Synchronous Generator Based Wind Turbine Research Articles

Assessment of proposed maximum power point tracking–unity power factor algorithms for optimum operation permanent magnet synchronous generator–based wind turbine

It is very important to select proper maximum power point tracking algorithm in order to achieve best performance and low cost for wind turbine–generator combination. A permanent magnet synchronous generator steady-state unity power factor analytical model based on a current source—equivalent circuit is provided. Validation of the identified load angle effect in current source as compared with that of the commonly used voltage source permanent magnet synchronous generator is presented. Then three new maximum power point tracking–load angle control algorithms based on current source model are presented. They all apply magnitude and frequency control techniques for Digital Signal Processor control systems. The first one presents maximum power point tracking–unity power factor applying constrained load angle control algorithm. The merits of the next two developed schemes are quickly and precisely tracking the maximum power output of the wind turbine; thus, the second and third algorithms are then characterized with linear control systems. The linearity of the second scenario is between load angle and reference speed while the third one has a load angle–torque linear relationship which shows its optimality. Finally, the controlled characteristics and implementation for the optimum case are presented for both stationary and synchronous reference frames (for vector control purposes). Simulation modeling for optimum case is provided and its results match well with the proposed predictive control algorithm.

Optimal torque maximum power point technique for wind turbine: Proportional–integral controller tuning based on particle swarm optimization

This article presents the problem of the energy system optimization for wind generators. The goal of this work is to maximize power extraction for a permanent magnet synchronous generator–based wind turbine with maximum power point technique. This goal is achieved using a proportional–integral controller for optimal torque tuning with the particle swarm optimization algorithm. In order to indicate the effectiveness and superiority of the particle swarm optimization algorithm–based proposal, a comparison with the genetic algorithm and the artificial bee colony algorithm is studied. The system is modeled and tested under MATLAB/Simulink environment. Simulation results validate the advantages of the designed particle swarm optimization–tuned proportional–integral controller compared to P&O and the proportional–integral controller manually in terms of performance index.

A Novel Adaptive Control Method for Performance Enhancement of Grid-Connected Variable-Speed Wind Generators

Huge penetration of grid-tied wind generators into the existing electricity networks increased various challenges in modern power grids. Tremendous attempts are accomplished to properly enhance the behavior of the wind generation systems. This article exhibits a new self-tuned control approach for enhancing the performance of a permanent-magnet synchronous generator-based wind turbine, which is interlinked to the electricity network. The self-tuned technique relies on an improved multiband-structured subband adaptive filter (IMSAF) algorithm, which achieves less computational intricacy over the least-mean-square approach. The IMSAF algorithm-based self-tuned proportional-integral (PI) controller is employed to adjust the interface voltage source converters through a cascaded control structure. The IMSAF algorithm updates the multiple PI controllers' gains on-line without the necessity to optimize or fine-tune. To achieve realistic responses, practical wind speed data measured in Zaafarana wind farm, Egypt, are implemented in this study. The efficacy of self-tuned control approach is compared with that realized using an optimized PI control approach by the water cycle and the genetic algorithms, considering symmetrical and unsymmetrical faults, as the network disturbances. The validity of self-tuned control approach is widely confirmed by performing simulation analyses using MATLAB/Simulink software, and satisfactory responses are achieved. Notably, the IMSAF-based self-tuned control approach is realized to be an accurate means for improving the characteristic of grid-tied wind generators.

Stability analysis of a PMSG based Virtual Synchronous Machine

This paper proposes a Virtual Synchronous Machine (VSM) strategy for Permanent Magnet Synchronous Generator based wind turbines which enables seamless operation in all operating modes. It guarantees Maximum Power Point Tracking in grid-connected operation, Load Following Power Generation in islanded operation and Low Voltage Ride Through capability during faults. To achieve optimal performance in all operating modes, the stability of the VSM is investigated in the event of small and large perturbations. The small-signal stability analysis of the VSM is conducted using a linearized state space model and the impact of the controllers on the dominant modes are derived using participation factor analysis. The transient stability and dynamic performance of the VSM are analyzed using a non-linear model. Based on this analysis, design guidelines and operational limits of the VSM are established. The results of this analysis are validated using time-domain simulations in MATLAB/SIMULINK.

