Direct torque control technology of brushless DC motor based on new four-level Inverter topology

The direct torque control technology of Brushless DC motor can only select one voltage vector in a control cycle, while the direct torque control method under traditional hysteresis control has only three voltage vectors that can be selected, therefore brushless DC motor will produce large torque ripple. For this reason, this paper proposes a new four-level inverter topology and establishes a lookup table of switch state for it, then gives the corresponding four-level direct torque control strategy. At the same time, the voltage of two capacitors is approximately equal by selecting different switch states. The proposed strategy can reduce torque ripple greatly. Finally, the proposed control strategy was simulated on MATLAB to verify its practicability and effectiveness.