A Novel MRAC Strategy for Fault Impact Mitigation in HVDC-Connected Offshore Wind Farm System

This paper proposes a strategy for fault impact mitigation in high-voltage direct current (HVDC) connected offshore wind farm (OWF) system. The OWF contains hundred and fifty variable speed wind turbines (VSWT) using permanent-magnet synchronous generator (PMSG). Each VSWT/PMSG in the OWF has its own ac-dc converter, through which these VSWT/PMSGs are interconnected in series. Technically, the good quality of power is ensured even with the presence of a fault using a new control method based on the model reference adaptive control (MRAC). This technique uses the error between the reference model and the real HVDC system to decrease the fault impact occurred in HVDC system through an adjustment mechanism. Further, integration of the nonlinear observers based on extended Kalman filter (EKF) which guarantee good estimation of the PMSG's speed and rotor position and that of the dc-bus voltage of the offshore side dc-ac inverter thereby eliminating expensive sensors and making the system economical. Effectiveness of the proposed method is analyzed with and without fault compensations of the system. Performance simulation of the proposed system using Matlab shows excellent results.