Grid code specifications for grid energy storage systems

This document contains the Grid Code Specifications for Grid Energy Storage Systems (hereinafter referred to as “Specifications”) required by Fingrid Oyj (hereinafter referred to as “Fingrid”), by virtue of the system responsibility imposed on Fingrid, of converter-connected grid energy storage systems which are to be connected to the Finnish power system and which provide system services. In addition to these Specifications, connecting parties shall fulfil Fingrid’s General Connection Terms (YLE) valid at the time of connection, the terms specified in the Main Grid Contract and the connection terms set by the relevant network operator.

The requirements have been set on the basis of the connection technology which is identical to power park modules. If other types of grid energy storage systems are to be connected to the power system, Fingrid will determine their requirements separately. The European grid connection network codes do not currently set any requirements on grid energy storage systems. These Specifications were established taking into account the shared goals of European grid connection network codes: to guarantee equal and non-discriminatory conditions for competition on the internal energy market, to ensure system security and to create harmonised connection terms for grid connections.

Nationally, the purpose of the Grid Code Specifications for Grid Energy Storage Systems is to ensure that:

- the grid energy storage system withstands the voltage and frequency fluctuations occurring in the power system,

- the grid energy storage system supports the operation of the power system during disturbance situations, and works reliably during and after such situations,

- while connected to the power system, the grid energy storage system does not cause any adverse impacts to the other installations connected to the power system, and

- the relevant network operator and Fingrid obtain the data on the grid energy storage system, necessary in the planning of the power system and its operation and in the maintaining of system security.

On 21 June 2023, Fingrid has published Specific Study Requirements (SJV2019 / chapter 5), "Specific Study Requirements for Grid Energy Storage Systems" (see Attachments section), which apply to certain type D grid energy storage systems. In the Specific Study Requirements, requirements are given for Grid Forming control, which is especially required in areas where the amount of converter-connected production (wind and solar power) is high.

When planning the grid connection, the Connectee must request from Fingrid an assessment of the Specific Study Requirements and consequently Fingrid will inform the Connectee whether these requirements apply to the grid energy storage system in question.