How Does Inverter Know Individual String Stats After Strings Are Combined?

[hxdy]

Just got my system installed, and am curiously looking into my new toy! The panels are grouped into 2 strings and are combined into 1 single cable to the inverter. The inverter is able to display individual string stats (voltage and current). I'm curious, how does the inverter know individual string stats while there is only 1 combined cable connected? And how does it do 2 MPP trackings individually when there is only 1 cable?

 

[arnolddeleon]

Assuming these are Tesla Solar Inverters: There are MCI (Mid Circuit Interrupters) in each string (I think it is roughly every 3 to 5 panels). They are what allows a string inverter to safely and quickly disconnect in a rapid shutdown event. The inverter is digitally communicating to those devices to tell them operate (I don't know what protocols they are using but it is relatively easy to put a data signal over a DC or AC powerline). If they don't get the right signal from the inverter they basically won't allow high voltage and current through. They almost certainly pass enough signal through to allow communications with all of them in the string. It is not surprising they can also tell what voltage and current are passing through and can communicate that back to inverter.

MPPT is done at the inverter and unless Tesla added optimizers to their modules/MCIs there is only MPPT voltage being set for both arrays if they are paralleled.

I should add that this all speculation (I think a pretty good one based on what I learned about how the Tesla Solar Inverter and panels are wired and basic engineering principles) . I don't have first hand knowledge.

 

[hxdy]

Thanks for the info! Appreciated.

 

[itsc]

Just got my system installed, and am curiously looking into my new toy! The panels are grouped into 2 strings and are combined into 1 single cable to the inverter. The inverter is able to display individual string stats (voltage and current). I'm curious, how does the inverter know individual string stats while there is only 1 combined cable connected? And how does it do 2 MPP trackings individually when there is only 1 cable?

The inverter only reports what it can see. The stats are combined for the two strings of they are connected in the roof. Because two channels must be used in the inverter due to per channel limit, the single wire from the roof goes to two or more channels. The two channels will be within a few volts of each other. The connection between the channels is done at the inverter. Basically jumper cables are used to connect the two channels. Tesla’s installation manual explains the configuration.
MCIs can report finer grain data to Tesla, as they told me during a support call, but I don’t think anyone knows how to access them through the inverte outside Tesla.