Speed sensorless AC drive for high dynamic performance and steady state accuracy

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 estimation.

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