Provision of Frequency Containment Reserve Using Battery Energy Storage System

Khatiwada, Bhupal

4. term

Energy Engineering, Master

2026

2026-05-27

64

This thesis examines how variations in grid frequency affect a battery energy storage system (BESS) that provides frequency containment reserve (FCR) — services that stabilize the grid by charging when frequency is high and discharging when it is low. We analyze grid-frequency behavior across different time scales, how to manage the battery’s state of charge (SoC), and the economics of operating the BESS for FCR. Four operating cases are compared: one without a deadband (a range around the nominal frequency where the BESS does not respond) and three with different deadband settings. We find that, on average, grid frequency sits slightly above its nominal value. This biases the BESS toward charging more often, so the SoC tends to drift toward SoC_max. To keep the SoC near a target level, we implement an SoC-balancing strategy based on small, controlled adjustments to charging and discharging within limits set by the transmission system operator (TSO). These adjustments can hold the SoC with relatively little net energy, but they are not symmetric between charging and discharging, and the required amounts differ when assessed over a day versus over a year because of how frequency varies over time. Increasing the deadband markedly reduces cycling, which lowers cyclic degradation and extends the BESS’s operational lifetime. The economic analysis shows that operating without a deadband is not viable due to the resulting short battery lifetime, whereas choosing an appropriate deadband improves both lifetime and overall profitability of FCR operation.

Dette speciale undersøger, hvordan variationer i elnettets frekvens påvirker et batterienergilagringssystem (BESS), der leverer Frequency Containment Reserve (FCR) — tjenester, som stabiliserer nettet ved at lade op, når frekvensen er høj, og aflade, når den er lav. Vi analyserer frekvensadfærd på forskellige tidsskalaer, håndtering af batteriets ladestand (SoC), samt økonomien i at drive BESS’et til FCR. Fire driftscases sammenlignes: én uden dødbånd (et interval omkring den nominelle frekvens, hvor BESS’et ikke reagerer) og tre med forskellige dødbåndsindstillinger. Vi finder, at elnettets gennemsnitsfrekvens ligger en smule over den nominelle værdi. Det får BESS’et til at lade oftere, så SoC driver mod SoC_max. For at holde SoC tæt på et målniveau implementeres en SoC-balanceringsstrategi med små, kontrollerede justeringer af op- og afladning inden for rammer fastsat af den systemansvarlige (TSO). Justeringerne kan holde SoC’en med relativt lidt nettoenergi, men de er ikke symmetriske mellem op- og afladning, og de nødvendige mængder er forskellige på dags- og årsbasis på grund af frekvensens tidslige adfærd. Et større dødbånd reducerer markant cyklingen, hvilket mindsker den cykliske nedbrydning og forlænger BESS’ets levetid. Den økonomiske analyse viser, at drift uden dødbånd ikke er rentabelt på grund af den korte batterilevetid, mens et passende dødbånd forbedrer både levetid og den samlede rentabilitet af FCR-drift.

[This apstract has been rewritten with the help of AI based on the project's original abstract]

BESS for FCR Provisionn

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Khatiwada, Bhupal:

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