大家一起学标准之IEC61400-1(14)

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点击听全文，今天大家继续一起学IEC61400-1。

7 Structural design

7.1 General

The integrity of the load-carrying components of the wind turbine structure shall be verified and an acceptable safety level shall be ascertained. The ultimate and fatigue strength of structural members shall be verified by calculations, tests or both to demonstrate the structural integrity of a wind turbine with the appropriate safety level.The structural ana lysis shall be based on ISO 2394.Calculations shall be performed using appropriate methods. Descriptions of the calculation methods shall be provided in the design documentation. The descriptions shall include evidence of the validity of the calculation methods or references to suitable verification studies. The load level in any test for strength verification shall correspond to the safety factors appropriate for the characteristic loads according to 7.6.Tower, rotor, and drive train resonances shall be identified for the frequency range up to and including 2 times the blade passing frequency excitation. Possible resonances shall be investigated at turbulence levels of 30 % of the NTM category C design turbulence for DLC 1.2, see 7.4.2. If high resonant loads are found at low turbulence, means shall be taken to avoid the resonances or they shall be included in the design loads.

7.2 Design methodology

It shall be verified that limit states are not exceeded for the wind turbine design. Model testing and prototype tests may also be used as a substitute for calculation to verify the structural design, as specified in ISO 2394.The design calculations shall be based on validated methods and recognized codes.The design methodology assumes that the aeroelastic simulation model used for the specific design calculations is subsequently validated by measurements. Such measurements shall be made on a wind turbine that is dynamically and structurally similar to, but may differ in detail (such as alternative tower designs) from the turbine designed. Requirements for load measurements can be found in IEC 61400-13.

7.3 Loads

7.3.1 General

Loads described in 7.3.2 through 7.3.5 shall be considered for the design calculations.

7.3.2 Gravitational and inertial loads

Gravitational and inertial loads are static and dynamic loads that result from gravity, vibration, rotation and seismic activity.The allowable tolerances in tower verticality shall be stated in the design documentation and shall include initial and long term effects due to permanent soil subsidence. The effect of tower verticality on gravitational loads shall be taken into account separately during the structural ana lysis of tower and foundation.

7.3.3 Aerodynamic loads

Aerodynamic loads are static and dynamic loads that are caused by the airflow and its interaction with the stationary and moving parts of wind turbines.The airflow is dependent upon the average wind speed and turbulence across the rotor plane, the rotational speed of the rotor, the density of the air, and the aerodynamic shapes of the wind turbine components and their interactive effects, including aeroelastic effects.It is not required in the aerodynamic load calculations to account for geometric tolerances in tower verticality of less than or equal to 3°.

7.3.4 Actuation loads

Actuation loads result from the operation and control of wind turbines. They are in several categories including torque control from a generator or inverter or both, yaw and pitch actuator loads and mechanical braking loads. In each case, it is important in the calculation of response and loading to consider the range of actuator forces available, including friction. In particular, for mechanical brakes, the range of friction, spring force or pressure as influenced by temperature, and ageing shall be taken into account in checking the response and the loading during any braking event.

7.3.5 Other loads

Other loads such as wake loads, impact loads, ice loads, tower loads resulting for example from vortex-induced vibrations might occur and shall be considered where appropriate. For other loads associated with cold climate, see Clause 14 and Annex L.

7.4 Design situations and load cases

7.4.1 General

Subclause 7.4 describes the design load cases for a wind turbine and specifies a minimum number to be considered.For design purposes, the life of a wind turbine can be represented by a set of design situations covering the most significant conditions that the wind turbine may experience.The load cases shall be determined from the combination of operational modes or other design situations, such as specific assembly, erection or maintenance conditions, with the external conditions. All relevant load cases with a reasonable probability of occurrence shall be considered, together with the behaviour of the control system. The design load cases used to verify the structural integrity of a wind turbine shall be calculated by combining the following:

·normal design situations and appropriate normal or extreme external conditions;

·fault design situations and appropriate external conditions;

·transportation, installation and maintenance design situations and appropriate external conditions.

If correlation exists between an extreme external condition and a fault situation, a realistic combination of the two shall be considered as a design load case.

