Design and simulation of sensorless control for nine-phase BLDC motor using back-EMF
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Date
2017-10
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Addis Ababa University
Abstract
The interest in multi-phase machines for high performance applications has been growing in recent
years due to their potential advantages over the conventional three-phase machines. Multi-phase
machines have advantages of fault tolerance and higher power capacity at low voltages compared
to three-phase machines. Nine-phase brushless DC motor has additional advantages of high torque
density, high efficiency and reduced stator current per phase without the need to increase the phase
voltage. Sensored control of BLDC machine generally requires measuring the speed and position
of rotor by using the sensor. The position sensors make the motor system more complicated,
mechanically unreliable and expensive. In this thesis, effective sensorless control of nine-phase
BLDC motor using Back-EMF waveform sensing is done. Thus, actual implementation of the
motor using mathematical model of the machine and nine-phase inverter function based on the
back-EMF sequence generated in the stator windings of nine-phase BLDC motor is simulated with
the help of MATLAB Simulink software.
For control of the motor PI speed controller is implemented to adjust DC-link voltage based on the
error between actual speed and desired speed reference. The controlled gain output of the PI
controller is fed to the pulse amplitude modulation controlled DC-link voltage source. The result
of the controller is investigated and the speed of the motor for different speed level using
MATLAB Simulink software. And the result of the simulated speed response of the controller for
different speed has been done and settling time is 0.005sec and rise time is 0.0026sec speed
response controller. Phase voltages of the motor controlled based on the back-EMF waveform
sequances . switching of nine-phase voltage source inverter controlled has been done efectively
based on the back-EMF. The simulation results obtained agree with the design objective.
Description
Keywords
Multiphase machine, eighteen-step inverter, nine phase BLDCM, sensorless control, back-EMF, zero-cross detection, commutation logic