for inverter
II. Better: Assign a default, start the conversation…
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11. AE Internal and Confidential
Conclusion: Real Barriers to Change
1. Manufacturers: Who moves first to share better data
publicly, not just for post-processing for large projects
2. Modeling Tools: investment and time to keep
improving inverter modeling as systems and
applications get more complex
1. …and getting good data from manufacturers
2. Maybe on an “opt-in” basis, otherwise use defaults
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12. AE Internal and Confidential
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13. AE Internal and Confidential
Gaming PVsyst?
Selecting only DC voltages for curve input?
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