A hybrid power flow controller for flexible operation of multi-terminal DC grids

This paper develops a hybrid power flow controller (HPFC) to take one step forward for building future flexible DC transmission system (FDCTS). The idea for proposing HPFC is inspired by the successful operation of flexible AC transmission systems (FACTS) devices, the FDCTS includes static power electronics-based elements to provide voltage regulation, power control and load flow control in the multi-terminal DC (MTDC) grids. The HPFC, as one of the devices of the FDCTS, has a hybrid connection scheme (i.e. series-parallel) to the grid and allows power flow control through DC transmission lines by imposing a series voltage to the controlled DC line. In this work, in order to demonstrate the eligibilities of the HPFC, the performance of this device is included in the DC power flow formulation for the power flow control purposes. Finally, it will be shown through dynamic simulations that the proposed HPFC is able to control the power flow through a particular DC transmission line.