Magnetizing rotor flux determination using a time-discrete voltage source inverter
ABSTRACT In the paper, a possible approach for sensorless determination of the magnetizing rotor flux frequency of the induction machine (IM) in rotor field frame is described. Field oriented speed control of the IM requires information on the exact position and magnitude of the magnetizing rotor flux vector. With sensorless control this can be evaluated by measuring stator voltages and currents provided that the certain IM parameters are known. The power stage of the drive consists of a conventional three phase time-discrete inverter with a supplemented LC filter. The role of the filter is active output voltage shaping, since its output voltage (also IM stator voltage) is attained trough an impressed filter capacitor current. Assuming a cosine capacitor current reference, the output of the filter is of sinusoidal shape. As a consequence of easily measured stator voltage, magnetizing rotor flux frequency and thus rotor speed are calculated from instantaneous values of stator voltages and currents.
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ABSTRACT: Controlled speed sensorless AC motor drives have reached a stage of development permitting good dynamic performance above 3% of rated speed. However, the accuracy of the rotor speed estimation under load remains sensitive to parameter errors of the internal machine model. This paper presents an approach that ensures high steady-state speed accuracy in addition to high dynamic performance. To eliminate the speed estimation error, the machine parameters are adapted online, based on the evaluation of rotor slot harmonic effects. A stator flux-oriented control scheme is implemented in a digital signal processor system to demonstrate the robustness of the speed estimation to parameter variations. Experimental results demonstrate that the control system advantageously combines high dynamic performance with accuracy of speed estimationIEEE Transactions on Industrial Electronics 05/1997; · 5.17 Impact Factor
Article: Vector Control of AC Machines
Article: Control of Electrical Drives