Assessment and control of a three-phase grid connected wind turbine

In this article, we process the modeling and control of a global chain of the wind energy conversion system based on a permanent magnet synchronous generator, and the injection of the produced energy into electrical grid. The proposed control technique of the wind energy system is based on a sliding mode control which is designed for a variable speed wind turbine. Sliding mode control is assessed on a wind turbine to supply three phases grid. The aim in this work is to operate over all the wind conversion system at its maximum power point. Initially, three controls have been designed by sliding mode control: the first is for electromagnetic torque of the used permanent magnet synchronous generator, the second is for the machine side converter, and the last is for the grid side converter. Thereafter, another proportional integral controller has been designed for the phase looked loop. Finally, the permanent magnet synchronous generator–based wind turbine and the grid are modeled, and proposed controls are applied, various simulations results by MATLAB/SIMULINK environment are presented and discussed.

An Efficient Wind Speed Computation Method Using Sliding Mode Observers in Wind Energy Conversion System Control Applications

Point wind velocity measurement given by nacelle-top mounted sensor may not be same as effective wind velocity, which strikes the wind turbine rotor blades. This article proposes a new method for the computation of effective wind velocity by inverting the turbine's aerodynamic model after estimating the turbine torque and its rotor speed. Nonlinear control theory-based sliding mode observers are used to estimate the wind turbine generator induced speed emfs, rotor speed, and aerodynamic torque imparted to generator shaft. While satisfying the Lyapunov inequality condition, design aspects of sliding mode observers are discussed in detail. The performance of the proposed wind velocity estimation method is evaluated by using permanent magnet synchronous generator-based wind turbine emulator in laboratory. Simulation and experimental studies confirm that the estimated wind velocity under different wind profile conditions is accurate and can be used in various control algorithms in wind energy conversion systems.

Monitoring and control of a permanent magnet synchronous generator-based wind turbine applied to battery charging

ABSTRACT The battery charging control within wind turbine applications is the most important challenge in standalone exploitation mode because of the random nature of wind energy and irregular use of electricity. Within this problematic, this paper deals with monitoring and control of a permanent magnet synchronous generator voltage for battery charging. In the proposed topology, the output direct drive PMSG is linked to the battery through a vector-controlled pulse modulated (PWM) rectifier. Most wind energy conversion systems are based on precise knowledge of the wind speed, which makes the adjustment of the charge voltage relatively complicated, and degrades the powers captured with erroneous measurements of this wind speed. In this context, all the efforts of this work are meant to simplify and improve the dynamic performance of the system. The technique used in this work is devoid of wind measurement. By neglecting different losses, the approach adopted leads us to the reference electromagnetic torque, assuming that the wind speed and consequently the rotational speed of the turbine vary slowly in steady state. Using the load current and voltage measures, the proposed controllers calculate permanently the power reference that corresponds to the fixed battery voltage. A vector control approach is adopted to achieve decoupled power control on the supply side power converter by generating the direct and quadrature control voltages. These voltages are necessary to generate the corresponding duty cycles of the PWM active switching devices. Hence, the PWM rectifier maintains the battery voltage at a fixed value by balancing both the rectifier output current and the load input current. To activate the vector control, two dynamic controllers are designed, simulated, and compared. The first controller is based on simple PI regulators. Meanwhile, the second one, which is a sliding mode technique, is applied to control the battery voltage. In order to assess the effectiveness of the used techniques, simulation models have been subjected to critical conditions of changing in speed and load. Simulation results revealed a poor accuracy of the first technique during transients and its close correlation under load disturbance. Whereas the sliding mode controller has high precision and strong robustness in steady state and during transient phases. The system simulation is performed using MATLAB/SIMULINK.

