Four-Degree-of-Freedom Control for Dual Active Flexbattery H-Bridge Converter

This paper proposes a four-degree-of-freedom control method for a dual active Flexbattery H-Bridge converter, which operates similarly to dual-active-bridge converters. The Flexbattery pack is constructed from multiple modular units and each unit contains one voltage source, one inductor and four switches. Due to the cascaded structure of the pack, it is able to generate high-frequency square-waveform signals with tunable amplitudes and duty cycles. Distinct from the well-known unified triple-phase-shift approach, the proposed control method includes one additional degree of freedom. The tunable control variables become one voltage amplitude, two duty cycles, and the phase shift. By taking the third harmonic into account, the proposed four-degree-of-freedom control method further reduces the circulating current.