Research on Control Strategy of VIENNA Rectifier under Unbalanced Power Grid

Aiming at the problems of traditional finite control set model predictive control (FCS-MPC) of VIENNA rectifier under unbalanced grid voltage conditions, such as DC bus voltage fluctuation, active reactive power pulsation and serious harmonic distortion of grid side current, an improved finite set model predictive control strategy is proposed. First of all, a mathematical model of VIENNA rectifier under unbalanced grid voltage condition is established, the network side current prediction model, power prediction model and midpoint balance prediction model are constructed respectively, so as to determine the objective function of multi objective constraints of FCS-MPC. Secondly, for the error caused by the computation delay and the prediction process, a delay compensation and feedback compensation link is introduced, update the objective function, the optimal switching state of the next time is obtained by minimizing the objective function and directly acting on the rectifier, this method satisfies the control objective of the VIENNA rectifier under the unbalanced condition of the power grid and reduces the complexity of the control. Finally, the proposed control strategy is simulated. The simulation results show that the method is correct and effective under the condition of unbalanced voltage.