Design and performance comparison of a stationary frame digital current control for a PM synchronous motor

An improved stationary frame-based digital current control technique for a permanent magnet (PM) synchronous motor is considered. The stationary frame current controller is known to have the advantage of simple implementation. However, there are some unavoidable limitations such as a steady-state error and a phase delay in the steady-state when using the proportional-integral (PI) controller. This control performance can be greatly improved by employing the exact decoupling control inputs for the back EMF, resulting in an ideal steady-state control characteristic irrespective of the operating condition, as in the synchronous PI decoupling controller. However, its steady-state response may be degraded by the inexact cancellation inputs due to the variation in the parameter. To improve the control performance in the stationary reference frame, the disturbance is estimated using a modified time-delay control. The proposed control scheme is implemented on a PM synchronous motor using DSP TMS320C31. The simulations and experiments verify that an improved control performance can be obtained in the stationary reference frame.