H∞Loop Shaping Robust Direct Current Control for Single-phase PWM Rectifier

The grid-side equivalent inductance parameter perturbation is a significant feature of the uncertainty in the single-phase pulse-width modulation rectifiers systemwhich tends to reduce the robustness of the rectifier system. An H∞ loop shaping robust direct current (H∞-LS RDC) control strategy based on robust control theory was proposed in this paper, which helps to reduce the influence of the model parameter perturbation caused by a measurement error or an operation condition change on the robustness of the control system. First, suitable compensators were connected in series before and after the current loop to construct the desired open-loop transfer function. On this basis, the normalized coprime factor decomposition was then used on the desired controlled objects, and the H∞ loop shaping design is further attributed to the problem of H∞ robust control problem for the coprime factor perturbation model. The basis of selecting compensators according to the characteristics of current high-order harmonics was finally put forward, and the Riccati equation was used to solve the H∞ loop shaping controller. The robust stability margin can well meet the design requirements. The hardware-in-loop system was adopted to verify the proposed algorithm via comparison with the direct-axis quadrature-axis current decoupling control strategy, and the results show that the H∞-LS RDC control strategy can efficaciously enhance the robustness of single-phase PWM rectifier system under the grid-side inductance parameters perturbation. © 2021, Power System Technology Press. All right reserved.