Nowadays electrical energy is playing an increasingly large role and the number of installed photovoltaic systems (PV systems) is on the rise. Inverters used in PV systems are taking more and more additional functions, and, in combination with an accumulator, the operation of PV systems in off grid mode is possible. The goal of this thesis is to model an inverter capable of off grid mode for simulation of a grid model in NEPLAN. This grid model aims to simulate and verify the behavior during blackouts or while restarting the grid. The thesis is structured as follows: The first chapter provides an introduction and describes the task. In the second chapter the different components of a PV system are introduced followed by a brief description of how they function. A detailed description is provided merely for the inverter because this component embody the key element of this paper. The third chapter introduces the solar power system, which is installed on the roof at the Vienna University of Technology. This PV system serves as basis for the modeling and delivers the required parameters. The measurements at the PV system were taken with and without a load in different operation modes (e.g. grid connected, off grid mode). The parameters obtained from the measurements, are used to rebuild the characteristics of the PV output and the frequency in MATLAB/Simulink. These MATLAB models are described in the fourth chapter. The fifth chapter focuses on the creation of simulations in NEPLAN and the embedding of the MATLAB models in NEPLAN. These dynamic simulations are reconstructions of the measurements and therefore depend upon the respective operation mode while the measurements were taken. At the end of the fifth chapter the simulation results are compared with the measurements to show their accuracy. The sixth chapter deals with the final simulation. This works for all operational modes and is extended with the simulations from the fifth chapter. Then the final simulation is extended with the battery charge level, to complete the model. The simulations were done with a reproduced daily load profile of a household and with different PV outputs and battery charge levels. The results of the performed simulations and the conclusions (chapter seven) wrap up this paper.