Abstract: In order to solve the problems of large volume and short service life of the traditional electrolytic

capacitor frequency converter，the thin film capacitor was used to replace the electrolytic capacitor to constitute the

AC-DC-AC frequency converter without electrolytic capacitor. Aiming at the problem of bus voltage oscillation in

the process of low frequency V/F operation of electrolytic capacitor-less inverter，firstly，the bus voltage ripple and

resonance in different working modes were analyzed according to the equivalent circuit model of induction motor，

and the stability condition of electrolytic capacitor-less drive system was analyzed by using Rous stability criterion.

Secondly，according to the mathematical model of the drive system without electrolytic capacitor，the relationship

between the bus voltage and the stator reactive current during the oscillation process was analyzed. Finally，a

reactive current feedback control strategy based on stator voltage direction was proposed to suppress bus voltage

oscillation and improve system stability. The simulation and experimental results show that the proposed control

strategy can realize the stable operation of the induction motor in the global range and effectively improve the

stability of the system.

      Key words: electrolytic capacitor-less inverter；reactive current；induction motor；resonance suppression