Nordic Common Grid Model Alignment
The Nordic Common Grid Model Alignment (CGMA) service provides the TSOs with information that allow them to create Individual Grid Models (IGMs) that fit together in the process of merging them into the Common Grid Model (CGM).
The market provides information on flow on bidding zone border connections in time horizons shorter than two days ahead of operation, in the spot market the day ahead and in the intraday market, intraday. In time horizons longer than this, there are no market results available which leaves the CGMs to be built based on forecasts from the TSOs.
All the European TSOs' forecasts are aligned in the pan-European Common Grid Model Alignment (CGMA) process to create a system in balance, with a total power production equal to the total load (consumption) in the system.
In the CGMA service, the forecasts on load and power production are collected from the four Nordic TSOs and aligned into a common Nordic forecast on net position (balance in an area, where a positive net position means the area is a net exporter of power) and power flow on each of the bidding zone borders. This forecast, which is created in a pre-process to the European CGMA, is sent as input to the pan-European calculations and aligned with the rest of the European system.
A post-process to the European CGMA service is run in the Nordic CGMA service after the CGMA results are finalised. In this post-process, power flow on HVDC connections are divided into flow on each of the poles constituting the HVDC connection (e.g. the Skagerrak link between Norway and Denmark has 4 physical poles/cables), and losses on the connections are calculated. By utilizing this information in the creation of the Individual Grid Models (IGMs), they are guaranteed to contain the correct flow on each of the poles. Similarly, the net position given by the CGMA process of the Swedish and Norwegian control areas are divided between the four Swedish and five Norwegian bidding zones, and the net positions of all the four Nordic countries are divided between the bidding zone borders before the results are provided to the TSOs. In this way, the Nordic CGMA service provides all the information needed to create IGMs that fit together.