###### Abstract  
To solve the problem of system output voltage fluctuation caused by interferences such as load fluctuation and internal inductor parameter perturbation in a flyback converter, a second-order linear active disturbance rejection control (LADRC) strategy based on output voltage is proposed in this paper. A small-signal model of a CCM flyback converter is established, and the equivalent transfer function of voltage control based on second-order LADRC is derived. A second-order LADRC is constructed, and a parameter design method for the controller is proposed. The response characteristics of the output voltage of the converter under five internal and external disturbances of different control strategies are compared and studied using MATLAB R2022b/Simulink simulation software, and a CCM flyback converter experimental platform based on dSPACE is built to verify the corresponding comparative experiments. The simulation and experimental results jointly verify the superiority of the control strategy for the anti-interference and robustness of the output voltage of the CCM flyback converter. flyback converter; linear active disturbance rejection control; PID control; immunity to disturbances +
Footnote †: journal: Applied sciences  
signal based on the past, present, and future trends in the error, namely the proportional integral derivative of the error [11; 12; 13]. This method is simple and convenient, but this \"simple processing\" also places certain limitations on the controller, such as difficulty in solving the contradiction between speed and overshoot, and weak robustness. With the rapid development in power electronics technology, requirements for the performance of converters are gradually increasing. Therefore, it is necessary to seek a more superior control method to apply this performance. The existence of a right-half-plane zero point in the CCM flyback converter makes the system appear nonlinear. When there is interference in the system, PID control is insufficient to balance the contradiction between speed and overshoot, and unstable phenomena may even occur. In response to these issues, many scholars have undertaken relevant research. Reference [14] reduces the error in feedback voltage by improving sampling accuracy in flyback converters, while reference [15] introduces specific algorithms to calculate voltage sampling values in the system and improve sampling accuracy. Neither were improved from the control algorithms; however, [16] improves the response speed of the converter by introducing a peak current inner loop control. However, in peak current mode, the duty cycle is controlled by many variables, such as input voltage, which increases the complexity and parameters of the control and also introduces noise; [17] introduces inner loop constant current control based on the PID control framework in the system, but this has the disadvantage of a complex control structure. There is relatively little research on the anti-interference control strategy for the output voltage of CCM flyback converters. PID controllers are widely used in industrial control applications due to their simple configuration. However, to achieve high performance, adjustments must be made [18]. Active disturbance rejection control (ADRC) [19; 20; 21] was proposed by [PERSON], a researcher of the Chinese Academy of Sciences, in 1999. Through development, ADRC has been widely used. In terms of engineering applications, ADRC research has gradually penetrated into a large number of engineering and scientific research fields such as motor drive systems, aircraft, power systems, and robots [22; 23; 24; 25; 26; 27; 28; 29; 30; 31]. Reference [22] applies ADRC to lane-keeping control in automotive autonomous driving. The application of ADRC in reference [25] for obstacle avoidance control of quadcopter aircraft reduces the impact of wind disturbance and measurement noise, and improves the accuracy of flight trajectory.