Legal background
As part of the amendment to the Grid Expansion Acceleration Act (NABEG) in April 2019, the legal regulations on congestion management for German electricity grid operators were fundamentally changed (Sections 13 et seq. EnWG). To this end, the previous regulation on the feed-in priority of plants in accordance with Section 3 (1) of the German Renewable Energy Sources Act (EEG) and plants within the meaning of Section 3 (1) of the German Combined Heat and Power Act (KWKG) as well as the subordination of the grid reserve have been modified. The aforementioned plants will be transferred to redispatch.
The aim of the amendments is to determine the installations to be adjusted as part of redispatch optimization in such a way that adjustments are made at the lowest possible cost while maintaining the modified feed-in priority. The subordination of the adjustment of the active power generation of installations pursuant to Section 3 (1) EEG and installations within the meaning of Section 3 (1) KWKG in relation to KWK electricity and the grid reserve is to be ensured by the introduction of so-called imputed prices[1].
The imputed prices for renewable energy installations and the grid reserve are to be determined uniformly by the transmission system operators (TSOs) and thus not based on installations or bottlenecks, and are to be taken into account by the grid operators in the selection decision for the installations.
The imputed prices must be determined in such a way that the minimum factors set by the Federal Network Agency are generally adhered to. These describe the minimum ratio from which the reduction in the generation capacity of non-priority-entitled plants can be replaced by priority-entitled plants so that intervention in the operation of priority-entitled plants is permitted. The minimum factors were set for the first time by the Federal Network Agency in its decision of November 30, 2020.
When determining the imputed prices, the respective minimum factors were converted using a formula from the study "Development of measures to efficiently guarantee system security in the German electricity grid" (page 80).