Download Power Electronics in Photovoltaic Power Systems

Power Electronics in
Photovoltaic Power
Systems
M.Sc. Tuomas Messo, 7.11.2013
Contents
1.Scale and cost of PV generation
2.Power electronics as a part of PV systems
3.Grid interfacing
4.Maximum power point tracking
5.Research in DEE
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Cost of PV electricity
 The cost of PV electricity has been coming down due to
increased volume and more efficient technology
 Grid parity will be likely to happen in the near future
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Small-scale PV production
Roof-top mounting, TUT, DEE, (Sähkötekniikan Laitos)
 13.1 kW peak power
 69 PV modules 190 watts each
 Research plant
Benefits
 Feed-in tarif (e.g., Germany)
 Own supply of electricity
Challenges
 Partial shading
 Snow and ice
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Small-scale PV production
 Modules need to be completely clean from ice to work
efficiently
 Ice creates a partial shade
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Building-integrated PV production
CIS Tower in Manchester, UK
 7,244 PV modules 80 watts each
 391 kW peak power
Benefits
 Cut-down electricity cost
 Large facades are already available
Challenges
 Losses due to partial shading
http://www.sharpmanufacturing.co.uk/
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Large-scale PV production (PV plants)
Waldpolenz Solar Park, Germany
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52 MW peak power
153,650 PV modules
220 hectares
Investment cost 130 M€
Benefits
 No pollutants
 Profitable investment?
Challenges
 Large power fluctuations
 Maintenance (dust, ice)
 Locating a fault
http://michaeltomczyk.com/images/juwi_waldpolenz_450.jpg
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PV production
In short
 The peak power of a PV plant can be almost anything
 Different power scales face different problems
 Power electronics are needed in all of them
www.abb.com
www.sma.com
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Contents
1.Scale of PV generation
2.Power electronics as a part of PV systems
3.Grid interfacing
4.Maximum power point tracking
5.Research in DEE
7.11.2013
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Power Electronics in Photovoltaics
 Voltage of the PV module has to be at the MPP to extract
maximum power
 The operating voltage can be determined using a power
electronic device
H. Häberlin, Photovoltaics System Design and Practice
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Power Electronics in Photovoltaics
 The DC electricity produced by PV modules has to be
transformed into AC in grid-connected PV power systems
 DC-AC transformation is done using a device called an
inverter
www.abb.com
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Power Electronics in Photovoltaics
 The inverter acts as an interface between the grid and the
PV modules
Grid
Load
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Power Electronics in Photovoltaics
The inverter is required to
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shut down if a grid fault occurs
ride-through capability
inject high quality current
be reliable
operate at the MPP
be cheap
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Power Electronics in Photovoltaics
PV inverter manufacturers
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ABB
SMA
Siemens
Danfoss
Vacon
kW range
MW range
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Contents
1.Scale of PV generation
2.Power electronics as a part of PV systems
3.Grid interfacing
4.Maximum power point tracking
5.Research in DEE
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Grid Interfacing
Different architectures exists
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Central 3-phase inverter
String inverter
Multistring inverter
Module-integrated inverter
S. Kjaer et. al., “A Review of Single-Phase Grid-Connected Inverters
for Photovoltaic Modules”, IEEE Trans. Industry applications
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Grid Interfacing
 The inverter should work with good efficiency
η
PAC
PDC
 This means that the inverter is designed to have small losses
Early 90’s transformer inverter.
Modern transformerless inverter.
H. Häberlin, Photovoltaics System Design and Practice
7.11.2013
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Grid Interfacing
 New type of inverters based on SiC devices have efficiencies up
to 99.5 %
 Not much room for improvement there
C. Ho et. al., “Practical Design and Implementation Procedure of
an Interleaved Boost Converter Using SiC Diodes for
PV Applications”, IEEE Trans. Power Electronics
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Reliability
 Lifetime of a PV module is more than 20 years
 Nobody knows the exact lifetime of a PV inverter (less than 10a)
G. Petrone et. al., “Reliability Issues in Photovoltaic
Power Processing Systems”, IEEE Trans. Industrial
Electronics
H. Häberlin, Photovoltaics System Design and Practice
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Reliability
 Significant amount of PV energy can be lost if the system is not
designed properly
H. Häberlin, Photovoltaics System Design and Practice
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Contents
1.Scale of PV generation
2.Power electronics as a part of PV systems
3.Grid interfacing
4.Maximum power point tracking
5.Research in DEE
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Maximum Power Point Tracking
 PV inverter controls the voltage of the PV generator to extract
maximum power
 Inverter A keeps disconnecting and inverter B fails to track the
MPP voltage
“Choosing the right inverter”, Photon International
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Maximum Power Point Tracking
 MPPT efficiency should be very close to 100% for modern
inverters.
 MPPT efficiency should be checked for different power levels.
The example inverter shown below exhibits superior MPPT
efficiency in high power conditions and very poor efficiency in low
power conditions.
H. Häberlin, Photovoltaics System Design and Practice
7.11.2013
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Maximum Power Point Tracking
 MPP can be traced by sweeping the voltage of the PV generator
but then power is lost
 Does it matter if the efficiency of inverter is 99 or 99.5% if power
is lost during the sweep?
H. Häberlin, Photovoltaics System Design and Practice
7.11.2013
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Maximum Power Point Tracking
 MPPT can get confused when irradiance changes
H. Häberlin, Photovoltaics System Design and Practice
7.11.2013
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Maximum Power Point Tracking
 Selecting the right parameters for the MPPT-algorithm is crucial
H. Häberlin, Photovoltaics System Design and Practice
7.11.2013
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Contents
1.Scale of PV generation
2.Power electronics as a part of PV systems
3.Grid interfacing
4.Maximum power point tracking
5.Research in DEE
7.11.2013
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Research in DEE
 Modeling and control of power electronic converters in PV
applications
 Optimization of MPP-tracking algorithms
 Modeling and operation of PV generators in real conditions
Conventional two-level three-phase inverter.
Three-phase Z-source inverter.
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Research in DEE
Outcomes:
 Component sizing
 Reliable control design
 Identifying potential stability issues
T. Messo et. al.,”Minimum dc-link capacitance requirement of a twostage photovoltaic inverter”, Energy Conversion Congress and
Exposition, 2013
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Interested in power electronics?
 DEE-32000 Tehoelektroniikan perusteet, 5 op
 DEE-33020 Tasa- ja vaihtosuuntaajat, 5 op
 DEE-33030 Sähkömoottorikäytöt, 5 op
 DEE-33040 Sähkömoottorikäyttöjen laboratoriotyöt, 3 op
 DEE-34000 Taajuudenmuuttajat, 5 op
 DEE-34030 Tehoelektroniikan suunnitteluprojekti, 5-8 op
 DEE-33106 Switched-mode Converters, 5 op
 DEE-34106 Converter Dynamics and EMC, 5 op
 DEE-53116 Solar Power Systems, 4 op
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Opintosuunnistus 14.11
Ohjelma:
– 10.15 tietoisku salissa SF213 Sähkövoimatekniikan ja
Tehoelektroniikan opiskelusta
– n. 10.45 labrakierrokset, esittelyssä mm.
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•
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aurinkovoimala
tuulivoimalasimulaattori
sähköauto
RTDS-verkkosimulaattori
suurjännitelaboratorio
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http://solarbackpacking.com/
Thank you!
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