The results of simulation in MATLAB/Simulink and on the real-time testbed of a digital control system for a plasma unstable vertical position are presented on the example of the tokamak T-15MD model. Feedback is implemented on two computers of the testbed: "Plant model-Controller". Real-time computers have communication devices with the plant: DAC and ADC together with their drivers. On one side of these devices there are digital signals (inside computers) and on the other side (outside computers) there are analog signals that characterize the operation of a closed-loop control system. The unstable plasma model in the tokamak control system is similar to the plasma models used to develop and tune the vertical plasma position control systems in the Globus-M/M2 tokamak (Ioffe Physical and Technical Institute, St. Petersburg) and the T-11M tokamak (JSC «SSC RF TRINITI», Troitsk). A voltage inverter relay model is used as an actuator, which puts the control system into a stable auto-oscillatory operating mode in the presence of negative feedback. The winding of the horizontal control field (WHCF) in the T-15MD is located between the chamber and the winding of the toroidal field (WTF). The digital controller is characterized by robust properties and can be additionally configured during the operation of the control system. The system was tested by two types of external actions: additive disturbance with imitation of a minor disruption of 400 A and a control set point of 0.1 m. The sampling time is set to 100 µs. © 2022 National Research Center Kurchatov Institute. All rights reserved.