Impact of frequency control from wind turbine generator linked to HVDC system on sub-synchronous oscillation

Abstract

With global trends of carbon neutrality, offshore wind energy is considered as the most promising resource. However, as large-scale renewable energy resources replace the existing synchronous generators (SG), concerns about the system stability are growing. Owing to the absence of system supports provided by the SG. Therefore, operators require the wind generators to participate in frequency control. In addition, controls have been devised to perform frequency support even when large-scale offshore wind farm (OWF) linked to High Voltage Direct Current (HVDC). However, this frequency support control’s impacts on the overall system stability are not investigated in deeply yet. Therefore, in this study, the impacts of frequency control from OWF-linked HVDC system using communication-less scheme on the system instability were investigated using small-signal stability analysis. Its results revealed that this frequency support control caused instability. Modal analysis and simulations support these interpretations and improve the understanding its mechanism and dynamics.

Keywords

• Wind-linked HVDC system
• Small-signal stability
• Frequency support control
• Modal analysis
• Sub-synchronous oscillation