Replying to my own post - seems I have SolarEdge production control working now…
The correct modbus settings are:
Write value type I have as:
61762: 32bit positive or negative integer
61441: 16bit positive or negative integer
61696: 16bit positive or negative integer
To limit production:
Write 1 to register 61762 to enable Advanced Power Control
Write 1 - 100 to register 61441 to set the percent output desired (1 - 100%)
Write 1 to register 61696 to ‘Commit Power Settings’
I’ll be able to do more testing tomorrow once the sun comes back up 
Well things are working… BUT… I do get an error on the ‘Thing’ for register 61696 which is the commit power settings register.
The error is ‘Message: Slave responded with error=4 (SLAVE_DEVICE_FAILURE)’
I’m trying to write a 1 to this register - but looking in Home Assistant, the value shown is ‘-3838’ so something isn’t quite right.
In spite of this, the ‘write’ seems to work and the inverter output is controlled as I need.
The Thing is configured as a holding register with write value type of 16bit positive or negative integer which is in line with the documentation.
Any suggestions? The Thing with the error is annoying me
