Research On Wake Modeling And Wind Farm Planning Optimization

In recent years,with the development of global wind power industry,the construction of onshore and offshore wind farms in various countries has increased.As a preliminary process of the wind farm project,the micro-siting of wind turbines in a wind farm plays an essential role in determining the wind farm’s generation capability and economic benefits.The wake model is very important in modeling a wind farm.In view of this,this project focuses on the key issues in the wind farm planning process,especially on the accurate modeling of wake.The simulations are conducted in MATLAB.The main contents of this thesis are summarized as follows:1)A two-dimensional Gaussian wake model: Frandsen-Gaussian(F-G)wake model is introduced and applied in the wind farm layout optimization with one type of wind turbines installed.The widely-used one-dimensional Jensen’s wake model is deduced based on the conservation of mass.However,the conservation of momentum has not been considered.Also,the Jensen’s model only takes the near wake region into account.Frandsen’s model is deduced according to the blade element momentum theory which considers the details of blades and offers a commendable evaluation for torques and thrust forces.It considers not only the conservation of mass,but also the conservation of momentum.It includes the near wake region and the far wake region and has been justified by the large eddy simulation(LES)data that the F-G wake model is closer to real wake.The F-G wake model and the Jensen’s wake model are used in the wind farm layout optimization.The F-G wake model is used to calculate the objective function after the wind turbines optimal positions are acquired by using the Jensen’s model.Simulation results demonstrate that the F-G model is more consistent with real wakes and thus the optimization result is more reasonable than the commonly used Jensen’s model.2)Based on the two-dimensional Gaussian wake model and shear effect,a novel three-dimensional(3D)Gaussian wake model is applied in the wind farm layout optimization with one type of wind turbines and multiple types of turbines installed.This model is also compared with the one-dimensional(1D)and the two-dimensional(2D)wake models with respect to the wind tunnel simulation results and the 3D wake model is justified to be the most accurate one.Test cases of various wind farm sizes,wind conditions,and different wake models are simulated and analyzed.The simulation results demonstrate that the 3D Gaussian wake model can effectively address the wind farm layout optimization problem and further illustrate that the nonuniform design is beneficial to increase the wind farm’s output power.3)A bi-hierarchy optimization framework is proposed to determine the capacity and layout of a grid-connected wind farm.The environmental impacts involved by the installation of a wind farm have been taken into consideration in this problem.The first-layer model optimizes the wind farm capacity and configuration with minimized comprehensive generation cost of wind energy and two sets of constraints.The sound pressure level(SPL)limit of the noise emitted by the wind turbines is handled to be one of the constraints of the first-layer model.The second-layer model determines the generation schedule of other conventional generators.The simulation results validate the effectiveness of the proposed model and prove that environmental influences of wind farms should not be ignored during the planning stage.4)A bi-level multi-objective optimization framework is presented,with the aim of simultaneously designing the configuration of wind turbines as well as the topology of electrical collector system in an offshore wind farm.The installation capacity of the wind farm,the positioning of the wind turbines and the planning scheme of the electrical system are balanced to achieve a better performance of the wind farm.In this proposal,there is an outer layer along with two inner layers.The objectives of the outer-layer model are the maximization of the WF’s daily profit rate,the daily average capacity factor,and power quality.The simulation results validate the adaptability and effectiveness of the proposed approach with the main factors that affect the wind farm layout being analyzed.