A Comparative Analysis of The New Excitation Controlled Synchronous Generator-Based Wind Turbine

Excitation Controlled Synchronous Generator-based Wind Turbine (ECSG WT) is a recently proposed wind turbine scheme which has not been fully investigated in detail. This paper is devoted to analyze performance of the ECSG WT scheme and to compare it with two mainstream wind turbine schemes based on electrically excited synchronous generator, i.e. VSC-based full converter wind turbine and diode bridge rectifier-based wind turbine equipped with boost converter on its DC link. The aim of this comparison is to demonstrate great potentials of ECSG WT for being considered in wind industry. To do so, two successful WT schemes at the market which are structurally close to ECSG WT are selected. The comparison includes different technical and economic aspects of the three schemes, assuming DC grid connection for the wind turbines. In addition, another comparison is made between the recently introduced Siemens 2nd generation DC Grid Access Offshore wind farm and a wind farm with similar structure, but using ECSG WTs. The results of these comparisons declare that ECSG WT scheme has promising characteristics, especially regarding economic, reliability and efficiency aspects.

Switching Fault Ride-Through of GSCs Via Observer-Based Bang–Bang Funnel Control

This letter proposes a switching-fault ride-through controller (SFRTC) for the grid-side converter of permanent magnetic synchronous generator-based wind turbines. The SFRTC switches between an observer-based bang-bang funnel controller (OBFC) and a vector controller via a state-dependent switching scheme. The design of OBFC does not rely on accurate system information, and it works with the estimates of high-order dynamics of system outputs obtained with a high-gain observer. The fault ride-through control performance of SFRTC was studied with hardware-in-the-loop experiments.

Design and implementation of a fractional nonlinear synergetic controller for generator and grid converters of wind energy conversion system

In this paper, a fractional nonlinear synergetic controller is developed for efficient power extraction and operation of a variable speed wind energy conversion system. The proposed fractional nonlinear synergetic control scheme includes: (1) rotational speed regulation for maximum power extraction at the generator converter side through the DC-DC boost converter; (2) DC link voltage regulation and active-reactive power regulation, by controlling the direct-quadratic components of the current, for power transfer at unity power factor, at the grid side converter through the inverter. Analytical design of aggregated regulator has been used in the nonlinear synergetic control design with the introduction of a fractional macro-variable in order to increase the degree of freedom of the classical synergetic controller. The stability of the closed loop system using the macro-variable is guaranteed and a fast convergence can be reached through the design parameter. Experimentation, on a permanent magnet synchronous generator based wind turbine setup, is conducted to validate the proposed fractional nonlinear synergetic control system for operating the generator and the grid sides of the power system. Different cases are studied and the experimental results have shown that the system controlled by the proposed control method is stable and tracks perfectly the desired reference.

Dynamic Aggregation Modeling of Grid-Connected Inverters Using Hamilton's-Action-Based Coherent Equivalence

The high penetration of renewable energy generation (REG) systems influences the dynamics of power systems. Accurate transient simulations and dynamic models are indispensable for the research on the dynamic behavior of REG systems. A large-scale REG system consisting of numerous grid-connected inverters consumes a large amount of computation time, so a dynamic aggregated model is needed for efficient simulation. The aggregated model established by coherent equivalence fits the detailed model well, and thus it is widely used in the aggregation of large-scale dynamic systems. Presently, the key challenge of the application of the coherent-equivalence method is to identify inverters that have similar dynamic characteristics. The Hamilton principle expressed by Hamilton's action has a simple form and indicates the comprehensive dynamic characteristics of inverters. Thus, this paper proposes a coherent-equivalence method of inverters based on Hamilton's action. The proposed method is applied to a wind farm of 16 permanent magnet synchronous generator-based wind turbines for demonstration. Compared with the existing equivalence method without considering coherency, the proposed method shows advantages in effectiveness and accuracy.

