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One of the main factors in triggering cascading outages is the unexpected tripping of backup protection caused by load encroachment (LE). Hence, LE should be identified quickly to avoid unexpected tripping. This paper proposes a fast LE identification method based on the wide-area measurement system (WAMS), applicable to transmission grids with high wind power penetration. Firstly, based on the improved shortest path algorithm, the method searches for critical lines greatly affected by the LE to determine the collected range of wide-area information. Then, by analyzing the hidden dangers of the existing calculation method for the active power estimation value (APEV) in the power system with wind farms, a fast calculation method of the APEV based on the WAMS is proposed to ensure that the existing LE identification criterion is still applicable in the high-penetration system of wind power. Finally, based on the PSASP platform, the wind farm model is integrated into the IEEE 39-bus New England system for simulation. The simulation results show that the method proposed in this paper can quickly search for the critical line set (CLS) and accurately identify the LE under high wind power penetration, effectively avoiding the unexpected tripping of backup protection and preventing cascading outages. [ABSTRACT FROM AUTHOR]

Ramp-rate limitation is a strategy to reduce wind power variability and to permit the integration of wind power into the grid. However, penalties occur whenever the ramp-rate limitations are not respected. The purpose of this paper is to compute the penalties to which a wind farm may undergo when a battery storage system is put alongside the wind farm. This is achieved by advancing a semi-Markov model which mimes the operations on the battery and considers a new reward structure which is dependent on the time length of the battery operations. Two Monte Carlo algorithms are proposed for simulating the penalty process. The paper shows the validity of the methodology by verifying the model assumptions directly on real data and through a comparison of the real and the simulated results. This paper contributes to the literature by extending previous stochastic models and providing a general methodology for the economical characterization of ramp-rate limitation policies. [ABSTRACT FROM AUTHOR]

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Wind energy is a widely used and developed the renewable energy, which has developed rapidly. At present, the design of the horizontal axis wind turbine blade mainly used Blade Element Momentum theory. In this paper, an optimization method of the wind turbine blade was proposed for improving the output power. The local twist angles of the blade were optimized. This method combined the surrogate model and the numerical simulation methods. The kriging surrogate model was selected and the next calibration point was chosen by the efficient global optimization algorithm. In this paper, the aerodynamic performances of the optimized blades were discussed in detail and obtained by the numerical simulation method. It was shown that the wind power coefficients and the output powers of the optimized blades were increased. The wind power coefficients of two optimized blades were increased by 4.83% and 3.44%, respectively. The optimized blades were able to capture more kinetic energy from the wind, but the optimized blades were subjected to a greater structural load. The thrust and torque coefficients maintained an increasing tendency for the optimized blades. [ABSTRACT FROM AUTHOR]

The use of combined wind and wave energy harvesting devices (CWWHDs) is an effective way to synergistically capture offshore wind and wave energy. However, the form of combined energy harvesting and coupled simulation techniques limit the development of CWWHDs. This paper classifies the existing CWWHDs based on wave energy converters and offshore wind turbines, summarizes the theoretical background and implementation forms of the numerical simulation of CWWHDs, and focuses on the technical details of wind-wave coupling and multi-body coupling simulation, which fills the gap in the research of the wind-wave coupling and multi-body coupling numerical simulation of CWWHDs. Finally, the current research focus and development direction of CWWHDs and their numerical simulation technology are summarized to provide a reference for the future development and application of CWWHDs and numerical simulation technology. [ABSTRACT FROM AUTHOR]

This paper presents a distributed wind power virtual simulation experiment system for cultivating students' ability to solve complex engineering problems. The experiment system was designed with complex engineering problems of real wind farms, both in a steady state and transient process. On the basis of the system, comprehensive practical contents were developed. According to engineering education certification, the virtual simulation practical contents provide support for improving students' ability to solve complex engineering problems. The system has been applied to a comprehensive practical course of renewable energy. From the designed assessment, the experiment system helped students to master the advanced technologies applied to real wind farms visually and enhanced their ability to solve complex engineering problems. After practical learning on the system, students' performance has been improved in graduation projects. It is proved that the virtual simulation experiment system is effective in cultivating students' ability to solve complex engineering problems. [ABSTRACT FROM AUTHOR]

When a hexagonal converter (Hexverter) is applied to high-power renewable energy generation such as offshore low-frequency transmission, using traditional PID control to ensure the stable global operation and strong robustness of the system is difficult due to the random fluctuation of renewable energy, system parameter uptake, its non-linear characteristics, and the possible unbalanced grid situation. This paper proposes a non-linear passivity-based control (PBC) strategy for Hexverter under an unbalanced grid. First, the passivity and stability of Hexverter objects are analyzed based on PBC theory. The unbalanced PBC strategy of Hexverter is then designed and derived. Three control objectives are designed according to different control requirements. Finally, the simulation system of the Hexverter under an unbalanced grid is built on Matlab/Simulink to verify the effectiveness and superiority of the proposed unbalanced PBC method. The simulation results show that the proposed method has fewer control parameters, faster response, lower harmonic content, and better overall control effect than PID control. [ABSTRACT FROM AUTHOR]

