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New challenges regarding system stability and efficiency arise when power systems operate with a high penetration level of inverter‐based renewable sources (IBRSs) and few synchronous generators. Since IBRSs have been on the rise, to secure the stable operation of future power systems, IBRSs will be required to support systems without having to rely on remaining synchronous generators. Also, to efficiently manage the uncertainty of renewable production, power‐to‐gas technology can provide the required flexibility. This study proposes modelling and a control coordination scheme (CCS) of a wind‐to‐hydrogen (W2H) set to optimise electricity production from a variable‐speed wind turbine generator (WTG) while helping balance between supply and demand in a system. To achieve this, a grid‐forming (GFM) inverter‐based WTG is modelled and a set of electrolyser and fuel cell is integrated at the DC circuit of a GFM‐WTG to be coordinated. Furthermore, the CCS offers an opportunity to reduce the investment cost for deploying a W2H set by utilising the control capabilities of a WTG and reducing the need for an additional device. The performance of the proposed W2H set with the CCS was verified considering the variations in system load and wind speed by using Power System Computer Aided Design (PSCAD)/ElectroMagnetic Transients including Direct Current (EMTDC). [ABSTRACT FROM AUTHOR]

This paper presents a novel simulation approach to evaluate new ancillary service controls in the context of large-scale wind power integration. We adopt and compare different types of turbine inertial control methods with the proposed modifications to cope with realistic wind conditions in the field. The simulation procedure is started with the software-based simulation, in which we employ the high-fidelity wind turbine simulator FAST that models a real three-bladed controls advanced research turbine (CART3). The advantages of using FAST are that it can provide convincing simulation results and address the interactions between turbine electrical and mechanical systems. The developed controller model is then rapidly prototyped for the real-time simulation with the hardware-in-the-loop scheme. CART3 will respond to a virtual frequency event triggered in the emulated electric grid modeled in a digital real-time simulator. The introduced simulation platform streamlines the procedure of designing turbine auxiliary controls, and these simulations results give insights on the turbine controls and their impacts on the interconnected power system, as well as the effects on turbine mechanical components. For example, the results indicate that the inertial controls tend to reduce the out-of-plane mechanical loadings in region 2, while such loadings are dominated by the pitch actions in region 3. [ABSTRACT FROM AUTHOR]

This paper presents the design considerations and analysis of a double-sided transverse flux machine (TFM) for direct-drive wind turbine applications. The proposed TFM has a modular structure with quasi U-core stators and toroidal ring windings. The rotor is designed with ferrite magnets in a flux-concentrating setup to achieve high air gap flux density. This paper presents the different aspects of the TFM, taking into consideration the critical geometric parameters affecting the back-EMF waveform, phase inductance, torque density, and power factor. Three-dimensional finite element analysis (3D-FEA) was used to analyze and optimize the critical TFM design parameters to meet the performance specification. A proof-of-concept prototype was developed based on the proposed design considerations. The prototype was experimentally tested at different operating points and the results showed good correlation with the 3D-FEA results. [ABSTRACT FROM AUTHOR]

This paper proposes a temporary frequency-support scheme of a doubly fed induction generator (DFIG) that can improve the frequency nadir while ensuring rapid frequency stabilization, particularly for high wind power penetration levels (WPPLs). Upon detecting a disturbance, the power reference is increased by the incremental power and maintained for a preset period. The proposed incremental power varies with the rotor speed and WPPL. Then, to force the rotor speed to converge to a stable operating range, the reference decreases with the rotor speed. During the deceleration period, the proposed scheme releases less kinetic energy, which helps in the rapid recovery of the rotor speed. During the acceleration period, to accelerate the rotor speed recovery, the reference smoothly decreases with time and rotor speed until it reaches the maximum power point tracking curve. The test results, which are based on the IEEE 14-bus system, demonstrate that even though less kinetic energy is released, the proposed scheme can improve the frequency nadir while rapidly recovering the rotor speed under various wind conditions and penetration levels, but it is particularly effective for higher penetration levels. The scheme helps providing a promising solution to the ancillary services of a DFIG in a power system with high WPPLs. [ABSTRACT FROM PUBLISHER]

