Abstract: The conditions for the excitation of current and voltage oscillations in the plasma of a three-electrode current and voltage stabilizer have been experimentally studied. It was found that the oscillations are due to negative conductivity of the plasma in the considered regimes. A highly efficient method is proposed for the suppression of plasma instabilities based on the control of the sign of differential plasma conductivity via adjustment of the concentration of thermal plasma electrons with an external electrode. The proposed method makes it possible to achieve a high level of stability of the stabilizer’s energy characteristics at a discharge current density of up to 5 A/cm² and a power of 500 W/cm².