How to configure my xtender and vario system for maximizing the self-consumption?

For grid-connected systems, adding battery storage provides a backup energy source in the case of grid failure. The Studer standard application maintains the battery fully charged and supplies loads using solar and grid energy. If grid injection is authorized, excess solar energy is exported to the grid. Otherwise, with standard settings, excess solar energy is not used.

With the self-consumption application, the xtender system allows the battery to be discharged at night in order to store excess solar energy during the next day, and thus increase the amount of solar energy consumed onsite.

The following options are available for configuring the self-consumption in your xtender system:

1. Battery priority function:
   By activating this function (1296) there is a battery priority voltage (1297) as reference and the behaviour of the xtender will be different if the battery voltage is above or below this level:
   • Battery voltage above battery priority voltage
     • The battery will be charged only with energy coming from variotrack/variostring (solar) and not from the grid.
     • The AC-in input limit will be automatically reduced from the value set by the user (1107) to a minimum of 1Amp
   • Battery voltage below battery priority voltage
     • The battery will be charged from both variotrack/variostring (solar) and from the grid (AC-in).
     • The AC-in input limit remains fixed at the value set by the user (1107)
   • Advantages:
     • The grid is always available to support in case of peak consumption on AC-out
     • The xtender is always at transfer/boost/charger function. There is no transition from one function to another
   • Disadvantages:
     • There is always a minimum of 1 Amp consumed from the grid. It is not possible to reach 0 consumption from the grid.
     • There is some excess of solar energy that will not be used

       

2. Grid as generator function
   In this case we use the grid as if it was a generator. The xtender will be disconnected from the grid as soon as the battery reach a level defined in the settings. The Remote Entry will be automatically activated according to Auxiliar 1 status. The Remote Entry will allow the connection to grid by disabling the transfer relay prohibition (1538).
   
   • Advantages:
     • The self-consumption of solar energy is maximized in comparison to the first option.
     • When the xtender is offgrid the consumption from the grid is 0.
   • Disadvantages:
     • There is a micro-shutdown (max. 15ms) during the transition from grid connected to offgrid.
     • In case of peak of demand in off-grid mode, the xtender will not have support from the grid and risk of overload is higher.

       

3. Self-consumption with Lithium Batteries (xcom CAN)
   Additionally, when the xtender works with Lithium batteries that are communicating through the bridge provided by the xcom CAN accessory, the self-consumption could be easily configured thanks to the “SOC for backup” parameter {6062}, by default set to 20%.