To mitigate the degraded power system inertia and undesirable primary frequency response caused by large‐scale wind power integration, the frequency support capabilities of variable‐speed wind turbines is studied in this work. This is made possible by controlled inertial response, which is demonstrated on a research turbine – controls advanced research turbine, 3‐bladed (CART3). Two distinct inertial control (IC) methods are analysed in terms of their impacts on the grids and the response of the turbine itself. The released kinetic energy in the IC methods are determined by the frequency measurement or shaped active power reference in the turbine speed–power plane. The wind turbine model is based on the high‐fidelity turbine simulator fatigue, aerodynamic, structures and turbulence, which constitutes the aggregated wind power plant model with the simplified power converter model. The IC methods are implemented over the baseline CART3 controller, evaluated in the modified 9‐bus and 14‐bus testing power grids considering different wind speeds and different wind power penetration levels. The simulation results provide various insights on designing such kinds of ICs. The authors calculate the short‐term dynamic equivalent loads and give a discussion about the turbine structural loadings related to the inertial response. [ABSTRACT FROM AUTHOR]

With increasing integrations of large-scale systems based on permanent magnet synchronous generator wind turbine generators (PMSG-WTGs), the overall inertial response of a power system will tend to deteriorate as a result of the decoupling of rotor speed and grid frequency through the power converter as well as the scheduled retirement of conventional synchronous generators. Thus, PMSG-WTGs can provide value to an electric grid by contributing to the system's inertial response through the inherent kinetic energy stored in their rotating masses and fast power converter control. In this study, an improved inertial control method based on the maximum power point tracking operation curve is introduced to enhance the overall frequency support capability of PMSG-WTGs in the case of large supply-demand imbalances. Moreover, this method is implemented in the CART2-PMSG integrated model in MATLAB/Simulink to investigate its impact on the wind turbine's structural loads during the inertial response process. Simulation results indicate that the proposed method can effectively reduce the frequency nadir, arrest the rate of change of frequency, and alleviate the secondary frequency dip while imposing no negative impact on the major mechanical components of the wind turbine. [ABSTRACT FROM AUTHOR]

With increasing integrations of large‐scale systems based on permanent magnet synchronous generator wind turbine generators (PMSG‐WTGs), the overall inertial response of a power system will tend to deteriorate as a result of the decoupling of rotor speed and grid frequency through the power converter as well as the scheduled retirement of conventional synchronous generators. Thus, PMSG‐WTGs can provide value to an electric grid by contributing to the system's inertial response through the inherent kinetic energy stored in their rotating masses and fast power converter control. In this study, an improved inertial control method based on the maximum power point tracking operation curve is introduced to enhance the overall frequency support capability of PMSG‐WTGs in the case of large supply–demand imbalances. Moreover, this method is implemented in the CART2‐PMSG integrated model in MATLAB/Simulink to investigate its impact on the wind turbine's structural loads during the inertial response process. Simulation results indicate that the proposed method can effectively reduce the frequency nadir, arrest the rate of change of frequency, and alleviate the secondary frequency dip while imposing no negative impact on the major mechanical components of the wind turbine. [ABSTRACT FROM AUTHOR]

For the fixed-gain inertial control of wind power plants (WPPs), a large gain setting provides a large contribution to supporting system frequency control, but it may cause over-deceleration for a wind turbine generator that has a small amount of kinetic energy (KE). Further, if the wind speed decreases during inertial control, even a small gain may cause over-deceleration. This paper proposes a stable inertial control scheme using adaptive gains for a doubly fed induction generator (DFIG)-based WPP. The scheme aims to improve the frequency nadir (FN) while ensuring stable operation of all DFIGs, particularly when the wind speed decreases during inertial control. In this scheme, adaptive gains are set to be proportional to the KE stored in DFIGs, which is spatially and temporally dependent. To improve the FN, upon detecting an event, large gains are set to be proportional to the KE of DFIGs; to ensure stable operation, the gains decrease with the declining KE. The simulation results demonstrate that the scheme improves the FN while ensuring stable operation of all DFIGs in various wind and system conditions. Further, it prevents over-deceleration even when the wind speed decreases during inertial control. [ABSTRACT FROM PUBLISHER]

