The connection network codes in Europe and more generally in the world are moving to require Grid Forming (GFM) capability from generation and storage devices. As GFM control will help stabilise the grid, it might create additional flows and stress in the battery and inverter. To evaluate the change in behaviour on the device and to provide both qualitative and quantitative insight on the expected solicitation, this paper will simulate the response to different events for three types of Energy Storage Module (ESM) installation:

• Grid Following Energy Storage Module providing Frequency Containment Reserve

• Grid Forming Energy Storage Module at constant power

• Grid Forming Energy Storage Module providing Frequency Containment Reserve

The models used in this study are fitted to match the expected requirements for GFM ESM in France, which are based on the draft version of Requirement for Generators V2 from ACER and the latest version of Technical Report on GFM technologies from ENTSO-E. The main impacting requirement is that as of today’s knowledge, France will ask for GFM only within storage and inverter capability, therefore, no additional storage nor oversizing of hardware is requested from a GFM than from a Grid Following (GFL) unit.

These models have been tested against actual voltage and frequency measurements from Phasor Measurement Unit acquired during different grid transients over 15 minutes periods. The impact of GFM requirement parameters, such as equivalent inertia or effective impedance, is also evaluated on the same test cases. Results illustrate that GFM controls only creates minor deviation of the power from its setpoint, with a standard deviation of less that 0.2% with the worst case of parameters.These variations have no significant effect on the ESM’s state of charge and are minimal compared to the stress induced by participation in Frequency Containment Reserve (FCR).

Additional simulations have been performed to showcase that even if the control impact on power in normal situation is very low; in case of more severe system events such as phase shift, the GFL and GFM act in a very different way. In such situations, the GFM contribution exceeds that of the GFL mode, but remains limited in duration.