Long-distance offshore wind power transmission systems utilize multi-terminal high voltage direct current (MT-HVDC) connections based on voltage source converters (VSCs). In addition to having the potential to work around restrictions, the VSC-based MT-HVDC transmission system has significant technical and economic merits over the HVAC transmission system. Offshore wind farms (OWFs) will inevitably grow because of their outstanding resistance to climate change and ability to provide sustainable energy without producing hazardous waste. Due to stronger and more persistent sea winds, the OWF often has a higher generation capacity with less negative climate effects. The majority of modern installations are distant from the shore and produce more power than the early OWF sites, which are situated close to the shore. This paradigm shift has compelled industry and professional researchers to examine transmission choices more closely, specifically HVAC and HVDC transmission. This article conducts a thorough analysis of grid connection technologies for massive OWF integration. In comparison to earlier assessments, a more detailed discussion of HVDC and HVAC topologies, including HVDC based on VSCs and line-commutated converters (LCCs), and all DC transmission systems, is offered. Finally, a selection criterion for HVDC transmission is advised, and its use is argued to be growing.

With the increase in reliance on doubly fed induction generator-based wind energy conversion systems (DFIG-WECSs), extracting maximum power from wind energy and enhancing fault ride-through (FRT) techniques meeting the grid code requirements is the foremost concern. This paper proposes a modified control scheme that operates in normal running conditions and during faults as a dual mode. The proposed control scheme operates in a coordinated wind speed estimation-based maximum power point tracking (WSE-MPPT) mode during normal running conditions to extract maximum power from wind energy and enhances the crowbar rotor active impedance-based FRT mode during faults. The proposed technique controls the rotor side converter (RSC) parameters during faults by limiting the transient surge in the rotor and stator currents. In this study, the transient behavior of the proposed technique is analyzed under a three-phase symmetrical fault with a severe voltage dip, and it is observed that, when the fault is over and the RSC is activated and connected to the system, a large inrush current is produced with transient oscillations; the proposed scheme suppresses this post-fault inrush current and limits the transient oscillation. During the FRT operating mode under a symmetrical fault, the simulation results of the proposed technique are validated by the conventional crowbar strategy. In contrast, during the WSE-MPPT operating mode under normal running conditions, a smooth achievement of system parameters after starting the inrush period to a steady state at fixed wind speed is observed.

In this paper, a nonlinear power transfer matrix model is presented for power control of Permanent Magnet Synchronous Generator (PMSG) wind turbines, incorporating the DC link dynamics to account for transient stability, thereby clarifying the technical aspect and purpose. The rising penetration of wind turbines (WTs) into the power grid necessitates that they remain connected during and after faults to ensure system reliability. During voltage dips, the stator and grid-side converter (GSC) of a permanent magnet synchronous generator (PMSG) system are directly impacted by the sudden voltage changes. These disturbances can induce large transient voltages and currents in the stator, which in turn may lead to uncontrolled current flow in the rotor circuit and stress the converter components. Moreover, Low Voltage Ride-Through (LVRT) is a critical requirement for grid connection to Wind Energy Conversion Systems (WECS). It ensures that WTs remain connected and operational during short periods of grid voltage dips (faults), instead of disconnecting immediately. This capability is essential for maintaining grid stability. However, in this paper, the authors propose an LVRT scheme for a grid-connected PMSG-based WECS. A sequence of attempts was performed to validate the effectiveness of the proposed control scheme under fault conditions and to improve its overall performance.