Portugal Makes Synthetic Inertia Mandatory for Grid-Scale Batteries

Portugal has made synthetic inertia a binding condition for battery energy storage systems connecting to its grid. The obligation took effect on 23 October. It covers new storage connected to the transmission grid, and separately any installation rated at 45 MW or more. State Secretary for Energy Jean Paulo Gil Barroca signed the order, which covers future grid connections; existing facilities face the requirements only when undergoing substantial expansion, repowering, or equipment replacement.

A lower threshold applies for automatic frequency response: storage units from 500 kW must switch from charging to discharging whenever system frequency falls. The technical parameters come from a framework drawn up jointly by the EU DSO Entity and ENTSO-E with three trade bodies: WindEurope, Energy Storage Europe and SolarPower Europe. Under the rules, a qualifying unit must have extra capacity and energy available during frequency excursions inside the 47.0–52.5 Hz band, where frequency moves at up to 2 Hz a second; the order does not, however, oblige plants to keep their state of charge permanently held back. Its emulated mechanical starting time must be adjustable between one and twenty seconds, with a default of twelve, while the power oscillation damping factor must reach at least ten percent.

For mid-range projects of 10–45 MW the obligation is not universal: whether it bites depends on what the permits, the tender documents or the titles to grid capacity say. Distribution-connected storage must additionally be capable of grid-following operation, and the choice between the two modes rests with the network operator. Pumped-hydro is exempt, as its turbines provide real mechanical inertia. Portugal moved ahead of a pending update to European network codes, driven by an anticipated surge in storage from its national strategy and a wave of competitive calls for storage funding under the recovery plan backed by the EU, covering over a gigawatt of projects between them. Lisbon is aiming for a storage fleet of 6.9 GW by 2030, and a separate tender covering 750 MVA of battery capacity is in preparation.

Source: ESS News (pv magazine)