Floating Ground in DC Couples BESS

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TheElectrician

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Hi, I am using a PV inverter that supports DC coupled BESS system. But the inverter manufacturer recommends to use a floating groung instead of a neagitevily grounded system. Can someone explain what is the science behind this on why a floating ground is required in a BESS system? Thanks
 
BESS = Battery Energy Storage System

The question really gets into broad inverter and system design questions. A disadvantage of grounded DC systems is that they must be galvanically isolated (with a transformer) from grounded AC systems, otherwise there will be a direct short through the inverter power electronics. But transformers make inverters less efficient, so manufacturers have developed non-isolated designs, but these inverters must absolutely not have a battery or PV conductor grounded by the installer. These systems use methods broadly similar to GFCI to stop operation if one of the DC conductors becomes unintentionally grounded, since that can lead to exposed parts becoming energized and other dangers.

Without knowing more about the inverter you're using, it's impossible to comment on its specifics. But I'd always go with the manufacturer recommendation. And if it's not an inverter with galvanic isolation, then that's almost certainly a requirement and you have no choice.

There is no general requirement that a BESS be grounded or not grounded, but inverter design will usually determine one or the other, and that cannot be messed with.
 
jaggedben said:
BESS = Battery Energy Storage System

The question really gets into broad inverter and system design questions. A disadvantage of grounded DC systems is that they must be galvanically isolated (with a transformer) from grounded AC systems, otherwise there will be a direct short through the inverter power electronics. But transformers make inverters less efficient, so manufacturers have developed non-isolated designs, but these inverters must absolutely not have a battery or PV conductor grounded by the installer. These systems use methods broadly similar to GFCI to stop operation if one of the DC conductors becomes unintentionally grounded, since that can lead to exposed parts becoming energized and other dangers.

Without knowing more about the inverter you're using, it's impossible to comment on its specifics. But I'd always go with the manufacturer recommendation. And if it's not an inverter with galvanic isolation, then that's almost certainly a requirement and you have no choice.

There is no general requirement that a BESS be grounded or not grounded, but inverter design will usually determine one or the other, and that cannot be messed with.
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May we request an illustration. Thanks for your answer
 
I'll venture that an example of a BESS might be the Tesla Power Wall. Used many times for temporary back up power in conjunction with a solar systems, that may or may not also be grid tied. (If you can afford or willing to pay for one.) The suggestion to just follow mfg instructions valid for typical installer, as alluded to the variables in design by mfg. would seem to make a one answer fit all near impossible.
 
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