Proposed General Decoupling and Input-Voltage-Sharing Control Strategy for Input-Series-Output-Parallel Dual Active Bridge Converter

Input voltage sharing (IVS) is necessary for the stable operation of an input-series-output-parallel (ISOP) dual-active-bridge (DAB) converter. However, the nonidentical high-frequency link (HFL) inductor is unavoidable, causing mutual interferences among submodules, and deteriorating the decoupling and voltage balance performances of conventional IVS strategies. Thus, a general decoupling IVS control strategy is proposed for ISOP DAB converter with nonidentical HFL inductors. First, an improved small-signal state-space model of ISOP DAB converter with a full-rank matrix is proposed to present the coupled performance of the ISOP DAB converter with nonidentical HFL inductors. Based on the improved model, a general decoupling method is proposed by invertible and gain-regulated matrices to achieve a diagonal matrix with uniform diagonal elements in the small-signal model, revealing and solving the sneak coupled performances among control loops. Next, a decoupling IVS control strategy is proposed by shaping full-order input impedance to solve the issues and coupled effects of multiple modes in the operation submodules. Then, the IVS controller is designed and detailed in the frequency and time domains, achieving input voltage balance and avoiding oscillation among submodules with better dynamics and more stable responsiveness. Moreover, the better characteristics of input impedance, output impedance, and input voltages in the proposed decoupling IVS control strategy are discussed and compared with traditional strategies. Finally, experiments are set up to verify the proposed general decoupling IVS control strategy for ISOP DAB converter with nonidentical HFL inductors.