Isolated Three-Port Bidirectional DC-DC Converter for Electric Vehicle Applications

To further reduce size, weight, and cost of power converters in an electric vehicle (EV), the dc-dc converter of onboard charger (OBC) and the auxiliary power module (APM) are electrically integrated. However, a key challenge of the electrical integration is to design a power-stage topology and its control which not only achieves high power density but also achieves independent regulation of voltage at each output port. In this paper, a new, isolated, three-port, bidirectional dc-dc converter topology and its control are proposed to achieve high power density and high efficiency in integrated OBC and APM for EV applications. The operation and control of the proposed converter is explained in detail in different operating modes. Finally, the design details about a 6.6 kW experimental prototype with three-winding transformer which integrates all the resonant inductors are provided. The experimental waveforms and measured efficiencies in charging mode, discharging mode, and EV running mode have also been provided. The measured efficiency in the charging mode at $\mathrm{V}_{\text{Bus}}=400\ \mathrm{V},\ \mathrm{P}_{\text{HV}}=4.5\ \text{kW},\ \mathrm{V}_{\text{LV}}=13.8\ \mathrm{V}$, and $\mathrm{P}_{\text{LV}} =300\mathrm{W}$ is greater than 97% at all HV battery voltage levels. The measured efficiency in the discharging mode at $\mathrm{V}_{\text{Bus}}=400 \mathrm{V},\ \mathrm{P}_{\text{Bus}}=4.4\ \text{kW},\ \mathrm{V}_{\text{LV}}=13.8\ \mathrm{V}$, and $\mathrm{P}_{\text{LV}} =300\mathrm{W}$ is greater than 96.9% at all values of VHV. Also, a peak efficiency of 96.5% is achieved in EV running mode at $\mathrm{V}_{\text{HV}} =380\mathrm{V}, \mathrm{V}_{\text{LV}} =13.8\mathrm{V}$, and $\mathrm{P}_{\text{LV}} =800\mathrm{W}$.