Sensorless Control of a PM Synchronous Motor in Over Modulation Regions for High Speed Operation

For the sensorless control of a PM synchronous motor without using rotor position sensors, the information on the actual voltages and actual currents of the motor are required. In the model based rotor position estimator of a PM synchronous motor, the reference voltages, which are the output of the current controller, are commonly used. The reference voltages in over modulation regions for high speed operation are different from the actual voltages applied to the motor so that the estimated rotor position and rotor speed may fail to track the real rotor position and real rotor speed. In this paper, the sensorless control for a PM synchronous motor in over modulation regions for high speed operation is proposed. Three phase voltages applied to the motor are measured by using additional voltage detection circuits, and the rotor position estimator based on the measured three phase voltages is validated through experiment.