Novel Coupled Three-Phase Inductor Structure for Interleaved Converters in Electric Vehicle Applications

Power density and efficiency are the key design criteria for the modern power electronics unit in Electric Vehicles (EVs). The limited vertical space on the chassis calls for innovative packaged vehicle electronics and components. This has increased the importance of interleaved DC-DC converters with integrated magnetic components, aiming for increased power density and system efficiency. However, the bulky inductor geometries serve as the bottleneck for increasing the power density. This research presents a novel three-phase star-shaped inductor geometry that retains the advantages of coupled inductors while ensuring high power density, as it can be packaged or placed in the vehicle with minimum vertical space available, tackling the problems of high airgap fringing flux losses, uneven flux distribution, and three-phase current unbalancing associated with the conventional bulky inductors. The inherent magnetic coupling in the star-shaped geometry ensures uniform flux linkage among the three phases, which naturally equalizes the phase currents even under open-loop operation. This self-balancing behavior minimizes the need for complex current-sharing control algorithms typically required in conventional interleaved converters, thereby simplifying the control design and improving system robustness. In closed-loop operation, it further enhances transient current sharing and reduces the controller bandwidth requirement, as the magnetic coupling itself mitigates phase current imbalance caused by device or parameter tolerances. Moreover, a new high-fidelity magnetic equivalent circuit (HFMEC) model was derived and applied to the design of this geometry, reducing the inaccuracies associated with traditional magnetic equivalent circuit (MEC) modeling. The model proved to be capable of evaluating the flux and current characteristics much more quickly and with less computational cost than the finite element analysis approach, especially when complex geometries are involved. The proposed inductor geometry is modeled based on HFMEC, designed in Solidworks, simulated in ANSYS (MAXWELL 3D), fabricated, and then implemented with a three-phase interleaved converter to evaluate the performance.