One-Cycle Controlled Bridgeless SEPIC with Coupled Inductors for PAM Control-Based BLDC Drive

Abstract

This paper presents a novel approach for the speed control of BLDC motor for residential air conditioning application, using pulse amplitude modulation (PAM) control of voltage source inverter (VSI). PAM control of VSI is accomplished by using a bridgeless SEPIC converter embedded with coupled inductors at the front end and adopting one-cycle control (OCC) technique in the inner voltage control loop. The DC reference voltage required for inner voltage control loop is obtained using a PI controller in the outer speed control loop and speed feedback signal. The PAM control (DC supply voltage control) of VSI reduces switching losses by allowing the operation of VSI at fundamental frequency. Bridgeless SEPIC with coupled inductors is designed to enable PAM control for VSI and is operated in discontinuous conduction mode (DCM) for the complete range of DC link voltage. DCM operation simplifies power factor correction control scheme to a simple voltage follower approach, since it has inherent input current shaping feature. The introduction of coupled inductors in the bridgeless SEPIC converter lowers the overall count of components, allows better integration and lowers the requirement of inductance, compared to conventional bridgeless SEPIC. OCC which is a nonlinear control technique, used in the voltage control loop, enhances the performance with improved startup and transient state response. It also improves the quality of supply current drawn by reducing the distortion compared to PI control technique. The proposed BLDC motor drive is modelled and simulated using MATLAB/Simulink. The performance of proposed system is evaluated for a wide range of speed control. The experimental prototype for bridgeless SEPIC with coupled inductors is implemented. The inherent power factor correction for supply voltage variations is validated using the results. The bridgeless operation of the converter with coupled inductor configuration is also described with experimental waveforms at rated supply voltage of 220 V.