Within each design situation, several design load cases shall be considered. As a minimum, the design load cases in Table 2 shall be considered. In that table, the design load cases are specified for each design situation by the description of the wind, electrical and other external conditions.

If the wind turbine controller can, during design load cases with a deterministic wind model, cause the wind turbine to shut down prior to reaching maximum yaw angle and/or wind speed, then it shall be shown that the turbine can reliably shut down under turbulent conditions with the same deterministic wind condition change.

Other design load cases shall be considered, if relevant to the structural integrity of the specific wind turbine design.

For each design load case, the appropriate type of an alysis is stated by "F" and "U" in Table 2. "F" refers to an alysis of fatigue loads, to be used in the assessment of fatigue strength. "U" refers to the an alysis of ultimate loads, with reference to material strength, blade tip deflection and structural stability.

The design load cases indicated with "U" are classified as normal (N) or abnormal (A). Normal design load cases are expected to occur frequently. The turbine is in a normal state or may have experienced minor faults or abnormalities. Abnormal design situations are less likely to occur. They usually correspond to design situations with severe faults that result in the activation of system protection functions. The type of design situation, N or A, determines the partial safety factor γf to be applied to the ultimate loads. These factors are given in Table 3.

7 结构设计

7.1 概述

应验证风力机承载构件的完整性，并确定可接受的安全水平。应通过计算、试验或二者相结合的方式验证构件的极限强度与疲劳强度，证明风力机结构具备相应的安全完整性。

结构分析应依据 ISO 2394。计算应采用合适的方法，设计文件中应当提供计算方法说明；说明内容需包含计算方法有效性证明，或引用适用的验证研究。任何强度验证试验中的荷载水平，均应采用 7.6 规定的、对应特征荷载的安全系数。

应识别塔筒、风轮与传动链在最高至 2 倍叶片通过频率激励区间内的共振。需在 DLC 1.2 工况、NTM C 类湍流 30% 湍流强度条件下，研究潜在共振；若在低湍流工况下发现较大共振荷载，应当采取措施规避共振，或将共振荷载纳入设计荷载。

7.2 设计方法

设计需验证风力机不会超出各类极限状态。按照 ISO 2394 规定，模型试验与样机试验可替代计算开展结构设计验证。

设计计算应当采用经过验证的方法与公认规范。该设计方法假定：特定设计计算所使用的气动弹性仿真模型后续需通过实测进行验证。实测对象为动力学与结构形式相似（细节可存在差异，例如塔筒方案不同）的风力机；荷载测量相关要求见 IEC 61400-13。

7.3 荷载

7.3.1 概述

设计计算应当考虑 7.3.2 至 7.3.5 所描述的各类荷载。

7.3.2 重力荷载与惯性荷载

重力荷载与惯性荷载是由重力、振动、旋转及地震作用产生的静荷载与动荷载。

塔筒垂直度允许偏差应在设计文件中明确，需包含初始偏差以及土体长期沉降带来的长期偏差。塔筒垂直度对重力荷载产生的影响，应当在塔筒与基础的结构分析中单独考虑。

7.3.3 气动荷载

气动荷载是气流与风力机静止、运动部件相互作用产生的静荷载与动荷载。气流条件取决于叶轮平面平均风速、湍流、风轮转速、空气密度、风力机构件气动外形及其耦合效应，包含气动弹性效应。若塔筒垂直度几何偏差不大于 3°，气动荷载计算时无需考虑该几何公差。

7.3.4 执行机构荷载

执行机构荷载由风力机运行与控制动作产生，包含发电机 / 变流器扭矩控制荷载、偏航与变桨执行机构荷载、机械制动荷载等类别。在开展结构响应与荷载计算时，均应当考虑执行机构可输出作用力范围（含摩擦力）。尤其对于机械制动器，在校核制动过程的结构响应与荷载时，应考虑温度、老化对摩擦力、弹簧力或压力区间带来的影响。

