Operating Characteristics in Low Speed Range of Vector Control of Induction Motor withoutSpeecl Sensor Using Speed and Flux Observers

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In the conventional MRAS method, the value of velocity estimation is the output of the PI controller that received its input signal from speed adaptive controller. As the value of velocity estimation includes time delay, the system responses are worse and the instability occurs in the low speed range.In the proposed method, the speed and flux observers are composed of the current model flux observer and voltage model flux observer. The value of new velocity estimation does not include time delay theoretically. So, the system responses are improved.In practice, the instability of rotor speed are caused by voltage detection error. The feedback of the out of current model flux observer to the input of voltage model flux observer is effective for stabilization in this case.Lastly, the simulated results show that the system responses are good and the instability does not occur in the low speed range.