A generic model of a master controller concept is presented to demonstrate the advantages of aggregating multiple flexible electrical power units. The master controller consists of various submodels with different features. A Power Balancing Controller ensures that the operation does not cause any imbalance with the traded power. A waterfall method that ensures that any ancillary service activations are handled using the appropriate units to obtain cheapest operation. Simulations of the concept include examples of step responses on aFRR activations, as well as actual aFRR data from the Danish TSO. The results suggest that if the system consists of slow units, the aggregation of units can increase the capacity offered to faster types of ancillary services. Additionally, by allowing certain units to shut down automatically more capacity can be offered as the units are no longer bound by minimum loads.