Bibliography : p. 89-92.

The integration of the renewable energy sources and more efficient utilisation of primary energy sources due to local generation result in a large number of decentralised generators in the LV-Grid. For most microturbines, wind plants, fuel cells and photovoltaic cells electrical power is generated as a direct current (DC) and converted to an alternating current (AC) by means of inverters. These inverters, which can be represented as ideal voltage sources with grid forming functions, control the active and reactive power. So, inverters influence the frequency and the voltage of the grid, consequently the stability of the grid depends on their behaviour. This work assesses the expandability and the stability of decentralised inverter-dominated electric supply systems (MicroGrids) which can be operated either in grid-connected or in stand-alone mode. The combination of droop-controlled voltage source inverters of different sizes as well as inverters with rotating generators have been investigated. This work shows that each of these combinations can be operated stably with respective constraints. The "universal parameter set", which enables a stable operation of droop-controlled voltage source inverters in almost all relevant scenarios, has been obtained.