Modeling and Decoupled Control of the Three-Level Interleaved DC–DC Converter With Coupled Inductors

For emerging high power dc-dc applications, such as those in power-to-x and energy storage systems, the three-level interleaved converter with coupled inductors offers several advantages, such as increased voltage and current ratings and a strong reduction of the output current ripple. However, due to series and parallel connections of the switching cells, voltage imbalance and circulating currents may appear, which is why their active suppression is necessary. This paper presents small-signal modeling and control design of the three-level interleaved converter with coupled inductors, focusing on the coupling between the duty cycles of the switching cells and the state variables. Transformations of state variables and control inputs are proposed to diagonalize the system and facilitate decoupled closed-loop control. Digital control implementation is analyzed, focusing on modulation and oversampled filtering of the inductor currents used to suppress aliasing and feedback noise. The experimental verifications are performed on the three-level two-phase interleaved buck prototype, for powers up to 100 kW.