Sensorless Trapezoidal control of a Brushless DC motor based on a Three-phase PLL

In drive systems based on Brushless DC motors (BLDC), sensorless detection of rotor position is preferred to achieve variable speed operation. In the literature, the most popular sensorless strategies are based on the zero-crossing detection of the back electromotive forces or back-EMFs Therefore, this work proposes a new sensorless control technique which ensures maximum torque generation and continuous synchronization with the rotor. In this technique, the rotor angular position is estimated based on a three-phase PLL. Compared with conventional techniques, the proposed method offers an increased immunity against Electromagnetic Interferences (EMI) which may cause erroneous switching sequences and unwanted oscillations of the electromagnetic torque.