Owing to the advantages of higher efficiency, greater reliability, and better grid compatibility, the direct-drive permanent-magnet synchronous generator (PMSG)-based variable-speed wind energy conversion systems (WECSs) have drawn the highest attention from both academia and industry in the last few years. Applying mechanical position/speed sensorless control to direct-drive PMSG-based WECSs will further reduce the cost and complexity, while enhancing the reliability and robustness of the WECSs. This paper reviews the state-of-the-art and highly applicable mechanical position/speed sensorless control schemes for PMSG-based variable-speed WECSs. These include wind speed sensorless control schemes, generator rotor position and speed sensorless vector control schemes, and direct torque and direct power control schemes for a variety of direct-drive PMSG-based WECSs.

A Review on Position/Speed Sensorless Control for Permanent-Magnet Synchronous Machine-Based Wind Energy Conversion Systems

A review on wind turbine control and its associated methods

Modeling, analysis and comparison of TSR and OTC methods for MPPT and power smoothing in permanent magnet synchronous generator-based wind turbines

With the increasing penetration of wind power in power systems, it is desirable for wind turbines to have similar characteristics as conventional synchronous generators Conventional generators provide frequency support to the grid through the methods of inertial response and primary and secondary frequency regulation, whereas variable-speed wind turbine generators (WTGs) do not have those desired abilities because they are integrated into the power grid via power electronic converters Although many different control strategies have already been published to enable WTGs to temporarily support the transient frequency, the published strategies may bring various negative effects to the system This paper proposes a new control strategy to compensate for inertia of the wind farm It can improve WTGs' temporary frequency support based on the coordinated control of the WTGs and the energy storage (ES) system The simulation results show that this strategy could provide better performance of temporary frequency support and overcome problems such as system frequency oscillation and a secondary frequency drop The proposed control strategy can be realized in all wind speed conditions with a small-scale ES system

Coordinated Control Strategy of Wind Turbine Generator and Energy Storage Equipment for Frequency Support

The growing trends in wind energy technology are motivating the researchers to work in this area with the aim towards the optimization of the energy extraction from the wind and the injection of the quality power into the grid. Over the last few years, wind generators based on permanent magnet synchronous machines (PMSMs) are becoming the most popular solution for the modern wind energy conversion systems (WECSs). This paper presents a concise review of the grid-integrated WECSs employing permanent magnet synchronous generators (PMSGs). It reviews the trends in converter topologies, control methodologies, and methods for maximum energy extraction in PMSG based WECSs, which have been reported in various research literatures primarily in reputed research journals and transactions during last few years. It also presents an overview to the grid interconnection issues related to output power smoothing and reactive power control in addition to fault-ride-through (FRT) and grid support capabilities of PMSG based WECSs. This review article will serve the researchers working in the area of grid-integrated PMSG based WECSs in the exploration of trends, developments and challenges in the past research works and in finding out the relevant references for their research work.

Grid-integrated permanent magnet synchronous generator based wind energy conversion systems: A technology review

This paper describes the performance comparison of a wind power systems based on two different induction generators as well as the experimental demonstration of a wind turbine simulator for the maximum power extraction. The two induction machines studied for the comparison are the squirrel-cage induction generator (SCIG) and the doubly fed induction generator (DFIG). The techniques of direct grid integration, independent power control, and the droop phenomenon of distribution line are studied and compared between the SCIG and DFIG systems. Both systems are modeled in Matlab/Simulink environment, and the operation is tested for the wind turbine maximum power extraction algorithm results. Based on the simulated wind turbine parameters, a commercial induction motor drive was programmed to emulate the wind turbine and is coupled to the experimental generator systems. The turbine experimental results matched well with the theoretical turbine operation.

Simulation Comparisons and Implementation of Induction Generator Wind Power Systems

The maximum power point tracking (MPPT) method is the key to notably improve efficiency and energy extraction in wind turbine systems. The MPPT method through the characteristic power curve is one of the popular MPPT methods. The reference current can be obtained using the relationship between power and current without requiring real-time wind speed information. This paper presents the steady-state and dynamic analyses of this MPPT method and proposes a single-pole transfer function to describe the effect of variation of wind speed on the generator speed. This is conducted by applying the small-signal analysis on a nonlinear turbine-rotor mechanical system. To verify the performance of the wind turbine system, both simulation and experimental systems are implemented based on MPPT power control. By the variation of wind speed, the behavior of the generator speed presents good consistency among the proposed theory, simulation, and experiments.

Stability Analysis of Maximum Power Point Tracking (MPPT) Method in Wind Power Systems

Variable-speed wind power systems are able to vary the rotor speed according to wind speed variation. The maximum power point tracking (MPPT) is the key to notably improve efficiency of such energy extraction systems. The characteristic power curve MPPT method is one of the popular MPPT methods. It does not need real-time wind speed measurement and by using the relationship between power and current, the reference current can be obtained easily. This paper presents the steady state and dynamic analyses of this MPPT method and proposes a single pole transfer function to describe the effect of variation of wind speed on the rotor speed. This is conducted by applying the small signal analysis on the turbine-rotor mechanical system. To verify the performances of wind turbine system, both simulation and experimental systems are implemented based on MPPT power control. By concentrating on step wind speed variation, all results - proposed theory, simulation and experiments - present good consistency.

Stability analysis of maximum power point tracking (MPPT) method in wind power systems

This paper presents the modeling and simulation of wind power systems based on two different induction generators; the squirrel-cage induction generator (SCIG) and the doubly-fed induction generator (DFIG). The techniques of direct grid integration of SCIG system and independent power control of DFIG system are discussed. Particularly, to solve the droop in distribution line voltage in SCIG system, a reactive power static compensator (STACOM) is used and a comparison of distribution line voltage is conducted between the SCIG and DFIG systems. Besides, in DFIG system, a fitting curve for optimal power versus speed is proposed for the turbine model and a cross-coupling relation between three phase choke and stator-side converter is also emphasized. Both wind power systems and their grid integration techniques are modeled and simulated in Matlab/Simulink. The results demonstrated the characteristics of both systems under varying wind speeds. Compared to the conventional constant speed SCIG system, variable speed DFIG reveals its superiority in terms of optimal power capture as well as constant distribution line voltage.

A Complete Modeling and Simulation of Induction Generator Wind Power Systems

To extract power more efficiently, Maximum Power Point Tracking (MPPT) methods are always applied in variable-speed generator wind power systems. However, due to the fast wind speed variation, fast and real-time calculations of optimal system operation points are difficult to achieve. Also, the dependence of optimal references on the system model can hardly be removed. This paper proposes a novel real-time MPPT algorithm which simply updates the reference power curve by tuning the curve coefficients. Due to the independence on system model, this method is immune to the potential system variations and thus robust. To verify its performance, the proposed algorithm is simulated in Matlab/Simulink and experimentally tested on doubly-fed induction generator (DFIG) wind power system. Both simulation and experimental results validate the proposed method.

Yu Zou

Papers

Simulation Comparisons and Implementation of Induction Generator Wind Power Systems

Stability Analysis of Maximum Power Point Tracking (MPPT) Method in Wind Power Systems

Stability analysis of maximum power point tracking (MPPT) method in wind power systems

A Complete Modeling and Simulation of Induction Generator Wind Power Systems

A novel Maximum Power Points Tracking (MPPT) operation of doubly-fed induction generator (DFIG) wind power system