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In meshed high voltage direct current grids, the current of each line cannot be controlled independently, since it depends on the resistances between nodes. Additional devices, such as current flow controllers (CFCs), may be needed to avoid bottlenecks or line overloads. This work presents a multiport dc–dc-based CFC topology to be connected to $n$ lines with unidirectional current flows. The device is able to control the dc lines’ currents to the desired value by inserting variable voltage sources in series. First, the modeling of the generic $n$ -port topology is presented and then, its modulation and control strategy are described. In the first case study, the concept is validated considering a 5-port CFC by means of dynamic simulations using different control methods. Finally, in the second case study, a 3-port CFC prototype is built and tested in an experimental platform in the laboratory considering different control modes. [ABSTRACT FROM AUTHOR]

In meshed High Voltage Direct Current (HVDC) grids, Current Flow Controllers (CFC) may be required to avoid bottlenecks or line overloads. The present paper proposes the concept of installing Distributed Current Flow Controllers (DCFCs) in different nodes of a meshed HVDC grid that are operated selectively. This concept allows to use simplified DCFC devices to prevent the overloads, with a reduction of the required CFC voltage compared with a single CFC in the grid. First, a methodology to investigate the effect of installing DCFCs in a generic meshed HVDC grid is presented. Several case studies with a 3-terminal and a 7-terminal meshed HVDC grids are conducted and the most suitable topology for the DCFCs is derived based on the previous analysis. Then, this work analyses the increase in the operational area brought by installing DCFCs in a 3-terminal HVDC grid and it is compared with the increase achieved by a Dual H-bridge CFC in one node. The CFC losses and voltage requirement depending on the location of the DCFCs are investigated. Finally, the operation and control of the DCFCs are designed and tested in a 3-terminal meshed HVDC grid using dynamic simulations. [ABSTRACT FROM AUTHOR]

This paper proposes a DC/DC current flow controller (CFC) for meshed high voltage direct current (HVDC) grids. The CFC has the advantage of a simplified structure that allows us to use the minimum number of switches when unidirectional current flows through the DC lines are expected. An extended CFC topology that is able to operate with all possible current flows is also presented. Then, the operating principle of the CFC is discussed and its structure is compared with a dual H-bridge analyzing advantages and disadvantages. This paper also details the applied modulation strategy and the control methodology. Finally, a five-terminal meshed HVDC grid is used to validate the CFC by means of simulations. [ABSTRACT FROM PUBLISHER]

This paper focuses on the modelling and control of an interline current flow controller (CFC) for meshed HVDC grids. The operation states of the CFC are presented, and an average model is derived. The average model is used to perform steady-state analysis on a 3-terminal meshed grid, showing the current change capabilities and the benefits on the operation area. The converter control is designed using a linearized model. The system performance of the CFC is tested by means of simulation in a 3-terminal grid and in a 5-terminal grid. [ABSTRACT FROM AUTHOR]