This thesis presents a transition method between rotor position and speed estimation methods without sensors for an interior permanent magnet synchronous motor (IPMSM). Through the proposed method, it is possible to estimate the rotor position for the whole speed region of the IPMSM. Considering that each sensorless scheme has a different operation region according to rotor speed for high estimation accuracy, a transition method between the two sensorless scheme is essential. In this study, a sensorless method based on extended back electromotive force (EEMF) is employed for high-speed operation. In addition, the rotor position during low-speed operation is estimated applying the slope of the current measured through the application time of the zero-voltage vector. The weight function is used to the position and speed information estimated by the two sensorless schemes. The combined information is applied throughout the whole speed region of the IPMSM. For smooth transition between the two sensorless methods, the weight function changes according to the rotor speed of the transition range. The effectiveness of the proposed transition method has been demonstrated through simulation and experiment.
