Regenerative braking operation PWM control method for brushless direct current motor

The invention discloses a regenerative braking operation PWM control method for a brushless direct current motor. The brushless direct current motor adopts a three-phase six-state two-phase winding conduction way; a rotor position is detected by a Hall sensor to output a Hall signal; in the regenerative braking operation state, torque closed-loop control is adopted; a torque feedback amount is compared with a torque set value to obtain torque error, and then the torque error passes through a torque controller, and next, the torque error and the Hall signal are input into a PWM-OFF-PWM module together; and a PWM-OFF-PWM modulation way is adopted, in the 120 degrees of electric angle period conducted by each switching tube, the front 30-degree and the last 30-degree periods are subjected to PWM, and the middle 60-degree period is switched off, and a PWM signal is output to control the switch on and switch off of each switching tube, so as to switch on the windings of the corresponding phases. By virtue of the c