| Summary: | The current practice in electric vehicles (EVs) is to use two separate converters i.e., the on-board charger (OBC) and the auxiliary power module (APM), to charge the EV high-voltage (HV) and low-voltage (LV) batteries. In this thesis,
the integration of the OBC and APM in a single multiport converter topology is investigated. The proposed architecture aims to reduce the overall volume and component count of the EV charger, as well as improve the charger’s efficiency.
Towards this direction, two different three-port isolated DC-DC converter topologies are investigated in this research and their performance for integrated on-board charger (IOBC) application is evaluated. First, the topology of the triple-active-bridge (TAB) converter is analyzed and a methodology to estimate the converter power losses based on 5-degrees-of-freedom (DOF) operation is presented. In addition, several optimized 5-DOF modulation schemes are proposed, targeting different design optimization objectives e.g., zero-voltage-switching (ZVS) operation and converter power loss minimization.
A new isolated three-port DC-DC converter with a reduced number of active devices is also proposed in this thesis. The proposed converter is based on a hybrid dual-active-bridge (DAB) and phase-shifted full-bridge (PSFB) topology and it is able to achieve independent charging of HV and LV batteries using a new 3-DOF modulation scheme, while all of the semiconductor devices of the proposed converter operate with ZVS over a wide HV and LV battery voltage range.
Finally, a comparison of the TAB and the new hybrid DAB-PSFB converter is performed in terms of efficiency, volume and component count. Moreover, the comparison includes the non-integrated counterparts of each converter topology, considering the conventional architecture of separate OBC and APM converters. Results from the experimental testing of the converters are utilized along with finite-element (FE) simulation results to evaluate the performance of each converter topology and validate their effectiveness for future integrated on-board charger application.
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