An Asymmetrical Pulsewidth Modulation With Even Harmonics for Bidirectional Inductive Power Transfer Under Light Load Conditions

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.