Possible system concepts and their reference points
The unit and component certification ensures the fulfillment of the individual functions and requirements for each component. The interaction and compliance at the system level can be implemented in different ways. Thus, prioritization can take place either only in the system controller, only in the inverter or, if the functions are implemented in different components, also in the system controller and inverter. Note that the overall system must satisfy the requirements.
In general, the systems used are equipped with a system controller according to VDE AR-N 4110 and VDE AR-N 4120, which can process and prioritize the specifications of the grid operator and direct seller.
There are two applications for PV and storage systems:
Full feed-in PV system
Mixing system (e.g. self-consumption system)
Loads available and/or
Various energy types present (hybrid, e.g. via PV and battery)
The fundamental difference lies in the fact that in a full feed-in PV system, all functions can be fulfilled with reference to the point of interconnection (POI), whereas in a mixing system, the different reference points point of interconnection (POI) and generation unit (GU) must be taken into account. The following table provides an overview of the requirements:
Function | Reference point in full feed-in PV system | Reference point in mixing system |
|---|---|---|
GSM active power setpoint (with redispatch) | Point of interconnection or generation unit (no significant control deviation present) | Generation Unit |
P(f) function | Generation Unit | |
DV active power setpoint | Usually, point of interconnection provided, possibly generation unit possible | |
Possibly PAV,E monitoring | Grid connection point | Grid connection point |