Design Considerations for Single-Stage Current Source Inverters with Discharge Path with Surface-Mounted PMSMs

A recently proposed single-stage CSI with discharge path exhibits the ability to control the drive from zero speed without the insertion of an additional pre-stage converter to control the input DC current. In this paper the characteristics of this power converter are analyzed deriving expressions for the voltage gain of the CSI connected to PMSM, in both low speed and high speed regions. Furthermore, the limitations of the topology in terms of critical speed (i.e. the maximum allowed speed) and maximum torque in the whole range are underlined. To solve the issue, a proper design of the coupled inductor is necessary to guarantee the nominal torque in the whole speed range. Simulations are reported to evaluate the proposed approach.