Implementation issues for fast initial position and magnet polarity identification of PM synchronous machines with near zero saliency

Initial rotor position detection in PMSM based on low frequency harmonic current injection

“…In this approach, polarity/phase of the second harmonic in 14th International Power Electronics and Motion Control Conference, EPE-PEMC 2010 978-1-4244-7855-2/10/$26.00 ©2010 IEEE T4-1 the voltage/current response of the machine is continuously observed as it is linked with the saturation (2 nd harmonic implies half wave asymmetry which is caused by saturation) [4]. In this case the initial rotor position ambiguity is automatically corrected by 0 or π when the saliency axis tracking converged so there is no need for special magnet polarity test (faster start-up [1]). For completeness we have to mention so called single point detection methods which detect rotor position in regular intervals (no continuous rotor position tracking) by applying signal injection within a short test sequence [6].…”

“…The magnet flux polarity is oriented in the controller d axis direction in which the test voltage pulse produces higher current peak. The magnet polarity can be tracked continuously with the tracking of the saliency axis [1]. In this approach, polarity/phase of the second harmonic in 14th International Power Electronics and Motion Control Conference, EPE-PEMC 2010 978-1-4244-7855-2/10/$26.00 ©2010 IEEE T4-1 the voltage/current response of the machine is continuously observed as it is linked with the saturation (2 nd harmonic implies half wave asymmetry which is caused by saturation) [4].…”

“…The high frequency injection methods apply relatively high frequency (typically 0.5Hz-2kHz) periodic harmonic injection in form a rotational or pulsating vector. The injected signal is used to estimate rotor position dependant effects on the stator inductance matrix which variation is caused by either rotor geometric saliency [4,5] or magnetic saturation [1][2][3]. The rotor position is tracked via detection of spatial position of the stator winding inductance saliency.…”

“…The harmonic injection methods can be classified in two major groups: the high [1][2][3][4][5][6][7] and low frequency [8][9][10][11][12][13] harmonic injection methods. The high frequency injection methods apply relatively high frequency (typically 0.5Hz-2kHz) periodic harmonic injection in form a rotational or pulsating vector.…”

“…For tracking of the rotor flux at low stator frequencies down to zero speed numerous techniques based on an auxiliary signal injection have been proposed [1][2][3][4][5][6][7][8][9][10][11][12][13] as an alternative or for enhancement of the fundamental frequency based sensorless control at low speeds. Normally injections of a voltage or current signal into the stator winding at a frequency different from the fundamental frequency are used to retrieve the rotor flux position from the stator current or voltage response.…”