This paper addresses a modeling and analysis methodology for investigating the stochastic harmonics and resonance concerns of wind power plants (WPPs). Wideband harmonics from modern wind turbines (WTs) are observed to be stochastic, associated with real power production, and they may adversely interact with the grid impedance and cause unexpected harmonic resonance, if not comprehensively addressed in the planning and commissioning of the WPPs. These issues should become more critical as wind penetration levels increase. We thus propose a planning study framework comprising the following functional steps: First, the best fitted probability density functions (PDFs) of the harmonic components of interest in the frequency domain are determined. In operations planning, maximum likelihood estimations (MLEs) followed by a chi-square test are used once field measurements or manufacturers' data are available. Second, harmonic currents from the WPP are represented by randomly-generating harmonic components based on their PDFs (frequency spectrum) and then synthesized for time domain simulations via inverse Fourier transform. Finally, we conduct a comprehensive assessment by including the impacts of feeder configurations, harmonic filters and the variability of parameters. We demonstrate the efficacy of the proposed study approach for a 100-MW offshore WPP consisting of 20 units of 5-MW full converter turbines, a realistic benchmark system adapted from a WPP under development in Korea and discuss lessons learned through this research. [ABSTRACT FROM AUTHOR]

If a large disturbance occurs in a power grid, two auxiliary loops for the inertial control of a wind turbine generator have been used: droop loop and rate of change of frequency (ROCOF) loop. Because their gains are fixed, difficulties arise in determining them suitable for all grid and wind conditions. This paper proposes a dynamic droop-based inertial control scheme of a doubly-fed induction generator (DFIG). The scheme aims to improve the frequency nadir (FN) and ensure stable operation of a DFIG. To achieve the first goal, the scheme uses a droop loop, but it dynamically changes its gain based on the ROCOF to release a large amount of kinetic energy during the initial stage of a disturbance. To do this, a shaping function that relates the droop to the ROCOF is used. To achieve the second goal, different shaping functions, which depend on rotor speeds, are used to give a large contribution in high wind conditions and prevent over-deceleration in low wind conditions during inertial control. The performance of the proposed scheme was investigated under various wind conditions using an EMTP-RV simulator. The results indicate that the scheme improves the FN and ensures stable operation of a DFIG. [ABSTRACT FROM PUBLISHER]

This paper investigates the potential for wind power plants (WPPs) to damp interarea modes. Interarea modes may be the result of a single or a group of generators oscillating against another group of generators across a weak transmission link. If poorly damped, these power system oscillations can cause system instability and potentially lead to blackouts. Power conversion devices, particularly, megawatt-scale converters that connect wind turbines and photovoltaic power plants to the grid, could be used to damp these oscillations by injecting power into the system out of phase with the potentially unstable mode. In our model, this power may be provided by a WPP. Over time, the net energy injection is near zero; therefore, providing this static damping capability is not expected to affect the energy production of a WPP. This is a measurement-based investigation that employs simulated measurement data. It is not a traditional small-signal stability analysis based on Eigenvalues and knowledge of the power system network and its components. Kundurs well-known two-area, four-generator system and a doubly fed induction generator (DFIG)-based WPP are modeled in PSCAD/EMTDC. The WPP model is based on the Western Electricity Coordination Council (WECC) standard model. A controller to damp interarea oscillations is added to the WECC DFIG model, and its effects are studied. Analysis is performed on the data generated by the simulations. The sampling frequency is set to resemble the sampling frequency at which data are available from phasor measurement units in the real world. The YuleWalker algorithm is used to estimate the power spectral density of these signals. [ABSTRACT FROM PUBLISHER]

