The paper deals with the problem of the voltage stabilization in the DC link of a frequency converter with an PWM inverter, which is part of AC drive with a frequency method of speed control. To stabilize the voltage in the DC link, energy storage technology is used, which is implemented with using an energy storage device based on supercapacitors, which is connected to the DC link by means of bi-directional DC-DC converter. The work uses the concept of stabilizing the DC bus voltage by compensating the PWM inverter load current with the external current of the energy storage device. The energy storage device is equipped with a single-loop tracking current control system. The current control system is based on the combined control method. The aim of the work is to improve the accuracy of voltage stabilization in the DC link of frequency converter. The sensitivity of the DC link voltage to various disturbing factors is investigated. The theoretical analysis of the error coefficient of the current control system is carried out. The simulation of the electric drive is carried out without and taking into account the discreteness of the DC-DC converter. The research results can be useful in the development of supercapacitor energy storage control systems for various applications. © 2022 IEEE.