Sensorless control for a synchronous reluctance motor based on current oversampling using standard PWM excitation

Abstract

This paper discusses a sensorless control technique for synchronous reluctance machines based on an alternative way to process the information obtained from the stator current oversampling. The mathematical background is presented and demonstrated through experimental validation. Implementation issues are highlighted throughout the paper.

Sensorless Control With Switching Frequency Square Wave Voltage Injection for SPMSM With Low Rotor Magnetic Anisotropy

“…As a matter of fact, the noise in current measurements can be usually assumed as Gaussian white noise with zero mean; therefore, by oversampling the current measurements and calculating the average over one switching period, the noise decreases [26][27][28][29]. In order to evaluate the effectiveness of the proposed solution, both the double sample per period technique (DS) and the oversampling technique (OS) are implemented and tested.…”

“…The anisotropy ratio was equal to 46% for the motor considered during experimental tests in [20], 67% in [21], 54% in [22], 40% in [23], 21% in [24] and 33% in [25]. Several articles deal with sensorless control exploiting PWM ripple and measuring the current derivative with a measure oversampling [26][27][28][29]. The current derivative evaluation can be performed during an active voltage vector [26] or during a zero voltage state [27]; in [28] the current derivative is calculated during the longer state, which can be an active vector or a zero vector depending on the working point.…”

“…Several articles deal with sensorless control exploiting PWM ripple and measuring the current derivative with a measure oversampling [26][27][28][29]. The current derivative evaluation can be performed during an active voltage vector [26] or during a zero voltage state [27]; in [28] the current derivative is calculated during the longer state, which can be an active vector or a zero vector depending on the working point. Nevertheless, also this technique is carried out on motors with high anisotropy ratio: 22% in [26], 78% in [28] and 17% in [29].…”

“…The current derivative evaluation can be performed during an active voltage vector [26] or during a zero voltage state [27]; in [28] the current derivative is calculated during the longer state, which can be an active vector or a zero vector depending on the working point. Nevertheless, also this technique is carried out on motors with high anisotropy ratio: 22% in [26], 78% in [28] and 17% in [29]. In [27], a SPMSM is considered, however a highly precise sigma-delta measuring system is needed.…”