Architecture design and implementation of the power distribution system on an electric vehicle
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Date
2026-10-07
Authors
Δρίβας, Παναγιώτης
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Abstract
The auxiliary low-voltage network of the experimental electric vehicle of the Laboratory of Electromechanical Energy Conversion (LEMEC) at the University of Patras, is supplied from the 76.8 V main battery through a single commercial 8.5 A converter, and its 12 V lead-acid battery has no dedicated charging profile. With the battery planned to rise to 160 V, the step-down ratio becomes too large for conventional hard-switched converters. This thesis proposes a two-stage, galvanically isolated, 250 W converter consisting of a ReSC stage that produces a 20 V intermediate bus and a push-pull stage that provide the isolation and control. Together supply the low-voltage network of the vehicle under normal operation and charge its 12 V battery when the main battery pack is charging. Both stages are designed, and the first is built and tested.
For the first stage three ReSC topologies (a Dickson ladder, a binary hybrid converter and three cascaded 2:1 modules) were simulated in MATLAB/Simulink and LTspice and compared. The cascaded 2:1 topology was selected because it needs only two complementary gate signals for each module, uses identical resonant tanks and changes from the 8:1 to the 4:1 ratio by bypassing its first module through the gate states alone, providing an intermediate 20 V bus. For the isolated regulating stage, a push-pull converter with a center-tapped rectifier was selected and designed, including its turns ratio, duty-cycle range and output inductor. The ReSC stage was analysed with the charge-flow method, including its output resistance, losses, bootstrap gate drive and the resonant-frequency split caused by the finite input capacitance, and was built on a four-layer printed circuit board with silicon MOSFETs, an AURIX microcontroller, isolated voltage sensing and two CAN interfaces. A dedicated circuit for the startup of this module was proposed.
Near-zero-current switching was obtained in all modules once each was tuned to its own resonant frequency and the first module was given the asymmetric duty cycle predicted by the analysis. In the 160 V mode the converter reached 93.7% efficiency near its rated power, and 95.7% at 535 W, more than twice its rating, while in the 80 V mode it reached 98.0%. The output voltage fell by about 0.3 V at the rated load. Load steps between 40 W and 200 W caused no overshoot, and the output followed input-voltage changes between about 100 V and 160 V smoothly. The main limitations are the low efficiency below about 120 W in the 160 V mode and the unregulated output, which follows the battery voltage and is left to the second stage to regulate. The results show that a silicon ReSC converter with a selectable ratio is a practical front end for the auxiliary supply of electric vehicles with supply voltages up to 160 V.
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Keywords
Electric vehicles, Power electronics, Resonant converters, DC-DC converters, Chargers