An improved method to calculate injection shift keys

• An improved method to calculate injection shift keys (ISKs) is proposed.
• ISKs are needed for the reduction of nodal to zonal electricity network models.
• ISKs are determined separately for different injections in the improved method.
• The improved method is applied to a case study of the European electricity grid.

Transmission network constraints become increasingly relevant in generation scheduling models, given the ongoing integration of market zones and the deployment of renewables in remote areas. However, a full nodal network representation in generation models is often not possible due to computational limitations. Therefore, reduced zonal network models are needed. A crucial step in the nodal-zonal network reduction is the calculation of injection shift keys (ISKs). Injection shift keys denote the nodal contribution to the zonal generation balance and are needed to compile different nodes into one equivalent node. This paper discusses injection shift keys in detail and proposes an improved method to calculate them. According to the improved method, the generation and load portfolio is split up in different categories, and injection shift keys are determined separately for each category. A case study of the central European electricity system indicates that the improved method is able to approximate the nodal network without a considerable increase in computational cost.