Research On Control Techniques For An Electrolytic Capacitor Less IPMSM Drive

Nowadays small film DC link capacitors are used instead of large electrolytic capacitors to increases reliability and lifetime of inverter used in IPMSM power drive.However due to remarkable decrease in capacity of the DC-link capacitor,the stored energy in it is hard to make DC-link voltage constant.As a result,normally DC-link voltage fluctuates with the twice frequency of input grid voltage.Extensive research has been completed to regulate these DC link voltage oscillations where mostly standard six switches three-phase inverter has been used in Power drive for IPMSM.Furthermore effects of motor speed transients and change in load on DC link voltage oscillations has not been considered in this standard inverter where mostly input grid control is coupled with motor control making the control very complex..In this thesis,an electrolytic capacitor-less control scheme for a low cost four-switch three-phase inverter(FSTPI)fed by half controlled rectifier is proposed,which is capable of regulating DC-link voltage oscillations not only during constant speeds but also during speed transients and change in input torque.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.