A Multiport Current Flow Controller for Meshed Multiterminal DC Grids

Abstract

In the meshed multiterminal dc (MTDC) grid, the individual line currents cannot be controlled precisely without additional equipment. To address this issue, the current flow controllers (CFCs) that can regulate the line current and avoid line overloads are adopted. A new multiport current flow controller topology with independent regulation capability has been proposed in this article. This CFC topology is composed of the main circuit and auxiliary circuit, which are connected via the coupled capacitors. The proposed CFC topology can regulate one or more line currents in the MTDC grids and can realize line currents regulation independently. Furthermore, it can be applied in medium voltage or high voltage dc systems due to the modular structure. The power losses of the proposed CFC are minimized because the auxiliary circuit transmits small power and operates in resonant mode. Meanwhile, the operation principle and the control strategy of the proposed CFC topology are illustrated in this article. The comparison with other CFC topologies previously proposed proves the advantages of the proposed topology. Simulations performed in MATLAB/Simulink and experiments based on a down-scaled prototype are completed to verify the operation principle and control strategy.