Optimal reactive power dispatch of permanent magnet synchronous generator-based wind farm considering levelised production cost minimisation

As wind power penetration increases, large wind farms (WFs) need to provide reactive power according to modern grid codes. Permanent magnet synchronous generator-based wind turbines (WTs) can generate reactive power, by assigning the appropriate reactive power to each WT to meet the reactive power requirements of the grid. This is a more economical method than setting up additional reactive power compensation equipment. This study proposes an optimal reactive power dispatch strategy for minimising a levelised production cost, and is implemented in two ways: minimising the power loss of a WF, and maximising the lifetime of WTs. The reactive power references of each WT are chosen as the optimisation variables, and a particle swarm optimisation algorithm is adopted to solve the optimisation problem. The proposed and traditional reactive power dispatch strategies are demonstrated and compared on a WF with 25 WTs to validate the effectiveness of the proposed approach.

Coordinated Control Strategies of PMSG-Based Wind Turbine for Smoothing Power Fluctuations

High penetration of wind energy in the modern power system exposes the need of smoothing the fluctuating output power in an effective and conducive way. In this context, this paper proposes two novel control strategies that utilize the self-capability of permanent magnet synchronous generator-based wind turbine to realize power smoothing. The first strategy pursues to offer power smoothing support via simultaneous utilization of dc-link voltage control, rotor speed control, and pitch angle control. The second control strategy seeks to coordinate the three concerned individual control schemes in a hierarchical manner, where the power smoothing tasks are allocated to individual control modules or their combinations dynamically in line with WT's operation status. Both two strategies are able to provide power smoothing support by fully exploiting wind turbine's self-capability, whereas the second strategy has the merits on 1) reducing the activation frequency of pitch angle control, and 2) enhancing wind energy harvesting. Case studies of the proposed control strategies are carried out to compare and verify their effectiveness in achieving power smoothing.

Enhanced Frequency Support From a PMSG-Based Wind Energy Conversion System Integrated With a High Temperature SMES in Standalone Power Supply Systems

In a small standalone power supply system containing renewable energy, the frequency response is usually supported during frequency excursion by the conventional generators only. This may result in a less effective recovery of the system frequency in a wind energy dominant standalone system. The support from the wind turbine in the frequency regulation will significantly improve the recovery performance. However, the natural inertia of the variable speed wind turbine is very small compared to that of the conventional generators. Therefore, a fast responding energy storage can significantly improve the frequency response capability. In this paper, a control technique has been proposed to utilize the superconducting magnetic energy storage to be integrated with the permanent magnet synchronous generator based wind turbine to improve the power system frequency regulation and the results are found to be promising.

Design of robust MPPT controller for grid-connected PMSG-Based wind turbine via perturbation observation based nonlinear adaptive control

This paper presents a robust maximum power point tracking (MPPT) control scheme for a grid-connected permanent magnet synchronous generator based wind turbine (PMSG-WT) using perturbation observation based nonlinear adaptive control. In the proposed control scheme, system nonlinearities, parameter uncertainties, and external disturbances of the PMSG-WT are represented as a lumped perturbation term, which is estimated by a high-gain perturbation observer. The estimate of the lumped perturbation is employed to compensate the actual perturbation and further achieve adaptive feedback linearizing control of the original nonlinear system, without requiring the detailed system model and full state measurements. The effectiveness of the proposed control scheme is verified through both simulation studies and experimental tests. The results show that, compared with the conventional vector controller and the standard feedback linearizing controller, the proposed control strategy provides higher power conversion efficiency and has better dynamic performances and robustness against parameter uncertainties and external disturbances.

