Modeling and Control of a Cyclo-Active-Bridge Inverter for Single-Stage Three-Phase Grid Interface

This paper presents the small-signal modeling and control of a cyclo-active-bridge (CAB) inverter for single-stage three-phase grid interface, featuring single-stage decoupled three-phase power flow control. The strengths of the CAB inverter and its control architecture include: (1) single-stage dc-ac power conversion; (2) highly integrated magnetic components; and (3) three independently controlled output phases. It allows for both balanced and unbalanced 3-Φ operation for grid forming and energy routing applications. The First Harmonic Approximation (FHA) method, along with the application of a correction factor, is used for finding an accurate small-signal model of the inverter. This small-signal model is then used to design a per-phase controller to control the per-phase output of the inverter as an ac output. A hardware prototype of this inverter is designed and tested in closed-loop to generate a3-Φ ac output at 60 Hz.