Wind Farm Model Research Articles

Robust Subsynchronous Damping Control of PMSG-Based Wind Farm

This paper provides an H∞ robust control strategy for a permanent magnet synchronous generator (PMSG)-based wind farm to realize subsynchronous resonance suppression (SSR) subject to uncertain system distortions and parameter perturbation. Firstly, an eighth-order state space mathematical model of a PMSG-based wind farm is established, including the grid-side converter (GSC), GSC controller, and phase-locked loop (PLL) model. Secondly, the SSR characteristics of a PMSG-based wind farm are analyzed through eigenvalue analysis. Thirdly, a robust subsynchronous damping controller is designed based on eigenvalue analysis of SSR. Finally, the designed robust subsynchronous damping controller is validated with case studies of wind farms. The results show that the controller can increase the stability of PMSG-based wind farm systems and restrain SSR.

Multilevel emulation for stochastic computer models with application to large offshore wind farms

Abstract Renewable energy projects, such as large offshore wind farms, are critical to achieving low-emission targets set by governments. Stochastic computer models allow us to explore future scenarios to aid decision making while considering the most relevant uncertainties. Complex stochastic computer models can be prohibitively slow, and thus an emulator may be constructed and deployed to allow for efficient computation. We present a novel heteroscedastic Gaussian Process emulator that exploits cheap approximations to a stochastic offshore wind farm simulator. We also conduct a probabilistic sensitivity analysis to understand the influence of key parameters in the wind farm model, which will help us to plan a probability elicitation in the future.

Impedance assessment of offshore wind farms

The tuning of Offshore Wind Farm controller and Statcom in order to deliver connection stability is a commonly understood challenge in the context of a HVAC connected wind farm. The more recent developments of long transmission HVAC solutions with multiple cabled routes of power transmission offshore, and associated configurations with device available together with a lower connection strength at the connection interface onshore, now electrically close to other sources of small signal injection has made this process of tuning more challenging; an area that sequence domain impedance modelling may be applied. The sequence domain impedance modelling of Offshore Wind Farm (OWF) has been widely used in the stability analysis between wind turbines and AC Grids, but less frequently in the understanding of the interactions present between the wider AC grid interfaces and the windfarm given the scale of model and computation required and the sheer range of scenarios that can emerge from such analysis; and the need for the OWF network results to align closely with time domain simulations of these same cases for interactions to then be used. For the method presented, an aggregated sub-division impedance model of the offshore wind farm is required in the analysis. Models used are encrypted in nature such that the impedance calculation is provided purely via this method, rather than being the artifact of any derivation that would only become possible via the opening up of such encryption.

Comparative research on DC braking choppers for VSC-HVDC with offshore wind farms

Overvoltage in the DC link of voltage source converter based high-voltage DC (VSC-HVDC) transmission for the offshore wind farm (OWF) due to grid-side faults can not only damage equipment but can also exacerbate grid faults if the converter trips as a result. DC braking chopper (DBC) is now widely used to avoid overvoltage in the DC link by dissipating excess energy in the resistive elements and maintain the normal operation of the OWF, providing fault ride through (FRT) capability. In this paper, the modelling and control of an entire offshore wind farm and VSC-HVDC transmission system with four different circuits of DBC will be developed and a comparative study for the FRT capability and technical performance of these four types of DBC is conducted.

Decentralized observer‐based integral sliding mode control design of large‐scale interconnected systems and its application to doubly fed induction generator‐based wind farm model

SummaryThis paper presents the design of a decentralized observer‐based control scheme for large‐scale interconnected systems based on the integral sliding mode control (ISMC) approach. To do this, a novel decentralized observer is designed via the ISMC approach that helps to estimate the unmeasured states. Then, by constructing a suitable Lyapunov function, sufficient conditions are derived in terms of matrix inequality, which guarantees the asymptotic stability of the interconnected system and the ultimate boundedness of estimation errors under external disturbances. An interconnected power system (IPS) integrated with a doubly fed induction generator (DFIG)‐based wind farm model is provided as a direct application. Theoretical conditions are validated through numerical simulations, in this regard, a well‐structured model of IPS with a DFIG‐based wind farm is introduced. From the simulation results, it is proven that the proposed decentralized observer‐based ISMC can provide a better estimation of the internal states in two area IPS with DFIG‐based wind farm.

