Bang-bang pulse magnitude modulation and binary search tree-based voltage balancing method of multilevel inverter for wireless power transfer

Abstract

The delta-sigma pulse magnitude modulated multilevel inverter-based wireless power transfer systems are suitable for high-power applications to realize zero voltage switching (ZVS) and continuous output, but the resolution is fixed, and the heavy computational burden of the voltage balancing algorithm is a concerning issue. To solve the above problems, first of all, a bang-bang pulse magnitude modulation (BBPMM) method is proposed for the multilevel inverter-based wireless power transfer (WPT) system. The resolution of the proposed BBPMM is continuously adjustable, which is more flexible than the delta-sigma pulse magnitude modulation (PMM). Moreover, it is found that the BBPMM WPT system can decrease the ripple and total harmonic distortion of the inverter current in a wide range by adjusting the resolution compared with the delta-sigma PMM WPT system. Second, this article proposes a binary search tree-based capacitor voltage balancing method for the flying capacitor multilevel inverter in the WPT system. It combines the online and offline processes of the capacitor voltage balancing method to simplify the algorithm online in a control cycle. Furthermore, theoretical analysis, computer simulation, and a 1.5-kW seven-level flying capacitor inverter-based hardware experimentation are given to verify the effectiveness of the proposed BBPMM flying capacitor multilevel inverter-based WPT system.