We are a heritage railway with a restaurant carriage equipped with electric cooking equipment (refrigerators, microwave, cooker and water heaters) which causes intermittent loads on the Victron as thermostats are cutting in-and-out. The load can fluctuate from a couple of hundred watts to over 8 kW at maximum load, albeit for just a few seconds. It is a 230V single phase system and the equipment list is as follows:-
Victron Quattro 10000/48 with A/C 1 input connected to the generator and A/C 2 input is connected to a shore supply to recharge lithium batteries overnight and pre-heat water early in the morning
4 x 100Ah 52.3 Volt lithium Topband batteries (~20kWh)
1 x Honda EU70IS 5.5kW/7kVA inverter generator
Cerbo GX
The generator is only required to run when the SoC is down to 25% towards the end of the day to make sure there is enough charge in the batteries to last the working day. It was never intended to provide a contribution to the base load.
We are finding that when the generator is running, the sudden load fluctuation passes through to the generator and the response of the generator cannot handle this. The generator momentarily trips, causing loss of synchronisation and then resets… and if this happens a number of times, the generator drops out completely and will only reset if switched off completely and restarted. When the load is (consistently) high, the generator operates happily; when the load is low, the generator also operates well - it is when the load is between 1kW and 3kW the problems really show up. Ideally we would like the demand on A/C 1 to be a constant value (say 5kW / 21A) and variation of load handled by the inverter / battery charging.
We have to have ‘UPS’ ON as the modern cooking equipment cannot otherwise take such fluctuations and switches off automatically.
We have ‘Dynamic Power Assist’ set to 2.
Is there a way (through Node-RED or otherwise) of changing the priority of power source or have we missed something?
It might be easier as you think as such little generators cannot handle well starting heavy loads as they do not have a sufficient mechanical mass (flywheel) to keep it rotating, so for a moment they drop in frequency and voltage and that is not ideal with an inverter.
Try first to lower the input current in the inverter to about 50% of the generator capacity, if then stable make 5% steps up and test again, suddenly it is unstable again, now go 5% back again, that is the easy test you can do.
The power boost (assist) factor of 2 is normally ok, you can raise it also so slightly to see if that helps.
We have tried lowering the demand current from the generator to about 12Amps and found it still not performing reliably (then one questions why have a 5.5kW generator only operating at less than 50%!). Maybe our next exercise is to drop it considerably lower - 25% maybe? We won’t be able to tackle this until the end of next week.
Do you know of anybody considering using a Node-RED modification to tackle this problem as I’m sure we cannot be the only installation with such an issue?
As said before, little gens sometimes are not so suited with an inverter due to not having sufficient flywheel mass, but indeed, try it on a lower value.
These gens do not like to start things but run quite ok when they have a constant load like charging a battery or running a cement mixer for example.
Make sure you have Dynamic Current Limiter turned on. This is supposed to ramp AC input current up and down slowly which is the way you are wanting the system to behave. In testing a much smaller system, step loads do in fact ramp the generator contribution slowly (over a few seconds).
One thing I have noticed is some loads pulse their consumption at a fast rate say a few cycles on / a few cycles off. These fast pulses of demand cause spikes in AC input power as the inverter tries to chase the power curve, but can not keep up. If this is what is happening there is not much I’ve found to help.
You really only want the UPS mode when you have a grid connection, or maybe a really big generator (>>50kVA or something) in a situation where the failure of the “main supply” is when the Quattro kicks in to do the work.
Instead, you’re saying you want the generator to do all the work (bad in your case with the little generator).
The load on the generator does step up, probably 1.5 kW per second (the refresh rate on the Cerbo), so we’re confident this is working as expected. It’s that looking at the load, one second it can be 4kW and in the next view, it might have dropped to 1.5kW. The generator, seeing the load dropping off, adjusts its output rather than ‘just running’ only to find when the load comes on again, struggles to take on the load. In electrical terms, we need something with much lower internal impedance.
Your comments regarding multi-pulsing of loads is interesting and something I had not considered. All our equipment is brand new, and even the fridges and water heaters are microprocessor controlled, so we seem to be on a ‘hiding to nothing’!
We tried empirically working the system with the UPS switched OFF. The result was the load, including the main (external) contactor connected to output A/C-1, would drop out when the generator was trying to keep up. This was resolved when UPS is left ON, so it seems we have to live with this and its subsequent implications.
It sounds as if the problem is with the generator not being able to handle the inrush current. IIRC, inverter generators don’t like sudden loads.
Something that may help is to make sure the Eco-Throttle is turned off. That will mean the generator doesn’t have to speed up when receiving sudden loads. However, this may still not totally solve the problem. I’d also set the Quattro to pull no more than 75% of the rated output. I see someone has recommended the generator guide, it’s a useful read. I remember I had to play around with my Quattro settings before I was happy with how it performed with the generator.
As to not wanting it to contribute to the base load and to draw a constant value, say 4kW , constant full load will shorten the life of the generator. The only solution I can see is having a separate charger connected between the generator and batteries and leave the inverter to handle the loads.