A wind power plant (WPP) is different from a conventional power plant in the sense that a WPP may consist of hundreds of small (e.g., 1.5-MW) wind turbine generators (WTGs), whereas a conventional power plant may consist of one or several large generators. Common practice in power system planning to simulate a WPP is to use a single-turbine representation. However, it is important to realize that the response of a single-turbine representation is not the response of an individual turbine; instead, it represents the collective behavior of a WPP. In this paper, we present our experience in validating WPP from available measured data. We investigate the discrepancies between the simulation results and the actual measurement, and we examine the probable causes of these discrepancies. Finally, we offer methods to validate WPP dynamic model to better match the simulation result to the measured data. Understanding the nature of a WPP and the meaning of WPP equivalency is very important to determine the representation of a WPP. [ABSTRACT FROM PUBLISHER]

Wind turbine drivetrains consist of components that directly convert kinetic energy from the wind to electricalenergy. Therefore, guaranteeing robust and reliable drivetrain designs is important to prevent turbine downtime. Currentdrivetrain models often lack the ability to model both the impacts of electrical transients as well as wind turbulenceand shear in one package. In this paper, the capability of the FAST wind turbine computer-aided-engineering tool,developed by the National Renewable Energy Laboratory, is enhanced through the integration of a dynamic model of thedrivetrain. The dynamic drivetrain model is built using Simscape in the MATLAB/Simulink environment and incorporatesdetailed electrical generator models. This model can be used to evaluate internal drivetrain loads due to excitationsfrom both the wind and generator. [ABSTRACT FROM AUTHOR]

The goal of this paper is to describe the approach in designing and constructing wind power laboratory experiments for undergraduate- and graduate-level courses in power and energy systems. These are separated into basic hands-on laboratory and advanced simulation-based experiments. The basic experiments are integrated into an undergraduate course that includes topics such as the steady-state operation of induction machines, fixed-speed, and variable-speed wind turbines. Advanced experiments are integrated into a stand-alone course dedicated to wind energy and power systems. Topics include the modeling of aerodynamic, mechanical, and electrical components for each type of wind turbine along with their steady-state and dynamic operations. The experiments were originally designed at the University of Texas at Austin. Their transferability to a different laboratory platform at the University of Texas Pan American is also discussed. [ABSTRACT FROM PUBLISHER]

Wind measurements for identifying and characterizing wind resources require instrumentation and analysis techniques for defining signal processing features for gusts, turbulence, and inflow winds. This paper describes the importance of those features for determining responses of wind turbines. In addition, when the system is deployed, the instrumentation that must be coordinated to manage the utility connection requirements, such as assessing reactive power supply, fault ride-through, and power quality monitoring, is also discussed. The control schemes for wind energy generation systems are discussed and associated with the system signal processing required to control active power generation. [ABSTRACT FROM PUBLISHER]

To accommodate the wind power fluctuations, a hybrid energy storage system (HESS) consisting of a battery energy storage system (BESS) and a supercapacitor is evaluated in this paper. A probabilistic approach for economically determining the power capacity specification for the HESS is proposed. This method would allow the capacities of the BESS and the supercapacitor to be properly designed to optimize the characteristics of high energy density of the BESS and high power density of the supercapacitor. Results show that the supercapacitor within the HESS helps to process the high frequency fluctuations, which contributes to the extension of the BESS lifetime. In addition, the supercapacitor helps to address the peaks in wind power fluctuations without the severe penalty of round-trip losses associated with a BESS. The proposed approach has been simulated using real wind data from an existing wind power plant in Iowa. [ABSTRACT FROM PUBLISHER]

A wind power plant (WPP) consists of a large number of turbines interconnected by underground cable. A pad-mounted transformer at each turbine steps up the voltage from a generating voltage (690 V) to a medium voltage (34.5 kV). All turbines in the plant are connected to the substation transformer, where the voltage is stepped up to the transmission level. An important aspect of WPP impact studies is to evaluate the short-circuit (SC) current contribution of the plant into the transmission network under different fault conditions. This task can be challenging to protection engineers due to the topology differences between different types of wind turbine generators and the conventional generating units. This paper investigates the SC behavior of a WPP for different types of faults. The impact of wind turbine types, the transformer configuration, and the reactive compensation capacitor will be investigated. The voltage response at different buses will be observed. Finally, the SC line currents will be presented along with its symmetrical components. [ABSTRACT FROM AUTHOR]

