fanda-eu avatar image
fanda-eu asked

Frequency shift too slow in the Quattro+ BYD battery +SMA SB solar inverter system


Running the Quattro with L series BYD battery (14kw) results in the battery shutting down, due to the Quattro taking extremely long time to start shifting the frequency (around 8-9 seconds from the point of BYD charging limit going to 0, utill the Quattro frequency actually start to increase)

I know the L series batteries are not current meant for the off-grid applications, but they are advertised for the backup applications, in which case Quattro has to be in position to adjust the solar inverter on time in order to prevent the battery overcurrent, should the grid fails during the day

Any suggestion if this problem can be fixed, or has a workaround ?

With best regards,

Oleksiy Frolov

MultiPlus Quattro Inverter ChargerBYDfrequencyac coupling
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2 Answers
fanda-eu avatar image
fanda-eu answered ·

Hello Guy

Thank you for all of your suggestions. The one which seem to have done the trick was the inverter power setting. However it actually worked other way around. After gradually reducing the PV parameter in the ESS assistant to 750watt, it is now working as it should - maintaining the voltage within +- 0.2 volts from the float voltage of the battery. No disconnects so far. In fact it seem to be more precise in maintaining the battery voltage than when connected to the grid.

What I've also done, is I've altered the frequency-power setting of the SMA as follows:

50.2 Hz to begin the power control. 51.7 to end the power control (1.5Hz window was needed to arrest the oscillations in the way ESS is changing frequency).

For now I've tested it through enire day with different PV levels and different loads, and it seem to maintain the voltage very well. I will be monitoring it over next days of course to see if at some point the problem returns. But so far so good

Thanks a lot for your help

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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @fanda_eu

The BYD L series handling and tolerance of overcurrent situations (both in charging and discharging) is one of the main reasons why this battery is not allowed for use in off-grid. The grid is required for reliable operation.

8-9 seconds to react does seem like a long time though. Are you counting the second by second frequency reporting in the Quattro menu of the GX device? Or some other way to calculate that delay?

Is the delay in frequency adjustment the same when a large load is connected / disconnected on a full battery (CCL already 0) as when the Charge Current Limit changes to 0?

Is it possible to do a recording of this behaviour so I can compare it to another system here?

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fanda-eu avatar image fanda-eu commented ·

Hello Guy. Thank you for a prompt answer

8-9 seconds is counted from the moment the charging current limit of the battery indicates 0 amps - as viewed in the GX color control under battery parameters menu, till the moment the Quattro start increasing frequency as seen in it's parameters of the GX

I've made a short video

0 current is indicated at index 0:55 and the Quattro start frequency increase at 1:06

The ESS assitant frequencies are set to 51.0 / 51.9 / 52.5 (however it almost seem like the assistant ignores this setting, different frequencies had no effect on the speed of increase)

To answer your second question: The problem is reproducable when

1. The PV production is at 100% and a large load using approx a half of the PV power is permanently connected, or

2. The PV production is about 20-60%

In any case, it is there when the charging power is between approx 1 and 2.5 kW

My PV inverter is SMA SB 5.0, battery is 14kW 48v, and the Quattro is 8 kVa

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ fanda-eu commented ·

Another variable on the frequency ramp is the reported size of the PV and AC PV inverter in the ESS assistant. Try setting the array and the inverter in the ESS assistant to 8000W and see if that has any effect.

I presume you set it to the reality of 5,000 W to begin with.

Could you also please post the VRM site id so I could have a look?

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fanda-eu avatar image fanda-eu Guy Stewart (Victron Community Manager) ♦♦ commented ·

Thank you, I will try your suggestion (frankly I've already tried 7000W, but did not record the time delay). Should I set both parameters to 8000 ?

Generally the system is connected to the intranet with no internet access, however I will reconfigure it for a day when we get some sun (finally) so that the problem is logged on the server

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ fanda-eu commented ·

I would try it, and see the results, but not expect success.

The battery itself behaves differently from the other BYDs, and I am not confident that the AC coupling will be responsive enough with these tweaks.

There is a whole host of other potential work arounds that get increasingly complex to work around this fundamental product behaviour limitation, depending on your willingness to tinker.

The first that comes to mind for me would be to connecting the AC PV to ACout2 on the Quattro, and then setup a series of assistants that opens the ACout2 relay when the state of charge gets to 95% while ACin1 is not connected, and then closes the relay when it drops below that, or ACin1 is reconnected.

That will require some learning on your side if you are not familiar with assistants. If you want to go down that path I would probably suggest opening a new question in the modifications section of the site.

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