Comprehensive frequency regulation scheme for permanent magnet synchronous generator‐based wind turbine generation system

Due to a growing penetration of permanent magnet synchronous generator-based wind turbine generation (PMSG-WTG) systems into the modern power grid, there is a strong interest in leveraging the potential capabilities of PMSG-WTG system to participate in the system frequency regulation during the grid event. In this work, a novel comprehensive frequency regulation (CFR) scheme is proposed specifically for rotor-speed-control-oriented PMSG-WTG systems. The step-wise inertial power response enables PMSG to perform the temporary frequency support. The rotor speed and pitch angle controllers are coordinated to curtail the wind power output for the persistent de-loaded operation, which can facilitate the primary frequency regulation through the variable-slope droop control. Furthermore, this CFR control scheme is implemented into the controls advanced research turbine 2 (CART2)-PMSG model, so as to investigate its potential impact on the structural loads of wind turbine. Simulation results show CFR can dramatically enhance overall frequency regulation capability of the PMSG-WTG's system and mitigate the frequency oscillations over a full range of wind speeds without causing large mechanical damages to the wind turbine.

Combined Primary Frequency Control Strategy of Permanent Magnet Synchronous Generator-Based Wind Turbine

To ensure the proper operation of power system, some independent system operators have specified that wind power plants should be able to manipulate power output for frequency control. This article presents a combined control scheme which exploits the self-capability of permanent magnet synchronous generator-based wind turbine to provide primary frequency response. Under normal condition, the wind turbine operates in de-loading mode to obtain the power reserve. Once frequency deviation is detected, the proposed control strategy can not only make use of the power reserve for frequency regulation by adjusting the rotor speed, but utilize the kinetic energy in rotor to provide frequency response as well. Besides, the energy stored in DC capacitor is also employed for frequency support. The simulation results reveal that the wind turbines with the proposed method can improve frequency performance under both constant wind speed condition and variable wind speed condition.

A Novel PI-Type Sliding Surface for PMSG-Based Wind Turbine With Improved Transient Performance

This paper presents the design, implementation, and performance testing of integral sliding mode control (ISMC) for a permanent magnet synchronous generator based wind turbine. More specifically, ISMC is combined with a feedback linearization (FBL) technique to recover its transient performance under model uncertainty and external disturbances. In this paper, we simplified the integral sliding surface structure to make it more convenient for real-time implementation. It turns out that the resulting integral sliding surface has a PI-like structure plus an additional part that has the role of preserving the nominal transient performance of the FBL. This key feature of the proposed PI-type sliding surface (PI-type SS) cannot be achieved under the conventional PI-type SS. Simulation and experimental tests are carried out to show the effectiveness of the proposed approach. The results revealed that the proposed PI-type SS is able to remove the steady-state error and retain the nominal transient performance of the FBL despite the presence of model uncertainty.

An Enhanced Control Scheme for an IPM Synchronous Generator Based Wind Turbine With MTPA Trajectory and Maximum Power Extraction

This paper proposes an enhanced control scheme for a direct drive variable speed wind turbine with an interior permanent magnet (IPM) synchronous generator. The proposed control scheme incorporates maximum torque per ampere (MTPA) trajectory and maximum power extraction, which ensures the generation of required torque for maximum power extraction with minimum stator current. This in turn minimizes stator copper loss and excessive heat generated in the IPM synchronous generator. The performance of the proposed control scheme has been validated through rigours simulation and experimental studies under varying wind speed conditions. The simulation and experimental results demonstrate the efficacy of the proposed control method.

Active Power Control of Grid-connected Permanent Magnet Synchronous Generator-based Wind Turbines in the Presence of Voltage Sags

This paper deals with the issue of active power control of power electronic converters and permanent magnet synchronous generator (PMSG)-based wind turbine (WT) during both balanced and unbalanced voltage sags. The paper first analyzes the adverse effects of voltage sags on WT systems and then proposes a new control strategy. The strategy consists of (i) a vector current control, which utilizes the feed-forward of the negative-sequence voltage (VCCF) to eliminate the effect of negative-sequence components during unbalanced voltage sags; and (ii) a power compensation factor control for the VCCF to maintain the balanced power flow from the WT to the grid irrespective of voltage sag. The latter also maintains the WT system's output currents within their safe limits to avoid potential damage to electronic components in the inverter. Unlike conventional control strategies, the proposed scheme allows the WT system to use optimally sized converters without the need of large DC link capacitors and crowbars. The effectiveness of the control strategy has been validated experimentally on a physical WT testing platform.