A composite current-constrained control for permanent magnet synchronous motor with time-varying disturbance

The problem of overlarge current protection of permanent magnet synchronous motor based on a single-loop control structure is discussed in this article. Under this structure, the previous limiting method of amplitude of q-axis current used in field-oriented control is unsuitable, which limits q-axis current by restricting the output of reference current. Conventional controllers (e.g. proportional-integral-derivative controller) usually cannot have a nice balance between satisfaction of current constraint and requirement of fast dynamic performance. Overlarge current may cause the damage of hardware. Aiming at this issue, a composite controller is proposed. Different from previous methods of state constraints, the effects of disturbance is taken into account of controller design. First, a finite-time current-constrained feedback control technique based on homogeneous approach is applied in the feedback design. Compared with conventional finite-time control, a punishment mechanism of over-current is added into the gain of controller. Second, a generalized proportional integral observer is adopted to estimate the uncertainties and disturbances. The estimated value is used in the feed-forward compensation design. Compared with the conventional proportional-integral-derivative controller and proportional-derivative + extended state observer controller, the proposed method not only limits q-axis current to a safe range but also shows a nice dynamic performance and a strong anti-disturbance ability. Both simulations and experiments are carried out, and the results demonstrate the effectiveness of the proposed control scheme.