The study and application of power flow controller for DC grids

With the development of modern power grid, traditional DC grid has evolved from multi-terminal HVDC (MTDC) to meshed DC grid. It can be realized through the control of converter station´s output voltage when one of the branches is over limit and need to be adjusted or must regulate the power flow to follow some dispatch orders. However, in the meshed DC grid, this adjustment will also significantly change the power flow of the other branches. This paper presents a new approach that series a converter into the branch which is under control. By changing the DC side voltage of the converter to regulate the voltage difference between the two ends of the branch, only the specific branch´s power flow will be changed remarkably, and there will just have a little change in the other branches. In this paper, several DC power flow control devices which had been proposed were analyzed through works and operating characteristics, and then the feasibility of the series voltage source was verified through the simulation.