7.3.5 其他荷载

还可能存在尾流荷载、冲击荷载、覆冰荷载、由涡激振动引发的塔筒荷载等其他荷载，在适用情况下均需予以考虑。寒冷气候相关其他荷载参见第 14 章及附录 L。

7.4 设计工况与荷载工况

7.4.1 概述

第 7.4 条阐述风力机设计荷载工况，并规定最低需考虑的工况数量。

从设计角度，风力机全生命周期可由一组设计工况表征，覆盖机组可能遭遇的最关键条件。荷载工况由运行模式或其他设计工况（如装配、吊装、运维工况）与外部条件组合确定。所有具备合理发生概率的荷载工况均应予以考虑，同时结合控制系统行为开展分析。用于验证风力机结构完整性的设计荷载工况，通过以下内容组合计算得到：

·正常设计工况，搭配适用的正常或极端外部环境条件；

·故障设计工况，搭配适用的外部环境条件；

·运输、安装与运维设计工况，搭配适用的外部环境条件。

若极端外部条件与故障工况之间存在相关性，应将二者进行符合实际的组合，作为一项设计荷载工况。

每种设计工况下均应考虑若干设计荷载工况；最低限度必须考虑表 2 内所列荷载工况。表 2 中针对各设计工况，通过风况、电气条件与其他外部条件对设计荷载工况进行定义。

在确定性风模型对应的设计荷载工况中，若风力机控制器能够在达到最大偏航角度和 / 或风速之前实现停机，则必须证明：在具备同等确定性风况变化的湍流条件下，机组同样能够可靠完成停机。

若某些工况会影响特定风力机结构完整性，则还应额外考虑对应的设计荷载工况。

每个设计荷载工况对应的分析类型在表 2 中以 “F” 和 “U” 标识：“F” 代表疲劳荷载分析，用于疲劳强度评估；“U” 代表极限荷载分析，关联材料强度、叶尖挠度与结构稳定性。

标注 “U” 的设计荷载工况分为正常（N）或异常（A）两类。正常设计工况发生较为频繁，机组处于正常状态或仅存在轻微故障、异常；异常设计工况发生概率更低，通常对应出现严重故障、触发系统保护功能的工况。设计工况类型（N 或 A）决定极限荷载所采用的分项安全系数γf，相关系数见表 3。

简单总结

第七章为风机结构设计核心条款，规定结构完整性验证要求、设计方法与模型验证规则；划分重力惯性、气动、执行机构、其他四大类荷载；明确各类运行、故障、吊装运维等设计工况组合原则，区分疲劳分析 (F) 和极限分析 (U)，并依据工况类别选用对应的分项安全系数。

来源：智慧强学斋

大家一起学标准之IEC61400-1(4)

