An Accurate Virtual Signal Injection Control for IPMSM With Improved Torque Output and Widen Speed Region

A method of current reference setting for interior permanent magnet synchronous motor based on virtual constant signal injection is proposed. Unlike traditional methods, the partial derivative of torque to d-aixs, q-axis currents is obtained by injecting a virtual constant signal into d-axis, q-axis currents, then the derivative of torque to current angle is obtained through the full differential equation. A scheme of current reference setting, which is applicable to constant torque region and flux-weakening region, is established by means of the derivative information. The difference between the voltage output by the current controller and the actual voltage applied to the motor is also analyzed. Filters that are essential in the virtual sinusoidal signal injection scheme are avoided. Moreover, the acquisition of partial derivative information avoids the influence of neglecting high-order partial derivative term from which the method of injecting virtual square wave signal along the current angle suffers. This method not only realizes maximum torque per ampere control, accurately, but also guarantees the speed range of constant torque region by the setting of q-axis current reference, which is parameter independent. Meanwhile, the torque output capacity is assured in the flux-weakening region. Finally, the proposed method is verified by experiments.