Passivity-based current controller design for a permanent-magnet synchronous motor

The control of a permanent-magnet synchronous motor is a nontrivial issue in AC drives, because of its nonlinear dynamics and time-varying parameters. Within this paper, a new passivity-based controller designed to force the motor to track time-varying speed and torque trajectories is presented. Its design avoids the use of the Euler-Lagrange model and destructuring since it uses a flux-based dq modelling, independent of the rotor angular position. This dq model is obtained through the three-phase abc model of the motor, using a Park transform. The proposed control law does not compensate the model's workless force terms which appear in the machine's dq model, as they have no effect on the system's energy balance and they do not influence the system's stability properties. Another feature is that the cancellation of the plant's primary dynamics and nonlinearities is not done by exact zeroing, but by imposing a desired damped transient. The effectiveness of the proposed control is illustrated by numerical simulation results.