With the development of interconnected power systems, low-frequency oscillations are becoming increasingly frequent. Researching measures to suppress these oscillations in order to enhance the stability and reliability of power systems has become an urgent issue. A method to suppress low-frequency oscillations in power systems is proposed by utilizing magnetic controlled transformers with additional damping control. Firstly, the working principle of the magnetic controlled transformer is introduced and its mathematical model is derived. Secondly, a linearized model of a single machine infinite bus system incorporating magnetic control transformers is established. The damping characteristics of magnetic control transformers are analyzed, and the principle that the magnetic control transformer provides damping for the power system is explained. Then the method of designing additional damping controller parameters is studied primarily based on the frequency domain method, and calculation examples of single machine infinite bus systems are provided. Finally, the effectiveness and feasibility of the additional damping controller for the magnetic controlled transformer are verified by Simulink time-domain simulation.