Search

The realization of zero voltage switching (ZVS) of the bidirectional inductive power transfer (BIPT) system is critical to system stability and transmission efficiency. For the symmetrical phase shift modulation (SPSM) strategy, as system transmission power decreases, it is necessary to reduce the phase shift angle of the fundamental component of ac excitation voltages on both sides to achieve ZVS. However, it will result in a decrease in the system transmission power factor and transmission efficiency. In this article, an asymmetrical pulsewidth modulation with even harmonics (APWMEH) strategy is proposed for the BIPT system to optimize the transmission efficiency under light load conditions. First, this article analyses the relationship between ZVS and transmission efficiency of the BIPT system with SPSM. Second, the APWMEH control technique is proposed, including the analysis of the working modes of both full bridges, the condition of the ZVS realization, and the efficiency optimization of the system. Then, the control scheme of power regulation and load matching of the system are given. Finally, the comparative analysis and experimental results are performed at a BIPT experimental platform. Compared with symmetrical triple phase shift and fundamental dual phase shift, the transmission efficiency of the BIPT system with AWMEH is improved significantly under the light load conditions. [ABSTRACT FROM AUTHOR]

In high-voltage output applications, the rectifier diodes in the conventional full-bridge converter have to bear the whole secondary voltage of a transformer. In this paper, a three-level rectifier structure with flying capacitors is proposed for the dc–dc converter. Compared with the conventional dc–dc converter, the converter with the proposed rectifier structure has the following advantages: low-voltage diodes could be used for high-voltage output applications; due to the secondary flying capacitors, there are no voltage spikes on the rectifier diodes even if no snubber circuits are attached; not only can the leading switches realize zero voltage switching (ZVS) as the same as the conventional converters, but also the lagging switches can realize zero current switching in discontinuous-conduction mode and ZVS in continuous-conduction mode; and the rectified voltage has no zero-state voltage, it has been raised to half of the input voltage, so the voltage fluctuation is lower than the conventional converter under the same modulation strategy, and the current ripple of the filter inductor can be reduced by half. The operation principle of the proposed rectifier structure is analyzed in details, and a prototype is fabricated to verify the features of the proposed converter. [ABSTRACT FROM PUBLISHER]

In high-voltage dc–dc applications, the switches in the conventional two-level dual active bridge (DAB) dc–dc converter have to bear the whole port voltage, so high voltage switches should be selected. The voltage stress of the switches in the three-level DAB converter can be reduced to half of the port voltage, so it is suitable for high-voltage applications. However, part of the switches still has to bear the entire port voltage under some operation conditions with the single phase-shifted (SPS) modulation strategy. A dual phase-shifted (DPS) modulation strategy is proposed for the converter, compared with SPS modulation strategy, it expands regulating range of transmission power and enhances control flexibility. Moreover, a control algorithm can be developed to ensure that the voltage stress of each switch is half of the port voltage. The detailed operation principle of the three-level DAB converter with DPS control is analyzed in the paper. The characteristics of each operation region and the critical conditions between different operating regions are derived. Finally, the performance of the three-level DAB converter and DPS modulation strategy are verified by the simulation and experimental results of a 125 kW prototype. [ABSTRACT FROM PUBLISHER]