Batt2ACInverter
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Use
The Batt2ACInverter is necessary to couple the DC-voltage storage with electric AC-voltage consumers or the AC-grid of a building. It combines the models of a DC converter, a DC control and a B6-converter or a B2-converter model.
The Batt2ACInverter covers the following applications:
Basic: The Batt2ACInverter converts the dc battery current to a 3-phase low voltage grid connection
1-Phase Grid Connection: The grid connection is changed to a 1-phase low voltage grid connection.
Parameters and Connectors
Basic
As connector, the Batt2ACInverter requires a specified target power ▶PRef where positive power values are an energy input into the storage and negative values represent the extraction from the storage. The reference charge (and discharge) power ▶PRef must be controlled by external controllers and is dependent on the inner building energy system or consumer states (e.g. renewable energy availability or simulated electricity prizes).
The relevant battery parameters are transmitted from the battery via the ▶ControlBus connector. These parameters are the state of charge SoC and the minimum and maximum battery voltage. Furthermore, the Battery is connected via the ▶DCBatt connector and the Grid via the 3-phase electrical grid connection (▶LVGrid3) or the 1-phase electrical grid connection (▶LVGrid1) .
The parameters under the Control group contain the settings for the PI controller of the Batt2ACInverter TPI and kPI, which defines the behavior of the DC converter. The battery converter acts as a PI-controller which controls charge and discharge power via a intermediate-circuit voltage at the DC-side, dependent on the reference power ▶PRef. If no precise details are known for the PI controller of the Batt2ACInverter, the set standard parameters can be used.
Furthermore, the maximum charging/discharging power of the battery or the inverter on the Batt2ACInverter model is PMax, the maximum SoC up to which charging is to take place SOCMax and the minimum SoC up to which discharging is to take place SOCMin.
To set the grid parameters, the number of grid phases nPhase (either 1 phase or 3 phases), the capacitive power factor cosPhi (proportion of active to apparent power) and inverter efficiency of a charging and discharging cycle eta.
1-Phase Grid Connection
For the 1 phase grid connection the parameter nPhase gets changed to 1 to better model the connection of the Batt2ACInverter for only one phase which allows a more granular definition of the electrical grid, e.g. check for overload on a specific phase. To connect the Batt2ACInverter with the AC grid Grid it must be defined which phase of the 3-phase grid will be used (see PhaseTap).
Model Background
Reference Power Calculation
Positive values for ▶PRef are ignored if the storage is already filled (SOC = SOCMax) and negative values are ignored in case of an empty storage (SOC = SOCMin). For stable operation, the model includes an internal hysteresis of 5% for the SoCs SOCMin and SOCMax, i.e. when the storage tank has reached its maximum SoC SOCMax of 90%, it is no longer charged until the SOC falls below 85%. The model behaves in the same way when the minimum SoC SOCMin is reached.
How to avoid numerical problems?
Ensure that the input parameters for the Batt2ACInverter correspond to the parameters of the coupled battery model.