Before v3.60, I controlled the output of my AC-PV inverters myself using Node-Red, but I thought it might be wiser to leave this to VenusOS now v3.60 has support for Sunspec compatible inverters. On first impression, al seems to work well: I see a power limiting request from the GX-device to the inverter every 5 seconds. The inverter executes the request as it should.
An interesting thing I noticed was the setting by the GX of the power limit tot 2 percent during nighttime. Cannot figure out why this is done, but it has no unwanted side effects.
Then a cloudy day happend. With many small clouds (no clouds, yes clouds, no clouds, etc, etc) the PV production varies heavily during the day, of course.
I noticed that this led to the GX device issuing changing PV power-limits every 5 seconds in an attempt to follow the changes at the grid meter. This, of course, does not work well because of the lag in the system (GX every 5 seconds, PV response takes time, too). Am I correct in assuming that some sort of closed loop method is used on the grid meter data to regulate the PV? If so, why?
As I wrote above, before 3.60 I managed the AC-PV from Node-Red. But I did not need any grid meter data. My algorithm was based on the sum of
- maximum feed-in limit
- Current Loads (averaged over last xx seconds)
- battery power going in/out
This regulates the PV to a maximum allowed. If a cloud blocks the sun, the output of the calculations does not change, therefore no change in powerlimit is needed leading to a much more stable behaviour.
Can someone enlighten me on this? 