Power Flow Controllers (PFCs) or Current Flow Controllers (CFCs) are expected to be required in future High Voltage Direct Current (HVDC) grids to aid in the current distribution. This work analyses the feasibility of this kind of devices from the implementation point of view. First, the needs of a PFC as a medium voltage converter floating at high voltage are assessed. Then, the paper discusses the challenges to implement one of these converters, such as the sizing of the power electronic elements, cooling management, insulation from ground, etc. Most of them are already tackled in other existing devices in the field of high voltage. Powering the PFC semiconductors gate-drivers and other auxiliary systems at high potential is seen as a particular point to take into account when building the device.