The energy supply systems of the Federal Republic of Germany have been
characterized by profound changes in the generation structure due to energy
policy requirements. As a result of the targeted promotion of renewable
generation units (RGUs), there was a massive expansion of regenerative
generation output in the area of distribution grids, which continues to
this day. In several regions the renewable generation capacity currently
exceeds the common peak load of subordinated medium voltage (MV) grids
significantly. Unfavorable feed-in situations can lead to overloads in the
high voltage grid. In such cases the Distribution System Operator (DSO) has
to reduce the feed-in from RGUs to preserve a secure system state. These
operational interventions will further increase because the realization of
grid reinforcement and expansion projects cannot keep up with the
continuously increasing integration of new renewable power plants. In
mainly meshed high-voltage (HV) and extra-high-voltage (EHV) grids, the
adjustment of the topology to the expected feed-in and load situation can
be a suitable means for congestion removal and for increasing the transport
capacity. This thesis investigates which energy amount of renewable
generation units can be additionally feed-in and transported through the
optimization of the switching state of existing 110-kV distribution grids.
In order to answer this research question, an expanded congestion
management method is proposed, which takes into account the topological
degrees of freedom and also includes further operational measures, e.g.
feed-in management. To evaluate the grid operation state, the load flow
calculation and (n-1) reliability calculation method is also integrated. In
this thesis, a novel discrete particle swarm optimization algorithm is
adapted to the optimal transmission switching problem to eliminate
congestions. This algorithm was selected because of its applicability and
robustness for this kind of optimization problem. In regards to shifting
requirements for power system operation, it allows the definition of
further optimization objectives. To reduce the number of decision variables
of the optimization problem, a novel modeling method of standard bus
couplers without busbar sectioning and universal bus couplers with busbar
sectioning is introduced. This method, which implicitly takes into account
local coupling constraints, allows a realistic mapping of all practical
coupling options. The validation of the proposed method is carried out
through exemplary case studies at two real medium-sized 110 kV network
groups. The investigations are based on real feed-in and load-time series
in quarter-hour resolution. The results show that the transmission capacity
of the existing grid can be increased by optimizing the switching state.
The exploitable maximization potential depends to a considerable extent on
the network structures and the meshing degree of the distribution grid.
Furthermore, it is demonstrated that it is possible to define over a period
of one year several seasonal grid normal switching states, which maximize
the feed-in of renewable generation units on the one hand or which minimize
the grid losses on the other hand.