Generalized Study on Analysis and Suppression Strategy of Circulating Current for Modular Multilevel Cascaded Converters

Modular multilevel cascaded converter (MMCC) is widely used in medium and high voltage energy conversion in power systems. Circulating current and branch power fluctuation are common problems in MMCC, and due to different topologies, submodule types and input/output properties, their characteristics vary greatly. In this paper, a general characteristic analysis method of circulating current based on MMCCs’ network topologies is proposed. On this basis, a general suppression strategy for circulating current is proposed, which is easy to implement and can be combined with a branch energy balance strategy. The correctness of the proposed theoretical analysis and control algorithm, which provides an important theoretical basis for the development and application of MMCC is verified by the PSCAD/EMTDC simulation platform.