BACKGROUND & AIM

Grid investments will increase worldwide from around 470 billion USD in 2025 to about 770 billion USD each year in the next decade according to IEA. The relevance of grid infrastructure as backbone of the energy transition is evident in the achievable expansion pathways for variable renewable energy sources (VRES):

In the IEA “grid delay” scenario, PV and wind reach 44% of the worldwide power generation and CO2 emissions of the power sector attain 8.3 Gt in 2050 compared to 59% / 3.2 Gt in the “announced pledges” scenario.

In Europe, 72 TWh of power production, mainly from VRES, was curtailed due to grid bottlenecks, and congestion costs were close to €9 billion in 2024.

Even being doubtless that grid reinforcement and expansion is needed to reach high shares of VRES, further solutions need to be explored to reduce and postpone grid investments.

This study was performed under task 19 of the PVPS programme. DSOs from involved countries answered a questionnaire on how they perform grid connection studies with focus on PV plants, how they define grid hosting capacity and which measures they take to increase it.

APPROACH

The hosting capacity of a grid segment may be defined as the maximum active power generation connected and operated within that segment, under existing equipment and operational constraints, such that no voltage, thermal, protection, or other reliability limits are violated across the segment or its associated upstream interfaces and without requiring grid reinforcements or operational changes beyond those already implemented.

The originality of this work lays in a comparison between the regulatory framework and implementation practices from DSOs in different countries. This helps to better understand how DSOs adapt connection requirements to increase hosting capacity and thus the penetration of decentralized VRES into the grid.

DSO begin to adopt different strategies to connect more VRES without systematically reinforcing the distribution grid. Among the measures mentioned, the following were cited most frequently:

- On-line Tap Changers (OLTC)

- Network reconfiguration

- Dynamic Line Rating (DLR)

- Reactive power management

- VRES curtailment

- P/U control

- Batteries

- Demand side management (DSM)

The full evaluation will give insights to understand how those measures enable increasing the grid hosting capacity.

CONCLUSIONS & PERSPECTIVES

Two opposite preliminary conclusions must be drawn with the first answers evaluated:

- Strategies to integrate VRES into distribution grids are quite similar from one country to another even when facing very different VRES production levels.

- Despite this first observation, very different voltage plans seem to be used leading to contrasted remaining room for new VRES connection on LV grid (only 1 or 2% in some countries and up to 6% in others).

Further work will help understand how DSOs manage such different implementations of voltage plan regulation.