Stability Analysis for DFIG-Based Wind Farm Grid-Connected System Under All Wind Speed Conditions

The stable operation capability of the doubly-fed induction generation-based wind farm grid-connected system (DFIG-WFGS) is closely related to wind speed, and the windward velocity of wind turbine unit at different locations may be discrepant due to wake effect. However, the existing mathematical models of DFIG is limited to some specific wind speed points, which may not be directly applied to stability analysis in all wind speed operating conditions. The wind speed is used to characterize the steady state operating point in this paper, meanwhile considering the wake effect and single-input and dual-output (SIDO) characteristics, the two-variable admittance models of wind farm based on DFIG are proposed. Further, the improved analysis method based on two-variable open-loop transfer function is proposed to investigate the stable wind speed interval with different series compensation level for a 50MW DFIG-WFGS in Qinghai, China. In addition, a design guideline of wind farm for oscillation suppression is studied to enhance the performance of DFIG-WFGS and avoid unstable operations. Theoretical analysis and simulation results show that the wake effect may discontinuous the stable wind speed interval, and the damping variation is not positively correlated with the wind speed, which provides basis for accurate analysis and effective improvement of the stability for wind power generation system.

Vector-variable based modeling method for large-scale wind farm considering collector system dynamics

Different from conventional power plants, a wind farm usually consists of hundreds of wind generators and collector systems with arbitrary topology. The numerous devices increase modeling efforts and computational burden. This paper proposes a vector-variable based method for dynamic modeling of the large-scale wind farm considering collector system dynamics. Using the vector variables, the modeling method converts the complex wind farm containing many components to a model consisting of two typical submodules, the wind generator module and the collector system module. These submodules can establish any number of wind generators and any topology of the collection systems considering dynamics freely, with good scalability. The correctness and high simulation efficiency of the established model are validated by the electromagnetic model. Furthermore, a detailed wind farm containing twenty-five wind generators is built via the proposed method. Compared with the aggregation model, the results show that the established model can reflect the wind farm stability accurately. Also, by comparing with the model neglecting the collector system dynamics, the results reveal the relative error caused by neglecting the collector system dynamics can lead to misjudgment of instability mode when analyzing the sub-synchronous modes.

Tropical cyclone wind hazard assessment for Donghaitang wind farm (Zhejiang Province, China): Case study

Currently, offshore and coastal wind power resources are growing rapidly around the world, especially in China. However, systematic research on the hazard assessment of wind farms under tropical cyclone conditions remains lacking. This study simulated the wind field of tropical cyclones based on a parameterized tropical cyclone wind field model, and analyzed the characteristics of historical tropical cyclones in Donghaitang wind farm (Zhejiang, China). Four extreme tropical cyclone hazard factors including the maximum wind speed (Vmax), maximum duration of wind direction change (Tmax), maximum cumulative wind direction change (Δθmax) and maximum rate of change in wind direction (ΔDmax) were proposed and examined. Then a comprehensive hazard assessment model for wind farms based on the analytic hierarchy process was established, and the risk to the Donghaitang wind farm represented by tropical cyclones during 1949–2021 was evaluated. Results showed that the number and intensity of tropical cyclones made landfall near the coast of Donghaitang wind farm gradually increased with time, which results in a gradual increase in the composite tropical cyclone risk level of the Donghaitang wind farm with time. The numbers and risk levels of tropical cyclones traveling northwestward were much larger than those traveling northward or northeastward. Moreover, the average composite risk index for tropical cyclones passing to the left of the wind farm was 14.3% higher than that for tropical cyclones passing to the right. The large values of Vmax and ΔDmax are main reasons for the high risk of the wind farm, while the other two hazard factors (Tmax, Δθmax) proposed to account for the wind turbine backup power are also of great importance in the design, selection and operation stages of offshore wind turbines. The findings of this study could provide support for hazard assessment of offshore and coastal wind farms exposed to tropical cyclones, including macro site selection of wind farms and type selection of wind turbines.

A Critical Review of Current and Future Options for Wind Farm Participation in Ancillary Service Provision

This paper presents a critical review, from a wind farm control perspective, of different methodologies in the open literature that enable wind farms to participate in ancillary service provision. Firstly, it considers the services currently provided in power systems with high levels of wind generation (specifically, Denmark, Ireland, and Great Britain), reviewing current regulatory frameworks and recommendations. Secondly, it reviews the ancillary service markets that wind farms do not currently participate in, considering the barriers to entry and discussing potential solutions using a proper control-enabled framework. Thirdly, it also considers the future perspective for wind farm participation in ancillary service provision, including a review of the body of published academic research on wind farm participation in ancillary service provision. Finally, this review concludes by suggesting where the gaps are in the academic literature, and subsequently suggests future work. Two examples are the disconnect between the mechanical and farm side approaches with power-system-based modelling, and how much wind farm modelling is very-low-fidelity-omittedkey aspects such as wake effects and component fatigue analysis.

