Balancing Flying Capacitor Multilevel Converters With Coupled Inductors: Multiresonant Dynamics

This article investigates dynamic balancing of flying capacitor multilevel (FCML) converters with coupled inductors. Coupled inductors help to reduce the ripple current, accelerate transient response, and balance the flying capacitors of FCML converters at steady-state. However, coupled inductors also change the dynamic balancing properties compared to uncoupled inductors, and these principles must be understood for robust design. As an extension of a previously developed feedback mechanism for understanding the steady-state behaviors of coupled inductors in FCML converters, this article derives models of coupled inductor FCML converters in dynamic operation, revealing several key insights: 1) the multiresonant behavior of large-order FCML converters and their dependence on the initial conditions, 2) how power dissipation relates to balancing speed, and 3) the relation between multiphase and multilevel FCML balancing. The insights uncovered by this article can provide useful guidelines for designing multiphase self-balanced FCML converters with coupled inductors.