Optimisation of PV installations for partial shadowing Micro-inverters and decentralised DC-DC...

Optimisation of PV installations for partial shadowing

Micro-inverters and decentralised DC-DC optimisation boxes

LeonardoENERGY www.leonardo-energy.org

Guy KasierE&D SystemsJanuary 2011

http://www.leonardo-energy.org/



Problems with a conventional configuration

• PV panels are connected in a string to a central inverter

• When there is shadowing on one panel (e.g. from a chimney or tree) the production of the entire string falls

• The generating capacity is not fully utilised




Partial shadowing of panel 4 causes a production loss in all panels of the string

Problems with a conventional configuration




Two possible solutions

Decentralised micro-inverters or

Decentralised DC-DC optimisation boxes




1. Micro-inverters (1)

• No central inverter, but a micro-inverter for each PV panel

• Micro-inverters convert the DC from a PV panel into 230 VAC

• The outputs are connected together in parallel and fed to the distribution board via a cable




1. Micro-inverters (2)

Each PV panel has its own inverter (fitted at the back of the panels)

The output of each PV panel can be monitored via a website




2. DC-DC optimisation boxes

• Each PV panel has its own optimisation box• The boxes maximise the energy output for each PV panel

and ensure a fixed DC string voltage• The boxes are connected together in series, and to a

central inverter• The output of each PV panel can be monitored via a web

page or smartphoneLeonardoENERGY www.leonardo-energy.org



Benefits of the two systems

• The output of each panel is optimised individually• Shadowing on one or more panels has no effect

on the generation of the other panels• Total generation can thus rise by 5% to 25%• Generation can be monitored from a web page. A

poorly operating panel, inverter or optimisation box can thus be detected quickly

• Inverters and optimisation boxes can be replaced individually in the event of any faults.




Disadvantages of the two systems

• The cost is higher than in a conventional system with one central inverter

• The total installation time is somewhat longer• In the event of a fault in a micro-inverter or

DC-DC optimisation box, the roof has to be accessed for maintenance




Micro-inverters versus DC-DC optimisation boxes

Micro-inverters• Output 230 VAC• No central inverter required• Parallel connection• Monitoring via web page

DC-DC optimisation boxes• Output DC voltage• Central inverter required• Serial connection• Monitoring via web page

and smartphone

Both systems ensure a higher output in the event of partial shadowing of the PV panels.




A few links

• Enphase website: www.enphaseenergy.com

• Enphase training video: video

• Solaredge website: www.solaredge.com

• Solaredge training video: video page

• Pros and cons of solar panel micro-inverters: video


http://www.enphaseenergy.com/

Optimisation of PV installations for partial shadowing Micro-inverters and decentralised DC-DC...

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