Designing schedule freeze policies for congestion management: Impacts on battery energy storage systems

This is the authors' abstract. We don't add key points for this paper.

The rapid growth of battery energy storage systems in Germany poses a challenge for transmission grid congestion management: while grid operators require reliable schedules several hours before delivery to plan redispatch measures, batteries can continue trading on wholesale markets until shortly before real time. This schedule uncertainty forces grid operators to reserve additional redispatch capacity, increasing system costs. Schedule freezes, as regulatory instruments that limit permissible deviations from submitted schedules during grid-critical periods, offer a preventive approach to increase planning security for grid operators. This paper investigates how different policy designs affect battery operator revenues and grid congestion, proxied by redispatch requirements. We extend the open-source ISEA Battery Revenue Index to simulate schedule freezes affecting cross-market operation in frequency containment reserve, automatic frequency restoration reserve, and intraday continuous trading. Using data from 2024 for two stylized locations in northern and southern Germany, we analyze sensitivity to freeze lead time, freeze frequency, and tolerance margins. Results show that revenue losses compared to unrestricted operation remain modest, amounting to roughly 0.18 € per MW and frozen hour per year ( ≈ -0.12%) at short lead times and increasing to about 3.40 € per MW ( ≈ -2%) at 8-hour lead times under a 20% freeze share. The findings suggest that well-designed schedule freezes can substantially enhance planning security for transmission system operators while imposing only limited costs on battery operators, providing empirical guidance for regulatory design in congested power systems.