An Effective Control Strategy Based on DC-Link Voltage Regulation for an Electrolytic Capacitor-Less IPMSM Drive

Small film DC-link capacitors are used nowadays to increase reliability of IPMSM power drives. However, due to decrease in energy storing capability, DC-link voltage oscillation seems inevitable which challenges the control for rectifier and inverter. Extensive research has been done to regulate the oscillation in a standard six-switch three-phase inverter. However, effect of motor speed transients on DC-link voltage has not been considered in this standard inverter, where mostly the grid input current control and the motor control are not decoupled, making the control very complex. In this paper, an electrolytic capacitor-less control scheme for a low cost converter comprising of a half bridge controlled rectifier and a four-switch three-phase inverter (FSTPI) is proposed, which can regulate the DC-link voltage not only at constant speeds but also during speed transients. Absorbed power by small film capacitors is regulated by controlling stored energy in them, which aims to make DC-link voltage follow its reference value. Effectiveness of the proposed method is verified by simulation results. It is observed that the harmonics of the input grid current meets the IEC 61000−3−2 standard.