Sweden/Poland power link: impact of variable frequency rectifier ripple currents on torsional stressing of turbine-generator shafts

Summary form only given. This paper makes an in-depth analysis of shaft torsional phenomena in steam turbine-generator-exciter shafts of generators in Poland and Sweden which may result from ripple current superimposed on the HVDC link current in an HVDC asynchronous link. The analysis relates to the 600 MW, 450 kV HVDC cable which is to connect Vattenfall´s Karshamn oil-fired power station in the South of Sweden to Dunovo in the North of Poland where the length of the submarine cable is approximately 237 km. The studies are performed for machines in close proximity to the converter station in both Sweden and Poland. It extends earlier work to analyze attenuation (or amplification) of DC ripple current at the inverter due to the submarine cable with its overhead line in Poland and the line´s associated smoothing inductors. It examines HVDC link harmonic scaling factors and AC system scaling factors for modulation product harmonic currents impressed on the generators of the Swedish and Polish grid networks by the inverter, not examined in-depth in the literature heretofore.