Automatic armature current control system of a motor with a pulsed converter model

The paper considers an automatic armature current control system of a braked electric motor using a pulse model of a thyristor rectifier that takes into account the discrete nature of the electric energy conversion process and the influence of the ripple component of the control signal on the dynamic characteristics of the closed-loop system. The relevance of the study is determined by the widespread application of subordinate control systems in DC electric drives and the necessity to improve their response speed, accuracy, and adequacy of the mathematical description of dynamic processes. It is shown that the use of conventional continuous models of thyristor rectifiers does not allow full consideration of the operating features of the power converter associated with its pulse operating mode and incomplete controllability. The aim of the study is the accurate description of dynamic processes in the automatic armature current control system using a pulse model of the thyristor rectifier and the investigation of conditions for ensuring the ultimate response speed of the system. Based on the z-transform, analytical relationships describing the dynamics of the automatic armature current control system were obtained. The conditions for implementing a finite-duration process were determined, and the parameters of the current controller were synthesized to ensure the maximum response speed of the system. To verify the adequacy of the obtained theoretical results, a simulation model was developed in the MATLAB/Simulink environment using the parameters of a 24 kW 2PO200L motor. The novelty of the proposed study in comparison with known approaches based on the use of a continuous thyristor rectifier model lies in taking into account the influence of the incomplete controllability of the thyristor rectifier on the dynamics of the closed-loop automatic control structure. The practical significance of the work consists in the fact that the application of the analytical relationships obtained in the paper during the development of an automatic control system for the output variable of the thyristor rectifier makes it possible to accurately describe the dynamic process of the armature current control loop in a subordinate speed control system and to calculate the system parameters required to achieve the ultimate response speed through the implementation of a finite-duration process.