Research on simplified modeling of large-scale wind farms based on equivalent transfer function and aggregate equivalent

Introduction: In grid-connected research of large-scale wind farms, the problem of long simulation time exists in the research based on detailed model. In order to realize the fast simulation and grid-connected transient research of wind farm, this paper presents a simplified equivalent model of wind farm based on equivalent transfer function and improved capacity weighting method.Methods: This paper analyzes the mathematical model of wind turbine, corresponding to the strategy of design simplification, and the simplified model is built according to the equivalent transfer function. In addition, this paper considers the equivalent line loss model of collector line, classifies and aggregates the simplified wind turbines, and calculates the equivalent value of the converged wind turbines by using the improved capacity weighting method, the grid-connected simplified modeling of large-scale wind farm is realized.Results: A model of wind farm-MMC-HVDC flexible grid-connected wind power system is built. The simulation results show that the simplified equivalent model improves the simulation speed greatly while guaranteeing the dynamic characteristics.Discussion: The simplified equivalent strategy of wind farm can keep the same dynamic performance with the detailed model, and improve the simulation speed, and realize the fast simulation and grid-connected transient research of wind farm.

Research on multi-energy cooperative participation of grid frequency inertia response control strategy for energy storage type doubly-fed wind turbine considering wind speed disturbance

With the proposal of carbon peaking and carbon neutralization, the penetration rate of wind power generation continues to increase. This paper focuses on the problem that doubly fed induction wind turbines are vulnerable to input “source” disturbances and have weak frequency modulation ability, which reduces the stability of the power grid. Based on the structural model of energy storage system embedded in doubly fed wind power generation system, it is compared the ability of super capacitor energy storage and releasing rotor kinetic energy to provide inertia response power and energy, and the feasibility of multi-energy coordinated inertia response is analyzed. Based on the inertia time constant of conventional synchronous generator set, the inertia time constant and actual inertia constant of energy storage doubly fed wind power generation system under variable wind speed are defined. An extended state observer is used to estimate the change of captured mechanical power caused by the change of wind speed, and a control strategy for doubly fed induction generator with super capacitor to participate in power grid frequency regulation is designed. Finally, considering the aggregation of wind power and the difference of the state of charge during the operation of distributed energy storage, the 3*3*3 wind farm model is established using Matlab/Simulink simulation software. The feasibility and advantages of the frequency modulation control strategy proposed in this paper are verified by building a power grid frequency modulation simulation involving wind farms and traditional generators.

Improving the performance of grid connected wind generator with a PI control scheme based on the metaheuristic golden eagle optimization algorithm

• A novel Golden Eagle optimization algorithm (GEOA) is proposed. • GEOA is used to improve the Transient and Dynamics stability of wind farm. • Transient and Dynamics stability of grid-tied PMSG-VSWT is investigated during symmetrical, unsymmetrical faults and Stochastics wind variation at that site. • The results of GEOA are compared with the results of NR, PSO and GOA. • The results shown that the GEOA is robust and competitive. Wind power installations are globally established thoroughly, resulting in significant electrical power penetration into power grids. Consequently, tremendous efforts are expended to improvise the performance of the grid-connected Permanent Magnet Synchronous Generator driven by a Variable-Speed Wind Turbine (PMSG-VSWT). In this work, eight cascaded Proportional Integral (PI) controllers in the machine side and grid side converters are optimally tuned by the golden eagle optimization algorithm with the purpose of enhancing the dynamics and transient stability performances of the grid connected PMSG-VSWT.The integration of the square error criterion was utilised as a fitness function in the optimization process, which was processed using the simulation-based optimization technique. The proposed control technique's efficacy was compared to various optimal PI controllers under symmetrical and unsymmetrical fault conditions. This study also employed the measured real-time events collected at the Coimbatore wind farm in Tamil Nadu (India) to produce realistic results and aid in the pursuit of higher performance. The wind farm modelling and simulation were processed using the DIgSILENT power factory/MATLAB Simulink environment and was utilized to test the proposed control approach's achievability. Finally, the study demonstrates that the golden eagle optimization technique improves the wind farm's performance when compared to observed events and other techniques.

