Integrated Reconfigurable Converter Topology for High Voltage Battery Systems

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Copyright: Momayyezan, Milad
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Abstract
Traditional high-voltage battery systems are implemented using multiple battery modules connected in series, with each battery module made up of many series/parallel connected cells, to provide the required voltage and power. In the series-connected battery systems, typically, separate converters for battery module balancing, bi-directional connection to a load and charging from an external power source are employed. In this thesis, an integrated reconfigurable converter (IRC) topology for high-voltage series-connected battery storage systems is proposed. The main advantage of the proposed converter is that it can be reconfigured to operate in a range of operating modes: ‘feeding a load’ from the battery system, ‘feeding a load from a backup’ power source, ‘regenerative’ mode, ‘battery module balancing’ mode and ‘charging’ mode. The proposed topology shares semiconductor devices and an inductor among the operating modes which makes it compact. It also exhibits redundant modes which, together with a backup mode, increase its reliability. Furthermore, the proposed IRC topology minimises the batteries’ stress during charging and discharging cycles. Operation of all modes is analysed and explained in detail. For the state of charge (SOC) ‘battery module balancing’ mode, two advanced strategies are developed. A distributed control strategy provides advantages in terms of reduced communication requirements and increased modularity, over a centralised battery management system. A load sharing balancing strategy distributes the load between the battery modules based on their SOC and is useful in applications where simultaneous balancing and load supply is required. In the initial IRC configuration, the ‘charging’ mode is implemented using a unidirectional DC/DC buck converter supplied by an external DC source. To further extend the IRC flexibility, an enhanced IRC configuration with bidirectional energy transfer between the battery modules and the AC grid is presented. The IRC topology can be used for hybrid energy storage systems (HESSs) as well. The proposed integrated reconfigurable configuration for HESSs allows direct energy transfer between the energy storage systems by using only a single converter and bypassing the DC link. This reduces stress on the DC link, reduces the DC link capacitor size and improves overall efficiency. All proposed IRC configurations and operating modes are experimentally verified.
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Author(s)
Momayyezan, Milad
Supervisor(s)
Hredzak, Branislav
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Publication Year
2017
Resource Type
Thesis
Degree Type
PhD Doctorate
UNSW Faculty
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