Mitigating Converter Thermal Stress in PMSG Wind Turbines Using Enhanced Control Strategy and Reduced Order Modeling

Frequent failures of converters in individual wind turbines (WTs) of modern wind farms (WFs) means sub-optimal operation, loss of generation, as well as increased operation and maintenance (O&M) costs. Improving sub-system and component reliability, including that of converters, is a key element in maintaining technical confidence and consequently minimizing losses for operators and energy cost for consumers. In this paper one dominating cause of failures in WT converters is studied: the thermo-mechanical stress of IGBT modules. Using a lifetime and stress evaluation methodology, the reliability of different subcomponents of a converter module is evaluated. The torque control of the generator, as well as the control of real and reactive power transfer to the grid, are considered. A detail sensitivity analysis and model order reduction of the whole methodology is undertaken. This addresses the need to maximize computational efficiency if such models are to be applied practically, for example in WT digital twins. A novel current control strategy that reduces the IGBT thermal stress without impacting the torque control of the PMSG WT is suggested and successfully applied to a test case.