Primary frequency control considering communication delay for grid-connected offshore wind power systems

Offshore wind farms are becoming increasingly distant from onshore centralized control centers,and the communication delays between them inevitably introduce time delays in the measurement signal of the primary frequency control.This causes a deterioration in the performance of the primary frequency control and,in some cases,may even result in frequency instability within the power system.Therefore,a frequency response model that incorporates communication delays was established for power systems that integrate offshore wind power.The Padéapproximation was used to model the time delays,and a linearized frequency response model of the power system was derived to investigate the frequency stability under different time delays.The influences of the wind power proportion and frequency control parameters on the system frequency stability were explored.In addition,a Smith delay compensation control strategy was devised to mitigate the effects of communication delays on the system frequency dynamics.Finally,a power system incorporating offshore wind power was constructed using the MATLAB/Simulink platform.The simulation results demonstrate the effectiveness and robustness of the proposed delay compensation control strategy.

Capacity Optimization Configuration of Hydrogen Production System for Offshore Surplus Wind Power

To solve the problem of residual wind power in offshore wind farms,a hydrogen production system with a reasonable capacity was configured to enhance the local load of wind farms and promote the local consumption of residual wind power.By studying the mathematical model of wind power output and calculating surplus wind power,as well as considering the hydrogen production/storage characteristics of the electrolyzer and hydrogen storage tank,an innovative capacity optimization allocation model was established.The objective of the model was to achieve the lowest total net present value over the entire life cycle.The model took into account the cost-benefit breakdown of equipment end-of-life cost,replacement cost,residual value gain,wind abandonment penalty,hydrogen transportation,and environmental value.The MATLAB-based platform invoked the CPLEX commercial solver to solve the model.Combined with the analysis of the annual average wind speed data from an offshore wind farm in Guangdong Province,the optimal capacity configuration results and the actual operation of the hydrogen production system were obtained.Under the calculation scenario,this hydrogen production system could consume 3,800 MWh of residual electricity from offshore wind power each year.It could achieve complete consumption of residual electricity from wind power without incurring the penalty cost of wind power.Additionally,it could produce 66,500 kg of green hydrogen from wind power,resulting in hydrogen sales revenue of 3.63 million RMB.It would also reduce pollutant emissions from coal-based hydrogen production by 1.5 tons and realize an environmental value of 4.83 million RMB.The annual net operating income exceeded 6 million RMB and the whole life cycle NPV income exceeded 50 million RMB.These results verified the feasibility and rationality of the established capacity optimization allocation model.The model could help advance power system planning and operation research and assist offshore wind farm operators in improving economic and environmental benefits.

Research on Reactive Power Optimization of Offshore Wind Farms Based on Improved Particle Swarm Optimization

The lack of reactive power in offshore wind farms will affect the voltage stability and power transmission quality of wind farms.To improve the voltage stability and reactive power economy of wind farms,the improved particle swarmoptimization is used to optimize the reactive power planning in wind farms.First,the power flow of offshore wind farms is modeled,analyzed and calculated.To improve the global search ability and local optimization ability of particle swarm optimization,the improved particle swarm optimization adopts the adaptive inertia weight and asynchronous learning factor.Taking the minimum active power loss of the offshore wind farms as the objective function,the installation location of the reactive power compensation device is compared according to the node voltage amplitude and the actual engineering needs.Finally,a reactive power optimizationmodel based on Static Var Compensator is established inMATLAB to consider the optimal compensation capacity,network loss,convergence speed and voltage amplitude enhancement effect of SVC.Comparing the compensation methods in several different locations,the compensation scheme with the best reactive power optimization effect is determined.Meanwhile,the optimization results of the standard particle swarm optimization and the improved particle swarm optimization are compared to verify the superiority of the proposed improved algorithm.

Design of Offshore Wind Power Foundation with Multi-bucket

Three- and four-bucket offshore wind power foundations with a new form of force-transferring structure are proposed in this paper, and the integrated finite element model of foundation-soil-transition structure is established by using ABAQUS. The carrying capacity of the proposed foundations is studied under vertical load, horizontal load and bending moment. It can be seen that the vertical bearing capacity of multi-bucket foundation can be roughly estimated by the vertical bearing capacity of single-bucket; the horizontal bearing capacity of the three-bucket foundation scheme is controlled by displacement, while that of the four-bucket foundation scheme is controlled by the internal forces of soils. Moreover, the carrying capacity is provided by the overall structure formed by multi-bucket before soil failure. Compared with the conventional single-bucket foundation, there are mainly tension and pressure that are applied to the multi-bucket foundation, so that the carrying capacity of the foundation can be fully utilized. The probability of soil failure can be well reduced with the proposed multi-bucket foundation, and the stress transmission of force-transferring structure is more consistent through steel beams with variable cross-section.

