A Compact Modular Multilevel Interline Power Flow Controller for Multiterminal DC Grids

The dc power flow controllers with wide-rangecurrent regulation have emerged as a promising solution tofulfill the power flow control demands of long-distance andhigh-voltage dc transmission. This paper presents a compactmodular multilevel interline dc power flow controller composedof two arms and three resonant tanks. The proposed topologyprovides a wide current regulation range, which can be furtherextended through its modular structure and piecewise control. Byadding the corresponding number of arms and series resonanttanks, the proposed topology can be flexibly extended to controlthe power flows of multiple line. Owing to its series interlinearchitecture, the proposed topology only needs to withstand afraction of the nominal transmission voltage while handling fullrated current, thereby exhibiting good power regulation leverage.The proposed topology is suitable for high-voltage and widerange current regulation applications as it exhibits modularityand scalability. The operation principle and control strategyare presented in this paper and validated through simulationsperformed in PSCAD/EMTDC and experiments based on abench-scale prototype.