Rotor speed detection method for vector control of induction motor without speed sensor utilizing slot harmonics

Abstract

SUMMARYSpeed sensorless vector controlled induction motor drives are the standard choice in many industrial applications, but this can hardly control torque and rotor speed at low speed. Recently, a method based on high-frequency signal injection has been studied. This paper presents a method for suppressing the effects of the saturation saliency by using a high-pass filter, and a new approach to estimate the rotor speed. The effectiveness of these methods is demonstrated through experimental results showing both good suppression of saturation harmonics and good sensorless speed control at low speed.

Speed estimation method for ultrahigh‐speed induction machine utilizing rotor slot harmonics appearing in neutral point voltage

“…7). Here the FFT sampling frequency f s is 200 kHz, and the number of FFT points N fft is 2 15 . Considering that the slip variation range is -0.5 to Fig.…”

“…A method using a digital adaptive filter was proposed to solve this problem [14]. In addition, some techniques were recently proposed for better control performance in the low-speed region, such as a method that estimates the speed by counting the pulses obtained from slot harmonics generated by high-frequency voltage excitation [15], and a rotor speed estimation method using an adaptive bandpass filter with rotating coordinate transformation of the slot harmonics included in the d-axis current [16].…”

Development of Motor Model of Rotor Slot Harmonics for Speed Sensorless Control of Induction Motor

“…Speed estimation methods using rotor slot harmonics (below referred to as slot harmonics) determined by the mechanical structure of IM have been proposed as an alternative technique without the use of motor models . These methods use slot harmonics depending on the mechanical structure of the IM, and hence apply to any drive scheme including sinusoidal PWM and square‐wave drive.…”

“…The frequency components can be accurately separated, thus providing precise detection. In particular, speed sensorless control of ultrahigh‐speed IM at several tens of thousands of revolutions per minute has been reported . In this method, the FFT results of analysis are restricted to the region of interest, and the third‐order harmonic component related to magnetic flux saturation is separated from the slot harmonics produced by harmonic currents related to square‐wave drive; thus, steady speed estimation is obtained.…”

“…In addition, aiming at better estimation accuracy at low speed, new approaches have recently been proposed, such as a method based on high‐frequency excitation to produce slot harmonics and pulse counting , and a method of rotation speed estimation by applying adaptive band‐pass filters to d ‐axis current slot harmonics detected in rotating coordinates .…”