By predicting the noise in the loop the delay of noise signal in digital feedback loop is compensated effectively, thus the control capability of the system on disturbance is enhanced.

The speed adjusting system with field weakening with voltage feedforward, current closed negative feedback and speed closed loop was designed by adopting digital signal processor (DSP).

The paper takes advantage of a single close-loop control method based on voltage feedback, and enables the inverter to produce steady sine waves by the digital PID adjuster designed.