The synchronous reluctance machine is a promising technology in the electrical machine market. They are now considered in various applications such as transportation or industries. Despite the lack of magnet in such machines, a small residual flux may remains in the ferromagnetic material. This residual flux produces back-electromotive forces as the machine rotates. In this paper, two methods are proposed to determine the back-electromotive forces of the machine online. One is based on the measurements of the short-circuit currents, the other utilizes a linear disturbances observer. The estimations of the back-electromotive forces are then used in the control of the machine in order to compensate their undesirable effects such as current ripples. Both techniques require only the knowledge of the speed and classical electrical parameters of the machine. Experimental results are shown to prove the effectiveness of the proposed approaches.