Extended State Observer Based Current Decoupling Control for PMSM

Vector control technique can decouple the PMSM into d- and q-axis subsystems, simplifying the control system design. However, effects of the inductance and the digital control delay still introduce coupling between the dual control loops, especially in dynamic process or in high frequency operation. The usually used feed-forward decoupling technique is sensitive to parameters, while the IMC scheme produces transient oscillations. In this paper, an extended state observer (ESO) is designed to observe the disturbances from the subsystem itself and the other. By compensating for the observed disturbances in the outputs of the current controllers, the coupling effects are able to be eliminated. Meanwhile, with the compensations one can find that the control plants in both subsystems are reduced to an integrator element, therefore the current regulator can be fulfilled just with a proportion term, allowing the saturation effects of the integrator, usually used if without the compensation, removed. The performance of the designed system is demonstrated through experiments on a 3kW PMSM test rig.