基于频率控制的多约束风电塔优化方法

提出了基于频率控制的多约束单管型风电塔优化方法.塔架简化成悬臂梁结构,其横截面参数作为设计变量,以最小化材料体积为目标函数,按照将塔架设计成刚-刚或刚-柔或柔-柔不同类型的要求设定塔架的固有频率约束,采用专业软件Bladed计算风荷载,按照风电塔规范考虑强度、稳定性和疲劳等约束,这使得优化结构更符合实际设计.考虑到采用Bladed荷载计算工作量很大,整个优化过程分为几个阶段,在每个阶段的开始,以前一个阶段的优化设计作为初始设计,并重新计算结构荷载,在该阶段内于固定荷载下用移动渐近线法(MMA)求解优化问题改进设计,所需的固有频率、强度及疲劳约束灵敏度采用解析法获得.对一现有塔架进行优化以说明方法的有效性.根据塔架固有频率和风机工作转速之间的关系,发展了高风电塔的分类.在此基础上,结合提出的优化方法,可以帮助设计者判定在指定高度和机型下哪种类型塔架更合适,为塔架概念设计提供有价值的参考.

Frequency-based optimization method for wind turbine tower under multiple constraints

A frequency-based optimization method for single tubular wind turbine tower under multiple constraints is proposed. The cross section parameters of tower are design variables, and minimizing the material volume of tower, which is considered as a cantilever structure is objective function. The natural frequencies of tower are constrained to ensure the tower being stiff-stiff or stiff-soft or soft-soft design. The wind loads are calculated by commercial software Bladed, and according to specification of wind turbine tower, the strength, stability and fatigue are included in constraints, these factors make the optimum structure conform to the practical design. Since the load evaluation by Bladed is very costly, the whole optimization process is broken into several stages. At the beginning of each stage optimization starts by using the previous optimum design as its initial design and the wind load of the initial tower design is recalculated. In each stage, optimization problem is solved by method of moving asymptotes (MMA) under the fixed wind load, and the sensitivities of the natural frequency, strength and fatigue constraints with respect to design variables are obtained by analytical method. A numerical example for improving the existing tower design demonstrates the optimization method. Furthermore, a classification of high wind turbine tower is developed based on the relationship between tower natural frequency and working frequency range of the wind turbine to be installed. By the above optimization method, it can help to decide that which type of the tower design is the potentially optimum candidate for specific height and turbine, and provide valuable suggestions for optimum design during concept design stage for wind turbine tower.