This article investigates a fault ride-through capability for grid-connected permanent magnet vernier generator (PMVG)-based wind turbine system (WTS) using coordinated active and reactive power control strategy. To do this, the generator peak current and speed limitation schemes are proposed for the machine-side converter to satisfy grid code requirements during grid fault conditions. At the same time, the reactive power control is implemented on the grid-side converter to meet the reactive current requirement of the grid code. And then, to suppress the DC-link power unbalance during grid fault conditions, an efficient variable exponential reaching law-based sliding mode control is designed. Further, the coordinated control schemes are employed to ensure the stable DC-link voltage and maintain the converter's maximum peak current during grid faults. Finally, the proposed control methods demonstrate their superiority through simulations on 5-kW PMVG, 1.5 MW PMSG-based WTS, and its application potential is shown through the experimental prototype of a 5-kW PMVG-based WTS.

The power system network grows yearly with a large number of nonlinear power generation systems. In this scenario, accurate modeling, control, and monitoring of interface systems and energy conversion systems are critical to the reliability and performance of the overall power system. In this trend, the permanent magnet synchronous generator (PMSG)-based wind turbine systems (WTS) equipped with a full-rated converter significantly contribute to the development of new and renewable energy generation. The various components and control systems involved in operating these systems introduce higher complexity, uncertainty, and highly nonlinear control challenges. To deal with this, state estimation remains an ideal and reliable procedure in the relevant control of the entire WTS. In essence, state estimation can be useful in control procedures, such as low-voltage ride-through operation, active power regulation, stator fault diagnosis, maximum power point tracking, and sensor faults, as it reduces the effects of noise and reveals all hidden variables. However, many advanced studies on state estimation of PMSG-based WTS deal with real-time information of operating variables through filters and observers, analysis, and summary of these strategies are still lacking. Therefore, this article aims to present a review of state-of-the-art estimation methods that facilitate advances in wind energy technology, recent power generation trends, and challenges in nonlinear modeling. This review article enables readers to understand the current trends in state estimation methods and related issues of designing control, filtering, and state observers. Finally, the conclusion of the review demonstrates the direction of future research.

This study presents a fast terminal synergetic control (FTSC) scheme to investigate the nonlinear control problem of permanent magnet vernier generator (PMVG)-based variable-speed wind energy conversion systems (WECSs). In wind turbines, better speed tracking and fast dynamic behavior is required to achieve the maximum power extraction. To do this, the FTSC method is firstly proposed to improve the dynamic performance of tracking the speedby, addressing the turbulent wind and uncertainties in the PMVG system, which improves the wind energy extraction efficiency and alleviates mechanical stress over the turbine. Next, the closed-loop FTSC with a macro variable and novel reaching law is presented to enhance the convergence of the speed error signal when it is far from equilibrium in finite time. At this time, the controller’s output is a zero chattering generator torque reference that can operate the system in both below- and above-rated wind conditions, in addition to pitch control. Then, the proposed control method is verified for its effectiveness in energy capture through numerical simulation and experimental verification of a 5 kW direct drive PMVG-based WECS. Finally, comparative results confirm the better performance of the proposed system under transients than other controllers considered in this analysis.

This study aims to enhance the reliability and availability of a three-level neutral point clamped (NPC) converter of a permanent magnet synchronous generator (PMSG)-based high-power wind turbine system by proposing a multiple open-switch fault diagnosis method. The open-switch (OS) faults lead to severe torque pulsation and distorted grid current in the system, hence requiring early detection and isolation. To do this, principal diagnostic variables are first formulated using the zero range value of instantaneous current amplitude and dc-link capacitor voltages. Then, the diagnostic variables detect the state of power electronic switches of each leg of the converters without being affected by torque pulsations, speed variations, and system power factor. Second, a fault localization scheme is introduced with identification thresholds to indicate the faulty switches of the machine side converter (MSC) and grid side converter (GSC). In GSC fault identification, an equivalent current transformation is employed to avoid errors in current normalization. Finally, the effectiveness of the proposed method is confirmed by verifying the results of comparative studies, simulations, hardware experimentation, and robustness against false indications in MSC and GSC.

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 presents an enhanced active power control (APC) strategy to track the desired reference power in a permanent magnet vernier generator (PMVG)-based wind turbine system (WTS). In order to mitigate the frequent pitch actuation requirement in the traditional APC, a rotor speed variation control (RSVC)-integrated with non-pitch regulation is conventionally employed. However, the fixed perturbation range of non-pitch regulation during downward pitch adjustments in existing approaches reduces power extraction because of the sluggish speed tracking response caused by higher rotor inertia. Additionally, the speed variation range for RSVC is considerably reduced. To deal with this, this study firstly proposes a novel method to achieve an adjustable range of non-pitch regulation to enlarge the speed variation range and improve the power extraction through generator-stator electric power dependent pitch compensation signal. In addition, the conventional method for RSVC is replaced by a conditional generator current reference setting according to the WTS operating regime. Next, a modified control strategy is proposed considering generator and turbine losses to improve the reference power tracking response. Finally, the superiority of the proposed control method is verified through the simulation of a 15-MW NREL WTS, its practical applicability is demonstrated through 5-kW experimental prototype with PMVGs.