A new multi-port interline DC power flow controller for multi-terminal HVDC grids

In Multi-Terminal High-Voltage Direct Current (MT-HVDC) Grids, the current of Direct Current (DC) lines are naturally dispersed depending on the DC line resistance and the difference in the voltage at various DC terminals. These characteristics can have direct impacts on the proper operation and stability of MT-HVDC systems and affect the DC power flow in such grids. Using multi-port Interline DC Power Flow Controllers (IPFCs) is an effective solution to improve the power flow controllability and reliability of MT-HVDC grids and also control the current of each DC line. This article aims at presenting a multi-port IPFC to be utilized in series with DC lines in High-Voltage Direct Current (HVDC) grids, providing bidirectional current flow with fewer power switches for each output port. Furthermore, the proposed multi-port IPFC benefits from lower Alternating Current (AC) voltage ripple in the case of increasing the number of the output ports and reducing total power losses in the multi-port IPFC. The operating principle, circuit features, modulation technique, and control scheme of the proposed multi-port IPFC are thoroughly presented. Through dynamic simulations, the performance of the proposed multi-port IPFC is validated using the CIGRÉ B4.58 DC Grid Test System. Finally, real-time Control-Hardware-in-the-Loop (C-HIL) testing under different operating conditions is performed to demonstrate the applicability and effectiveness of the proposed multi-port IPFC.