Proposed 4 GW Russia-Germany link-impact of 1 GW inverter station on torsional stressing of generators in Poland

The European power systems are in the process of a new orientation which will facilitate and promote exchange of electric power between Eastern and Western European nations. One such example is the 4 GW HVDC link from Russia to Germany where a 1 GW power converter substation has been proposed for Central Poland. This paper considers the impact of the proposed 4 GW Russia-Germany HVDC link on the Polish grid network and possible excitation of torsional vibrations in shafts of steam turbine-generator exciter units connected to the system by noncharacteristic currents due to the link. Excitation of torsional vibrations in machine shafts due to modulating currents and the level of risk of damage to machine shafts due to subsynchronous currents injected into the network by the inverter is assessed. Dynamic parameters of system loads and the power factor of loads which influence system scaling factors are also discussed. The paper also examines the most probable location of the proposed 1000 MW converter on the Polish grid network. System scaling factors are evaluated for different system configurations for each generator at risk and generators most at risk are identified. The paper then investigates transient behaviour of the Polish power system following loss of the proposed link at full import. Transient stability performance is also evaluated for a range of system faults of different fault durations, distances and locations from power plants.