I had a dispute with my fellow. In his opinion, a power inverter can be damaged if the load is much lower (e.g 100W) than installed capacity (e.g. 10kW) of the solar system.

I am of the opinion that even in case of zero load, the inverter will not be damaged. Because as far as I know, power is "pulled" from the system and the current is not "pushed" from PV panels to inverter. The lower the load on the power inverter, the lower the load will be on PV panels. Right?

  • \$\begingroup\$ Look up the term "discontinuous conduction mode"; I think that could answer some of your questions. Long story short, when the load on a dc-dc converter is too small, it requires different control methods. \$\endgroup\$ – Hearth Jun 28 '19 at 15:21
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    \$\begingroup\$ @Hearth: The question is about damage, not control methods. \$\endgroup\$ – Dave Tweed Jun 28 '19 at 16:04
  • \$\begingroup\$ @DaveTweed And running a converter with a controller that doesn't work in discontinuous conduction mode under this condition will probably break things, as I learned the hard way less than a week ago. \$\endgroup\$ – Hearth Jun 28 '19 at 17:32
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    \$\begingroup\$ @Hearth: In that case, you need to explain what you mean, because your comment is too cryptic as it stands. \$\endgroup\$ – Dave Tweed Jun 28 '19 at 18:33

An inverter can indeed supply a lower current than the solar panel rating without any system damage to the system.

If an inverter is not supplying as much power as the panels can deliver it will simply draw less current from the solar panel. If you follow the IV-curve of the solar panel you will see that lower current from the panel allows the voltage to increase toward the panels open circuit voltage. The solar panel is not damaged by sypplying no current, and providing the inverter can withstand the maximum ("open circuit") voltage the panels produce it will not be damaged.

enter image description here Image taken from this question

The solar panel output voltage varies both with load current an temperature. The colder the panels, the higher is the output voltage. But in a good design the panels should be chosen and connected to the inverter in a way that they can never exceed the maximum voltage rating of the inverter.


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