Dynamic Optimal AC Line Current Regulation Method for Three-Phase Active Power Conditioners

The main feature of the three-phase back-to-back active power conditioner (APC) is to improve the power quality of the microgrid. During the large power variation transient, the severe voltage surge/sag on the dc-link of the APC may cause its malfunction. Therefore, the dynamic optimal ac line current regulation (DOCR) with flexible dc-link voltage slope (FDVS) is proposed in this paper. The proposed DOCR can determine the accurate input current reference value to regulate the dc-link voltage under the large power variation condition. On the other hand, the proposed FDVS can further mitigate the dc-link voltage variation during the large power variation transient. The mathematical equations of the proposed control strategy are derived thoroughly. Furthermore, procedures to determine the dc-link capacitance with the proposed DOCR are developed. Finally, the experimental results obtained from a 5-kVA back-to-back APC verify the feasibility and the performance of the proposed line current regulation strategies.