Design and simulation of a safety-aware and health-monitoring charging system for UDT transit capsules
Hettiarachchi, Mayura (2026)
Diplomityö
2026
School of Energy Systems, Sähkötekniikka
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe2026061268812
https://urn.fi/URN:NBN:fi-fe2026061268812
Tiivistelmä
This thesis presents the design and simulation of a safety-aware and health-monitoring DC-DC battery charging system for transit capsule battery swapping station of UDT Technologies, implemented in the MATLAB Simscape environment. The transit capsule is an urban mobility concept developed by UDT Technologies in Finland. Depleted battery packs in the capsules are swapped at a centralised charging station rather than being charged onboard. The charging station is designed to have independent charging modules, each comprising eight charger bays on a shared DC bus, allowing the station to be scaled depending on the location.
The battery pack is designed using Panasonic NCR18650BD lithium-ion cells in a 24S17P configuration, yielding a nominal voltage of 86.4 V and a capacity of 51.51 Ah. An LLC resonant DC-DC converter is selected for the charging due to its high efficiency and soft switching characteristics and is represented by an averaged model in simulation due to limitations of simulating the full converter. The CC-CV charging strategy is implemented at a 0.5C rate with charge termination at 95% SoC. A fault detection system monitoring overvoltage, undervoltage, overcurrent, overtemperature, charge timeout, and overcharge for each charger bay is implemented using SR latch architecture that ensures shutdown of the affected bay without interrupting the remaining bays.
The simulation results confirm correct charging behaviour across multiple initial SoC conditions, successful charge termination at the defined threshold, and independent fault isolation at the charger bay level.
The battery pack is designed using Panasonic NCR18650BD lithium-ion cells in a 24S17P configuration, yielding a nominal voltage of 86.4 V and a capacity of 51.51 Ah. An LLC resonant DC-DC converter is selected for the charging due to its high efficiency and soft switching characteristics and is represented by an averaged model in simulation due to limitations of simulating the full converter. The CC-CV charging strategy is implemented at a 0.5C rate with charge termination at 95% SoC. A fault detection system monitoring overvoltage, undervoltage, overcurrent, overtemperature, charge timeout, and overcharge for each charger bay is implemented using SR latch architecture that ensures shutdown of the affected bay without interrupting the remaining bays.
The simulation results confirm correct charging behaviour across multiple initial SoC conditions, successful charge termination at the defined threshold, and independent fault isolation at the charger bay level.