Abstract: The isolated AC-DC solid-state transformer (SST) usually consists of multiple converter stages, a nonlinear and strong coupling system. Without an efficient control strategy, the different power responses of the two converter stages lead to the poor dynamic performance of the SST. The unbalanced power grid makes the control of the converters more difficult, resulting in the voltage stress borne by the two-stage capacitor of SST and the grid connected current quality on the AC side not to be ensured, which affects the operation safety and applicability of SST. Therefore, An affine nonlinear model of SST integration under the unbalanced three-phase power grid is established. The integrated decoupling method of the exact feedback linearization is proposed to control the AC-grid current in the front stage, the capacitor voltage between the two converter stages, and the DC-grid voltage. This method enhances the consistency of the power transfer between the two converter stages, and guarantees the quality of the grid connected current at the AC side of SST. Furthermore, the integral sliding mode controllers are adopted for controlling the currents and voltages of the SST, achieving better dynamic performance and robustness. Simulation and experimental results verify the correctness and effectiveness of the above method.