This paper investigates and evaluates coupled inductors (CIs) in the interleaved multiphase three-level dc-dc converter. If non-CIs are used in the multiphase three-level dc-dc converter, interleaving operation of the converter will increase inductor current ripple, although the overall output current ripple and common-mode (CM) voltage will become smaller. To reduce inductor current ripple, inverse-CIs are employed. The current ripple in the CI is analyzed in detail. The benefits of the three-level dc-dc converter with CIs under interleaving operation are evaluated. By adding CIs and working under interleaving operation, smaller inductor current ripple, smaller overall output current ripple, and smaller CM voltage can be achieved simultaneously compared with the noninterleaving case. The analysis results are verified by simulations and 10 kW scale-down experiments.

This paper presents an improved phase-shifted carrier pulse width modulation (PSC-PWM) scheme for the hybrid modular multilevel converter (MMC) consisting of half-bridge submodules (HBSMs) and full-bridge submodules (FBSMs). When the traditional PSC-PWM schemes for the HBSMs-based MMC and the FBSMs-based MMC are directly applied to the hybrid MMC, some mismatch pulses will occur on the arm voltages because the HBSMs and the FBSMs have different characteristics. These mismatch pulses not only generate undesirable harmonics on the output voltages, but also induce the significantly uneven loss distributions between the HBSMs and the FBSMs. Therefore, an improved PSC-PWM scheme for the hybrid MMC is proposed in this paper to deal with these issues. The improved PSC-PWM scheme can eliminate the mismatch pluses in the output voltages, alleviate the uneven loss distributions between the HBSMs and the FBSMs, and reduce the total switching loss of the converter. The mathematical analysis of the improved PSC-PWM scheme for the hybrid MMC is conducted and its harmonic characters are investigated. The analysis results are verified and compared with the traditional PSC-PWM scheme by the simulated and experimental results.

Wireless power transfer (WPT) is more convenient and safer than conductive charging for power consumer electronics, biomedical devices, transportation systems, etc. Inductive power transfer is the most widely studied and commercialized WPT technique; however, capacitive power transfer (CPT) is becoming an attractive alternative, offering better misalignment tolerance and lower cost and weight. The electrical-field-resonance-based six-plate coupler system is one of the most typical configurations for high-performance CPT systems, but the associated large number of circuit parameters is always a critical issue for system design. In this article, a parameter optimization method is proposed for this topology. The ratio of the reactive power in the compensation network to the system transferred power is set as the main optimization goal. To solve the high-order optimization problem, a two-stage method is proposed to significantly reduce the optimization complexity while providing the optimized parameters of the whole system. To verify the effectiveness of this method, a 3-kW, 1-MHz CPT system with a 16-pF coupling capacitor is built. Both the simulation and experimental results show that the optimized parameters effectively improve the system efficiency, experimentally achieving 95.7% dc–dc overall efficiency under a 100-mm gap distance at the rated power.

Bidirectional Inductive Power Transfer (IPT) systems could enhance the flexibility of energy interaction between electric vehicles (EVs) and the grid, as well as other electrical equipment. Achieving zero-voltage switching (ZVS) conditions is a critical factor in improving the efficiency of bidirectional IPT systems. This paper proposed a double-sided LCC compensation parameter design method, particularly suited for Vehicle-to-Grid (V2G) applications, which realizes the constant current (CC) output during charging process and the constant voltage (CV) output during discharge process of the bidirectional IPT system. A detailed analysis of parameter tuning methods is provided, with the aim of achieving CC/CV output and wide ZVS operation during charging and discharging processes. The inverter turn-off current is accurately estimated, considering the impacts of higher harmonics and the reflected reactance of the rectifier, to optimize the system’s compensation parameters. The effectiveness of the proposed method is verified by a 10-kW bidirectional IPT prototype, and the CC/CV feature and wide ZVS range are achieved. The experimental results demonstrate that the peak efficiency reaches 96.6% when transmitting power as a current source during charging, and 96.2% when transmitting power as a voltage source during discharging.

Wireless power transfer technology is being widely used in electric vehicle wireless-charging applications, and foreign object detection (FOD) is an important module that is needed to satisfy the transmission and safety requirements. FOD mostly includes two key parts: metal object detection (MOD) and living object detection (LOD), which should be implemented during the charging process. In this paper, equivalent circuit models of a metal object and a living object are proposed, and the FOD methods are reviewed and analyzed within a unified framework based on the proposed FOD models. A comparison of these detection methods and future challenges is also discussed. Based on these analyses, detection methods that employ an additional circuit for detection are recommended for FOD in electric vehicle wireless-charging applications.

A half-turn transformer with symmetrical magnetic flux is proposed for high-frequency isolated DC/DC converters. The transformer structure can reduce the minimum number of turns from 1 to 0.5. By adopting a novel winding and circuit configuration, a symmetrical magnetic flux is realized to make full utilization of the ferrite core. A simple EI core, which is easily manufacture and commercially available, can be used to make the half-turn transformer. The operation principles of the transformer are analyzed and simulated. The performance of the transformer is experimentally evaluated on a 750 kHz, 380/12V, 600 W LLC converter using gallium nitride (GaN) devices with a peak efficiency of 98%.