Limiting Charging Current when DC Injection is active

Node-RED
, , , , ,
1

Hello!
Normally, when DC injection from MPPT’s is active, the system does not respect the charging current limit set in DVCC (Dynamic Voltage and Current Control). This can lead to overcharging and potential stress on the battery.

To solve this issue, a custom Node-RED flow has been implemented, which continuously monitors the following parameters:

  • Charging current limit from DVCC (dvcc_current)
  • Actual battery charging current (battery_current)
  • Battery voltage (battery_voltage)
  • MPPT power output (mppt_power)
  • DC feed status (dc_feed)
  • AC grid input (ac_in)

If DC injection is active and the battery charging current exceeds the allowed threshold (either the DVCC value or a fixed 50A limit when DVCC is disabled), the flow automatically calculates and applies a negative grid set-point value. This action reduces the charging power, effectively enforcing the desired current limit.

This solution ensures proper charging control even when the standard system behavior fails to enforce DVCC limits during active DC injection.

I attached the flow from NodeRed with this limitation.

Charge Current limit by Atelierul de Tehnologii.zip (2.2 KB)

6 Likes
No battery current limit possible when DC-grid-feed-in active
Discharge current limit (DCL) is being ignored.
DVCC max charge current is ignored by the Multiplus
2

Hi , how does the system will behave when my SOC is going to 95+ ? as there is no SOC considered in maximum charge current formula.

because there is always set 50A as the max current for battery charge.

if i am not wrong the higher SOC the lower limit of current should be used for battery.

i would like to understad it.

3

Hello! A new line of code can be added to respect the minimum value between the current set in DVCC and the charging current received via CAN from the battery bms.