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System strength and inertia inherently provided by synchronous generators (SGs) empower a power system to ride through voltage and frequency disturbances. The requirements of system strength and inertia were not enforced in the National Electricity Market (NEM) of Australia since SGs dominated the generation fleet in the past. However, the increasing wind and solar generation continuously displaces SGs and consequently reduces system strength and inertia in the NEM. This paper proposes a formulation of system strength and inertia constrained generator dispatch to reassure NEM operational security in light of emerging high renewable penetration. A fault current iterative solver is developed to evaluate system strength, in which the current limitation and voltage control logic of inverter-based generators, and the fault current contribution from VAR compensators are properly modelled in the phasor domain. The system strength contribution factor of an SG is defined to linearize system strength constraint for unit commitment (UC). System and sub-network inertia constraints are also formulated for the UC to limit the rate of change of frequency (RoCoF) in the event of generator/interconnector trip. The proposed generator dispatch formulation can fully meet system strength and inertia requirements in the NEM. [ABSTRACT FROM AUTHOR]

Synchronous generators are operating for less time than before or being decommissioned in the National Electricity Market (NEM) of Australia, due to the proliferation of asynchronous wind and solar generation. Sub-networks of the NEM will face inertia shortages in the near future. This paper develops a formulation of zonal inertia constrained generator dispatch for power systems with a diversified generator portfolio including synchronous generators, synchronous condensers, inverter-interfaced generators and energy storages. Zonal inertia constraints are formulated in unit commitment and optimal power flow to limit the rate of change of frequency (RoCoF) in the event of network separation. Load frequency relief is also considered to reduce the ramp rate requirement of primary reserve. The proposed formulation can reduce the average cost of primary reserve and maintain zonal inertia adequacy to constrain RoCoF in case of the trip of the interconnector(s). [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 proposes a disturbance-adaptive short-term frequency support scheme of a doubly fed induction generator (DFIG) that can improve the frequency-supporting capability while ensuring stable operation. In the proposed scheme, the output of the additional control loop is determined as the product of the frequency deviation and adaptive gain, which is modified depending on the rate of change of frequency (ROCOF) and rotor speed. To achieve these objectives, the adaptive gain is set to be high during the early stage of a disturbance, when the ROCOF and rotor speed are high. Until the frequency nadir (FN), the gain decreases with the ROCOF and rotor speed. After the FN, the gain decreases only with the rotor speed. The simulation results demonstrate that the proposed scheme improves the FN and maximum ROCOF while ensuring the stable operation of a DFIG under various wind conditions irrespective of the disturbance conditions by adaptively changing the control gain with the ROCOF and rotor speed, even if the wind speed decreases and a consecutive disturbance occurs. [ABSTRACT FROM AUTHOR]

This paper proposes a torque limit-based inertial control scheme of a doubly-fed induction generator (DFIG) that supports the frequency control of a power system. If a frequency deviation occurs, the proposed scheme aims to release a large amount of kinetic energy (KE) stored in the rotating masses of a DFIG to raise the frequency nadir (FN). Upon detecting the event, the scheme instantly increases its output to the torque limit and then reduces the output with the rotor speed so that it converges to the stable operating range. To restore the rotor speed while causing a small second frequency dip (SFD), after the rotor speed converges the power reference is reduced by a small amount and maintained until it meets the reference for maximum power point tracking control. The test results demonstrate that the scheme can improve the FN and maximum rate of change of frequency while causing a small SFD in any wind conditions and in a power system that has a high penetration of wind power, and thus the scheme helps maintain the required level of system reliability. The scheme releases the KE from 2.9 times to 3.7 times the Hydro-Québec requirement depending on the power reference. [ABSTRACT FROM PUBLISHER]

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 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]

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]

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]