Pulse Magnitude Modulation and Token Rotation-Based Voltage Balancing Method of Multilevel Inverter for Wireless Power Transfer

The multilevel inverter has attracted more and more attention in high-power wireless power transfer (WPT) systems, but its switching loss and capacitor voltage balancing are worrying issues. To solve these problems, this article proposes and implements a sigma-delta (Σ-Δ) pulse magnitude modulation (PMM) of a flying-capacitor multilevel inverter (FCMLI) for WPT systems. It can achieve wide-range output voltage regulation and zero voltage switching simultaneously. Besides, a token rotation-based flying-capacitor voltage balancing method of the FCMLI for WPT is proposed. It can balance the capacitor voltages of the FCMLI with arbitrary voltage levels while maintaining little ripples and resisting the step dynamic. The corresponding parameter selection of the flying capacitors is discussed. Theoretical analysis, computer simulation, and an 850 W seven-level flying capacitor inverter-based hardware experimentation are given to verify the effectiveness of the proposed Σ-Δ PMM FCMLI-based WPT system.