Internal model control based protection strategy for MMC-HVDC offshore wind farm under unbalanced grid
DOI:10.7667/PSPC171831
Key Words:offshore wind farms  unbalanced grid faults  low voltage ride-through  modular multilevel converter  internal model control
Author NameAffiliationE-mail
CHEN Yanhong School of Electrical Engineering, Hunan Mechanical & Electrical Polytechnic, Changsha 410151, China longxilongxi1982@126.com 
LI Shijun Hunan Provincial Key Laboratory of Wind Generator and Its Control, College of Electrical & Information Engineering, Hunan Institute of Engineering, Xiangtan 411101, China  
LI Yanping Hunan Provincial Key Laboratory of Wind Generator and Its Control, College of Electrical & Information Engineering, Hunan Institute of Engineering, Xiangtan 411101, China  
XIE Weicai Hunan Provincial Key Laboratory of Wind Generator and Its Control, College of Electrical & Information Engineering, Hunan Institute of Engineering, Xiangtan 411101, China  
Hits: 3051
Download times: 1427
Abstract:To solve the universal low voltage ride-through problem of the offshore wind farm based on MMC-HVDC under unbalanced grid fault, a new control strategy by combining PI voltage outer loop and internal model current inner loop is proposed along with the auxiliary protection scheme. First, the performance characteristic of Modular Multilevel Converter (MMC) under unbalanced grid fault is analyzed, the mathematical mode of MMC in αβ two-phase static coordinate is established. Then, the system control strategy based on Internal Model Control (IMC) method is designed in the aforementioned coordinate to suppress negative sequence current, meanwhile, aimed at the busbar voltage rise problem caused by MMC current-limiting feature in the case of two-phase grounding fault, the system auxiliary protection scheme based on DC discharge circuit is developed. Finally, the simulation model is established in Matlab/Simulink under the unbalanced operating condition of one- and two-phase grounding fault. Results indicate that the proposed control strategy and auxiliary protection scheme can ensure the offshore wind farm based on MMC-HVDC to implement the low voltage ride-through running even under the unbalanced grid fault, the low voltage ride-through capability of offshore wind farm is improved effectively. This work is supported by National Natural Science Foundation of China (No. 61673164).
View Full Text  View/Add Comment  Download reader