The steadily growing number of renewable, decentralized generation plants and the increasing use of electronic switching power supplies are increasingly leading to limit violations in low-voltage distribution grids (rising harmonic levels, non-compliance with the required voltage band). In order to increase the load capacity of the grids while maintaining high grid quality, small, decentralized systems will also have to participate in the provision of grid services in the future. To ensure optimal interaction between a large number of operating resources (battery storage systems, PV inverters, longitudinal controllers and CHP units), these are to be communicatively connected to a central master computer at the transformer station. The aim is to design a robust and practical control concept for controlling the individual operating resources. The concept will first be examined using simulations, implemented in the laboratory and then tested for suitability in a subsequent field test.

Due to the increasing integration of renewable energies into the interconnected system and the associated geographical imbalance between generation and consumption, there will be more frequent power transfers over long distances in the future. These power flows place new demands on the grid infrastructure and, above all, require new lines in order to avoid overloading the grid and keep voltages within permissible limits. In addition, the increasingly decentralized generation structure increases the interactions between the distribution and transmission grid. With the help of a detailed model of the interconnected system, dynamic simulations of power oscillations can be carried out in addition to load flow calculations to identify overloaded lines (see figure). A suitable simulation of the distribution grids, primarily in Germany, can be used to investigate the effects of inverter systems on the dynamic behavior of the overall system.

In the distribution grids in rural and rural areas, compliance with the voltage tolerance band, which is defined in the EN 50160 standard, primarily limits the maximum connection capacity of generation plants. A solution to the voltage problem in the distribution grids therefore leads directly to a reduction in the need for grid expansion and thus the costs of the energy transition. The U-Control project aims to compare different methods for static voltage maintenance at medium and low-voltage level, to evaluate the effectiveness of these methods, to optimize the parameterization of the methods and to fundamentally investigate the stability of these methods for the first time in simulations, laboratory and field tests.

See also: www.u-control.de

The ever-increasing number of decentralized feeders poses new challenges for grid supply companies. While the power flow has always been directed from large power plants to end customers since the creation of the grids until a few years ago, there are now also times when power is fed back from the low and medium-voltage grid.
In cooperation with Munich University of Applied Sciences and e.on Bayern, the current grid status of a medium-voltage grid and some subordinate low-voltage grids with high PV penetration is being analyzed in the “Grid of the Future” research project. The use of intelligent electricity meters by system operators and measuring points at transformer stations and substations is intended to show the effects of feeding renewable energy into both grid levels. The results will be used to develop concepts and measures to expand and manage the grid as efficiently as possible and thus ensure the usual security of supply even with high PV penetration.