Long-term fatigue life loss of turbine blades owing to noncharacteristic harmonic currents in asynchronous HVDC links

Abstract

The long-term effect of noncharacteristic harmonic currents in asynchronous HVDC links on fatigue life expenditure in turbine–generator blades is studied in this paper. Because the frequencies of the two main harmonic current terms are subsynchronous and offer a probability distribution due to the asynchronous operation in a HVDC link, a systematic fatigue estimation approach was devised to investigate the long-term impact for the low-pressure turbine blades. From the simulation results, it is clear that the sustained excitation of these harmonics becomes a cause of blade failure even though the harmonic current is still normal for only one generator connected to the inverter station bus. By the effect analysis of uncertainty in electrical and mechanical parameters, several schemes for the fatigue loss alleviation were then found.