Decoupled and Analytical Model of the Quad-Active-Bridge DC/DC Wind Converter under Transmitting Instantaneous Pulsating Power

The quad-active-bridge (QAB) DC/DC converter has shown superior advantages in eliminating the low-frequency voltage ripple in the cascaded wind power converter. However, the power flowing into the QAB converter contain low-frequency pulsation, causing low-frequency envelope oscillation issues inside the QAB converter. This paper proposes a decoupled and analytical model for quantitively analysis of the corresponding operation characteristics. Specifically, a summation difference transformation is proposed to decouple the multivariable coupling model as a diagonal decoupled model. The QAB converter voltages with time-varying angles are decomposed as the supervision of multiple frequency components by the Bessel function. Various characteristics such as input current stress (peak and rms), low-frequency envelope oscillations have been thoroughly analyzed under instantaneous pulsating power transmission with the proposed model. These results can be further used for designing more high-performance control strategies to optimize operation. Simulation and experimental results are presented to validate the proposed analytical model.