The increasing amount of Distributed Energy Resources (DER) components into distribution networks involves the development of accurate simulation models that take into account an increasing number of factors that influence the output power from the DG systems. This paper presents two simulation models: a PV system model using the single-diode four-parameter model based on data sheet values and a Vanadium Redox Battery (VRB) system model based on the efficiency of different components and the power losses. The unit models were implemented first in MATLAB/Simulink and
the simulation results have been compared with the data sheet values and with the characteristics of the units. To point out the strong dependency on ambient conditions and to validate the
simulation models a complex data processing subsystem model has also been developed. A PV and a VRB inverter models have also been developed and implemented in PowerFactory to study
load flow, steady-state voltage stability and dynamic behavior of a distribution system.