This thesis proposes an improved sensorless control method to estimate the rotor position of an permanent magnet synchronous
motor. The rotor position can be estimated using a phase-locked loop (PLL) based on extended electromotive force(EEMF) because
the EEMF contains information of rotor position. In order to operate the permanent magnet synchronous motor, a current controller
can be used for the initial operation and after that, the controlling method of the permanent magnet synchronous motor is changed
to a method for using a speed controller for the sensorless control. At the time of changing the controlling method, the rotor speed
overshoot is generated due to a rapid change of the controlling method and increased calculation amount of the speed controller.
The proposed. The proposed algorithm is able to reduce the overshoot of a rotor speed by compensating the estimated feedforward
value to the current component of the speed controller. Additionally, this thesis proposes the full-dimensional flux observer algorithm
which shows improved performance in both low and high velocity regions. The existing full-dimensional flux observer tends to show
decrease in estimation performance due to the angular speed value included in the denominator of the gaining numerical formula of
the observer. The proposed full-dimensional flux observer makes the angular speed value of the denominator to a constant value,
applies it as the optimal value according to the velocity region and therefore improves the weakness of the existing full-dimensional
flux observer. The optimal constant value is the constant value in which the difference between the estimated angle and the actual
angle is minimized, and this value is accurately verified through simulation and experimental procedures. The performance of the
proposed algorithm, its excellence and validity shall be verified through the simulation and experiment results.
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