Performance Comparison Between Hydropower and Battery-Based Frequency Containment Reserves in the Nordic Power System

Abstract

As power systems transition toward high shares of renewable energy generation, maintaining grid frequency stability becomes increasingly complex. This degree project investigates the performance of hydropower and battery energy storage systems (BESS) as frequency containment reserves (FCR) in the DK2, SE4, and SE3 bidding zones during contingency events in a future power system scenario characterized by high wind generation and varying demand. The investigation assesses potential improvement in transmission capacity and grid efficiency in the congested area of southern Sweden and eastern Denmark during contingencies. Using updated Nordic 56 that contains 56 busbar and a detailed DK2 grid models with 141 busbars as the simulation environment in PowerFactory, the work evaluates network robustness under both pre-contingency and post-contingency conditions. Static contingency simulations focused on the operational envelope of the 0.95–1.05 voltage in p.u. and phase angles of ± 30◦ within transmission networks to identify deficiencies and assess proximity to voltage violations and angular instability. The simulations showed that increased BESS FCR participation relieves transmission capacity in contingencies during current and future high wind high load conditions, but also corresponded to increased losses in future high wind low load conditions. The increased losses likely correlate to a future shift in generation and demand centers in the Nordics, with a corresponding shift in congested transmission corridors across the Nordic power system, rendering BESS FCR located in DK2, SE3 and SE4 less effective during low load conditions. Consequently, depending on the grid loading conditions, these potential alleviations could unlock previously reserved transmission capacity for energy markets, thereby influencing electricity price. Limitations concerning the simulations were noted, including the lack of dynamic modeling which likely influenced the static simulation outcomes.