This document discusses opportunities for improving inverter performance models used in the solar industry. It notes that current models may not fully account for factors like temperature and voltage derating effects. The document recommends a phased approach to developing more accurate common industry models. This would involve initially using existing manufacturer data, followed by new testing standards and data to refine the models over time. The goal is to have models that better predict inverter performance under different operating conditions and applications.

1. Inverter performance models
Opportunities and requirements for
the future
Jaspreet Singh, PG Solar, May 5th 2014
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A global leader in power and automation technologies
Leading market positions in main businesses
 145,000 employees in about 100
countries
 $39 billion in revenue (2012)
 Formed in 1988 merger of Swiss and
Swedish engineering companies
 Predecessors founded in 1883 and
1891
 Publicly owned company with head
office in Switzerland

3. Solar PV
applications
Product,
system and
solutions
offering
Solar inverters Low voltage products PV power plants
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for trackers
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• Micro inverters
• String inverters – single
phase
• String inverters – three
phase
• Central inverters
• Turnkey inverter solutions
• Switching (switch-
disconnectors, circuit
breakers, contactors)
• Protection (miniature-
circuit breakers, residual
current devices, fuses,
surge protective devices
• Metering and monitoring
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• Other (terminal blocks,
pilot devices, etc).
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system (BoS) and eBOP
(electrical balance of
plant) offering
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maintenance, SCADA
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optimization
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(monitoring relays, timers,
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data converters, interface
relays, opto couplers…)
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ABB in solar: Most comprehensive value proposition
Full range of products and solutions for key applications
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 External tools
 CEC efficiency - Sandia guidelines, factory witnessed
 CEC efficiency - includes auxiliary power
 OND files - certified by 3rd party IE partner
 Post processing tools - simplified Excel files with derating
factored
 Derating plots - temperature, voltage, altitude
 Internal tools
 Inverter models - coefficients for temp/voltage derating
 Array model - single diode equation models from public
data
 Combined model to spot check and approve applications
Inverter performance models
What we share
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 CEC efficiency
 Revised Sandia guidelines
 Auxiliary load Inclusion
 Thermal derating
 Ambient temperature
 Solar gain
 Voltage derating
 DC input voltage
 Power factor operation
 Voltage dependence
 Temperature dependence
Inverter performance models
Opportunities
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 DC/ AC ratios
 Derating
 Efficiency
 Multi MPPT configurations
 Different orientation
 Variable conditions
 MPPT Efficiency
 Static
 Dynamic
Inverter performance models
Opportunities
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 Multiple manufacturers
 Large product portfolios
 Multiple topologies
 Different thermal designs
 Different coefficients
 Extensive testing
 Data validation
Inverter performance models
Complexities
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 Initial models can be created based on design parameters
 Final modified models can be based on measured data
 Irradiance and other application effects need to be discussed
Inverter performance models
Thermal derating
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 Nominal power window and operating windows may be different
 Temperature dependence on operating voltage need to be
discussed
Inverter performance models
Voltage derating
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May 05, 2014 | Slide 9

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 Inverter output power ∝ inverter internal temperature
 Inverter temperature = α1 x ambient temperature + solar
gain
 Solar gain = irradiance (W/m2) x solar absorption (%) +
surface area (m2)
 Inverter output power ∝ DC input voltage
 DC input voltage = f (array voltage, MPPT operating point)
 Array voltage = f (temperature, irradiance, Rsh)
Inverter performance models
Developing a model
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 Modeled PV array using single diode model and inverter
derating model
 Focus is on approving applications rather than energy
harvest
Inverter performance models
Developing a model
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May 05, 2014 | Slide 11

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 A common industry benchmark is recommended
 Phase approach can be used
 Scientific community needs to support
Inverter performance models
Phase approach
Derating
models
• Existing data
Efficiency • New standards
• New testing
Applications
• Power factor
• Grid support
• CPUC Rule 21
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