question

Eugenio Velasco avatar image
Eugenio Velasco asked

AC coupling Fronius BYD SOC 100% - System Shuts down

Buenas tardes,

En un sistema formado por un Quattro 48/8000, Color control GX, BYD 10 kWh, Fronius Primo 5.0.1 (Conectado en la salida AC1) Todo esta actualizado hasta la última versión.

Color control con DVCC activo y monitor batería en BMS BYD.

Asistente PV inverter cargado en Quattro.

Cuando la batería está en el 100 % de SOC, y el sistema tiene unas cargas en AC por ejemplo 800 W, Fronius esta generando los 800 W. Si la carga se apaga, lo que sucede es lo siguiente:

La tensión en DC sube de los 55.2 V mucho mas rápido de lo que Victron sube la Frecuencia HZ (ratio de subida observado 0.1 Hz/s ) cuando la batería llega a los 57 V el BMS interno produce un pico que hace que Victron se apague (DC >66 V). Apagandose Fronius y dejando un 0 en la instalación que no se restablece solo en algunas ocasiones.


La pregunta es si se podría acelerar lo sufiente el ratio de subida Hz/ms de Victron con la tensión del bus de DC, o si bien en vez de ese criterio indirecto para hacer el derating de potencia, se podría implementar el del SOC leído desde el Color control.

O bien se podría emplear el SOC para regular la máxima corriente de entrada en la batería o frenar su carga dejando un colchon de seguridad 95 % por ejemplo.

Cualquier solución que haga que el AC coupling no se vuelva inestable ante bajadas en escalón de las cargas en AC


Gracias de antemano por vuestra respuesta


In English


Good afternoon,


In a system consisting of a Quattro 48/8000, Color control GX, BYD 10 kWh, Fronius Primo 5.0.1 (Connected to the output AC1) Everything is updated to the latest version.


Color control with active DVCC and battery monitor in BMS BYD.


PV inverter assistant loaded in Quattro.


When the battery is at 100% SOC, and the system has loads in AC for example 800 W, Fronius is generating 800 W. If the load goes out, what happens is the following:


The voltage in DC rises from 55.2 V much faster than Victron increases the HZ Frequency (observed rise rate 0.1 Hz / s) when the battery reaches 57 V the internal BMS produces a peak that causes Victron to turn off (DC> 66 V). Shutting down Fronius and leaving a 0 in the installation that is not restored only in some occasions.


The question is whether Victron's Hz / ms rise ratio could be accelerated with the DC bus voltage, or if instead of that indirect criterion for power derating, it could be implemented that of the SOC read from the Color control.


Or you could use the SOC to regulate the maximum input current in the battery or slow down its load leaving a 95% safety cushion for example.


Any solution that makes the coupling AC does not become unstable before decreases in steps of the loads in AC




Thank you in advance for your response





FroniusAC PV CouplingBYD
2 comments
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Do you mind if I have a look at the VRM site installation number?

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Eugenio Velasco avatar image Eugenio Velasco Guy Stewart (Victron Community Manager) ♦♦ commented ·

As soon as we have internet connection i'll give you the installation number. Thanks

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6 Answers
cquinones (Victron Energy Staff) avatar image
cquinones (Victron Energy Staff) answered ·

Hola Eugenio ,

Por favor envíeme un correo electrónico a espana@victronenergy.com a la atención de Carlos Quinones y buscaremos la mejor la solución , estudiando su instalación .


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peterwolff avatar image
peterwolff answered ·

Hi I have exactly the same issue. New system with Quattro 8000, Primo 6.0 on ac out. When SOC reaches 100% and the fronius shuts down the quattro stops completly. All lights are off and no output. VE communications still works. Restart needed manual from the quattro and same happends when power comes back to the Fronius.


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Hello @peterwolff,

Cargastes el asistente fotovoltaico Pv (017A)?

Did you load Pv Inverter support (017A)?

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peterwolff avatar image peterwolff cquinones (Victron Energy Staff) ♦♦ commented ·

Yes, we sorted the problem. We lowered the battery charging voltage by 0.5Volts as it took to long for the frequency shift to stop charging.

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peterwolff avatar image
peterwolff answered ·

We still got some issue with this setup, as we lowered the charging voltage with 0,5V the batteries do not show 100% anymore and slowly lower day after day. Ending in 70% max charge (BMS telling that). That means we only have 40% untill generator kicks in (at 30%). As this system has also DC Coupled PV i need to login in, raise the solarcharger voltage for short time to get voltage up to 56,2V and then lower it again. The ac coupled part is causing the issue when we use the recomended settings from the battery manufacturer. Should i leave the DC charger at the higher volage (meaning cancel extern control of it) and the ac coupled at the lower voltage?


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Saad Maakaron avatar image
Saad Maakaron answered ·

We have the same issue on multiple setups with Multiplus II with Fronius and BYD.

I observed that when the following conditions occur: (BYD SOC = 100%, relatively Low Loads, Fronius producing energy during sunny hours),
Victron Inverter/Charger cannot control Fronius charging power effectively to prevent high DC Ripple. BYD BMS Charging Current Limit is set to Zero during this time,
The Inverter Charger restarts (shutdown, Start again), and continues to do so until one of the conditions change.

Has anyone found a permanent solution?

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Eugenio Velasco avatar image
Eugenio Velasco answered ·

With de firmware at last level in Cerbo/Color Control and Multiplus, I used to increased the rate of change %/HZ in fronius setapp, i.e. 69% / HZ derating gradient. With this feature Fronius get down more quickly than Victron expected, prevents rise up of DC Ripple and AC shutdown

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rob-craig avatar image
rob-craig answered ·

Hi. I wouldn't call this a permanent solution, but a temporary solution that has worked for me was to adjust the PV Inverter support frequency setpoints.

The system is comprised of:

- Multiplus II 5kVA 48V

- BYD LVS Premium 8.0

- Fronius Primo 5kW

- Blue Solar 150/35

The system was having High DC Voltage alarms most days and the Multiplus II was shutting down and restarting under certain load conditions once or twice a week.

I increased the Output Power Minimum frequency to 52.9Hz and the Converter Disconnect frequency to 53.1Hz.

I also set the Max Charge Voltage in the GX to 56.5V

Over past last week I have had no alarms and no shutdowns.

Ideally I would have preferred to have reduced the Fronius MG50 frequency setpoint downwards instead, but the system is remote and changing Fronius settings means an entire day of travel.

I plan to monitor the system for a few weeks and if it remains stable under various load conditions I will travel to the site to adjust the MG50 Hz setpoint downwards and return the VE Hz setpoints back to default.

I think the permanent fix would need to be a firmware update from BYD. When the BYDreaches 100% SOC the VCL from the BMS moves from 58.4V anywhere down to 55V and this happens almost immediately - too quickly for the frequency shift to react.

I have a similar system with the older BYD B-Box system and have noticed that the VCL never deviates from 56.5V, no matter what stage of the charge cycle.



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