Smoothing reactors are vital components in HVDC systems. The purpose of the reactor is to reduce the so called current ripple on the DC side of the system.
ABB provides oil immersed reactors for all HVDC applications. A smoothing reactor in a HVDC system can be much larger than even the largest shunt reactor. ABB has supplied several different sizes up to the largest ones needed in HVDC lines for transmission of high power and on high voltage levels.