Research on the Critical Buckling Pressure of Bucket Foundations with Inner Compartments for Offshore Wind Turbines

In the process of suction penetration of bucket foundations with inner compartments for offshore wind turbines,most researches focus on soil seepage failure and soil plugs,while the buckling of foundations is rarely investigated.Therefore,theoretical calculation methods for critical buckling pressures of the skirt and bulkheads of the bucket foundation are first presented according to the stability theory of a cylindrical shell and the small deflection theory of a thin plate,respectively.Furthermore,two types of models with and without considering the skirt-soil interaction are developed for the calculation of critical buckling pressure of the bucket foundation.Taking a practical project as an example,theoretical and numerical methods are used to obtain the critical buckling pressures of a bucket foundation.In this work,the theoretical method and the finite element model considering the skirt-soil interaction for calculating the critical buckling pressure of bucket foundations are firstly proposed.The results can help to optimize the design process of offshore wind turbine foundations and improve the safety of offshore wind power systems.

Design of Large-Scale Prestressing Bucket Foundation for Offshore Wind Turbines

The key in the force transmission between the tower and the foundation for offshore wind turbines is to transfer the large moment and horizontal loads. The finite element model of a large-scale prestressing bucket founda- tion for offshore wind turbines is set up and the structural characteristics of the arc transition structure of the founda- tion are analyzed for 40-60 channels(20-30 rows) arranged with prestressing steel strand under the same ultimate load and boundary conditions. The mechanical characteristics of the key parts of the foundation structures are illus- trated by the peak of the principal tensile stress, the peak of the principal compressive stress and the distribution areas where the principal tensile stress is larger than 2.00 MPa. It can be concluded that the maximum principal tensile stress of the arc transition decreases with the increasing number of channels, and the amplitude does not change signifi- cantly; the maximum principal compressive stress increases with the increasing number of channels and the amplitude changes significantly; however, for the distribution areas where the principal tensile stress is larger than 2.00 MPa, with different channel numbers, the phenomenon is not obvious. Furthermore, the principal tensile stress at the top of the foundation beams fluctuantly increases with the increasing number of channels and for the top cover of the bucket, the principal tensile stress decreases with the increasing number of channels.

Offshore Wind Power for Marine Conservation

The seas of northern Europe are strongly affected by human activities and there is a great need for improved marine conservation. The same region is also the current hotspot for offshore wind power development. Wind farms can have negative environmental impacts during construction, but during the operational phase many organisms are attracted to the foundations and thereby may also find refuge from fisheries. Given the recent implementation of marine spatial planning in Europe and elsewhere, this is a critical time to address potential compatibility and synergies between marine conservation and wind power. This review concludes that offshore wind farms can be at least as effective as existing marine protected areas in terms of creating refuges for benthic habitats, benthos, fish and marine mammals. The degree of advantage for these organisms depends on the location of the wind farm and the level of imposed fishing restriction. Under certain conditions wind farms may even be more efficient means of conservation than ordinary marine protected areas. However, offshore wind farms can be negative for several species of seabirds, essentially as occupying preferred feeding or wintering grounds. In areas important to these seabirds wind farms may not comply with conservation. The results bring important messages to marine spatial planning as some but not all wind farms can be spatially combined with, and even synergistic to, marine conservation.

Study on the Horizontal Movement State of Suction Anchor Piles for Offshore Wind Power during Horizontal Pulling

The subsea anchor piles of offshore wind power floating platform structures are mainly subjected to uplift and horizontal loads, and this paper focuses on the case of horizontal loads. A three-dimensional numerical simulation study of the horizontal pullout characteristics of wind power suction anchor piles in clay layers was carried out to reveal the horizontal movement state of the anchor piles during horizontal pile pullout, the range of pile depth at the pullout point where the horizontal movement is achieved (referred to as the horizontal movement range), the relationship between the pullout load and the ultimate load during the horizontal movement, and the optimal location of the pullout point for the horizontal movement. The results show that at certain pull-out points, the anchor pile produces an overall horizontal movement state under suitable horizontal pull-out loads. The depth of the pile pull-out point for horizontal movement is in the middle and lower part of the pile, i.e. 14.2 m to 14.5 m. The horizontal pull-out load of 24,000 kN at a depth of 14.5 m within the pile horizontal movement range of 14.2m to 14.5 m is the maximum ultimate horizontal pull-out load;the optimum pull-out point depth is 14.5 m at 0.275 L (L is the pile length). For each pull-out point of the anchor pile in horizontal movement, the horizontal pull-out load in horizontal movement and the horizontal ultimate pull-out load existed and it was found that the two values were not exactly the same, the values were compared and it was found that at the optimum pull-out point the value of the ultimate horizontal pull-out load/horizontal pull-out load in horizontal movement tended to 1.