With the advent of power electronics, the size, weight, and cost of power converters have been drastically reduced while efficiency is improved. The use of variable-speed wind power generators has seen considerable growth. The use of gearboxes in the wind turbines allows for smaller size, lower weight, and higher speed generators. However, gearboxes have shown to be one of the least reliable components of the wind turbines. In this paper, we propose a method that can extend the life and reliability of wind turbine gearboxes by reducing the mechanical stress on gearbox components. Reduction of mechanical stress is achieved by the generator torque control that minimizes resonant torsional vibrations within a drivetrain caused by variations in wind velocity. A detailed model for the drivetrain of a 750-kW wind turbine, including a gearbox is presented. Experimental results are used to calculate the parameters of the gearbox. A controller is designed to adjust the generator torque at the end of the drivetrain to remove the unwanted and damaging torque variations from the drivetrain. Simulation results verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper summarizes the work of the Ad Hoc Task Force on Wind Generation Model Validation. The paper describes the concept of model validation, how this applies to wind turbine generation systems, and then gives clear examples of the most recent efforts to achieve model validation for wind turbine power plants. The document ends with a summary of the learning from the work presented and the conclusions which can be derived. Recommendations are made on the path forward for wind turbine generator modeling and model validation, primarily focused on generic models (i.e., standardized and publicly available) for stability analysis in power system studies. [ABSTRACT FROM PUBLISHER]

A doubly fed induction generator wind turbine is a variable-speed wind turbine widely used in the modern wind power industry. Unlike a fixed-speed wind turbine, the maximum power extraction of the turbine is affected by (1) electrical characteristics of the generator, (2) aerodynamic characteristics of the turbine blades, and (3) maximum power extraction control strategies. This article presents a doubly fed induction generator maximum power extraction study through the integrated steady-state and transient close-loop control evaluation approach so as to benefit the development of enhanced peak power tracking control techniques for variable-speed wind turbines. The generator characteristics are examined for different d-q control conditions; the peak power tracking and extracted wind power characteristics of the turbine blades versus generator slip are presented. Then, all three characteristics are analyzed in a joint environment to investigate doubly fed induction generator maximum power extraction principles. A nested current- and speed-loop control structure is developed using the stator-flux-oriented frame, which is then used to evaluate factors that may affect doubly fed induction generator peak power tracking control performance. Simulation studies are conducted to investigate how doubly fed induction generator maximum power extraction is influenced by wind turbine electrical and aerodynamic characteristics, different peak power tracking control designs, and variable and gusting winds. [ABSTRACT FROM AUTHOR]

With the advance of power electronics, direct-driven permanent magnet synchronous generators have drawn increased interest to wind turbine manufacturers due to its advantages over other variable-speed wind turbines. This article studies permanent magnet synchronous generator characteristics under the general d-q control strategy in the rotor-flux-oriented frame so as to benefit the development of advanced permanent magnet synchronous generator control technology. Compared to traditional approaches, the specific features of the article are (1) a steady-state permanent magnet synchronous generator model in a d-q reference frame, (2) a simulation mechanism that reflects the general permanent magnet synchronous generator d-q control strategy, (3) an integrative study that combines generator-converted power with extracted wind power characteristics, and (4) a joint investigation incorporating both steady-state and transient evaluations. Extensive simulation-based analysis is conducted to study how permanent magnet synchronous generator characteristics are affected by different d-q control conditions and are interacted with wind power drive characteristics in power generation and speed regulation of a permanent magnet synchronous generator wind turbine. [ABSTRACT FROM AUTHOR]

