A frequency conversion and speed regulation system of electric motor, wherein, the system comprises: • an electric motor, comprising: - a first stator winding having the pole pair number G of a first winding for connecting to a high-voltage AC power supply; - a second stator winding having the pole pair number D of a second winding; - a rotor winding; • a frequency conversion and speed regulation device, comprising: - a rectifying unit, its input end being connected to the low-voltage AC power supply; - a inverting unit, at least one of its input ends being connected to the output end of the rectifying unit, its output end being connected to the second stator winding; - a first current detecting unit for detecting a three-phase current of the first stator winding; - a second current detecting unit for detecting a three-phase current of the second stator winding; - a controller, one of its input ends being connected to the first current detecting unit, the other of its input ends being connected to the second current detecting unit, one of its output ends being connected to at least another one of the input ends of the inverting unit for controlling fundamental components and harmonic components separately based on the given value, into which the detected three-phase currents of the first stator winding and second stator winding are respectively separated, to obtain the control signal outputted to the inverting unit; characterized by the fact that the rotor winding is of a multiphase wire wrapping type, and the number of phases is m, wherein, m=(G+D)/m k, wherein, when G+D is odd, m k =1, and when G+D is even, m k =2. • an electric motor, comprising: - a first stator winding having the pole pair number G of a first winding for connecting to a high-voltage AC power supply; - a second stator winding having the pole pair number D of a second winding; - a rotor winding; - a first stator winding having the pole pair number G of a first winding for connecting to a high-voltage AC power supply; - a second stator winding having the pole pair number D of a second winding; - a rotor winding; • a frequency conversion and speed regulation device, comprising: - a rectifying unit, its input end being connected to the low-voltage AC power supply; - a inverting unit, at least one of its input ends being connected to the output end of the rectifying unit, its output end being connected to the second stator winding; - a first current detecting unit for detecting a three-phase current of the first stator winding; - a second current detecting unit for detecting a three-phase current of the second stator winding; - a controller, one of its input ends being connected to the first current detecting unit, the other of its input ends being connected to the second current detecting unit, one of its output ends being connected to at least another one of the input ends of the inverting unit for controlling fundamental components and harmonic components separately based on the given value, into which the detected three-phase currents of the first stator winding and second stator winding are respectively separated, to obtain the control signal outputted to the inverting unit; - a rectifying unit, its input end being connected to the low-voltage AC power supply; - a inverting unit, at least one of its input ends being connected to the output end of the rectifying unit, its output end being connected to the second stator winding; - a first current detecting unit for detecting a three-phase current of the first stator winding; - a second current detecting unit for detecting a three-phase current of the second stator winding; - a controller, one of its input ends being connected to the first current detecting unit, the other of its input ends being connected to the second current detecting unit, one of its output ends being connected to at least another one of the input ends of the inverting unit for controlling fundamental components and harmonic components separately based on the given value, into which the detected three-phase currents of the first stator winding and second stator winding are respectively separated, to obtain the control signal outputted to the inverting unit;