Homebrewed Electricity > Solar
What happens when you generate more than the inverters rating?
Rob Beckers:
--- Quote from: Amy on April 19, 2023, 05:41:45 AM ---
If you generate more power than your inverter's rating, it can result in a decrease of efficiency and cause damage to the inverter. Additionally, it could also increase the risk of fire or personal injury due to electrical overload. It is important to make sure you are not overloading the inverter by verifying that the total solar output is less than the inverter rating. If you need to increase your solar output, you will need to upgrade to an inverter with a higher rating before doing so. Ultimately, it is always best practice to match the inverter's rating as closely as possible with the total solar output of your system.
--- End quote ---
Amy, that's not actually how inverters work (or what they can handle). It is very common practise to oversize the PV array vs. the inverter rating. I've commonly seen 150% PV rated output vs. inverter rated output, and those systems have been working just fine for many, many years now.
Solar inverters will actively limit their output power to keep it at their rated limit (or maybe slightly above). Solar panels in full sun don't "produce" anything, unless you allow current to flow and Voltage to exist. A panel in the sun with its leads open has zero current, and therefore zero output power. A short-circuited PV module will produce lots of current, at zero Volt, and therefore again zero output power. Inverters make sure to run on the curve between those two extremes, normally in such a way that they produce maximum output power from the available sunlight (that's the MPPT-point, of the Maximum Power Point Tracking that it stands for). But if doing so violates the inverter limits, either the current limit or output power limit, the inverter will pick a point that ensures it's within its limits. No damage done.
You have to limit solar panels to stay within the Voltage limits of the inverter (a 1000 Volt string into a 600 Volt inverter will of course let the magic smoke out). In theory there is the issue that an oversized PV array will run the inverter "harder" but in practise with A-brand inverters we've never seen any issue with that (for one, 50% of the time the inverter is doing nothing!). There is also a theoretical maximum, where the inverter's on-board processor simply can't respond fast enough in regulating down the output power, but that too is more of a theoretical than practical limit (and some inverter designs use hardware to limit-as-a-last-resort, rather than software). Extra fusing may be required when oversizing the PV input, because the short-circuit current of the solar array may exceed the UL/CSA-listed limits of the wiring in inside the inverter, and series fusing makes this safe. But that's about it. Go ahead and oversize the PV array! It'll make for better ROI.
-RoB-
DamonHD:
I agree that oversizing of PV relative to the inverter/controller is common for better overall return, and for more generation throughput when ReallyNeeded(TM) such as in winter. I'm doing it a bit on my grid-tied system and a lot (~4x) in my off-grid system. Not all inverters/controllers will accept this safely but many are explicitly specified to, such as mine.
Rgds
Damon
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