Brushless direct current motor rotor position estimation method and system based on line voltage

The invention discloses a brushless direct current motor rotor position estimation method and system based on line voltage. The method comprises the steps: acquiring the line voltage of a brushless direct current motor; acquiring a back electromotive force constant E of the brushless direct current motor, and solving a three-phase back electromotive force of the brushless direct current motor; according to the line voltage and the three-phase counter electromotive force, solving the line counter electromotive force and the electrical angle of the line counter electromotive force zero crossing point; adding a sign function to the solved line counter electromotive force, and then converting the line counter electromotive force into digital signals HAC, HBA and HCB of a rotor position; and according to a rotor position digital signal diagram converted by linear back electromotive force, accurately judging the position interval of the rotor so as to complete rotor position detection. By adopting the method for es