Analysis and Application of the Direct Flux Control Sensorless Technique to Low-Power PMSMs

Abstract

In the field of sensorless control of permanent magnet synchronous motors (PMSMs), different techniques based on machine anisotropies have been studied and implemented successfully. Nevertheless, most proposed approaches extract the rotor position information from the measured machine currents, that, when applied to low-power machines, might require high-bandwidth current sensors. An interesting alternative is given by sensorless techniques that exploit the star-point voltage of PMSMs, such as the direct flux control technique. This work aims at analyzing the conditions of applicability of such technique by considering a more thorough description of the machine inductance matrix. After a comprehensive mathematical description of the technique and characterization of the machine anisotropy information that is extracted from the star-point voltage, simulation as well as experimental results conducted on a test machine are presented and discussed in order to validate the proposed theory.

Influence and compensation of the stator flux on the direct flux control sensorless technique for PMSMs

“…As shown in [28] and [39], starting from ( 33), since Γ and Γ are position dependent, the rotor position can be estimated. Let us define the complex number:…”

“…Let us now discuss the conditions of applicability of the DFC technique. As shown in [39], the DFC is based on zero-sequence voltage measurements v . It is easy to show that v = −v NV .…”

“…However, the proposed model is valid only under restrictive assumptions. In fact, (23) neglects magnetic saturation effects which generate a phase shift on the inductances, as reported in [39]. Therefore, in order to take into account these effects, as proposed in [36], the following formulation of L abc has been considered:…”

“…As shown in [4,38], this can be done by strengthening or weakening the magnetic field along the estimated d-axis revealing the actual polarity. In [39], the application of the DFC technique to PMSMs has been presented, leading to a formulation of the obtained measurements and of the estimated electrical rotor position. Moreover, it has been shown that the estimated position using this technique usually presents an error with respect to the real electrical rotor position which is related to the machine inductances matrix.…”

Improvement of Position Estimation of PMSMs Using an Iterative Vector Decoupling Algorithm

“…Secondary saliencies at four times the electrical frequency have shown to be the most significant in PMSMs and are therefore usually the main focus of compensation efforts [8,9]. When the zero-sequence voltage is used as the source of measurements, fourth harmonics are even introduced as a systematic condition even if the self and mutual inductances of the machine phases are perfectly sinusoidal functions of two times the rotor position [10,11] and are therefore also of particular importance in these approaches.…”