Criterion of aerodynamic performance of large-scale offshore horizontal axis wind turbines

With the background of offshore wind energy projects, this paper studies aerodynamic performance and geometric characteristics of large capacity wind turbine rotors （1 to 10 MW）, and the main characteristic parameters such as the rated wind speed, blade tip speed, and rotor solidity. We show that the essential criterion of a high- performance wind turbine is a highest possible annual usable energy pattern factor and a smallest possible dimension, capturing the maximum wind energy and producing the maximum annual power. The influence of the above-mentioned three parameters on the pattern factor and rotor geometry of wind turbine operated in China＇s offshore meteoro- logical environment is investigated. The variation patterns of aerodynamic and geometric parameters are obtained, analyzed, and compared with each other. The present method for aerodynamic analysis and its results can form a basis for evaluating aerodynamic performance of large-scale offshore wind turbine rotors.

Analysis and Prospects of Jiangsu Offshore Wind Power Resources

Jiangsu is a province with massive energy consumption. Although it is short of energy and mineral resources, it has abundant renewable energy resources, especially offshore wind energy. In this paper, the condition and spatial distribution of wind energy in Jiangsu are introduced, and also the recommendations to develop offshore wind power are put forward.

Feasibility analysis and implementation of marine ranching integration of offshore wind power development in Guangdong Province

Marine ranching is a new model for restoring marine ecological environment and conserving offshore fishery resources.Offshore wind power is a new clean energy industry in China.Based on the analysis of the construction of offshore wind farms in Guangdong Province,this article proposes to actively promote the integrated development of offshore wind power and marine ranching.The suitability and deployment conditions of Sargasso algae reef construction in offshore wind farms,the feasibility of developing an integrated development model featuring artificial algae reefs+offshore wind farms in Guangdong Province,as well as the importance of ecological sea area use and management were discussed.Regarding the necessity of intensive and economical utilization of sea and sea resources,it is believed that the development model of"marine ranching+offshore wind power"will become an important direction for improving the comprehensive utilization of sea areas in the future.

Offshore wind power projects set sail

China will choose the sea off eastern Jiangsu Province to build the country’s first batch of offshore wind power projects. The four

Design and Evaluation Tool for Operations and Maintenance Logistics Concepts for Offshore Wind Power Plants

In this article, the authors give an overview of different logistics concepts for operation and maintenance of OWPP （offshore wind power plants）. These can be generally classified into onshore based and offshore based concepts. The operation of OWPPs can still be improved as research has shown that the availability of OWPPs is low compared to onshore wind power plants. There are a few tools to calculate operating costs and to evaluate the different concepts. However, most tools have a weak focus on logistics although logistics account for a big share of the costs. The tool the authors are introducing in this article focuses on the logistics processes. It is first explained and then tested with an OWPP scenarin

Offshore Wind Power Evaluation Based on Nearshore Wind Power Correlations

As the increasing number of wind energy is integrated into the national power grid,analyses of wind energy are becoming increasingly more crucial.The interaction between the topography and the northeast(NE)monsoon brings abundant wind resources to the Taiwan Strait in autumn and winter.The offshore area has stronger and more stable wind resources,so deployment of offshore wind power is also actively being carried out.However,development of offshore wind power systems requires stricter evaluation and decision-making.Therefore,this study implements a multi-site measurement verification to establish the relationship between the wind resources of the nearshore wind turbine system and a potential offshore power site in Chanbin.In the absence of a wind turbine at a specific location,potential of offshore wind energy is analyzed through wind resources.The findings showed that although the distance between these two sites is substantial,the nearshore and offshore areas at Chanbin experience similar wind conditions,and nearshore wind turbine can respond well to changes in wind speed and generate power accordingly.Afterwards,on this basis,the offshore power potential was evaluated and compared with the nearshore wind turbine systems.The results suggested the advantages of offshore wind power.A further analysis of the differences between power generation on a monthly basis was carried out to determine the distribution of wind turbine operation modes and illustrate the influence of the NE monsoon.

Analysis of offshore wind energy resources of China

With the economic development, the problems of energy shortage become increasingly severe. As offshore wind energy has advantages, namely it is clean, renewable, not accounting for land area, without noise pollution, with large reserves, etc., which gradually attracts people＇s attention. In this paper, China＇s offshore annual average wind field and monthly average wind field under the mean climate state conditions are obtained, and the corresponding wind density distribution is calculated. China＇s offshore wind energy reserves and distribution conditions through the analysis of wind energy density distribution are summarized, and finally some suggestions for coastal offshore wind energy development and utilization in China are put forward.

