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This paper proposes a frequency‐control scheme for Doubly Fed Induction Generator (DFIG)‐based (Type‐3) wind turbines to improve the primary‐frequency‐control when the grid power balance is disturbed. The increasing penetration level of renewable energy sources, like wind power plants, reduces the total available inertia of modern grids, which deteriorate the frequency response in case of sudden power‐mismatches. The proposed closed‐loop participation of wind power plant interacts with the thermal units to reduce the frequency nadir and frequency settling‐time, during the inertial and primary stages. The designed disturbance observer decreases the uncertainties in the estimation of grid parameters, which results in robust PI performance in adjusting the ancillary power provided by wind turbines. Certain measures considered within the control loop to limit the rate‐of‐change‐of‐frequency within the permissive range to avoid the protective relays tripping. Comparative simulations studies on modified IEEE 9‐bus and 68‐bus test systems verify the effectiveness and advantages of the proposed method. [ABSTRACT FROM AUTHOR]

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]

As the deployment of wind and solar energy increases in the USA, energy storage (ES) will play an important role in future electric power grids to help manage the variability from high penetration levels of renewable generation, ES can provide promising power/energy demand to coordinate with renewables generation, as a virtual power plant (VPP). There is an industry need for the capability in power system studies to model ternary pumped storage hydropower (T-PSH), a pumped storage technology that offers increased system benefits. This study presents a comprehensive vendor-neutral dynamic model of T-PSH in GE's commercial software positive sequence load flow. A new governor model is developed with detailed gate valve modelling and a shared-penstock function. Specifically, this model is designed to simulate the seamless transition among three operation modes: generation mode, pumping mode, and hydraulic short-circuit mode. The developed T-PSH model has been tested and validated on a 10-bus test system. A comparison study of T-PSH to conventional pumped storage hydropower has also been conducted on the Western interconnection system. [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]

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]

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]

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]

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]

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.

Investigates the methods used to adjust the aerodynamic power of pitch control and generator load control both employed to regulate the operation of wind turbines. Characteristics of wind turbines; Wind turbine power generation; Overall control strategy.

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.

This paper has a two pronged objective: the first objective is to analyze the general effects of wind power plant (WPP) integration and the resulting displacement of conventional power plant (CPP) inertia on power system stability and the second is to demonstrate the efficacy of PMU data in power system stability analyses, specifically when knowledge of the network is incomplete. Traditionally modal analysis applies small signal stability analysis based on Eigenvalues and the assumption of complete knowledge of the network and all of its components. The analysis presented here differs because it is a measurement-based investigation and employs simulated measurement data. Even if knowledge of the network were incomplete, this methodology would allow for monitoring and analysis of modes. This allows non-utility entities and study of power system stability. To generate inter- and intra-area modes, Kundur’s well-known two-area four-generator system is modeled in PSCAD/EMTDC. A doubly-fed induction generator based WPP model, based on the Western Electricity Coordination Council (WECC) standard model, is included to analyze the effects of wind power on system modes. The two-area system and WPP are connected in various configurations with respect to WPP placement, CPP inertia and WPP penetration level. Analysis is performed on the data generated by the simulations. For each simulation run, a different configuration is chosen and a large disturbance is applied. The sampling frequency is set to resemble the sampling frequency at which data is available from phasor measurement units (PMUs). The estimate of power spectral density of these signals is made using the Yule–Walker algorithm. The resulting analysis shows that the presence of a WPP does not, of itself, lead to the introduction of new modes. The analysis also shows however that displacement of inertia may lead to introduction of new modes. The effects of location of inertia displacement (i.e. the effects on modes if WPP integration leads to displacement of inertia in its own region or in another region) and of WPP controls such as droop control and synthetic inertia are also examined. In future work, the methods presented here will be applied to real-world phasor data to examine the effects of integration of variable generation and displacement of CPP inertia on inter- and intra-area modes. [ABSTRACT FROM AUTHOR]

Traditionally, inertia in power systems has been determined by considering all the rotating masses directly connected to the grid. During the last decade, the integration of renewable energy sources, mainly photovoltaic installations and wind power plants, has led to a significant dynamic characteristic change in power systems. This change is mainly due to the fact that most renewables have power electronics at the grid interface. The overall impact on stability and reliability analysis of power systems is very significant. The power systems become more dynamic and require a new set of strategies modifying traditional generation control algorithms. Indeed, renewable generation units are decoupled from the grid by electronic converters, decreasing the overall inertia of the grid. 'Hidden inertia', 'synthetic inertia' or 'virtual inertia' are terms currently used to represent artificial inertia created by converter control of the renewable sources. Alternative spinning reserves are then needed in the new power system with high penetration renewables, where the lack of rotating masses directly connected to the grid must be emulated to maintain an acceptable power system reliability. This paper reviews the inertia concept in terms of values and their evolution in the last decades, as well as the damping factor values. A comparison of the rotational grid inertia for traditional and current averaged generation mix scenarios is also carried out. In addition, an extensive discussion on wind and photovoltaic power plants and their contributions to inertia in terms of frequency control strategies is included in the paper. • Extensive review about inertia values for power systems and wind power plants. • Wind turbine and photovoltaic installation frequency control: inertial response. • New proposal to estimate the averaged inertia constant of power systems. • Estimation and comparison of averaged inertia constant in regions and countries. • Relevant information for grid frequency studies with high renewable integration. [ABSTRACT FROM AUTHOR]