点击听全文，今天大家继续一起学IEC61400-1。3.20 fail-safe 故障安全design property of an item which prevents its failures from resulting in critical faults.设备自身具备的设计特性，可避免自身失效引发致命重大故障。3.21 gust 阵风temporary change in the wind speed.风速的瞬时短时突变。Note 1 to entry: A gust may be characterized by its rise time, its magnitude and its duration.本条注释 1：阵风可由上升时间、幅值大小、持续时长三个参数表征。3.22 horizontal axis wind turbine 水平轴风力发电机组wind turbine whose rotor axis is substantially horizontal。风轮旋转主轴基本呈水平布置的风力发电机。3.23 hub 轮毂 fixture for attaching the blades or blade assembly to the rotor shaft.用于将单支叶片或叶片总成固定安装至风轮主轴的连接件。3.24 hub height 轮毂高度 height of the centre of the swept area (3.57) of the wind turbine rotor above the terrain surface.< 风机专用 > 风轮扫掠面几何中心距离地面地形的垂直高度。3.25 idling 空转待机 condition of a wind turbine that is rotating slowly and not producing power.风轮低速旋转、机组不向外输出电能的运行状态。3.26 inertial sub-range 惯性子区frequency interval of the turbulence spectrum, where eddies – after attaining isotropy – undergo successive break-up with negligible energy dissipation.湍流谱中的一段频率区间：涡旋达到各向同性后逐级分裂耗散，此过程能量损耗可忽略不计。Note 1 to entry: At a typical 10 m/s wind speed, the inertial sub-range is roughly from 0.2 Hz to 1 kHz.本条注释 1：常规 10m/s 风速下，惯性子区大致范围为 0.2Hz ~ 1kHz。3.27 limit state 极限状态state of a structure and the loads acting upon it, beyond which the structure no longer satisfies the design requirement.结构与所受载荷构成的临界状态，一旦超出该状态，结构将不再满足设计规定的安全要求。Note 1 to entry: The purpose of design calculations (i.e. the design requirement for the limit state) is to keep the probability of a limit state being reached below a certain value prescribed for the type of structure in question (see ISO 2394).本条注释 1：结构设计计算（即极限状态设计要求）的核心目的，是将结构抵达极限状态的概率控制在该类结构规范限定的允许值以内（参见 ISO 2394）。3.28 mean wind speed 平均风速statistical mean of the instantaneous value of the wind speed averaged over a given time period which can vary from a few seconds to many years.对可从数秒至数年不等的给定时长内的瞬时风速取统计平均值。3.29 medium wind turbine 中型风力发电机组wind turbine with a rotor swept area or, in the case of a ducted or shrouded turbine, the larger of the duct or shroud entry and exit areas greater than 200 m² and less than or equal to 1000 m².风轮扫掠面积大于 200㎡且不大于 1000㎡；对于导流罩式机组，取导流罩进出口面积中的较大值，满足该面积区间即为中型风机。3.30 nacelle 机舱housing which contains the drive-train and other elements on top of a horizontal axis wind turbine tower.安装在水平轴风机塔筒顶端，容纳传动链及其他核心部件的舱体结构。3.31 network connection point 并网点 cable terminals of a single wind turbine or, for a wind power station, the connection point to the electrical bus of the site power collection system.单台风机的电缆接线端子；风电场场景下，指机组接入场内集电系统母线的连接点位。3.32 network loss 电网失电 / 电网脱网loss of electrical network (grid) for a period exceeding any ride through provision in the turbine control system.电网供电中断，且断电时长超出风机控制系统具备的低电压穿越能力时长。3.33 normal shutdown 正常停机 shutdown in which all stages are under the control of the control system.停机全过程完全由机组控制系统有序管控的停机流程。3.34 operating limits 运行限值set of conditions defined by the wind turbine designer that governs the activation of the turbine control functions.由风机设计方划定的一组边界条件，一旦触发将启动机组各类控制保护功能。3.35 parked wind turbine 停机静置风机turbine being either in a standstill or an idling condition, depending on the design of the wind turbine.依据机组设计方案，风轮处于完全锁死静止或低速空转待机状态的风机。3.36 performance level (PL) 性能等级discrete level used to specify the ability of safety-related parts of control systems to perform a safety function under foreseeable conditions.用于分级定义控制系统安全相关部件，在可预见工况下执行安全保护功能能力的离散等级。3.37 power collection system 场内集电系统 electric system that collects the power from one or more wind turbines.汇集单台或多台风机发电量的电气系统。Note 1 to entry: It includes all electrical equipment connected between the wind turbine terminals and the network connection point.本条注释 1：包含风机接线端子至电网并网点之间全部电气设备。3.38 power output 输出功率power delivered by a device in a specific form and for a specific purpose.设备以特定形式、为特定用途向外输送的功率。Note 1 to entry: For a wind turbine, it is the electric power it delivers.本条注释 1：针对风力发电机组，特指其输出的电功率。3.39 primary layer protection function 主层级保护功能protection function (3.40) in a protection system with two or more independent layers which may be implemented as a part of the wind turbine control system and is separate from a secondary layer protection function (3.52) with a similar purpose.多层独立防护体系中的第一层保护逻辑，可集成在机组主控系统内，与功能目的相近的次级保护层级相互独立、分设冗余。3.40 protection functions 保护功能 functions of the control system which ensure that a wind turbine remains within the design limits.控制系统内置的各类逻辑功能，用于保障机组运行参数始终不超出设计限值。简单总结该部分属于 IEC 61400-1:2019 第 3 章术语续篇，依次定义风况、机型、整机结构、电网接口、停机方式、安全防护层级、极限状态等核心专业名词，明确惯性湍流区间、中型风机面积界定、主次级保护架构等设计判定依据，是后续载荷工况、保护逻辑、机型分级设计的统一术语基准。今天就学到这里，明天我们继续学习，每天十分钟大家一起学标准。来源：智慧强学斋