The "SysAnDUk"-project: Ancillary services provided by distributed generators to support network operators in critical situations and during system restoration

The different measures for voltage and frequency maintenance as well as black start capability, which are mainly provided by conventional power plants today, are a matter of discussion in this paper. The ongoing energy transition, together with a politically decided phase out of nuclear and coal fired power plants in Germany, leads to a lack of availability of ancillary services which has to be filled up with distributed generators (DG). Especially in critical network situations and during power system restoration, there is a need for direct assignable ancillary services by the network operator. Within the research project "SysAnDUk", methods for creating power plant characteristics to provide ancillary services for the network and system operation with a large number of DG shall be developed. Two ideas are pursued: the aggregation of numerous of wind power plants (WPP) connected to the high voltage grid considering the network topology, and the aggregation of a multitude of small photovoltaic units connected to the low voltage and medium voltage grid based on defined geographical areas. Appropriate probabilistic forecasts are implemented in both concepts to display available active power with different safety margins. In an exemplarily case study it is shown by dynamic simulation, that a WPP can provide service to maintain the voltage within predefined limits by means of coordinated reactive power feed-in acc. to a Q(U)-characteristic curve and by voltage control during early stage of system restoration starting in the high voltage grid. Both require online setpoint provision from the network operator. This provides new options for necessary compensation of unloaded lines.