Prediction and Mitigation of Wind Farm Blockage Losses Considering Mesoscale Atmospheric Response

The engineering wind farm models currently used in industry can assess power losses due to turbine wake effects, but the prediction of power losses due to farm blockage is still a challenge. In this study we demonstrate a new prediction method of farm blockage losses and a possible strategy to mitigate them for a large offshore wind farm in the North Sea, by combining a common engineering wind farm model ’FLORIS’ with the ’two-scale momentum theory’ of Nishino and Dunstan (2020). Results show that the farm blockage losses depend significantly on the ’wind extractability’ factor, which reflects the strength of mesoscale atmospheric response. For a typical range of the extractability factor (assessed using a numerical weather prediction model) the farm blockage losses are shown to vary between about 5% and 15% of the annual energy production (AEP). However, these losses may be mitigated by adjusting turbine operating points taking into account the wind extractability. It is shown that a simple adjustment of the blade pitch angle and tip-speed ratio used below the rated wind speed may increase the AEP by up to about 2%.

GIS-based weighted overlay model for wind and solar farm locating in Sri Lanka.

With regard to wind and solar energy, research has shown a clear discrepancy between the amount of energy currently being used with the existing potential. The present research has attempted to develop a geographic information systems (GIS) based weighted overlay model to identify potential locations for the development of wind and solar farms in Sri Lanka, which are rapidly advancing renewable energy resources globally. Four major land-use types were considered for the model development as least productive land areas to establish wind and solar farms, namely, barren lands, sand areas, open forests, and scrublands. Nine and seven criteria were identified for the wind and solar farm siting respectively, and the relative weights for each criterion were obtained through focused group discussions. The weighted overlay model was used to locate suitable areas and higher the values generally indicate that a location is more suitable. The outcome of the weighted overlay model shows that for the wind farm locating, 141km2 of highly suitable lands available accounts for 3% of the total land area of Sri Lanka. Furthermore, the model results indicated a total area of 99km2 as highly suitable for solar power generation. Central, Sabaragamuwa, Uva, and Northern provinces were found to be the most suitable for wind farm locating and Eastern, Southern, and Northern provinces we identified as highly suitable for the solar farm locating. The model validation performed by overlaying the results with the existing solar and wind farm map of Sri Lanka indicated that the highly suitable, moderately suitable, and marginally suitable lands identified by the weighted overlay lied within 1km radius of the existing wind and solar power plants. Thus, it can be concluded that GIS-based weighted overlay model can serve as a primary screening tool to shortlist the optimum land areas to locate future solar and wind farms in any selected geographical location.

Impact of aggregated model-based optimization for wind farm and electric vehicle on power system stability

This paper analyses an aggregated battery charging model for Electric Vehicles (EVs) and Wind Farms (WFs). The effects of EVs and WFs on stability have become a substantial problem with comprehensive apprehension due to the intermittence power flow and irregular battery-charging behaviour. It results in undesirable operation and malfunction in the system to cause instability. In this work, it is integrated with various controllers to enhance the stability. The rotor speed deviation has been considered an objective function with various constraints for particle swarm optimization to provide the controller's optimized value and combination. It also studies the influence of transient stability problems using time-domain simulation. From stability analysis, coordinated controllers intensify the capability of SGs and WF under extreme disturbances. The effectiveness and robustness of the proposed approaches have been verified using the IEEE-11 bus test system.

Interaction of two axisymmetric turbulent wakes

The interaction between turbulent axisymmetric wakes plays an important role in many industrial applications, notably in the modeling of wind farms. This work proposes an experimental study on the interaction between two bluff bodies. We find that a simple mathematical expression for the wake interaction length based on nonequilibrium turbulence scalings can be used to collapse the streamwise developments of the second, third, and fourth moments of the streamwise fluctuating velocity.

Ensemble-Based Flow Field Estimation Using the Dynamic Wind Farm Model FLORIDyn

Wind farm control methods allow for a more flexible use of wind power plants over the baseline operation. They can be used to increase the power generated, to track a reference power signal or to reduce structural loads on a farm-wide level. Model-based control strategies have the advantage that prior knowledge can be included, for instance by simulating the current flow field state into the near future to take adequate control actions. This state needs to describe the real system as accurately as possible. This paper discusses what state estimation methods are suitable for wind farm flow field estimation and how they can be applied to the dynamic engineering model FLORIDyn. In particular, we derive an Ensemble Kalman Filter framework which can identify heterogeneous and changing wind speeds and wind directions across a wind farm. It does so based on the power generated by the turbines and wind direction measurements at the turbine locations. Next to the states, this framework quantifies uncertainty for the resulting state estimates. We also highlight challenges that arise when ensemble methods are applied to particle-based flow field simulations. The development of a flow field estimation framework for dynamic low-fidelity wind farm models is an essential step toward real-time dynamic model-based closed-loop wind farm control.

