平顶长脉冲强磁场的优化设计理论和方法

发布时间：2018-05-02 22:37

本文选题：平顶脉冲强磁场 + 脉冲发电机　；参考：《华中科技大学》2014年博士论文

【摘要】：强磁场作为一种极端实验手段,其在科研、医疗和工业等领域都有着广泛的应用。许多重要的科学发现都是直接得益于极端强磁场条件。根据磁场持续的时间可将强磁场分为脉冲强磁场和稳态强磁场等类型,这两种类型的磁场在各领域都已经有了重要的应用,但二者也都有一定的应用局限性。平顶脉冲强磁场则是介于脉冲强磁场和稳态强磁场之间的一种强磁场装置,由于它综合了脉冲场的场强高和稳态场的纹波小的特点,而且造价成本比稳态场要低很多,所以平顶脉冲强磁场得到了许多科学家的青睐。由于平顶脉冲强磁场的场强高且脉宽长,磁体的功耗、温升和应力都很大,这对电源系统和磁体系统都是极大的挑战。另外平顶脉冲强磁场的电源系统和磁体系统之间存在电和热等耦合关系,在进行设计时必须将电源和磁体进行迭代耦合计算,这增加了设计的复杂性。本文即以在综合考虑电源和磁体特性的基础上进行平顶脉冲强磁场的系统优化设计为主要内容。在数学模型方面,文章基于华中科技大学国家脉冲强磁场中心现有的装置条件,建立了脉冲发电机-整流器型电源、电容器型电源和蓄电池型电源的数学模型并分析了其工作特性,同时将磁体系统的电磁学、热学和力学特性进行了解耦分析和建模。在建立的电源和磁体系统的数学模型的基础上,详细阐述了平顶脉冲强磁场系统的设计流程和优化方法。以单目标优化设计为例分析了遗传算法在平顶脉冲强磁场系统优化设计中的应用,并用枚举法验证了遗传算法在进行平顶脉冲强磁场系统的优化设计时的可行性。针对单目标优化设计只单一追求磁场最高而使电源和磁体系统的其他参数都处于装置运行极限的情况,引入了差分进化算法进行平顶脉冲强磁场系统的多目标优化设计。将电源系统的电压、电流和功率等关键参数与磁体的磁场和温度等进行统一综合优化。分析了加权法在低维多目标优化设计中的优化设计流程及其所得最优解在Pareto前沿上的直观分布情况。在高维多目标优化设计方面,引入了根据各优化目标的优劣情况进行分层打分的可视化优化设计方法,并以发电机-十二脉波整流器电源给单线圈供电为例阐述了该优化方法的详细设计流程。根据武汉国家脉冲强磁场科学中心现有几种电源供电特性,本文将武汉国家脉冲强磁场科学中心现有的几种电源进行了各种有效组合,分析了各组合电源的可行性和工作特性,详细讨论了各组合电源分别给单线圈和双线圈磁体供电时的工作情况,并以差分进化算法对各种系统进行可视化的多目标优化设计,给出了每种组合能实现的最优平顶脉冲强磁场的设计方案。最后将所得最优设计方案进行对比,选出磁场场强最高的方案进行详细的仿真验证。
[Abstract]:As an extreme experimental method, strong magnetic field has been widely used in scientific research, medical treatment and industry. Many important scientific discoveries benefit directly from extreme magnetic field conditions. According to the duration of the magnetic field, the strong magnetic field can be divided into pulse strong magnetic field and steady-state strong magnetic field. These two kinds of magnetic field have been used in various fields, but both have some limitations. The flat-top pulsed strong magnetic field is a kind of strong magnetic field device between the pulsed strong magnetic field and the steady strong magnetic field. Because it combines the characteristics of the high field intensity of the pulse field and the small ripple of the steady field, the cost is much lower than that of the steady field. So the flat-top pulsed strong magnetic field has been favored by many scientists. Due to the high field intensity and long pulse width of the flat-top pulse strong magnetic field, the power consumption, temperature rise and stress of the magnet are all very large, which is a great challenge to both the power supply system and the magnet system. In addition, there is an electric and thermal coupling relationship between the power supply system and the magnet system of the flat-top pulse strong magnetic field. The iterative coupling calculation between the power supply and the magnet must be carried out in the design process, which increases the complexity of the design. In this paper, the system optimization design of flat-top pulse strong magnetic field based on considering the characteristics of power supply and magnet is considered as the main content. In terms of mathematical model, based on the existing equipment conditions of the National Pulsed strong Magnetic Field Center of Huazhong University of Science and Technology, a pulse generator rectifier power supply is established. The mathematical models of capacitor power supply and battery power supply are analyzed, and the electromagnetic, thermal and mechanical characteristics of the magnet system are analyzed and modeled. Based on the mathematical model of power supply and magnet system, the design flow and optimization method of flat-top pulsed strong magnetic field system are described in detail. Taking single objective optimization design as an example, the application of genetic algorithm in the optimal design of flat-top pulsed strong magnetic field system is analyzed, and the feasibility of genetic algorithm in the optimal design of flat-top pulsed strong magnetic field system is verified by enumeration method. Because the single objective optimization only pursues the highest magnetic field and the other parameters of the power supply and magnet system are at the operating limit of the device, the differential evolution algorithm is introduced to design the flat-top pulsed strong magnetic field system with multi-objective optimization. The key parameters of the power system, such as voltage, current and power, are integrated and optimized with the magnetic field and temperature of the magnet. The optimal design process of weighted method in low dimensional multiobjective optimization design and the visual distribution of the resulting optimal solution on the Pareto front are analyzed. In the aspect of high-dimensional multi-objective optimization design, a visual optimization design method is introduced, which is based on the merits and demerits of each optimization objective. Taking the generator-12 pulse rectifier power supply to single coil as an example, the design flow of the optimization method is described in detail. According to the current power supply characteristics of Wuhan National Pulsed strong Magnetic Field Science Center, this paper has carried out a variety of effective combinations of the existing power sources of Wuhan National Pulsed strong Magnetic Field Science Center, and analyzed the feasibility and working characteristics of each combined power supply. The working conditions of each combined power supply to the single coil and double coil magnets are discussed in detail, and the multi-objective optimization design of the system is visualized by the differential evolution algorithm. The design scheme of the optimal flat-top pulse strong magnetic field for each combination is given. Finally, the optimal design scheme is compared and the scheme with the highest magnetic field intensity is selected for detailed simulation.
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TM15

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