I recently added a Multiplus 3000 as a battery charger from Generator to a system which has 2x MP2-3000 in parallel, and 13kWh of lithium battery. The idea what as no headroom (spinning reserve) needed to be added for AC loads switching on and off, the generator could be operated at a higher level, reducing charging time in poor weather. This system is completely off grid.
On the first run, there were no major issues, but the Multiplus charging (AC Current) was somewhat unstable, varying as much as 1-2A about the 7.4A set point.
About a month later, when next needed, the Multiplus was very unstable in it’s AC current, and would frequently trip out the generator (i.e. disconnect from the generator due to overloading it) AC current was set at 6.4A, to warm up the generator, but currents as high as 12A were observed.
The generator has a continuous rating of 2500W, peak of 3500W (8.1/15.2A). Now the Multiplus will try to connect to the gen 2 or 3 times, then go into a fault condition.
mp_3ksettings.TXT (1.6 KB)
So the short video shows the unstable operation as seen by the connected cerbo, the settings are for reference.
During the charging operation, Both the AC input current and the DC charging current exceed the limits set: Hence the charger control loop needs to be improved.Once warmed up and with a steady load, the generator does operate in a stable condition: there is no hunting about the operating point. The charger is introducing a great deal of instability into the system.
Inverter firmware is up to date. Adding “Weak AC” to the settings makes no difference.
As well as improving the stability of the charger loop, It would be nice if Victron could also introduce “Droop control” for charging regulation, this would assist for operation with generators in off grid systems, as the generator frequency decreases, the load / charge current is also decreased. Generators also need a warm up profile to operate near maximum load continuously, this should also be built into a “Generator source” charging algorithm. Whilst the current system does load the generator gradually (when it works), the ramp is too rapid to allow a proper warm up: The generator needs to be operated at about 75% of the ultimate charging current for about 5 minutes, before ramping up to full load.