Asymmetric duty control of the dual-active-bridge DC/DC converter for single-phase distributed generators

The dual-active-bridge (DAB) and a half-bridge inverter are integrated back-to-back for a converter/inverter system. The power source is isolated by a high frequency transformer, and a 60 Hz inverter is directly connected to the secondary side of the converter via DC link capacitors. Thus, the proposed converter-inverter topology greatly reduces the size and the number of parts count, while providing isolation. But, the inverter causes the DC link voltage unbalance, leading to coupled dynamics between converter and inverter. In this work, a voltage balancing algorithm and a decoupling control algorithm are derived from the average model of the DAB converter. Its usefulness is validated by experimental results.