Investigation of Sub-synchronous Oscillation in HVDC-connected PMSG-based Offshore Wind Farm: Comprehensive Modeling and Analysis

This paper investigates the sub-synchronous oscillation occurring in high voltage direct current (HVDC)-connected permanent magnet synchronous generator (PMSG)-based offshore wind farm. To do so, firstly, a comprehensive system model is developed, which incorporates the dynamics of the PMSG-based wind energy conversion system (WECS), the ac collection grid, and the HVDC transmission system. Subsequently, small signal model of the comprehensive system is derived. Based on the small signal model, the critical system mode is obtained using modal analysis. Special attention is paid to the influence of sub-synchronous mode on the onshore grid. Moreover, the influence of controller parameters on the sub-synchronous mode is investigated, which facilitates the design of converter controllers in HVDC-integrated PMSG-based offshore wind farm. Additionally, the modal analysis results are verified through time-domain simulations.