I have (2) 48/5000/70 Quattros wired split-phase 120/240V in a grid-tied ESS system.
I have some DC solar panels, and some LiFePO4 batteries.
I also have some solar panels driving Enphase micro-inverters. These are presently on the Output side of my Quattros. A Cerbo GX with (wonderful) Node-Red runs/supervises the system.
The Enphase micro-inverters are monitored by a Victron AC Current Sensor which displays as 'PV Inverter' in my VRM dashboard and Remote Console.
This all works well together, up to a point. What works great is on those rare times when the grid fails, such as during a heavy snowstorm when a utility power pole falls down. Then when the sun comes out and charges up our batteries to maximum, the Victron system will raise its frequency enough to stop the Enphase micro-inverters from overcharging the batteries. Great!
But now I am considering increasing the power from the solar panels on the micro-inverters, by upgrading the solar panels and the micro-inverters. Since the AC from the 'PV Inverter' goes through the Quattros to the grid, there is a situation I want to correctly accomodate:
1. Grid is working. Excess solar power is exported to the grid,
and
2. The 'PV Inverter' generates more then the Quattros are rated for.
In this situation, since the grid is working, there is no need for the Quattros to limit the PV Inverter power. Now, it makes more sense for the micro-inverters to be on the AC Input side of the Quattros. That way, the micro-inverters will synchronize with the grid and all of their excess production will be exported to the grid. Since none of the PV Inverter power is flowing from the Quattros' output to their input, the power sent to the grid is not limited (except by my local utility company).
So to get the 'best of both worlds,' I am building an ac switcher with multiple 120A AC relays. Based upon a Node-Red generated control signal to a Cerbo GX relay, these power relays will be able to put the PV Inverter on either the Input or the Output side of the Quattros.
When the grid is working, the PV Inverter will be on the Quattro Input. When the grid fails, a Node-Red node will sense this and activate the relays to switch the PV Inverter to the Quattro Output. That way, the frequency control of the Quattros will once again be able to limit the micro-inverters as needed, so if it is quite sunny, my batteries will not overcharge.
This brings up some questions, mostly about the monitoring capabilities and use of the Victron AC Current Sensor:
1. When the Victron System determines how much power is available to export to the grid, does it use the AC current measurements reported by the Victron AC Current Sensor in its calculations? Or are the measurements from the Victron AC Current Sensor for monitoring only - to display on the VRM Dashboard, and be available in Node-Red, but not used elsewhere?
2. I'd like to leave the Victron AC Current Sensor in place if possible - reading my PV Inverter power on the VRM Dashboard. When I previously set up the system, I told the ESS Assistant that I have a PV inverter on the Quattros Output. If I move the PV inverter to the Quattros Input, but but leave ESS Assistant with the setting that there IS a PV Inverter on the Quattros' Output, what will happen? Wouldn't it be like a night-time situation, where the PV Inverter (on the Quattros Output) is just producing no power?
3. In order for the Victron system to correctly raise the output frequency in the "Grid Off" situation, I think the ESS Assistant will need to know I have a PV Inverter connected to the Quattro Output. Does ESS Assistant know that I have a Victron AC Current Sensor installed? Will the ESS Assistant, with "PV Inverter is connected" work regardless of whether a Victron AC Current Sensor is present or not?
4. Lastly, any comments or suggestions about a PV Inverter Switcher like this are welcome. I know some others have tried this, or something like it, and might have some insights for me before I try it.
Thanks again for this great forum and all the help it has given me so far!
