Sensorless vector control of non-salient BLAC machines based on a modified rotor flux-linkage observer

The major problems of flux-linkage observer based sensorless techniques are drift and offset effects. To solve such problems, a modified rotor flux-linkage observer is firstly proposed to eliminate the drift phenomena. However, the offset occurrence still exists. Therefore, an adaptive offset cancellation technique is sequentially introduced to solve the offset phenomena. In addition, to further improve the performance of the proposed modified rotor flux-linkage observer, the influence of inaccurate machine parameters to the observer in terms of the estimated rotor position accuracy has been analyzed and, consequently, a simple steady-state rotor position error compensation technique has been introduced which, theoretically, makes the steady-state rotor position error become negligible and parameter insensitive. The performance of the proposed techniques, which was implemented on a low-cost fixed point DSP, is demonstrated experimentally.