Due to their weak nature, such as low inertia, offshore energy hubs are prone to unprecedented fast dynamic phenomena. This can lead to undesired instability problems. Recent literature, with main focus on onshore systems, suggests that electrolysers could be an attractive option to support wind generators in the mitigation of balancing problems. This paper presents an Electromagnetic Transient (EMT) model for real-time simulation based study of the dynamics of active power and voltage responses of offshore hubs due to wind speed fluctuations. The purpose of this study was to ascertain the ability of an electrolyser to support an offshore energy hub under different scenarios and with different locations of the electrolyser. Two locations of Proton Exchange Membrane (PEM) electrolysers were considered: centralised (at the AC common bus of the hub) or distributed (at the DC link of the wind turbines). Numerical simulations conducted in RSCAD® on a 2 GW offshore hub with 4 × 500 MW wind power plants and 330 or 600 MW PEM electrolysers show that electrolysers can effectively support the mitigation of sudden wind speed variations, irrespective of the location. The distributed location of electrolysers can be beneficial to prevent large spillage of wind power generation during the isolation of faults within the hub. [ABSTRACT FROM AUTHOR]

Wind farm design and analysis heavily rely on computationally efficient engineering models that are evaluated many times to find an optimal solution. A recent article compared the state-of-the-art Gauss-curl hybrid (GCH) model to historical data of three offshore wind farms. Two points of model discrepancy were identified therein: poor wake predictions for turbines experiencing a lot of wakes and wake interactions between two turbines over long distances. The present article addresses those two concerns and presents the cumulativecurl (CC) model. Comparison of the CC model to high-fidelity simulation data and historical data of three offshore wind farms confirms the improved accuracy of the CC model over the GCH model in situations with large wake losses and wake recovery over large inter-turbine distances. Additionally, the CC model performs comparably to the GCH model for single- and fewer-turbine wake interactions, which were already accurately modeled. Lastly, the CC model has been implemented in a vectorized form, greatly reducing the computation time for many wind conditions. The CC model now enables reliable simulation studies for both small and large offshore wind farms at a low computational cost, thereby making it an ideal candidate for wake-steering optimization and layout optimization. [ABSTRACT FROM AUTHOR]

Models of a wind energy conversion chain using classical Simulink models of a diode bridge exhibit significant simulation time making difficult its combination with large scales optimization approaches. For this purpose and to increase the degree of compatibility of wind turbine models with large scales optimization approaches such as those based on Genetic Algorithms, a wind energy conversion system having an horizontal axis propeller, an axial generator with permanent magnets, recharging a battery energy accumulator through a diode rectifier is modeled by simplified method reducing simulation time. Indeed, a model of the three phase's diode rectifier making the simulation time considerably reduced compared to the existing model in the Simulink library is developed. This model is validated by comparison with the model using the classic Simulink library. Another objective of this study is the formulation of the useful torque optimization problem having an essential constraint the reduction of the generator phase's inductance in the goal to reduce the overvoltage in generator phases. [ABSTRACT FROM AUTHOR]

An aggregation method is proposed that transforms the multiple DFIGs into an equivalent DFIG model that retains the major collective dynamic characteristics of a group of DFIGs. It is intended for Electromagnetic Transients Simulation (EMT). The aggregated machine can take into account different speeds and parameters of each of the individual DFIGs and the connecting impedance of individual DFIGs. Starting with a State Variable (SV) model of an individual DFIG, aggregation is carried out recursively, by combining two DFIGs at a time and then reducing the order of the aggregate to match the state variable equations of a single DFIG so that the steady state performances are identical. Validation is carried out by comparing the detailed electromagnetic transient (EMT) simulation of the unreduced system with the reduced aggregate system. It is shown that the proposed aggregation method accurately matches the steady state response and also accurately reproduces the dominant transient response of the unreduced system. As the aggregate DFIG has the same number of state variables as a single DFIG, the overall wind farm's order is reduced significantly to increase the modelling and simulation efficiency. [ABSTRACT FROM AUTHOR]

We study the generation, propagation, and dissipation of wind-generated near-inertial waves (NIWs) in a global 1/258 Hybrid Coordinate OceanModel (HYCOM) simulation with realistic atmospheric forcing and background circulation during 30 days in May-June 2019. The time-mean near-inertial wind power input and depth-integrated energy balance terms are computed for the total fields and the fields decomposed into vertical modes to differentiate between the radiative and (locally) dissipative components of NIWenergy. Only 30.3%of the near-inertial wind input projects onto the first five modes, whereas the sum of the NIW energy in the first five modes adds up to 58% of the total NIW energy. Almost all of the depth-integrated NIW horizontal energy flux projects on the first five modes. The global distribution of dissipation and decay distances of NIW modes confirm that lower latitudes are a sink for NIW energy generated at higher latitudes. The locally dissipated fraction of NIW energy qlocal is found to be uniform throughout the global ocean, with a global mean value of 0.79. The horizontal NIW fluxes diverge from areas with cyclonic vorticity and converge in areas with anticyclonic vorticity; that is, anticyclonic eddies are a sink for NIWenergy fluxes}in particular, for higher modes. Most of the residual energy that does not project onto modes propagates downward in anticyclonic eddies. The global near-inertial wind power input is 0.21 TW for the 30 days, of which only 19%is transmitted below 500-m depth. [ABSTRACT FROM AUTHOR]

