Load Sharing in Parallel AC inverters without communication

[adnan012]

hi,
I want to discus load sharing in parallel connected dc/ac inverters. Which technique is used to achieve load sharing when there is no synchronization bus/ communication between then two inverters. Is it droop method?

regards

 

[BradtheRad]

All inverters must produce AC waveforms exactly in phase with each other. Without synchronization you have disaster because inevitably one inverter outputs positive voltage while another inverter outputs negative.

 

[adnan012]

Thanks for reply.
I am trying to understand the functionality of a 2K watt pure sine-wave inverter. The secondary side has dspic33 series microcontroller and few op-amp circuits for sensing current , voltage etc. I can connect the output of two inverters while both inverters are on and they can handle 4k load.

--- Updated Oct 16, 2020 ---

There is not interconnecrton between the inverters.

 

[KlausST]

Hi,

I see a misunderstanding.
"Synchronisation" in the OP's meaning is the cummunication from one inverter to the other converter to push identical power to the grid.
Example one solar panel system providing 4kW of power with two inverters. How to achieve that each inverter is driving 2kW to the grid and not 1kW + 3kW.

For sure every inverter needs to synchronize to the grid frequency.

I don't know the answer to the OP's initial question.

Klaus

 

[Easy peasy]

Without some signal means of forcing the inverters to have the same phase ( and Vout and current limiting ) paralleling will be a disaster ... - unless one is run in master mode and the second looks at the first's voltage and synchronises to it ...

 

[dick_freebird]

I think that I've seen "stuff" about using the current
along the cycle to keep the inverter output slightly
leading the mains-reference, in grid tied inverters,
so as to always be delivering energy into the
waveform.

But who's in charge when you have two identical
inverters with no master, is a tricky bit.

I see inverter generators with parallel capability
but they want a special expensive cable. What's
so terrible about imposing communication on
the two inverters? You're already running 3 wires
(hot, neutral, ground), right?

Seems like an opportunity for "power line
communications" protocols, to throw sync and
demand messaging.

 

[Easy peasy]

Some inverter makers allow setting one to master and others to slaves ...

 

[FvM]

The question isn't quite clear. You are asking about grid-tied or islanding inverters? In the former case, the inverters can individually synchronize to the grid but there's no option for equal load sharing without a control link between the inverters.

In case of stand-alone inverters, the inverters must be designed with a master-slave synchronization feature, as stated by Easy peasy.

 

[mtwieg]

The OP hasn't made it clear whether one or both of the inverters is a GTI.