The invention provides a method for injecting a
harmonic voltage to restrain a
harmonic current of a PMSM (
permanent magnet synchronous motor), which is characterized in that a ring to restrain the
harmonic current is added to realize the closed-
loop control for the harmonic current on the basis of extracting harmonic current components in the PMSM in real time, thus calculating to obtain harmonic
voltage components which are required to be injected to restrain 5-order and 7-order harmonic currents of the PMSM; and then the obtained harmonic
voltage components are injected into a three-
phase control voltage in a
speed control system of the PMSM so as to offset the 5-order and 7-order harmonic components in a motor current when the PMSM runs, thereby reaching the purpose of restraining the 5-order and 7-order harmonic currents. The method is used to solve the technical difficulty that current ZCP (
zero crossing point) is required to detect accurately in a traditional mode to restrain the harmonic current, remarkably improves the current waveform of the motor, effectively restrains the 5-order and 7-order harmonic currents caused by the nonlinear characteristics of an
inverter and the air-gap field
distortion of the motor, effectively reduces the additional loss caused by the 5-order and 7-order harmonic current components, reduces the
electromagnetic torque and the revolving speed pulse of the PMSM and improves the running efficiency and the running reliability of the PMSM.