Model Predictive Current Control of Doubly Fed Induction Generator with Controllable Switching Frequency under Unbalanced Grid

The traditional finite-state-set model predictive current control has of doubly-fed induction generator different switching frequencies at different operating points, which is not conducive to heat dissipation management and filter design. On the basis of model predictive current control, a PI controller is adopted to adaptively adjust the weight coefficient in the objective function. So that the switching frequency can track the reference value, and the switching frequency can be kept constant when the output power and speed change. In addition, when the grid voltage is unbalanced, the positive and negative sequence components of the grid voltage are obtained by the signal delay method, and the positive and negative sequence components of the reference value of rotor current are calculated, and the control goals of sinusoidal symmetry of stator current and constant switching frequency are achieved at the same time. Experiments are carried out on the doubly-fed machine platform and the effectiveness of the proposed method is verified. The results show that the proposed method does not sacrifice the steady-state performance because of the control of switching frequency, and the switching frequency can be kept constant under the change of operating point and unbalanced power grid which is convenient for filter design.