Grid-Constrained Distributed Optimization for Frequency Control with Low-Voltage Flexibility
For flexibility service providers operating distributed assets, this work addresses a practical regulatory constraint but is incremental, applying known distributed optimization to a specific grid problem.
The paper analyzes the impact of a new Belgian regulation limiting frequency control providers to 10 per 100m radius on low-voltage grid flexibility, finding that at 5% participation only 90% of capacity is usable with significant neighborhood variation, and proposes a distributed optimization framework that balances optimality gap and convergence iterations.
Providing frequency control services with flexible assets connected to the low-voltage distribution grid, amongst which residential battery storage or electrical hot water boilers, can lead to congestion problems and voltage issues in the distribution grid. In order to mitigate these problems, a new regulation has been put in place in Belgium, imposing a specific constraint: in any circle with a radius of 100m, there can be at maximum 10 connection points providing frequency control at any time. This paper presents an impact analysis and a coordination strategy of a Flexibility Service Provider (FSP) that operates a pool of assets and is exposed to this new regulatory constraint. Results show that at 5% participation, only 90% of total control capacity can be used, with a large difference between neighbourhoods with different population densities. A distributed optimization framework to coordinate the assets arises naturally, in which the assets are able to keep their local cost functions private and only have to communicate with neighbouring assets that are geographically close, and with the FSP. Analysis of the proposed distributed optimization algorithm shows a clear trade-off between optimality gap, owing to the mixed-integer nature of the problem, and iterations to convergence.