Pulse Amplitude Modulation Control of BLDC Motor using Bridgeless SEPIC with Coupled Inductors

Abstract

This thesis presents a novel approach for the control of brushless direct current (BLDC) motor using pulse amplitude modulation (PAM) control of voltage source inverter (VSI). The PAM control of VSI is accomplished by using a one-cycle controlled bridgeless single ended primary inductance converter (SEPIC) with coupled inductors. The PAM control also known as DC link voltage control of VSI, reduces switching losses by allowing the operation of VSI at fundamental frequency. The adoption of the coupling between the input and output side inductors in the bridgeless SEPIC converter reduces the value of the inductance required, allows better integration of magnetic components and hence lowers the overall size compared to conventional bridgeless SEPIC. In the work presented in this thesis, the design of coupled inductors for the bridgeless SEPIC is done using the split winding scheme. The conventional method of achieving the desired coupling by adjusting the air-gap is tedious. Using the split winding scheme, a mathematical approach is proposed to obtain the closed form solution for distribution of windings over three limbs of E-core to achieve the desired coupling. The bridgeless SEPIC with coupled inductors is designed to get a wide variation of DC link voltage and is operated in discontinuous conduction mode (DCM) for the complete range of DC link voltage. The DCM operation simplifies power factor correction (PFC) control scheme to a voltage mode control, since it has inherent input current shaping feature. One-cycle control technique which is a nonlinear control technique, applied in the voltage mode scheme improves the quality of supply current by reducing the distortion compared to proportional-integral (PI) control technique. The one-cycle control also enhances the performance of DC link voltage control, with improved start-up and transient state response.The proposed BLDC motor drive is modelled. The superiority of one-cycle control technique over PI control for a wide range of speed control is validated using simulation results. Using the laboratory prototype of bridgeless SEPIC with coupled inductors, the achievement of supply current shaping and adjustable speed in the BLDC motor drive is verified experimentally using field programmable gate array (FPGA) based digital PI controller.