Back EMF Observer Based Sensorless BLDC Motor Drive With SEPIC Converter For EV Application

This paper deals with the design and development of observer-based position sensorless scheme of brushless DC motor (BLDCM) drive with optimal torque and current control for electric vehicle application. Conventional back EMF based rotor position detection algorithm fails in lower speed range as magnitude of back EMF is too small to measure directly. As, back EMF of the BLDCM is one of the few parameters, which gives accurate commutation instants, an indirect method of sensing back EMF using an observer is introduced here which estimates line back EMF even during starting with great accuracy. Secondary inverted polarity Cuk (SEPIC) converter is used for efficient maximum power point tracking (MPPT) operation with less input current ripple, ensuring soft starting of the motor. Non- inverted property of the SEPIC eliminates the need of sensing negative voltage at DC link. Coupled inductor is introduced with SEPIC, which reduces cost and space on PCB than two separate inductors. This BLDCM drive is capable of energy regeneration as a provision of having extended driving range. This system topology is designed and analyzed using the simulated results in MATLAB/SIMULINK environment.