Speed control of BLDC motor using bridgeless SEPIC PFC with coupled inductors

摘要

In this paper Bridgeless (BL) Sepic PFC with Coupled Inductors (CIs) is proposed for controlling the DC voltage of Three phase VSI to control the speed of BLDC motor. DC voltage control method enables 3 phase VSI to operate at fundamental frequency and thus reduces switching losses. Sepic converter provides output voltage of positive polarity and allows both step up and step down of input voltage in order to facilitate for the speed control of motor over a wide range. Discontinuous Conduction Mode (DCM) operation of Sepic converter, automatically shapes input current. Thus provides inherent Power Factor Correction (PFC). Also it eliminates the necessity of inner current loop and thereby reduces the number of sensors required. For the same power requirement, if CIs are introduced in the power circuit of BL Sepic, it results in reduction in size and cost of the system. This also gives improved efficiency due to the reduction in core loss. 500 W BL Sepic PFC with CIs is designed ensuring its operation in DCM to supply DC voltage in the range 70 V-310 V for a BLDC motor rated 375 W, 310 V and 3000 rpm. The proposed system is simulated for above range of voltages and performance is analysed. Results indicate that BL Sepic with CIs gives better performance with regard to efficiency and THD in addition to the reduction in overall size of converter.