基于PSO-SVR的海缆刚度预测模型研究

海缆刚度是表征海缆截面力学特性的重要指标。精细数值模拟方法可考虑层间接触、摩擦等非线性行为,实现刚度的精确获取。但在海缆的截面初步设计中需进行不同几何参数下刚度的对比分析,这一过程需投入大量的人力物力以完成多个对比模型的建模与计算。依托Nysted海上风电工程,建立海缆的有限元模型,采用正交试验法确定影响海缆抗拉刚度、逆时针抗扭刚度和顺时针抗扭刚度的主要因素;将主要影响因素作为粒子群优化算法-支持向量回归模型(PSO-SVR)的特征输入,分别建立海缆抗拉刚度、逆时针抗扭刚度和顺时针抗扭刚度的预测模型,并对比分析PSO-SVR模型与GRNN神经网络模型、BP神经网络模型的预测性能。计算结果表明:导体直径、钢丝直径、钢丝节距和铠装层数对海缆刚度的影响较大,而钢丝弹模对其影响较小;PSO-SVR模型的决定系数高于0.95且误差较低,预测效果均优于GRNN神经网络模型和BP神经网络模型,该预测模型可为海缆结构初步设计提供技术支撑。

具备黑启动和构网能力的远海风电经DRU-MMC送出方案

由于具有成本低、体积重量小和可靠性高等特点,送端采用二极管整流器(DRU)、受端采用模块化多电平换流器(MMC)的送出方案在远海风电送出领域备受关注。鉴于DRU不能构建交流电网且无法倒送有功功率,文中提出一种具备黑启动和构网能力的远海风电经DRU-MMC送出方案。所提方案在DRU-MMC送出技术的基础上增加了常规小容量电压源型辅助换流器、耗能单元和必要的快速开关,通过直流海缆复用和快速开关倒闸重构拓扑,分别构建黑启动电源低压回路和风电传输高压回路,实现黑启动和功率传输2种工况在线切换;提出辅助换流器在不同运行阶段的构网控制策略,解决海上交流电网构建、DRU无功补偿和谐波抑制等问题,消除DRU-MMC送出方案对风电场类型的限制。最后,通过经济性分析和算例仿真,验证了所提方案的优越性和有效性。

基于VC-综合赋权法的海上风电APF配置优化方法研究

大容量海上风电机组的接入改变了传统电力系统结构,给电网带来了谐波等问题,影响了电能质量。为抑制海上风电机组产生的低次谐波,文章首先建立了海上风电机组并网电流的低次谐波理论模型;然后,在仿真软件ETAP上搭建海上风电机组仿真模型,验证不同出力情况下风电场的输出谐波特性;最后,基于风电场输出谐波特性,提出变异系数(Variation Coefficient,VC)综合赋权法对风电场有源滤波器(APF)进行优化配置,提升了风电场谐波的治理效果。基于实际算例验证了所提方法的有效性。

基于ATP-EMTP的海上风电送出海缆工频过电压仿真分析

海底长电缆线路的充电电容较高,在不同的运行工况下会产生较严重的过电压,而在高抗退出运行情况下,陆上架空送出线路故障产生的过电压会传送至海底电缆。结合工程实际,基于ATPEMTP软件对某海上风电场220 kV送出海缆及架空线路进行建模,对不同运行工况下送出海缆工频过电压、送出架空线路短路故障及断线故障时的海缆工频过电压进行仿真计算,结果表明,合理的高抗配置方案可有效降低海上风电送出海缆的工频过电压水平。

Coupled Time-Domain Investigation on a Vertical Axis Wind Turbine Supported on a Floating Platform

The dynamic responses of a floating vertical axis wind turbine(VAWT)are assessed on the basis of an aero-hydro-mooring coupled model.The aerodynamic loads on the rotor are acquired with double-multiple stream tube method.First-and second-order wave loads are calculated on the basis of 3D potential theory.The mooring loads are simulated by catenary theory.The coupled model is established,and a numerical code is programmed to investigate the dynamic response of the semi-submersible VAWT.A model test is then conducted,and the numerical code is validated considering the hydrodynamic performance of the floating buoy.The responses of the floating VAWT are studied through the numerical simulation under the sea states of wind and regular/irregular waves.The effects of the second-order wave force on the motions are also investigated.Results show that the slow-drift responses in surge and pitch motions are significantly excited by the second-order wave forces.Furthermore,the effect of foundation motion on aerodynamic loads is examined.The normal and tangential forces of the blades demonstrate a slight increase due to the coupling effect between the buoy motion and the aerodynamic loads.