Demand-appropriate utilisation of free reactive power potentials from Renewable Energy plants in the framework of system management of the 110 kV distribution grids

Inhalt:
The politically forced expansion of the Renewable Energy plants (RE plants) causes conventional power plants for the generation of electrical power from coal, nuclear power and gas to be increasingly pushed out of the system. To be able to continue maintaining the reliability of electrical energy supply as well as the static and dynamic stability of the electrical energy supply system in the course of the “Energiewende” the RE plants must take over the system services of these conventional power plants. A key requirement is the provision of steady state reactive power, which is currently used exclusively to ensure local voltage stability (compliance with defined voltage bands) in the electrical environment of the RE plants. The object of the present contribution is a novel control method for the demand-appropriate utilisation of free reactive power potentials from RE plants in 110 kV distribution grids. This innovative method allows utilizing reactive power potentials, not absolutely needed for local voltage stability in the connection area of the RE plants, for the optimisation of the distribution grid and for participation in voltage stability in the transmission grid. The method was developed in cooperation with the distribution system operators E.DIS AG, ENSO NETZ GmbH, Mitteldeutsche Netzgesellschaft Strom mbH, TEN Thüringer Energienetze GmbH and WEMAG Netz GmbH and verified by using grid models of real 110 kV grid groups with representative RE percentage. At this time, the basics for the implementation of the method into network control systems are accomplished. The authors express their thanks at this point for all participants for the trusting and constructive cooperation.