说明：  用SVPWM控制电机转速，通过SVPWM技术在电机中产生圆形旋转磁场，用于启动电机和调节转速
(The speed of motor is controlled by SVPWM, and a circular rotating magnetic field is generated in the motor by SVPWM technology, which is used to start the motor and adjust the speed)