Current control; High voltage direct current(HVDC) transmission system; Modular multi-level converter(MMC); Transformerless; Unbalanced grid; Vector proportional-integrator control
Issue Date
2018-09
Publisher
KOREAN INST ELECTR ENG
Citation
JOURNAL OF ELECTRICAL ENGINEERING & TECHNOLOGY, v. 13, no. 6, page. 2319-2328
Abstract
This paper introduces a control method for a transformerless MMC-HVDC system. The proposed method can effectively control the grid currents of the MMC-HVDC system under unbalanced grid conditions such as a single line-to-ground fault. The proposed method controls the currents of the positive sequence component and the negative sequence component without separating algorithms. Therefore, complicated calculations for extracting the positive sequence and the negative sequence component are not required. In addition, a control method to regulate a zero sequence component current under unbalanced grid conditions in the transformerless MMC-HVDC system is also proposed. The validity of the proposed method is verified through PSCAD/EMTDC simulation.