A self-excited induction generator (SEIG) is very simple and robust, has a reduced unit size, is easy to implement and simple to control, and requires very little maintenance compared to other types of generators. In variable operating conditions, the SEIG requires a power electronics interface to transform from the variable frequency voltage output of the generator to a battery voltage output or the related applications. In our study, we tied the SEIG to the power electronics system comprising a diode rectifier and DC/DC converter, and then a final DC load for fuel cell applications was connected. An example of such an application is an electrolyzer where an equivalent circuit is modeled for use in this study. To accomplish the proposed system, we utilized PSCAD and MATLAB for its simulation, control, and analysis. A new system configuration considering three different wind speeds and breaker conditions is modeled and analyzed. The results show that the suggested strategies in this study would contribute to designing and analyzing a more practical power electronics interface system for a wind turbine generator with a DC load. [ABSTRACT FROM AUTHOR]

In this paper, we illustrate the effect of adding a hypothetical 100-MW doubly fed induction generator (DFIG) wind power plant to a weak transmission system. The effects of various wind plant load factors (100, 60 and 25% of nameplate rating) are investigated. System performance is compared to a 100-MW conventional synchronous generator interconnected at the same location. The conventional generator is installed some distance away. The simulations demonstrated that DFIG generators provide a good damping performance under these conditions. These results support the conclusion that modern wind power plants, equipped with power electronics and low-voltage ride-through capability, can be interconnected to weak power grids without reducing stability. To conduct the studies, we selected an area of the Western Electricity Coordinating Council power system that is electrically far from major generation centers and is weakly connected to the bulk transmission system. The area contains large motor loads. We observed the dynamic response of large motors in the vicinity, especially their ability to ride through fault events. The studies were conducted using positive sequence phasor time-domain analysis. [ABSTRACT FROM AUTHOR]

Presents a study that analyzed a hybrid power system consisting of wind turbines, diesel generators, and a local load. System configuration; Impact of wind power on the entire system; Effect of the start up of the wind turbine on the system.

Examines the zero sequence method for energy recovery from a variable speed wind turbine generator. Output of the unity power factor; Control techniques in capturing the variable-speed wind turbine; Presentation of the simulation and experimental verification.

Discusses a study which applied a combination of modular, axial flux and torroidal stator winding to a permanent-magnet (PM) generators used for wind turbines. Components of the generator; Design analysis of the generator; Conclusion.

Discusses the method in determining the annual energy production of a wind turbine. Calculation of annualized energy; Variable speed turbine control; Energy production with constant speed turbines; Energy production with variable-speed wind system.

The main objective of this special issue is to collect and disseminate publications that highlight recent advances and breakthroughs in the area of renewable energy resources. The use of these resources for production of electricity is increasing rapidly worldwide. As of 2015, a majority of countries have set renewable electricity targets in the 10%?40% range to be achieved by 2020?2030, with a few notable exceptions aiming for 100% generation by renewables. We are experiencing a truly unprecedented transition away from fossil fuels, driven by environmental, energy security, and socio-economic factors.Electric machines can be found in a wide range of renewable energy applications, such as wind turbines, hydropower and hydrokinetic systems, flywheel energy storage devices, and low-power energy harvesting systems. Hence, the design of reliable, efficient, cost-effective, and controllable electric machines is crucial in enabling even higher penetrations of renewable energy systems in the smart grid of the future. In addition, power electronic converter design and control is critical, as they provide essential controllability, flexibility, grid interface, and integration functions. [ABSTRACT FROM AUTHOR]

Not much more than a decade ago, the desired action for a wind generation facility was to shut down or disconnect electrically in the event of a disruption on the bulk electric system. This, of course, was a reflection of the novelty that was wind generation at the time, as well as prudent engineering judgment, as the loss of a small amount of generation—the wind plants that were in service at the time—posed little risk to system reliability. [ABSTRACT FROM PUBLISHER]

Highlights: [•] Type 2 WTs are perceived unable to contribute to power system stability. [•] IEEE FBM for SSR studies is modified with an aggregate Type 2 WPP model for the study. [•] Simple damping control scheme for Type 2 WT based on WAMS as input signal is proposed. [•] Simulation results show promising performance of Type 2 WPP for SSR mitigation. [Copyright &y& Elsevier]