The attached project contains a small medium voltage network with four loads of different behaviour. The loads are supplied by a synchronous generator driven by a diesel engine. Additionally there is a PV system, which supports the diesel. In the study cases "AsDispatched_ByReferenceMachine" (indicating already the used load flow command settings), the diesel engine acts as slack element. In case of a higher PV feed in than the current load consumption, the generator switches into a motoric operation, which is not desired.

The study case "SecondaryControl" shows the same setup with different settings. In this case, the PV feeds all power in as long as the load is high enough to not lead into operating points of the diesel engine, where its active power falls under 10% of the rated value. If the lower limit is reached, the generator remains at this limit and the feed in of the PV system is then curtailed.
The load flow calculation command has to be set to an active power control according to the secondary control. A secondary controller respectively frequency controller has to be created and both the diesel enginge and the PV system assigned to it. The generating units itself have to be configured as follows:
- Diesel engine: The active power operation point in the Load Flow page is the lower limit, which is held in case of PV curtailment (in the example 10% of the rated value).
- PV System: The operation point in the Load Flow page / General tab should be set to zero. In the operational limits tab enter the watt-peak value of the PV system as maximum active power and assign to this parameter the PV profile as characteristic (set to relative to scale the max. active power operational limit).

This setup shows a possible way to model a co-generation of PV and a diesel engine, where the feed in of the diesel does not fall under its limit and the PV is curtailed if the solar radiation exceeds the networks demand (minus the min. limit of the diesel).

The study cases are available for only one day quasi dynamic simulations and for a whole week to show different load behaviours at the weekend. The according diagrams are available and activated in the graphics board.