Smart transformer (ST) is usually used to solve system level problems. However, ST low-voltage side converter will couple with the grid-connected converters and stability and harmonic oscillations problems occur. To solve this problem, this paper studies the filter impact on the stability and an asymmetric resonant filter is proposed. Based on the proposed filter, the stabilizing control strategy is proposed to make system perform better. The proposed control strategy has following advantages: 1) It can realize centralized control, and avoid complex calculations and operation processes; 2) Compared with other methods, the implementation method is relatively simple, only the harmonic frequency should be given. The simulation results are used to verify the effectiveness of the proposed control strategy.