Supply of reactive power by renewable energy generation facilities

Renewable energy facilities have statutory obligations that demand that their output must, in some ways, be equivalent to that of conventional power stations. As a result of the rapid development of renewable energies and the simultaneous decommissioning of conventional power stations the future safety and stability of the electrical energy supply should be ensured.

A key point of the requirements is the supply of the standard reactive power within the basic requirements defined in the BDEW directive (medium voltage guideline) or the TransmissionCode.

For the distribution network operators the question is, if and to what extent the available reactive power can be used for system management at the 110-kV network level. For the transmission grid operators the question is, to what extent standard reactive power from the subordinate grid levels is available for the grid management of their own EHV network.

Over the past years P&M Power Consulting has conducted extensive grid studies on this problem on the basis of grid models, which show in detail both the EHV level and the 100-kV network groups down to the subordinate MV grids.

In detail the following partial tasks were analysed for current and future development stages of the Renewable Energy Act:

  • determination of the reactive power which could be supplied currently and in future by renewable energy facilities in the distribution grids
  • analysis of the usability of the standard reactive power within the framework of the management procedures of HV and MV grids
  • definition of requirements for voltage maintenance in connection with the demand of the standard reactive power
  • determination of available reactive power control ranges at the interfaces with the EHV grid
  • analyses of basic principles on controlling reactive power flows in the mesh HV grids

The existing findings are currently being extended and the studies are being continued with regard to further research.