Low-frequency signal-demodulation-based sensorless technique for induction motor drives at low speed

The paper presents a method to compute the air-gap flux position in induction motors at very low including zero-stator frequency. A low-frequency (50 /spl divide/ 100 Hz) sinusoidal stationary signal is added to the normal stator variables to provide the machine with a suitable permanent excitation. Such an additional excitation modulates the saturation level of the magnetic core of the machine according to the angular position of the air-gap flux. As a result, a new zero-sequence stator-voltage component is generated that contains useful information about the position of the air-gap flux unaffected by load variation. Such a zero-sequence voltage can be easily employed to provide a wide bandwidth measurement of the air-gap flux position. A key feature of the proposed approach is that a low-frequency (0 /spl divide/ 5 Hz) signal is demodulated, thus avoiding any drawback featured by previous sensorless techniques operating with high-frequency signal injection.

[1]  A. Vandenput,et al.  Sensorless direct field orientation at zero flux frequency , 1996, IAS '96. Conference Record of the 1996 IEEE Industry Applications Conference Thirty-First IAS Annual Meeting.

[2]  R. Lorenz,et al.  Using multiple saliencies for the estimation of flux, position, and velocity in AC machines , 1997, IAS '97. Conference Record of the 1997 IEEE Industry Applications Conference Thirty-Second IAS Annual Meeting.

[3]  Joachim Holtz,et al.  Sensorless control of induction motor drives , 2002, Proc. IEEE.

[4]  Veli-Matti Leppänen,et al.  Speed-sensorless induction Machine control for zero speed and frequency , 2004, IEEE Transactions on Industrial Electronics.

[5]  Alfio Consoli,et al.  A new zero frequency flux position detection approach for direct field oriented control drives , 1999, Conference Record of the 1999 IEEE Industry Applications Conference. Thirty-Forth IAS Annual Meeting (Cat. No.99CH36370).

[6]  M. Schroedl.  Operation of the permanent magnet synchronous machine without a mechanical sensor , 1990 .

[7]  Jung-Ik Ha,et al.  Sensorless field orientation control of an induction machine by high frequency signal injection , 1997, IAS '97. Conference Record of the 1997 IEEE Industry Applications Conference Thirty-Second IAS Annual Meeting.

[8]  Thomas A. Lipo,et al.  Flux Tracking Methods for Direct Field Orientation , 1999 .

[9]  Mark Sumner,et al.  Analysis and suppression of high-frequency inverter modulation in sensorless position-controlled induction machine drives , 2003 .

[10]  Alfio Consoli,et al.  An Alternative to High Frequency Current Detection Techniques for Zero Speed Sensorless Control of AC Motor Drives , 2003 .

[11]  Joachim Holtz,et al.  Elimination of saturation effects in sensorless position controlled induction motors , 2002 .

[12]  Robert D. Lorenz,et al.  Transducerless position and velocity estimation in induction and salient AC machines , 1994, Proceedings of 1994 IEEE Industry Applications Society Annual Meeting.

[13]  T. A. Lipo,et al.  New observer-based DFO scheme for speed sensorless field-oriented drives for low-zero-speed operation , 1998 .

[14]  Thomas A. Lipo,et al.  Air-Gap Flux Position Estimation of Inaccessible Neutral Induction Machines by Zero-Sequence Voltage , 2002 .