Stability analysis of a medium voltage local energy system with decentralized generation

In this paper the impact of the decentralized generation provided by renewable sources, as e.g. wind parks, fuel cell power plants and photovoltaic plants, on the stability of a Local Energy System (LES) are studied. Small dimensions, small power, and the neighbourhood of generators and consumers characterize these systems. Decentralized generation in the power system is studied not only in direct connection with the high voltage transmission grid, but also as islanded network with distributed generation on various levels of the power system itself. In the first case, the generating units could be disconnected from the system during disturbances. In the second case the generation units have to remain connected, because they participated at the stability of the network. Therefore appropriate control schemes are required. The paper presents the simulation of a LES, modelled as a meshed medium voltage network with lumped loads, connected to the conventional high voltage network and supplied from local generation units as well. Control schemes and protection of the decentralized generators are implemented and tested. Numerical results under ATP-EMTP assuming disturbances of short duration are reported.