Superordinate control for increasing feed-in capacity and improving power quality in low voltage distribution grids

The ever increasing amount of distributed generation in low voltage distribution grids (mainly PV and micro-CHP) can lead to reverse load flows from low to medium / high voltage levels at times of high feed-in. Reverse load flow leads to rising voltages that may even exceed the limits specified in the grid codes. Furthermore, the share of electrical loads connected to low voltage distribution grids via switched power supplies continuously increases. This paper illustrates a possible concept for smart grids in order to increase the feed-in capacity, improve power quality and to ensure safe operation of low voltage distribution grids at all times. The key feature of the concept is a hierarchically structured control strategy that is run on a superordinate controller, which is connected to several distributed grid analyzers and inverters via broadband over power line (BPL). The control strategy is devised to ensure both quick response times as well as a smart usage of the available inverters in the grid (PV-inverters, batteries, stepless line voltage regulators). The presented results have been obtained during the government-funded project “Verteilnetz 2020”.