With the planned construction of vast offshore wind farms along the US East Coast, identifying and understanding key coastal processes, such as sea breezes, has become a critical need for the sustainability and development of US offshore wind energy. In this study, a new two-step identification method is proposed to detect and characterize three types of sea breezes (pure, corkscrew and backdoor) over the US northeastern coast from a year-long WRF (Weather Research and Forecasting) simulation. The results suggest that the proposed detection method can identify the three different types of sea breezes in the model simulation. Key sea breeze features, such as the calm zone associated with pure sea breezes and coastal jets associated with corkscrew sea breezes, are evident in the sea breeze composite imagery. In addition, the simulated sea breeze events indicate a seasonal transition from pure to corkscrew sea breeze between March and August as the land-sea thermal contrast increases. Furthermore, the location and extension of the sea breeze front are different for each type of sea breeze, suggesting that the coastal impact of sea breeze varies with sea breeze type. From the wind energy perspective, the power production associated with a 10MW offshore wind turbine would be approximately 3 to 4 times larger during a corkscrew sea breeze event than the other two types of sea breezes. This highlights the importance of identifying the correct type of sea breeze in numerical weather/wind energy forecasting. [ABSTRACT FROM AUTHOR]

Wind energy considers an important source for a clean power generation. Several problems in the wind-power generation are due to its uncertainty the sudden change in both wind speed rates and direction. Especially, for small wind power generation system, when wind turbines are connected to a small system or isolated grid, the output power fluctuates from time to time. More so, the need for a new wind blade design that works at low air velocities and different direction wind currents requires further investigation. In this work, the numerical and experimental analysis of mixed flows turbine, the possibility of air currents with horizontal and vertical directions on rotating the proposed models was studied. Firstly, two models of a mixed flows turbine were designed and fabricated for experiments. The experiments were conducted to test two important parameters; inlet velocity at 0.8, 1.4, 2.8, and 4.3 m/s, and yaw angles at 45° and 70°, respectively. Secondly, the modeling has been conducted in the environment of CFD, and the turbine system simulation utilized a SST k-ω model to solve and post process the problem. The results can be drawn from the analysis: the characteristics of the mixed flows turbine have the best self-starting and the lower-starting torque as standard for developing the turbine; the starting torque is dependent on the yaw angle for the blade, in which the wind turbine with a large yaw angles for blades is needed to the smaller starting torques; also the output power increased by increasing the wind velocity. [ABSTRACT FROM AUTHOR]

We present a review of existing wind–wave coupling models and parameterizations used for large-eddy simulation of the marine atmospheric boundary layer. The models are classified into two main categories: (i) the wave-phase-averaged, sea surface–roughness models and (ii) the wave-phase-resolved models. Both categories are discussed from their implementation, validity, and computational efficiency viewpoints, with emphasis given on their applicability in offshore wind energy problems. In addition to the various models discussed, a review of laboratory-scale and field-measurement databases is presented thereafter. The majority of the presented data have been gathered over many decades of studying air–sea interaction phenomena, with the most recent ones compiled to reflect an offshore wind energy perspective. Both provide valuable data for model validation. We also discuss the modeling knowledge gaps and computational challenges ahead. [ABSTRACT FROM AUTHOR]

Future energy systems must mainly generate electricity from renewable resources. To deal with the fluctuating availability of wind and solar power, new versatile electricity markets and sustainable solutions concentrating on energy flexibility are needed. In this research, we investigated the potential of energy flexibility achieved through demand-side response for the wastewater treatment plant of the Benchmark Simulation Model 1. First, seven control strategies were simulated and assessed. Next, the flexibility calls were identified, two energy flexibility scenarios were defined and incorporated into the model, and the control strategies were evaluated anew. In this research, the effluent ammonia concentration needed to be maintained within the limits for as long as possible. Strategy 5, which controlled ammonia in Tank 5 at a low value and did not control any nitrate in Tank 2, of Scenario 1, which was characterized by an undetermined on/off aeration cycle, was then found to be the best. Although this control strategy led to high total energy consumption, the percentage of time during which aeration was nearly suspended was one of the highest. This work proposes a methodology that will be useful to plant operators who should soon reduce energy consumption during spikes in electricity prices. [ABSTRACT FROM AUTHOR]