Sliding Mode Control-Based Decoupling Scheme for Quad-Active Bridge DC–DC Converter

As a multiport DC–DC converter, quad-active bridge (QAB) has been widely used in energy routers, photovoltaic energy systems, and vehicle power supplies because of its advantages of high efficiency and high power density. However, every port of the QAB converter is coupled together through a high-frequency (HF) transformer, which poses a challenge to the controller design. This article proposes a sliding mode controller (SMC)-based decoupling control scheme, which combines input matrix diagonalization and extended state observer (ESO). The input matrix diagonalization realizes most coupling and the SMC realizes the remaining coupling. To effectively reduce the chattering caused by the SMC, the ESO is applied to estimate the total disturbances. Theoretical analysis shows that the proposed decoupling control scheme transforms a multiple input multiple output (MIMO) control system into three independent single-input single-output (SISO) control systems, which realizes independent control of all the port voltages. Besides, experimental results show that the proposed scheme can almost eliminate the coupling relationship between ports, and improve the dynamic response of the system.