Developing an Extended Virtual Blade Model for Efficient Numerical Modeling of Wind and Tidal Farms

Harnessing renewable and clean energy resources from winds and tides are promising technologies to alter the high level of consumption of traditional energy resources because of their great global potential. In this regard, developing farms with multiple energy converters is of great interest due to the skyrocketing demand for sustainable energy resources. However, the numerical simulation of these farms during the planning phase might pose challenges, the most significant of which is the computational cost. One of the most well-known approaches to resolve this concern is to use the virtual blade model (VBM). VBM is the implementation of the blade element model (BEM). This was done by coupling the blade element momentum theory equations to simulate rotor operation with the Reynolds averaged Navier–Stokes (RANS) equation to simulate rotor wake and the turbulent flow field around it. The exclusion of the actual geometry of blades enables a lower computational cost. Additionally, due to simplifications in the meshing procedure, VBM is easier to set up than the models that consider the actual geometry of blades. One of the main unaddressed limitations of the VBM code is the constraint of modeling up to 10 renewable energy converters within one computational domain. This paper provides a detailed and well-documented general methodology to develop a virtual blade model for the simulation of 10-plus converters within one computational domain to remove the limitation of this widely used and robust code. The extended code is validated for both the single- and multi-converter scenarios. It is strongly believed that the technical contribution of this paper, combined with the current advancement of available computational resources and hardware, can open the gates to simulate farms with any desired number of wind or tidal energy converters, and, accordingly, secure the sustainability and feasibility of clean energies.

Research on Operation and Maintenance Route Planning of Offshore Wind Farm Based on Multiagent

Recently, the ant colony algorithm has been widely used in the field of path planning, which is a key technology required for ship operations in offshore wind farms to improve navigation efficiency and power generation. However, the ant colony algorithm has the defects of a long search time and stagnation in the early stage of the operation and maintenance path planning of offshore wind farms, and it easily falls into the problem of local optima; furthermore, the ant colony algorithm uses incremental construction to build a complete itinerary path, it takes a lot of time to search the path, and only the suboptimal solution is obtained. To address the above problems, in this paper, we propose a multi-agent-based operation and maintenance model for offshore wind farms. Specifically, the introduction of the heuristic factor can optimize the local optimal solution and make the ant colony algorithm clearer when searching for the target. Based on this, increasing the pheromone adjustment factor can eliminate the invalid path from searching and select a high-quality path. In addition, by integrating the genetic algorithm, it is possible to select, cross, and mutate to simulate the natural evolution process to search for the optimal solution, reduce the similarity of the paths constructed by the ant colony, reduce the probability of algorithm stagnation, improve the convergence speed, and improve the time efficiency and solution accuracy of the algorithm. Simulation experiments on a series of benchmark datasets show that the proposed GA-PACO algorithm achieves better performance in global search and path planning than the existing three algorithms.

Stability analysis and parameter coordination of the grid-connected wind farm with heterogeneous PMSGs

Improper setting of phase-locked loop (PLL) control parameters is one of the key factors for the adverse dynamic interaction between wind turbine generators, resulting in the oscillation instability of wind power systems. In this study, considering the spatial distribution characteristics and dynamic heterogeneity of multiple PMSGs, the PLL-induced instability mechanism of the grid-connected PMSG wind farm is studied and a stability criterion is proposed to guide the parameter coordination of the PLL for multiple PMSGs. First, based on the dynamic equivalent modeling method of the homogeneous multi-agent system, a reduced-order model of the homogeneous wind farm dominated by PLL is proposed. The parameter region of PLL control to ensure stability was analytically examined based on the proposed stability criterion. Then, the stability of heterogeneous wind farm is analyzed by constructing an equivalent homogeneous wind farm that has the same dominant oscillation mode as the heterogeneous wind farm; that is, the stability is equivalent. Furthermore, the stability criterion of the heterogeneous wind farm is deduced, and the parameter coordination method of PLL control for multiple PMSGs is proposed. Modal analysis and nonlinear simulation were conducted to confirm the accuracy of the theoretical analysis.