Inverter R

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Inverter RD and Testing Activities at arsenal
research

• Roland Bründlinger
• Business Unit Renewable Energy Technologies
• IEA PVPS Task 2 Meeting, 19.9.2006

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Contents

• Lab testing as RD support
• PV inverter RD and testing Areas
• Test facilities - Overview
• The race for efficiency
• Climbing the hill Characterising MPPT
  performance
• Ride through vs. Disconnect at the first sign of
  trouble PV inverters during network
  disturbances

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1 Lab testing as RD support

• Why is lab testing necessary?
• During product development
• Feedback
• Concept
• Validation of prototypes and specs
• Research
• Performance of products
• Synergy with simulations Calibration and
  validation of models
• Conformity assessment of new products

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2 PV inverter RD and testing Areas

• Safety
• Grid interface
• Safety of persons
• DC injection
• Power Quality and EMC
• Emission and Immunity
• Performance during network disturbances
• Compatibility assessment

• Performance
• Conversion efficiency
• MPPT accuracy
• Steady State
• Dynamic
• Under irregular conditions
• Thermal behaviour

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3 Test facilities - Overview
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4 The race for efficiency Background

• Factors
• Strong competition between inverter companies
• Efficiency as key argument for product selection
• Issues
• ?f(P,UDC,)
• Efficiency under which conditions?
• Unclear specifications by manufacturers
• Difficult to compare products
• Design factors (Input voltage window)
• Precise and meaningful measurements

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4 The race for efficiency Example
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Climbing the hill
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5 Climbing the hill Characterising MPPT

• MPPT Key component of the PV system
• First stage during energy conversion
• Direct influence on energy yield
• MPPT Characterisation
• Steady State accuracy Straightforward to
  determine
• Dynamic accuracy Difficult, no commonly accepted
  methods available
• Impact of irregularities in the I/V curve on the
  MPPT partial shading of PV arrays

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5 Climbing the hill Steady State accuracy
Difference 0,5 ? significant for the
manufacturer
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5 Climbing the hill DynamicMPPT assessment

• Existing approaches not satisfactory

• New approach
• Analysis of high-res (1 second) irradiance
  profiles
• Identification of typical irradiance patterns
• Application of real, measured irradiance profiles

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5 Climbing the hill Dyn. Accuracy New
Method

• Results
• Accurate weighing of steady state and dynamic
  conditions
• ?G_1s lt 50 W/m2 ?G_5s lt 160 W/m2
• Test sequence

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Impact of partial shading?
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5 MPPT during irregular Conditions Partially
shading (1)

• Background How much does partial shading impact
  the energy yield?
• Investigation of the performance of the MPPT
  under partially shaded conditions
• Examples for results
• Whole day test ?Video1
• MPPT Algorithm ?Video2

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5 - MPPT during irregular Conditions Partially
shading (2)

• Examples for typical I/V curves Comparison of
  tested MPPTs integrated into state-of-the-art
  inverters

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Power Quality Grid feedback Grid Disturbances
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6 PV inverters during grid disturbances
Background

• DISPOWER Project Impact of
• Voltage harmonics
• Voltage dips and interruptions (most critical PQ
  events)
• Background (Causes, statistics, relevance)
• Voltage dips and DG Open questions
• Loss of energy and returns
• Dissatisfaction (Operators)
• Burden on components
• PQ events
• Voltage stability (at high generation density)
• Tests at 12 WR (1500 Tests)

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6 PV inverters during grid disturbances
Sensitivity
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6 PV inverters during grid disturbances
Examples (1)

• Fast disconnection
• 85 - 20 ms, Inv 4

Current peaks at voltage recovery 75 - 80
ms, Inv 2
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6 PV inverters during grid disturbances
Examples (2)

• Influence on MPPT
• 60 - 40 ms, Inv 3

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6 PV inverters during grid disturbances
Examples (3)

• Ride-thru
• 60 - 80 ms, Inv 8

• 10 - 140 ms, Inv 9

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6 PV inverters during grid disturbances
Conclusions

• Generally high sensitivity against voltage dips
  Reasons
• Grid monitoring
• Problems with current control at voltage recovery
• Dynamic performance determined by
• Current control
• MPPT
• Implementation of grid monitoring
• Lack of awareness
• Unclear requirements in standards Immunity not
  concerned

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6 PV inverters during grid disturbances
Conclusions
Ride-thru instead of disconnect at first sign of
trouble!
Source Christian Sasse, AREVA
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Inverter RD at arsenalConclusion

• Laboratory tests deliver valuable information
• Performance of products under realistic
  conditions
• Feedback during product development
• Research on grid-relevant issues
• Synergy with simulation (e.g. real world
  waveforms)
• Contribution for development of innovative
  components.

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Kontakt

• Roland Bründlinger
• arsenal research
• Giefinggasse 2
• A-1210 Wien
• ph 43 (0) 50550-6355, f 43 (0) 50550-6390
• roland.bruendlinger_at_arsenal.ac.at