Under the contract, ABB will be responsible for the upgrade and life extension of the converter valves, valve cooling systems, control and protection systems and other related equipment at the converter stations.
The firm said that the upgrade work will help improve grid reliability and facilitate efficient power transmission.
ABB Power Grids division president Claudio Facchin said: "The upgrade will extend life and greatly enhance reliability of this important transmission link, thereby helping to secure power supply for consumers in the region.
"The focus on service and lifetime support is a key element of ABB’s Next Level Strategy."
The ± 400kV HVDC transmission system, which is 700km long, is capable of transferring 1,000MW of electricity between Underwood, North Dakota and Buffalo, Minnesota.
Commissioned by ABB in 1978, the current HVDC system was has provided over 99% availability during its operational lifetime.
Great River Energy project leader Greg Schutte said: "Maintaining Great River Energy’s high reliability standards for this vital system is not only critical for delivering power in the short term, but also because it will continue to provide a corridor for delivering energy from North Dakota in the future."
