The article is devoted to a comparative study of VIs (Voltage Inverters) in the RAO (Relay Auto-Oscillatory) mode and in the multilevel PWM (Pulse Width Modulation) mode as actuators in closed-loop control systems of vertical plasma motion in the T-15MD tokamak. The new digital multilevel PWM controller was developed. Both systems were put under equivalent conditions in terms of the same response to external signals. The discrete robust controller is single for both control systems and has been designed by LMI (Linear Matrix Inequalities) approach using the LPV (Linear Parameter Varying) plant model. The main criteria for comparison are the control power and signal spectrum on the HFC (Horizontal Field Coil). The simulations were performed on the real-time test bed consisting of two real-time target machines connected in a feedback loop “Plant Model – Controller”, to basically bring the system as close to reality as possible. The comparison results have showed the significant superiority of the 9-level PWM VI over the VI in RAO mode according to the selected criteria.