A T-Type DAB-Based Isolated DC-DC-AC Three-Port Converter With High Power Efficiency

This article proposes a high-efficiency isolated dc–dc–ac three-port converter (TPC) intended for residential photovoltaic-battery systems. The TPC is derived from a dual active bridge based dc–ac converter. Its dc-side provides two bidirectional dc ports by sharing the full-bridge topology, while its ac-side enables direct ac-load connection via a unique T-type half-bridge structure. Due to the shared branches and T-type topology, the proposed TPC has few components but offers single-stage power conversion and substantial control degrees of freedom (CDFs). Sufficient CDFs facilitate the TPC to maintain high efficiency when performing decoupled power flow control among the three ports. To maximize the benefits of sufficient CDFs, a pulsewidth modulation (PWM) plus triple-phase-shift (TPS) modulation scheme based on these CDFs is presented. PWM is employed to control the dc–dc power flow while TPS is used to regulate the dc–ac power flow. Benefiting from the TPS optimization, this TPC features low rms current and excellent soft-switching performance. Compared to state-of-the-art, the efficiency of the proposed TPC is improved by up to 1% under the proposed modulation scheme. The effectiveness of the proposed TPC is verified by a 220-V 500-W experimental setup.