Subsynchronous Resonances in the Shaft Train of Large Turbosets and High Voltage DC Transmission

Abstract

Because of the energy recovery and other technical and economic changes, high-voltage direct-current transmission is to be increasingly used in the nourishing future. The required inverter stations cause subsynchronous frequencies in the three-phase system near the connection point. These may possibly be close to mechanical subsynchronous torsional natural frequencies of large turbosets. The excitation of subsynchronous resonances in power stations means a serious risk for the shaft train. In order to be able to assess the risk for a shaft train in advance, the calculation of the occurring moments as well as the resulting fatigue due to such an excitation is usually required on the basis of detailed models. In addition, less complex models which are used in the analysis of larger networks can be derived from these detailed models.