This study presents an effective control strategy for regulating the DC-link voltage in a variable-speed direct-driven (DD) wind energy conversion system (WECS) using a permanent magnet vernier generator (PMVG). To do this, at first, the overall system is configured using back-to-back (BTB) voltage source converters, and the whole system’s dynamical equations are modeled and presented. Following that, a non-linear sliding mode control strategy is introduced as the grid-side converter’s DC-link voltage controller to improve the dynamic performance of the PMVG system and achieve the stable power transfer with the grid. To accomplish this, a proportional and integral (PI)-based sliding surface is designed, and a hybrid reaching law is proposed to suppress chattering and deliver a faster response of DC-link voltage with negligible steady-state tracking error. Finally, the effectiveness and superiority of the proposed control strategy are validated through comparisons with existing methods using simulation and experimental results from a 5-kW PMVG system.

As the impacts of environmental change become more severe, reliable and sustainable power generation and efficient aerodynamic power collection of onshore and offshore wind turbine systems present some of the associated key issues to address. Therefore, this review article aims to present current advances and challenges in the aerodynamic power extraction of wind turbines, associated supporting technologies in pitch, yaw, and torque control systems, and their advantages and implications in the renewable energy industry under environmental challenges. To do this, first, mathematical modeling of the environmental characteristics of the wind turbine system is presented. Next, the latest technological advances consider the environmental challenges presented in the literature, and merits and drawbacks are discussed. In addition, pioneering research works and state-of-the-art methodologies are categorized and evaluated according to pitch, yaw, and torque control objectives. Finally, simulation results are presented to demonstrate the impact of environmental issues, improvement claims, findings, and trade-offs of techniques found in the literature on super-large wind turbine systems. Thus, this study is expected to lay the groundwork for future intensive efforts to better understand the performance of large-scale wind turbine systems in addressing environmental issues.

This study aims to present a cascade-free finite-control-set (FCS) model predictive control (MPC) strategy for machine-side converter (MSC) as well as grid-side converter (GSC) of a large scale wind turbine system (WTS). The proposed cascade-free MPC is applied to a direct drive (DD) Permanent magnet synchronous generator (PMSG) to increase its energy output. To do this, a hybrid maximum power point tracking (MPPT) method which is the combination of both the optimum torque (OT) MPPT method as well as the tip speed ratio (TSR) MPPT method, is implemented in the proposed MPC to capture maximum power from the available wind. This proposed MPC controls electromagnetic variables and electrical variables in the same control structure, thus increasing the dynamic responses of the system. Similarly the active and reactive power control presented in this study is done using the MPC by decoupling the grid currents during the current control. Finally, the control strategy proposed in this study demonstrates its applicability through a numerical example of a DD PMSG-based WTS with power rating, and demonstrates its superiority compared to existing control methods.