question

*** There is a better solution in the next answer ****

I have a node with inputs coming from the grid and voltage.

msg5.payload =clampValue((252 - voltageIn) * 800 - grid,0,13000)

Msg5 is an output going to the ESS max feed in value node.

The clamp value makes sure the result is in the range 0 - 13000 for the feed in. It is just a max/min function.

This simple function keeps the voltage from the Quattro below 253V which is hopefully extends the life of my household equipment some what.

You might need to fiddle with the value of 800 to stop it hunting too much. I really should have an average over the last 20 seconds or so as changing the ESS max feed in value doesn't have an instant response. This is good enough as a start point.

var feedIn = context.get("feedIn")
var vDiff = 250-voltageIn
var gridDiff=feedIn+grid
var correction =0

if (vDiff<0) {
    // Greater than the voltage we want. make a big correction
    feedIn=feedIn+vDiff*800
} else if (vDiff>.55 && gridDiff<500 ) //.55 stops continued hunting due to viltron discrete steps of 100watts on feed in.
{
    // Creep up on the export figure from below. Can go faster at the start.
    correction=(30 *Math.pow(vDiff,2))
    feedIn=feedIn+correction
}
//node.warn(feedIn+":"+vDiff+":"+gridDiff+"c:"+correction)
feedIn = clampValue(feedIn, 0, 13000)
context.set("feedIn",feedIn)
msg5.payload=feedIn

This code is better as it is more stable for the ESS algorithm. It makes a big change if over voltage but otherwise more slowly increases the export until within .5 volts of the required maximum. In this case I am using 250V.

In node OnStart you will need to set your initial export figure.

context.set("feedIn",5000) // Initial allowed export of 5000