A master thesis from Aalborg University
Development and Analysis of Modular Multilevel Converter Integrated with Battery Storage for Grid Support
Author(s)
Term
4. semester
Education
Publication year
2024
Submitted on
2024-06-03
Pages
128 pages
Abstract
This thesis investigates grid support using battery energy storage systems. Initially, a problem analysis is conducted to understand various converters, energy storage systems, and control algorithms used in grid support. The focus then shifts to Modular Multilevel Converters (MMC) integrated with second-life batteries in each submodule via bidirectional buck-boost converters. Dynamic modeling of the MMC for output current control and circulating currents is developed, accompanied by electrical circuit simulations. Various control algorithms, including output current control, active/reactive power control, circulating current suppression, and balancing strategies, are analyzed and implemented. A small-signal model of the bidirectional buck-boost converter is derived, and controllers are tuned for a constant current and constant voltage protocol for battery charging and discharging. Second-life batteries are examined, and an electrical equivalent model is defined, with parameters identified based on the state of charge and charge-discharge cycles to simulate aging processes. Integration of batteries into the MMC is performed, with preliminary analyses showing that battery-integrated MMCs can assist with active power supply and demand regulation. Finally, further research aspects are identified to enhance system model accuracy and simulation fidelity.
Documents
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